Encyclopedia of Environmental Microbiology, 6 Volume Set / Edition 1 available in Hardcover
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- Approximately 350 articles provide A-Z coverage of the entire field of environmental microbiology and all important topics
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About the Author
Gabriel Bitton is Professor Emeritus of Environmental Microbiology and Toxicology at University of Florida, Gainesville. He is an international authority in water-associated microbial contamination. This is the fourth edition of his classic work and will be followed by a new work on Drinking Water Microbiology.
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Note: Figures and /or Tables mentioned in this sample chapter do not appear on the Web.
TIMOTHY J. SHEERAN
Department of Defense
Washington, D. C.
The views expressed in this article are those of the author and do not reflect the official policy or position of the Department of Defense or the U. S. Government.
History has illustrated the utility of biological agents as weapons of war. Although at least ten countries are suspected to have offensive biological warfare programs at the national level, the threat of biological attack from state and non-state-sponsored terrorists is a growing concern. Biological warfare may be defined simply as the use of a biological organism or biologically derived toxin or other substance to cause lethal or incapacitating effects. Agents may be used to target humans, crops or livestock, or nonliving but economically vital material such as an oil supply. An act of biological terrorism may be employed in a multitude of scenarios ranging from a small-scale attack on a restaurant salad bar incapacitating tens to hundreds, to the covert aerosolization of smallpox virus in a crowded auditorium that would kill an estimated 15,000 people causing confusion, hysteria, and civil unrest (1). Understanding the threat of bioterrorism is crucial in developing proper procedures and countermeasures to provide an effective response to an attack.
This article focuses mainly on the technical aspects of biological warfare as they apply to a terrorist attack. A history of biological warfare, employment scenarios, agent characteristics, aspects of dispersion, and countermeasures are covered in this review. Because of the sensitivity of this topic, some areas are covered more generally than others, so as not to provide helpful information to a would-be terrorist.
HISTORY OF BIOLOGICAL WARFARE
Humans have known of the utility of biological organisms and toxins as weapons of war well before the germ theory of disease was understood. One of the first recorded events in which a biological agent was used in war was the siege of Kaffa, which occurred in the fourteenth century in what is now Feodosia, Ukraine. The attacking Tartar force took advantage of a plague outbreak among their ranks by catapulting bodies of their deceased into the city to create a plague epidemic. The ensuing spread of plague led to the fall of Kaffa to the Tartar force (2,3). For centuries to follow, diseased animals and humans were used to contaminate the water supplies of would-be aggressors in the hope of creating an epidemic that would affect the outcome of the battle. During the French and Indian war in 1763, the British successfully used smallpox-infected blankets to create epidemics among the native American tribes opposing the British (3).
World War I
Advances in microbiology through the nineteenth century allowed the isolation and identification of disease-causing microorganisms, which could be used to attack with some degree of specificity. World War I saw the use of biological agents to attack livestock. Strong evidence exists indicating that Germany used Bacillus anthracis and Burkholderia mallei, the causative agents of anthrax and glanders, to infect livestock during transshipment. Anthrax and glanders agents were reportedly used by Germany to infect Romanian sheep being transported to Russia. Additionally, German covert operators also may have used glanders to infect 4,500 mules in Mesopotamia and horses in France. They were also used in operations in the United States targeting horses bound for allied forces in Europe (2).
Extensive use of chemical weapons during World War I prompted the creation of the Geneva protocol of 1925, which called for the prohibition of the use in war of asphyxiating, poisonous or other gases, and of bacteriological methods of warfare. Although the Geneva Protocol prohibited the use of biological weapons, it did not prohibit research and development, production or storage of biological weapons. Many countries, while signing the protocol, maintained the right and capability to respond in kind to a biological attack. These countries included Belgium, Canada, France, Great Britain, Italy, the Netherlands, Poland, and the Soviet Union (2).
World War II
During World War II, Japan conducted extensive biological weapons (BW) research from 1932 to 1945 (2). The focal point of the Japanese BW program, called Unit 731, was located near the town of Pingfan and had a staff of over 3,000 scientists working in over 150 buildings and five satellite camps. Unit 731 conducted at least 12 biological weapons field trials and utilized prisoners of war as their test subjects (2). Agents tested include B. anthracis, Neisseria meningitidis, Shigella species, Vibrio cholerae, and Yersinia pestis. Japan used biological weapons on at least 11 Chinese cities during World War II. The tactics used in these attacks included contamination of food and water supplies as well as tossing cultures directly into homes and spraying agents from aircraft. The Japanese allegedly used fleas fed on plague-infected rats to drop from aircraft over Chinese cities. As many as 15 million fleas were used per attack to infect the population with plague (2).
The use of biological weapons by the Japanese during World War II also made clear the dangers to the attacking force if they employed biological weapons. A biological attack on Changteh in 1941 led to a reported 10,000 Chinese casualties and 1,700 deaths among Japanese soldiers. Japan stopped field trials in 1942, but basic research in biological warfare continued until the end of the war (2).
The U. S. Program
The United States Biological Warfare Program began in 1942, and included a research and development facility at Camp Detrick (now Fort Detrick), Maryland, test sites in Mississippi and Utah, and a production plant in Terra Haute, Indiana. Experiments were performed on potential biological agents such as B. anthracis andBrucella suis. Experiments were also performed using nonpathogenic simulants such as Serratia marcescens and Bacillus globigii to test production, storage, and aerosolization methods for biological warfare agents (2). The United States also collaborated with its allies, including Canada and Great Britain, on biological warfare applications. Live fire tests by the allies in 1943 were conducted using anthrax bombs at Gruinard Island off the coast of Scotland. These experiments led to long-term contamination of the island due to the persistence of the anthrax spores tested. In 1986 and 1987 the island was successfully decontaminated using formaldehyde and was handed over to its original owners in May 1990 (2,4).
Expansion of the U. S. program during the Korean War included construction of a new production facility in Pine Bluff, Arkansas, and a countermeasures program for biological defense, which began in 1953. Animal studies using live agents were also carried out at Camp Detrick, remote desert sites, and on barges in the Pacific Ocean. Human tests were begun in 1955 using military and civilian volunteers to evaluate the effects of aerosol exposure to Francisella tularensis and Coxiella burnetti (2). By the late 1960s the United States had developed a substantial biological arsenal that comprises bacterial and toxin agents for antipersonnel use. This arsenal included both lethal and incapacitating agents such as B. anthracis, F. tularensis, Brucella suis, C. burnetti, botulinum toxin, and Staphylococcal enterotoxin B. The United States also developed plant pathogens as biological weapons, which would be used to target an enemy's food supply. These agents included rice blast, rye stem rust, and wheat stem rust (2).
In 1969 President Richard M. Nixon terminated the U. S. biological weapons program. Because of the already robust stockpiles of conventional, chemical, and nuclear weapons, it was believed that a biological weapons arsenal was not needed as a strategic deterrent. Furthermore, because of ethical and public health reasons, the true potential of biological weapons could not be tested. For this reason, BW was considered unproven as well as unpredictable and uncontrollable thus making them potentially hazardous to the attacking party (2,3). All stockpiles of biological weapons were destroyed by 1973, but research related to defense against biological warfare agents continues.
Former Soviet Union
The Soviet biological warfare program, which reportedly began during the early 1900s, was the largest of all national programs. After the signing of the Biological Weapons Convention in 1972, the Soviet biological weapons program continued under a clandestine organization called Biopreparat. Biopreparat operated over 40 research and production facilities scattered across the Soviet Union, employing up to 55,000 scientists. Many government agencies were involved in the BW program, including the Ministries of Defense, Agriculture, and Health, the Soviet Academy of Sciences, the Central Committee to the Communist Party, and the KGB (5).
The Soviet BW program considered scores of lethal bacteria, toxins, and viruses for use in its biological program, including anthrax, plague, ricin, ebola, marburg, and smallpox. Hundreds of tons of anthrax and dozens of tons of plague and smallpox were stockpiled for use against the United States and its allies (5). The Soviet Union also reportedly used biological agents as assassination weapons. For example, ricin toxin weaponized into a small pellet in an umbrella gun was reportedly used by the secret service of the Soviet Union to assassinate Georgi Markov, a Bulgarian defector living in London (2,5).
In April 1979, an outbreak of inhalational anthrax occurred in the city of Sverdlosk in Russia, which caused at least 77 clinical cases and 66 deaths. Persons working and living within 4 km from the suspected source were affected, whereas livestock were affected up to a distance of 50 km from the facility. Although an initial cover-up by the Soviet government claimed that the epidemic was caused by infected meat, suspicions that an accident occurred at a secret Soviet anthrax facility in Sverdlosk were prevalent (2,6). In 1992, Russian President Boris Yeltsin admitted that the outbreak at Sverdlosk was caused by the accidental release of anthrax spores from an offensive biological warfare production facility, specifically from the inadvertent removal of air filters on the exhaust stacks at the portion of the plant were the anthrax agent was dried (1,5). Since the fall of the Soviet Union, Russia claims that it has shut down all remaining remnants of its offensive biological warfare program.
Before the Persian Gulf War, intelligence reports indicated that Iraq was engaged in an extensive offensive biological warfare program. When the Gulf war ended, the United Nations Special Commission on Iraq (UNSCOM) obtained information that confirmed these reports. Iraqi officials admitted to having an offensive biological warfare program, which included basic research on anthrax, rotavirus, camelpox, aflatoxin, and botulinum toxins, as well as T-2 mycotoxin, and the anticrop agent wheat cover rust (2). Some of these agents were reportedly weaponized in missile warheads and bombs. The Iraqi government claims to have destroyed its biological arsenal after the war, and some research and production facilities were destroyed under the supervision of UNSCOM in the mid-1990s (2). The United Nations Monitoring and Verification Commission (UNMOVIC) is positioned to reenter Iraq and resume the monitoring and verification of the destruction of Iraq's weapons of mass destruction programs. UNMOVIC will replace the UNSCOM inspection regime, which was ousted by Iraq in late 1998. Iraq has not yet given permission to allow UNMOVIC to re-enter the country, and thus the status of the Iraqi biological warfare program remains unknown.Aum Shinrikyo
Although the Aum Shinrikyo cult is most famous for its March 20, 1995 Sarin attack on the Tokyo subway system, subsequent investigations indicate that the cult was also involved in biological terrorism as well. In addition to producing chemical agents, Aum Shinrikyo reportedly performed research on botulinum toxin, anthrax, cholera, and Q fever. In 1992, a team of Aum cult members was detected in Zaire on an alleged medical mission; whereas the actual purpose of the trip was to obtain samples of the Ebola virus. Cult members also reportedly launched three biological attacks in Japan using botulinum toxin and anthrax, which were unsuccessful. Although many of the cults leaders are either in jail or still on trial, the Aum may still be capable of carrying out future attacks using biological agents (7).
BIOLOGICAL AGENT CHARACTERISTICS
Biological Versus Chemical Weapons
Although the terms '' biological'' and '' chemical'' weapons are used synonymously, there are profound differences between these two types of weapons of mass destruction. The most obvious difference is that chemical agents are nonliving poisons made by humans, whereas biological agents are infectious living entities that reproduce inside the host to cause incapacitating or fatal disease. Biologically derived toxins such as botulinum toxin or ricin share characteristics of both chemical and biological agents (8).
With regard to biological agent use, the phrase, '' a little goes a long way'' has direct meaning. Pathogenic organisms multiply within the host to cause disease, meaning that relative to chemical agents small quantities of biological agent, if properly disseminated through the air, have the ability to inflict casualties over a large area (8,9). The inhaled infectious doses for biological organisms are measured from tens to tens of thousands of cells depending on the organism (Table 1). '' Weight for weight, biological and toxin weapons are hundreds to thousands of times more potent than the most lethal chemical warfare agents'' (8). Figure 1 illustrates the lethal dose range in terms of quantity of agent for chemical, biological, and toxin weapons (8). Even a small-scale operation only producing a few hundred grams or agent may be sufficient to cause significant casualties. Some biological agents such as Yersinia pestis and Variola major (smallpox) have the added characteristic of being easily contracted from human-to-human contact. Thus, unlike chemical agents, biological agents have the potential to spread through human transmission from the area immediately affected to produce casualties of epidemic, or possibly pandemic proportions.
On a small scale, production of biological agents does not require a large amount of specialized equipment. All equipment necessary for production of biological agents is commercially available and procedures for their production are readily available in the scientific literature and require little specialized expertise outside of a basic knowledge of microbiology. Comparatively, some processes required for production of chemical agents are more complex and may require special knowledge and equipment. Furthermore, production of chemical agents requires the procurement of some specialized and controlled precursor chemicals, which are not readily available (8). Because the production of biological agents does not require large amounts of chemicals or equipment, facilities used for production on a terrorist scale may be relatively easy to hide.
Although the production of biological agents appears relatively simple compared with that of chemical agents (Table 2), some obstacles exist. First only a small amount of pure starter culture is required, however, it may be difficult to acquire. Until recently, many infectious agents were accessible through commercially available culture collections and were fairly easy to obtain. Cases such as that of Larry Wayne Harris, who was arrested after obtaining cultures of Yersinia pestis through mail order in May 1995 and again in February 1998 after obtaining a B. anthracis strain have prompted tighter governmental regulation of those organisms that could be used as biological warfare agents (Table 3). Additionally, working with biological and toxin agents does pose a significant health risk to the operator if agents are not handled properly. Production of highly infectious or toxic biological agents will probably require some sort of personal protection or containment to be handled safely (8).
Another major difference between biological and chemical weapons use is the timescale in which an attack may be detected. Generally, chemical agents produce symptoms of exposure in less than a minute to a few hours. These agents may have an acrid smell or taste, produce a colored smoke, or a burning sensation on the skin, lungs and mucous membranes (8). These factors combined will most probably lead to a relatively quick determination that a toxic chemical was involved. This was illustrated during the March 1995 Sarin gas attack on the Tokyo subway system by the Aum Shinrikyo cult, which killed 12 and injured almost 3,800. Authorities were able to assess within a short time that a chemical attack had occurred and were raiding Aum Shinrikyo facilities within 48 hours (7); however, this would have not been the case if this attack had been performed covertly with anthrax or plague.
The onset of symptoms from exposure to biological agents may vary from less than minutes to a few hours for toxin agents, to a range of a few days to weeks for infectious agents. Furthermore, for infectious biological organisms, and most biological toxins, the agent cloud is odorless, colorless, and produces no immediate sensation upon contact with the skin, lungs, or mucous membranes. These factors increase the chances that a biological agent may be covertly employed in a terrorist scenario with little or no warning until symptoms appear.
Biological agents used in a terrorist scenario may beendemic or exotic to a particularenvironment. A biological attack that utilizes a common or indigenous organism may be difficult to attribute to a terrorist attack because of the commonality of the organism, which was used. This was the case in a September 1984 outbreak of salmonellosis caused by a strain of Salmonella typhimurium in the community of Dalles, Oregon, which affected 751 people. Followers of the religious commune Bhagwan Shree Rajneesh, evaluated the use of S. typhimurium as an incapacitating biological agent in an attempt to influence a community vote affecting the construction of their new international headquarters. At least ten restaurants were affected in two phases spanning a total period of approximately four weeks (12). Although the S. typhimurium infections comprised the largest outbreak of food-borne disease reported to the Centers for Disease Control (CDC) in 1984, it took over a year after the outbreak had occurred to acquire sufficient evidence to attribute the unusual outbreak to the Rajneesh commune. Because salmonellosis is a common food-borne pathogen, the intentional nature of the outbreak in Dalles went initially unrecognized. An extensive epidemiological investigation was required to rule out the hypothesis that the outbreak occurred from '' other factors'' (12).
A biological attack that utilizes an exotic or nonendemic organism may be easier to identify as unusual once identified, however, a different set of problems exist regarding diagnosis. The initial symptoms of infection are similar for many pathogens, both lethal and nonlethal. Fever, chills, headache, fatigue, persistent cough, nausea, and vomiting comprise many of the initial symptoms of exposure to a biological agent by inhalation or ingestion. These symptoms are also prevalent in common, non-life- threatening illnesses such as respiratory infection, common cold, or influenza. Because they are similar to those of common illnesses, initial symptoms of exposure to a biological agent may not be properly diagnosed until symptoms appear that would discern from a common illness. The delay in proper diagnosis also causes delays in treatment and prophylaxis that may mean the difference between patient-survival and death. This is illustrated clearly when looking at the symptomology of inhalational anthrax exposure. Initial symptoms of anthrax exposure include fever, malaise, fatigue, cough, and mild chest discomfort. These symptoms are followed by respiratory distress and other severe symptoms. Shock and eventual death usually occur within 24 to 36 hours after onset of these severe symptoms and treatment at that point is largely ineffectual (6).
All of the factors that describe the nature of a biological terrorist event indicate that the emergency response may not be immediate, unlike the Aum Shinrikyo Sarin attack on the Tokyo subway. Because of the delayed onset of discerning characteristics of a biological attack, the first responders will probably not be hazardous materials teams, fire departments and police, but instead will be health care professionals working in emergency rooms, health clinics, and doctors offices. In the event of a biological attack, pressure will be placed on these individuals to have the ability to recognize a biological attack by symptomology and frequency of cases (13). Pressure will also be placed on the clinical laboratories to maintain the equipment, assays, and expertise to detect and characterize exotic or uncommon infectious agents rapidly and decisively. Moreover, disease surveillance and communication systems are required to quickly collate and analyze epidemiological data to recognize an outbreak of disease that may be attributable to a biological attack (13).
There are hundreds of biological organisms and toxins that can be used in a terrorist scenario to cause incapacitating or lethal disease, or produce toxic effects. The following comprises some of those that are most commonly considered biological warfare agents.
Anthrax ( B. anthracis). Bacillus anthracis, the causative agent of anthrax is a gram-positive, spore-forming, rod-shaped, bacterium that is found primarily in herbivores. Cattle, sheep, goats, and horses are common domestic animal hosts. The disease may be contracted by humans from eating infected and improperly cooked meat, introduced through cuts or abrasions in the skin, or possibly by flies. Inhalational anthrax may be contracted by handling contaminated animal materials such as blood, flesh, hides, and bones (9,10). Anthrax was employed by both the United States and Russia as a biological warfare agent (5,10). Iraq has also admitted to performing research on weaponized anthrax before the Gulf War (9). B. anthracis, in its spore form is extremely resistant to environmental stresses. The sporulated form can survive for years in water and soil, and is also resistant to heat and ultraviolet light. This allows it to maintain viability during long-range travel through the air (9,14). Although the infectious inhaled dose for B. anthracis is higher than that of other biological agents (Table 1), its durability makes it desirable as a biological agent. The incubation period for anthrax varies from one to six days depending on the inhaled dose, and human-to-human transmission is rare. Initial symptoms include fever, malaise, fatigue, cough, and mild chest discomfort followed by severe respiratory distress, shock, and death (10). An effective FDA licensed vaccine does exist and inhalational anthrax is treatable with antibiotics. However, once the onset of severe symptoms has occurred, treatment is largely ineffective (9). In humans, the mortality rate of untreated cutaneous anthrax ranges up to 25%; in inhalational and intestinal cases, the mortality rate in untreated patients is virtually 100% (10).
Brucellosis ( Brucella spp.). There are four organisms in the genus Brucella that are pathogenic to man. Although closely related, these bacterial organisms primarily infect different animal hosts (9). Brucella melitenis infects goats, B. suis infects swine, B. abortus infects cattle and B. canis infects dogs. The severity of human disease from these organisms also varies with B. melitensis being the most severe followed by B. suis, B. abortus, andB. canis. Organisms of the Brucella species are small, slow-growing, gram-negative coccobacilli that are susceptible to heat and most disinfectants, but may survive for several weeks in dust, soil, or water. Most human infections are caused by contact or ingestion of contaminated raw meat or dairy products, and person-to-person transmission is rare (9,10).The United States weaponized B. suis in the 1950s but stopped offensive work on this organism a decade later (9).
Although Brucella species are non-spore-forming and may be considered relatively fragile, these organisms are extremely infectious by the aerosol route. It is estimated that as few as 10 to 100 inhaled bacteria are sufficient to cause infection in humans. The incubation period is highly variable ranging from 5 to 60 days and the symptoms are nonspecific. Symptoms include irregular fever, chills, headache, sweating, depression, and mental health changes (10). Respiratory symptoms may also occur in about 20% of those infected (9). The mortality rate for untreated brucellosis in humans is approximately 5%, and it is primarily considered a disabling or incapacitating type of disease (10).
Cholera ( V. cholerae). Vibrio cholerae is a waterborne pathogen affecting multiple animal species. Cholera is usually contracted through ingestion of contaminated water and is endemic to many third world countries where poor sanitation and overcrowding are common. A recent and extremely large cholera outbreak in Peru produced over 250,000 symptomatic cases in Peru alone and spread to surrounding countries as well (9). V. cholerae affects multiple animal species including humans but is not readily transmitted from host to host. V. cholerae is easily killed by desiccation, steam and boiling, and is not viable in pure water. However, the organism may survive up to 24 hours in sewage and as long as six weeks in water containing organic, matter including sewage (10,14). Vibrio cholerae was reportedly considered by some countries for use as a biological warfare agent, however, because the amount of agent required to produce mass casualties is high, the organism is not considered to be effective. The use of V. cholerae on a small scale may still be effective in producing casualties in a terrorist scenario. V. cholerae is a short, motile, gram-negative, non-spore-forming rod. Two serotypes, O1 and O139, have been associated with disease in humans (10). The incubation period ranges from four hours to five days depending on the amount ingested and the ratio of symptomatic to asymptomatic cases is approximately 1 : 400. Symptoms include vomiting, headache, and intestinal cramping followed by severe and painless diarrhea that may produce fluid losses of 5 to 10 liters per day. Death may occur from severe dehydration, decreased amount of blood in the body, and shock. The mortality rates in humans for untreated cholera may be as high as 50%. Treatment includes continuous administration of fluids and electrolytes, as well as antibiotics. A licensed vaccine is available, but only provides 50% protection for as long as six months (10).
Glanders ( Burkholderia mallei). Burkholderia mallei, the causative agent of glanders, is a gram-negative rod, which produces disease primarily in horses, mules, and donkeys. Human cases of glanders historically have been associated with veterinariansas well as horse and donkey caretakers. Although reports of human infection are rare, laboratory cultures of B. mallei have shown to be extremely infectious via the aerosol route. Because of the lack of a vaccine and effective therapy to treat the infection, B. mallei can be considered a potential biological agent (10). B. mallei was reportedly used during World War I to infect large numbers of horses and mules supporting allied operations in Russia. The Japanese also used B. mallei on horses, civilians, and prisoners of war during World War II. The United States and Russia also reportedly considered B. mallei as a biological warfare agent during the World War II era (2,10).
Glanders may occur in four forms in humans; an acute localized form, a septicemic and rapidly fatal form, an acute pulmonary form, and a chronic form. No form of glanders is readily transmissible from person to person. Aerosol infection may produce any of these four forms of glanders, or a combination of several. Incubation periods range from 10 to 14 days after exposure. Symptoms from inhalational exposure to B. mallei include fever, rigors, sweats, myalgia, headache, chest pain, swelling in the lymph nodes, and pustular eruptions. The mortality rate for septicemic infection is almost 100% if untreated. Recovery may occur for the chronic form, although this form may also turn septicemic (10).
Plague ( Y. pestis). Yersinia pestis, the causative agent of plague is a nonmotile, gram-negative, non-spore-forming rod, which exists naturally as a zoonotic disease of rodents (rates, mice, and ground squirrels). Human plague is most commonly caused by bites from fleas, which live on infected rodents. Transmission to human by fleas produces the common bubonic form of the disease. Naturally occurring inhalational plague in humans is extremely rare. Although both the United States and Russia considered Y. pestis as a biological agent, only Russia chose to weaponize it. The Japanese Unit 731 reportedly inflicted heavy casualties by releasing plague-infected fleas of China during World War II (2,9). Y. pestis may remain viable in water and some moist environments for several weeks, and may survive for months to years at near freezing temperatures, but is susceptible to heat and ultraviolet light. Although Y. pestis is a relatively fragile organism, its low infectious dose and ability to spread from person to person make it a desirable biological agent capable of causing massive casualties if released in the aerosol form. The incubation for the pneumonic or inhalational form of plague in humans is two to three days. Symptoms include high fever, cough, chills, headache, and bronchial hemorrhaging, which progresses rapidly causing death by respiratory failure and circulatory collapse. The incubation time for the bubonic form of plague is approximately 2 to 10 days. Symptoms include fatigue, high fever, and tenderness in the lymph nodes, liver, and spleen (9,10). The bubonic form may also produce skin lesions and pustules containing virulent plague bacteria, and may spread spontaneously to the blood stream, the central nervous system, lungs, and other organs. Although a licensed vaccine is available, it is not effective against exposure to plague through the aerosol route. The mortality rate for untreated pneumonic and bubonic forms of plague are 100 and 50%, respectively (10).
Tularemia ( F. tularensis). Francisella tularensis, the causative agent of tularemia is a small, gram-negative, non-spore-forming cocco-bacillus. The disease is primarily zoonotic, and human cases are usually caused by contact with tissue or fluids from infected animals, or from the bites of infected insects. Human cases caused by inhalation or ingestion of F. tularensis are less common (9,10). Exposure by aerosol route, typical of a biological attack, would produce a pneumonic tularemia (10). The United States weaponized F. tularensis during its biological warfare program during the 1950s and other countries are suspected of its use as well. F. tularensis is easily killed by heat and disinfectants, but may remain viable for weeks in water, soil, carcasses and hides, and for months in freezing temperatures (10). As few as 10 to 50 organisms are sufficient to produce disease in man, which makes F. tularensis a desirable biological warfare agent. The incubation period for tularemia is 2 to 10 days depending on the dose. Characteristics of pneumonic tularemia include fever, headache, fatigue, weight loss, and pneumonia with nonproductive cough. The nonspecific symptoms of the pneumonic form of tularemia make it difficult to diagnose initially. Tularemia is treatable with antibiotics and an investigative live vaccine is available. The mortality rate for untreated pneumonic tularemia is approximately 35%. (9,10).
Smallpox (variola major and minor). Variola virus, the causative agent of smallpox occurs in at least two strains; variola major and minor. The last reported case of smallpox occurred in Somalia in 1977. In 1980, the World Health Organization (WHO) declared that smallpox has been eradicated from the planet (9,10). No animal reservoir for smallpox is known to exist, although monkeys are susceptible to infection (9). Although only two laboratories in the world (The Centers for Disease Control in Atlanta, Georgia and The Vector State Research Center of Virology and Biotechnology in the Novisibirsk region of Russia) are WHO-approved repositories for the variola virus, concerns still exist that the virus may be used as a biological weapon. The aerosol infectivity, stability, high mortality rate, contagiousness, and lack of vaccinated population would make the variola virus a desirable biological agent in a terrorist scenario (9). Russia reportedly weaponized and stockpiled smallpox as part of its biological arsenal (5). The average incubation period for smallpox is approximately twelve days. Initial symptoms from aerosol exposure include malaise, fever, rigors, vomiting, headache, and backache. Fifteen percent of patients also develop delirium (9,10). Approximately two to three days after initial symptoms appear, eruptions in the mucous membranes appear with a rash about the face, hands, and forearms. Lesions or pox, formed in the mucous membranes produce infectious secretions during the first few days of illness and are the primary means of transmission from person to person (9). The rash then spreads to the lower extremities, and finally to the trunk, producing lesions that progress to pustules. From 8 to 14 days after onset of initial symptoms, pustules progress to form scabs that may contain live variola virus. Currently, there is no effective treatment for smallpox virus. Although a live vaccine does exist, vaccinations for the general population were stopped in the early to mid-1970s leaving a large portion of the U. S. population susceptible (10). Furthermore, the smallpox vaccine, a live Vaccinia virus strain, may complicate vaccination because of its negative effects on immunocompromised patients (9). The mortality rate for smallpox in vaccinated and unvaccinated personnel is 3 and 30% respectively (10).
Venezuelan Equine Encephalitis Virus (VEE). Venezuelan Equine Encephalitis virus is an arthropod-borne alpha-virus that is endemic to many areas in North and South America. Of the eight distinct viruses in the VEE complex that have been associated with human disease, the two most significant are variants A/ B and C of the 1 subtype (10). Natural infections are caused by mosquito bites. and can also cause severe disease in horses, mules, burros, and donkeys. These animals serve as the host to VEE and are responsible for transmission of mosquito-borne infections. VEE was weaponized by the United States during its biological warfare program during the 1950s, and other countries may have also considered VEE as a biological agent (9,10). Besides being transmitted by mosquitoes, VEE is also highly infectious by aerosol, surviving best at low temperatures and relative humidity, but is easily killed by heat and disinfectants (10,14). The incubation time for VEE ranges from two to six days. Symptoms include malaise, spiking fever, rigors, headache, and light sensitivity. These symptoms may be followed by nausea, vomiting, cough, sore throat, and diarrhea. These symptoms may persist for 24 to 72 hours and full health is usually regained in one to two weeks. Four percent of children and few adults develop neurological complications because of infection. An investigational vaccine exists for VEE, and antiviral treatments have proven effective in postexposure treatment in animals, but clinical data do not exist to assess its efficacy on humans (10). The mortality rate for VEE is less than 1%, but is higher in the very young and very old (10). VEE is considered an incapacitating agent because of its low mortality rate.
Viral Hemorrhagic Fevers (Ebola and Marburg Viruses). Although the viral hemorrhagic fevers are caused by a number of virus families, Ebola and Marburg that are part of the Filovirus familyare twoofthe mostdangerous and have been considered for use as biological warfare agents in the past (5,9). The first cases of Ebola virus were recognized in Sudan and Zaire in 1976. These two outbreaks produced mortality rates of 53% and 92%, respectively (9). Subsequent outbreaks have occurred in Sudan in 1979 and in Zaire in 1995, which have produced a large number of casualties. In 1989, a strain of Ebola determined to be nonpathogenic to humans was found in a monkey quarantine facility in Reston, Virginia. Marburg was first recognized in 1967 in Germany where it produced 31 cases and 9 deaths. Human infection from these RNA viruses seems to be associated with contact with monkeys; however, the reservoir for these viruses in nature is not known. Human-to-human transmission of these viruses is not fully understood, but they definitely spread from direct contact with infected bodily fluids and organs (10). Russia reportedly performed extensive research and development on the production and weaponization of Ebola and Marburg (5). The high mortality rate, low infective dose, and lack of effective treatment would make these agents desirable for use as a biological warfare agent. The incubation times for viral hemorrhagic fevers may range from 4 to 21 days (10). Symptoms include fever, muscular pain, headache, vomiting, and diarrhea. Viral hemorrhagic fevers produce vascular damage, and changes in the permeability of the vascular system. Full blown viral hemorrhagic fever evolves into shock and hemorrhaging from the mucous membranes, and may be accompanied by neurological or pulmonary difficulties, or hemorrhaging on the skin (9,10). The mortality rate for Ebola may range between as high as 50 and 90%, depending on the strain. No vaccine or effective treatment is available for the Ebola and Marburg viruses, however, recent research is ongoing to develop a DNA vaccine for the Ebola using genes coding for virus proteins (9).
Botulism ( C. botulinum toxin). Clostridium botulinum toxin, the causative agent of botulism is comprised of seven related neurotoxins, A through G, which are produced from the anaerobic, gram-positive, spore-forming bacillus C. botulinum. The most common form of botulism in humans is caused by ingestion of contaminated foods and canned goods. However, the symptoms caused by food-borne exposure to C. botulinum toxin are very similar to those produced by aerosol exposure. C. botulinum toxin in extremely small amounts also has medicinal uses in treating muscle spasms and wrinkles. C. botulinum toxin has been researched by numerous countries for use as a biological weapon. Iraq admitted to The United Nations that it had performed research on and weaponized at least 100 munitions with C. botulinum toxin before the Persian Gulf War (9,10). The time from inhalation of botulinum toxin to onset of symptoms ranges from 24 to 36 hours to several days depending on the inhaled dose. Symptoms include bulbar palsies, blurred vision, and sensitivity to light. This is followed by skeletal muscle paralysis, which descends down the body as it progresses. Death is usually caused by respiratory failure caused by paralysis of respiratory muscles. With proper respiratory assistance, mortality ratesdue to exposure toC. botulinum may be less than 5% (9). The time taken from onset of symptoms to respiratory failure may be as little as 24 hours in food-borne botulism (9,10). An investigational vaccine is available for C. botulinum toxin types A through E, and has been shown to be effective in preventing botulism and in the treatment of botulinum exposure. Botulinum toxins are among the most toxic substances known (Table 1), and are 100,000 times more toxic than sarin gas, a well-known chemical warfare agent (10). Although it is not an infectious organism, the high toxicity and availability of C. botulinum would make it an effective agent in a bioterrorist attack.
Staphylococcus aureus enterotoxin B( SEB). Staphylococcus aureus is a gram-positive cocci that produces a number of exotoxins including enterotoxin B. Exotoxins comprise those toxins that are released outside of the cell. The term enterotoxin indicates that the primary effects of the toxin occur in the intestines (9,10). SEB intoxication is caused by ingestion of improperly handled foods, and is extremely common, however, inhalation of SEB produces a distinctly different set of symptoms (10). Although SEB exposure through ingestion or inhalation does not normally produce death, 80% of those exposed may be incapacitated for 1 to 2 weeks (9,10). Symptoms may occur from 3 to 12 hours after inhalation. These symptoms include sudden onset of fever, headache, chills, muscular pain, and a nonproductive cough. Severe cases may also experience shortness of breath and chest pain. Inadvertent ingestion of the toxin may also produce nausea, vomiting, and diarrhea. Symptoms from SEB inhalational exposure are similar to those for common respiratory pathogens, which may complicate the diagnosis. Although several SEB vaccines are under development, no human vaccine is available, and treatment is supportive in nature, designed to alleviate the symptoms (10).
Ricin Toxin ( R. communis). Ricin toxin is produced by the R. communis or castor plant, which is grown worldwide for the production of castor oil that is extracted from the castor bean. The waste product from castor oil production may contain as much as 5% ricin toxin by weight. The toxin is fairly persistent in the environment and is extremely toxic when inhaled, ingested, or injected (10). A few countries are suspected of performing research on ricin to be used as a biological weapon. Ricin injected from a specially designed umbrella gun was allegedly used to assassinate the Bulgarian exile Georgi Markov in London in 1978 (5,10). Because of its large availability and relative ease of production, ricin toxin could be used in a terrorist attack. Onset of symptoms may occur within 18 to 24 hours after exposure. Symptoms from inhalation of ricin toxin vary depending on the dose inhaled, but may include fever, chest tightness, cough, shortness of breath, nausea, and joint pain. Although data on human exposure to lethal doses of ricin are not available, animal models indicate that destruction of cells in the respiratory system may be sufficient to cause death if sufficient toxin is inhaled. Ricin toxin may cause severe gastrointestinal symptoms, followed by vascular collapse, and death when ingested, and circulatory and multiple organ failure when injected (10).
No human vaccine is available for Ricin exposure, and treatment is given to attempt to alleviate the symptoms (10).
Yellow Rain (trichoethecene mycotoxins). The trichoethecene of T-2 mycotoxins are low molecular weight compounds produced by several types of filamentous fungi including Fusarium, Myrotecium, Trichoderma, and Stachybotrys. Mycotoxins may produce casualties when inhaled, ingested, or from contact with the skin, making them unique in that they are one of the only dermally active biological agents. Controversial reporting indicates that mycotoxins may have been used in biological attacks in Laos, Kampuchea, and Afghanistan during the 1970s and the early 1980s, producing an estimated 8, 300 deaths resulting from exposure (10). The term '' yellow rain'' is derived from the characteristic yellow cloud that is created from aerosolization of the toxin in the liquid form. These toxins are resistant to inactivation by ultraviolet light, and are only destroyed by heat when exposed to temperatures of 1,500 ° F for 30 minutes. Because of their stability in the environment and toxicity, the T-2 mycotoxins would be an effective biological agent for use in a terrorist scenario. The onset of symptoms may begin minutes after exposure and include burning skin pain, redness, and blistering. In lethal cases, blackening and sloughing of the skin occurs. Nasal contact from inhalation of T-2 mycotoxins produces pain, itching, sneezing, and nasal discharge. Lung exposure produces symptoms of shortness of breath, wheezing, and coughing, and ingestion produces symptoms of anorexia, nausea, vomiting, and bloody diarrhea. Because of the similarity in symptomology, exposure to T-2 mycotoxins may be misdiagnosed as a chemical weapon attack from an agent such as mustard gas. No vaccine, antidote, or therapy is available for exposure to mycotoxin and treatment is designed to alleviate the symptoms (10).
As previously indicated, biological agents can be employed in a terrorist scenario using several different methods. These methods vary in levels of difficulty and effectiveness, but dispersion through aerosolization proves to be the most useful.
Waterborne and Food-borne Application
History has shown that contamination of a water source can be an effective dispersion aerosol attack, contamination of a water source may provide a centralized means to reach a population and cause disease when ingested. Many bacterial agents have potential for use as a waterborne threat because of their stability in an aquatic environment. For instance, B. anthracis spores have been shown to survive for up to two years in pond water (14). Vibrio cholera, one of the most noted aquatic pathogens can survive for as long as six weeks in aquatic environment containing organic matter, and F. tularensis, primarily an epizootic disease of animals can survive for months in water or mud and may even multiply during that period (14). The viral diseases that are considered potential biological warfare agents, except the enteric viruses and possibly smallpox, have virtually no utility as waterborne threats (14). Toxin agents are fairly stable in aquatic environments, and given sufficient quantities, may be useful as potential waterborne threats. Although numerous biological agents may be suitable for waterborne contamination in a terrorist scenario, advances in water purification technology have significantly decreased the threat. Early use of biological agents to contaminate water sources proved effective primarily because of the absence of effective water treatment systems. A well-designed and well-operated water treatment system can be expected to remove significant amounts of bacteria and toxins from the water supply. Furthermore, disinfection of potable water using chemical additives such as chlorine decreases the threat of waterborne contamination (14). It should be noted that gaps do exist in the evaluation of the susceptibility of potable water supplies to biological attack, however, the dose of any biological warfare agent required to cause adverse affects is directly related to the proximity of the contamination to the consumer and the size of the body of water to be contaminated. Contamination of large bodies of water such as reservoirs would be impractical because of the immense magnitude of the agent required to produce disease (14). An effective biological attack through contamination of water sources would be most effective on small localized areas.
Similar to a waterborne attack, biological agents may also be applied to foodsources to producehuman disease. Contamination of food with the intent of infecting the consumer is a kind of terrorist scenario that has proved effective in the past. Advancements in food safety standards and packaging of food products will increase the chance that these attacks will be insignificant because of the need to place the agent in close proximity to the consumer, as was done in the Dalles Oregon incident. Intentional contamination of feed supplies to infect livestock and poultry may have serious economic consequences (15).
Vectors facilitate the transmission of disease from one species to another and apply mainly to zoonotic or epizoonotic diseases. Examples of natural vectors include deer flies and fleas with F. tularensis and Y. pestis, respectively. The use of plague-infected fleas by the Japanese illustrates the usefulness of vector-borne biological attacks (2). Although not attributed to biological terrorism, the August 1999 outbreak of West Nile virus in New York and its spread to points south in 2000 is a modern-day example of the affects of a vector-borne outbreak on a large population. West Nile virus taxonomically belongs to the Japanese encephalitis subgroup and is readily transmitted by mosquitoes, through which it can infect a wide variety of vertebrates including humans (16,17). During the period of August 23 (when the first case of West Nile Virus was identified), to September 28, 1999, there were 17 confirmed human cases, 20 probable cases, and 4 deaths in New York City and the surrounding counties of Westchester and Nassau (17). Although the incidence of infection is insignificant compared with the millions of people living in the affected areas, the outbreak sparked widespread fear in the population and necessitated extensive aerial and ground application of mosquito adulticides and larvacides. Other control measures that were instituted included the distribution of 300,000 cans of mosquito repellent, and 750,000 public health leaflets with personal protection information. Local radio and TV networks, and newspapers were also used to distribute information (17). The New York City West Nile virus telephone hotline, set up on September 3, 1999 to address public inquires regarding the outbreak and pesticide applications, received more than 130,000 calls in a 25- day period (17). The West Nile virus outbreak may be considered an indicator of the public response that could be expected from a mild biological attack on a large population.
Airborne infection has long been known to be a major factor in the spread of disease. The utility of aerosol spread of disease was readily illustrated in the investigation of respiratory disease experienced in recruit barracks at armed services training centers during World War II. This investigation showed that increasing the space between bunks substantially decreased the incidence of disease because the infectious aerosol particles had a further distance to travel to infect the adjacent individual (18). Dissemination of biological agents via the aerosol route is the most effective means of dispersion in a biological attack. Dispersion of biological agents through aerosol dissemination has the potential to affect the largest area compared with waterborne, food-borne, or vector-borne dispersion methods. Biological agents that are disseminated as bioaerosols using a spray or explosive device in a terrorist scenario have the capability to travel long distances through the air covering large areas indiscriminately. For example, the hypothetical human health impact of 50 kg of anthrax sprayed by an aircraft along a 2 km-line upwind of a population of 500,000 would result in 95,000 dead, 125,000 incapacitated, and have a downwind travel distance of more than 20 km (15). Similar tests performed by the United States off the coast of San Francisco during the 1950s using B. globigii, an anthrax simulant, also illustrated the large area coverage potential for aerosol dissemination of biological organisms (1,19). Because of the nonspecific nature of an aerosol release of biological agent, the effects may be more widespread than other dispersion mechanisms. For example, an outdoor aerosol attack targeting a human population with anthrax may also kill livestock, contaminate food supplies, or cause vector-borne transmission to occur, as well as cause contamination inside buildings and homes because of transport of contaminated air. Additionally, biological attacks that occur indoors may also produce a large number of casualties because of modern-day heating ventilation and air conditioning (HVAC) systems that recirculate indoor air, requiring a smaller amount of '' clean'' makeup air from the outdoors (19). Decontamination of such a large area is also problematic, especially in the case of environmentally persistent spore-forming bacteria such as B. anthracis. For example, anthrax spores exploded on Gruinard Island from allied biological warfare testing during World War II, survived for at least 40 years in the soil before the area was decontaminated (4).
Some of the environmental factors that govern the effectiveness of an outdoor aerosol dissemination are wind patterns, turbulence, atmospheric conditions, temperature, and humidity (20). Another factor includes the efficiency of the dissemination device, which determines the size and amount of the particle disseminated. The dissemination device also produces shear forces during dispersion, which may damage the organisms to the point of nonviability. Other factors that affect the viability of the organism are ultraviolet radiation, atmospheric oxygen, and environmental pollutants such as ozone and other synthetic chemicals (21). The size of the particle disseminated is also an important factor as it controls the ability of the biological agent to travel downwind. For example, the sedimentation velocity for a 5-µ m particleis 0. 75 cm/ s compared with 7.28 cm/ s for a 50-µ m particle (22). The increase in particle size leads to a decrease in the ability of a particle to remain airborne for an extended period, thus reducing its coverage area.
Particle size also plays a substantial role in infectivity. Small size particles (1 to 10 µ m), if inhaled can penetrate into the distal bronchioles of the lung and alveoli to cause infection (9). Studies performed in the late 1950s using B. anthracis spores showed that the concentration of spores in the 12 micrometer particle size range required to infect 50% of exposed animals was 17-fold greater than those spores in the 5-µ m size range. This relationship of particle size to infectivity is a consequence of the shape and structure of the upper and lower respiratory system (19). Larger particles are impacted onto the walls of the upper respiratory tract and are removed with the help of ciliated membranes and mucosal secretions in the lining of the nasal-pharyngeal region. Smaller particles evade the natural defenses of the respiratory system and deposit in the terminal alveoli of the lung where the infection occurs (8,19)
AGROTERRORISM; THE BIOLOGICAL THREAT TO PLANTS AND ANIMALS
Although one usually thinks of the threat to humans when considering a bioterrorist scenario, a vulnerable target remains in the plant and animal industry. The United States, like many developed nations is vitally dependent on its cash crops, livestock, and poultry to sustain its quality of life and provide economic stability. The utility of a biological attack on plants and animals was realized during the early 1900s and continued through the Cold War (2). Although the initial purpose of these weapons was to render crops or animals unfit for consumption, the terrorist threat is also motivated by economic factors (23). An outbreak of disease in livestock or cash crops not only renders it unfit for use but also has the added implication of industry restrictions on international trade and disruption of internal distribution caused by eradication efforts (23). Procedures for disease eradication in plants and animals may be severe. For example, an outbreak of avian influenza in Eastern Pennsylvania in 1984 almost eliminated the poultry population. Although 40 to 60% of these animals would have survived the epidemic, containment procedures mandated that they be destroyed. Examples of antiplant and animal agents include: rice blight, corn blight, wheat stem rust, tobacco mosaic virus, foot and mouth disease of cattle, rinderpest or cattle plague, and Newcastle disease of poultry (24). Unlike most human biological warfare agents, many plant and animal pathogens are contagious and may be spread from host to host (15). The spread of a contagious disease among livestock may be amplified by large-scale, high-density husbandry methods, transportation practices, and centralized feed supply systems. Furthermore, many of the agents pathogenic to livestock have been eradicated from the United States, and vaccinations are not required, leaving the animal population increasingly susceptible to infection (15). Plant and animal pathogens may be dispersed in the same ways as those utilized for an attack on a human population. Although not attributed to a terrorist attack, the recent foot and mouth disease outbreak Great Britain illustrates the devastating nature of a widespread agricultural epidemic.
With regard to a bioterrorist scenario, environmental sampling may serve numerous purposes similar to those in an epidemiological, environmental, or public health investigation; its primary function is to identify the disease-causing biological agent. Sampling may be performed in response to a perceived attack, or in response to an unusual outbreak of disease. Sampling may be used to determine the source of exposure, determine the area of coverage, or to render an area free of contaminants, or determine if remediation is required. Types of sampling may include air, water, soil, or surface swipes. Methods of analysis may include live cultures, polymerase chain reaction (PCR), or immunoassays and vary depending on the organism being sought after, the sampling method, and the circumstances surrounding the event. Environmental sampling of air and water, for example, may also be used for continuous monitoring of the environment to serve as an alarm system for immediate notification that a biological attack has occurred. Detailed information on sampling methods and techniques used in environmental monitoring and detection directly applicable to the topic of bioterrorism, and are covered in other entries in this encyclopedia.
The threat of domestic bioterrorism has captured the concern and attention of the American public and government officials alike. Concern for this issue is further amplified by the widespread belief that at the current time, the United States is not well prepared to respond to a biological attack on its own soil. Without considering the likelihood that an attack will occur, the social, economic, and public health consequences of a biological attack are severe enough to warrant a comprehensive plan to respond to a bioterrorist event. As the national center for disease control and prevention, the Centers for Disease Control (CDC) has been given the responsibility by the U. S. Department of Health and Human services to coordinate and lead efforts to upgrade national public health capabilities at the local, state, and national levels to effectively respond to a biological attack (25). The CDC has outlined five major areas that make up a comprehensive bioterrorism response plan.
1. '' Detection (Surveillance) ''. An essential part of the response plan is recognition of unusual and unexplained illnesses. If an attack can be detected early, those exposed may receive prophylaxis, vaccination, or other medical treatment to minimize loss of human life (25).
2. '' Rapid Laboratory Detection''. Rapid diagnosis of unexplained and unusual outbreaks is dependent on the ability of diagnostic clinical laboratories to detect and characterize pathogenic agents that are likely to be used in a biological attack. The CDC is working with metropolitan health departments to enhance their capability to identify biological threats, as well as creating a '' rapid response and advanced technology laboratory'' to provide local and state health departments and bioterrorism response team analytical support 24 hours a day (25).
3. '' Epidemiological investigation and implementation of control measures''. Epidemiologists at the local and state levels will have the responsibility for investigating unusual disease occurrences to identify sources of exposure and route of transmission. The CDC is providing training at the state and local level to ensure that biological threat agents are considered when investigating an unusual outbreak (11).
4. '' Communication''. As in any large-scale domestic emergency, rapid and secure communications are critical in achieving a prompt and organized response as well as providing emergency-related guidance to the public through the media. The CDC is working to develop a national health alert network linking local health departments to each other, the CDC, other federal agencies, and local health care providers to ensure the efficient transmission of crucial information regarding a bioterrorist incident. (25).
5. '' Preparedness Planning and Readiness Assessment''. The CDC has enhanced its capabilities including new hires, pertinent training, and enhanced interagency collaborations to ensure that i t is prepared to respond to a bioterrorist incident. The CDC is also providing support to state and local governments to develop similar public health response plans (25).
Other initiatives involved in developing a response to a biological attack include the creation of a national pharmaceutical stockpile for use in response to mass casualties from a bioterrorist incidents that overwhelm the local health systems. This program would provide the area affected with rapid access to vaccines, antitoxins, and therapeutic drugs used to treat a large number of biological casualties (25).
Biological warfare has shown its utility in causing disease, hysteria, and death, and is not limited to military applications or targeting only humans. The multitude of agents available for use and the variety of dispersion mechanisms that can be utilized increase the complexity in identifying and treating the intentional use of biological agents as weapons of mass destruction. Furthermore, the relative ease of obtaining and producing biological agents increases the chances that they will be used as a terrorist weapon targeting humans, plants, or animals.BIBLIOGRAPHY
1. T. O'Toole, Emerg. Infect. Dis. 5, 540-546 (1999).
2. G. W. Christopher, T. J. Cieslak, J. A. Plavin, and E. M. Eitzen, JAMA 278, 412-417 (1997).
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8. U. S. Congress, Office of Technology Assessment, Technologies Underlying Weapons of mass Destruction, Government Printing Office, 1993.
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10. E. Eitzen et al., Medical Management of Biological Casualties, 3rd ed., United States Army Medical Research Institute of Infectious Diseases, 1998.
11. Centers for Disease Control, Preventing Emerging Infectious Diseases: A strategy for the 21st Century, United States Department of Health and Human Services, 1998.
12. T. J. Torok et al., JAMA 278, 389-395 (1997).
13. J. A. Plavin, Emerg. Infect. Dis. 5, 528-530 (1999).
14. W. Dickinson and S. E. Renner, Environ. Health Perspect. 107, 975-984 (1999).
15. D. F. Franz, Ann. N. Y. Acad. Sci. 894, 100-104 (1999).
16. Centers for Disease Control, MMWR 48, 845-849 (1999).
17. Centers for Disease Control, MMWR 49, 640-642 (2000).
18. T. C. Eickhoff, Am. J. Epidem. 144, S39-46 (1996).
19. H. Salem and D. E. Gardner, in B. Lighthart and A. J. Mohr, eds., Atmospheric Microbial Aerosols, Chapman & Hall, New York, 1994, pp. 304-330.
20. J. Kim, in B. Lighthart and A. J. Mohr, eds., Atmospheric Microbial Aerosols, Chapman & Hall, New York, 1994, pp. 28-67.
21. E. Israeli, J. Gitelman, and B. Lighthart, in B. Lighthart and A. J. Mohr, ed., Atmospheric Microbial Aerosols, Chapman& Hall, New York, 1994, pp. 166-191.
22. B. Lighthart, in B. Lighthart and A. J. Mohr, ed., Atmospheric Microbial Aerosols, Chapman & Hall, New York, 1994, pp. 5-27.
23. W. A. Deen, Ann. N. Y. Acad. Sci. 894, 164-167 (1999).
24. S. A. Watson, Ann. N. Y. Acad. Sci. 894, 159-163 (1999)
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Table of ContentsArticle Title.
Activated Sludge - Foaming.
Activated Sludge - G-Bacteria.
Activated Sludge - Microbiology of Nitrogen Removal.
Activated Sludge - Molecular Techniques for Determining Community Composition.
Activated Sludge - Sequencing Batch Reactors.
Activated Sludge - The Floc.
Activated sludge - the process.
Activated Sludge - The Protozoa.
Activated Sludge Models - Microbiological Basis.
Activated Sludge- The Microbial Community.
Adhesion (primary) of Microorganisms onto Surfaces.
Adhesion, immobilization and retention of microorganisms on solid substrata.
Aerobic Respiration, Principles of.
Aerobic Spores: Application in monitoring drinking water treatment.
Aggregates and Consortia, Microbial.
Airborne Toxogenic Molds.
Algal Blooms - Impact on Treatment, Taste and Odor Problems.
Algal Turf Scrubbing: Potential Use For Wastewater Treatment.
Alkaliphiles: Alkaline Enzymes and their Applications.
Anaerobic Granules and Granulation Processes.
Archaea in biotechnology.
Archaea in Marine Environments.
Archaea in soil Habitats.
Archea: Detection Methods.
Assimilable Organic Carbon.
Bacterial Phytostimulators in the Rhizosphere: from Research to Application.
Bacteriophage Detection Methodologies.
Bacteriophage of Enteric Bacteria: Occurrence and Persistence in the Environment.
Bacteriophage: Basic biology.
Bateriophage as indicators.
Bioaerosol Sampling and Analysis.
Bioaerosols in Agricultural Outdoor Settings.
Bioaerosols in Industrial Settings.
Bioaerosols: Transport and Fate.
Biochip-based devices and methods in microbial community ribotyping in environmental microbiology.
BioContaminants in Residential Environments, Bacterial.
Biocontrol, microbial agents in soil.
Biocorrosion: Role of Sulfate Reducing Bacteria.
Biodegradability: Methods for assessing biodegradability under laboratory and field conditions.
Biodegradable Dissolved Organic Carbon in Drinking Water.
Biodeterioration of Mineral Materials.
Biodiversity in soils: Use of Molecular Methods for its Characterization.
Biofilms in natural and drinking water systems.
Biofilms in the Food Industry.
Biofilms: Bacterial-fungal biofilms.
Biofouling in the Marine Environment.
Biofouling Industrial System.
Biofouling: Chemical Control of Biofouling in Water Systems.
Bioleaching of metals.
Biomass: Soil Microbial Biomass.
Biomineralization in Subsurface Environment.
Bioremediation of Soils.
Bioremediation: An Overview of How Microbiological Processes Can be Applied to the cleanup of organic and inorganic environmental pollutants.
Bioremediation: Aquatic Ecosystems.
Biosolids: Anaerobic Digestion of.
Biosurfactants: Types, Screening Methods and Applications.
Biotrickling filters for air pollution control.
Bottled Water, Microbiology of.
Campylobacter jejuni and other Enteric Campylobacter.
Carbon Transformations and Activity in Biofilms.
Caves and Mines: Microbiological Sampling.
Caves and Other Low-Light Environments: Aerophitic Photoautotrophic Microorganisms.
Chemical weapons, biodegradation of.
Coagulation - Pathogens and parasites removal by.
Cold-Adapted Microorganisms: Adaptation Strategies and Biotechnological Potential.
Coliform Bacteria - Control in Drinking Water Distribution Systems.
Coliform Bacteria as Indicators of Water Quality.
Compost: Biodegradation of Toxic Organic Compounds.
Conditioning films in Aquatic Environment.
Cretaceous Shales and Sandstones.
Cryptosporidium: Basic Biology and Epidemiology.
Cyanobacteria - Toxins in drinking water.
Cyanobacteria in aquatic environments (freshwater and marine).
Cyclospora: Basic Biology, occurrence fate and methodologies.
Data Analysis and Modeling.
Denitrification in the Marine Environment.
Desert Environments: Biological Soil Crusts.
DESERT ENVIRONMENTS--SOIL COMMUNITIES IN COLD DESERTS.
Desication by Exposure to Space Vacuum and extremely Dry Desserts: Effects on Microorganisms.
Desulfurization of Fossil Fuels.
Diatoms in biofilms.
Disinfection of protozoa.
Disinfection: Chlorine, monochloramine, chlorine dioxide.
Drinking Water Distribution Systems.
Ecological Significance of Subsurface Microorganisms.
EndolithicMicroorganisms in Arid Regions.
Endosymbiosis in Ecology and Evolution.
Enhanced Detection of Airborne Microorganisms.
Entamoeba Histolytica: Entamoeba Dispar.
Enteroviruses in Water: Concentration and Dectection.
Enteroviruses: Basic Biology and Diseases.
Enteroviruses: Occurrence and Persistence in the Environment.
Enzymes: Biotechnological Applications.
Eutrophication and algae.
Evolution of Matabolic Pathways.
Explosives, biodegradation of.
Extracellular Enzymes in Biofilms.
Extracellular Polymeric Substances (EPS) Structural, Ecological and Technical Aspects.
Extremophiles: Life in Extreme Environments.
Fate and Microbial Degradation of Halogenated Aromatics.
Fate of viruses or protozoan parasites in aquatic sediments?
Fecal Contamination, Sources of.
Fecal Streptococi/Enterococci in Aquatic Environments.
Field release of bacteria.
Filamentous Bacteria in Activated Sludge: Current Taxonomic Status and Ecology.
Filamentous Bulking in Activated Sludge: Control of.
Filtration - Removal of Microbes by.
Fluorescent In-situ rRNA Probes for Microbial Labeling in Environmental Samples.
Free-Living Amebas Present in the Environment can Cause Meningoencephalitis in Humans and Other Animals.
Freeze Drying: Preservation of Microorganisms by Freeze-Drying.
Fungal Allergy and Allergens.
Fungi and Indoor Air.
Fungi in Marine/Estuarine Waters.
Fungi, for Biotechnology.
Gallionella ferruginea: An Iron-Oxidizing and Stalk-Forming Groundwater Bacterium.
Gene exchange in biofilms.
Genetically engineered microorganisms For Biodegradation of Recalcitrant Compounds.
Genetically Modified Microorganisms (GMM) in Soil Environments.
Geological and Geochemical Significance of Subsurface Microorganisms.
Giardia: Basic Biology.
Giardia: Detection and Occurrence of in the Environment.
Green Fluorescent Protein.
Halophiles: Aerobic Halophilic Microorganisms.
Halophiles: Anaerobic Prokaryotes for Hypersaline Environments.
Hepatitis Viruses (HAV-HEV).
High Hydrostatic Pressure: Microbial Inactivation and Food Preservation.
Home Treatment Devices - Microbiology of Point of Use and Point of Entry Devices.
Hot Desert Soil Communities.
Human Caliciviruses: Basic Virology and Epidemiology.
Hydrophobicity of Microorganisms.
Hydrothermal Vents: Biodiversity in Deep-Sea Hydrothermal Vents.
Hydrothermal vents: Prokaryotes in Deep Sea Hydrothermal Vents.
Identification of Airborne Fungi.
Identification of Microbial Isolates.
Igneous Rock Aquifers Microbial Communities.
Image Analysis in Microorganisms.
Infectious Airborne Pathogens.
Influence, activity, and growth of subsurface microfilms in petroleum reservoirs.
Inorganic Nutrient Use by Marine Microorganisms.
Invertebrate and Protozoa (Free Living) in Drinking Water Distribution Systems.
Isospora Basic Biology.
Kinetics (microbial): Theory and Applications.
Kinetics of Microbial Processes and Population Growth in Soil.
Landfilling of Municipal Wastes.
Laser Scanning Microsopy in combination with Flourescence Techniques for Biofilms Study.
Legionella in the Environment: Persistence, Evolution, and Pathogenicity.
Lipid Biomarkers in Environmental Microbiology.
Lithotrophic Microbial Ecosystems in the Subsurface.
Luciferase and Green Flourescent protein as Bioreporters in Microbial Systems.
Marine Biofilms, Ecology of.
Metabolism of Mixtures of Pollutants.
Metal (U,Fe, Mn, Hg) cycling.
Metal Stressed Environments, Bacteria In.
Metals: microbial processes affecting metals.
Methanogenesis in the Marine Environment.
Methanotrophic Bacteria: Use in Bioremediation.
Methods for flow cytometry & Cell Sorting.
Microarrays: Applications in Environmental Microbiology.
Microbial Degradation of Fuel Oxygenates.
Microbial Diversity of Petroleum Reservoirs.
Microbial Flocs suspended biofilms.
Microbial Starvation Survival in Subsurface Environments.
Microbial Water Quality of Rainwater Roof Catchment Systems.
Microbiology of Atlantic Coastal Plain Aquifers and other Unconsolidated subsurface sediments.
Microbiology of Deep High-Temperature Sedimentary Environments.
Microbiology of Granular Activated Carbon.
Microorganisms in Soil: factors influencing activity.
Microsporidia, Occurrence, fate and methodologies.
Microsporidia: Basic biology.
Modeling of biofilms.
Modeling the Transport of Bioaerosols.
Mycobacterium Avium complex.
Mycorrhizae: Arbuscular Mycorrhizae.
Mycorrhizae: Ectomycorrhizal fungi.
Neuston Microbiology: Life at the Air Water Interface.
Nitrification in Aquatic Systems.
Nitrifying Bacteria in Drinking Water.
Nitrogen Cycle in the Marine Environment.
Nitrogen fixation in soils - free living microbes.
Nitrogen fixation in soils (Symbiotic).
Nitrogen fixation in the Marine Environment.
Norwalk-Like Viruses: Detection Methodologies and Environmental Fate.
Nuclear Waste Repository in Yucca Mountain: Microbiological Aspects.
Occurence of Protozoa in Spent Filter Backwash Water.
Oxygen: Effect on Marine Microbial Communities.
Oxygenase Enzymes: Role in Biodegradation.
Paleolimnology: Use of Algal Pigments as Indicators.
Paleolimnology: Use of Siliceous Structures of Chrysophytes as Biological Indicators in Freshwater Systems.
Paleolimnology: Use of Siliceous Structures of Chrysophytes as Biological Indicators in Freshwater Systems.
Parasitic Protozoa: Fate in Wastewater treatment plants.
Pathogenic Escherichia coli.
Pathogens in environmental biofilms.
Pesticide Degradation in Soils.
Petroleum and Other Hydrocarbons, Biodegradation of.
Phosphorus cycling in the marine environment: role of bacteria in.
Phototrophic Anoxygenic Bacteria in Marine and Hypersaline Environments.
Phylogenetically-Based Methods in Microbial Ecology.
Pigments: Photosynthetic bacterial and algal pigments in the marine environment.
Planktonic algae in the Marine environment.
Planktonic Microorganisms: Bacterioplankton.
Plant-Microbe interactions in the Marine Environment.
Polar Marine Phytoplankton.
Primary Productivity in the Marine Environment.
Protein profile analysis of aquatic microorganisms.
Protistan Communities in Groundwater.
Protozoa in Marine/estuarine waters.
Protozoan Ciliates in Freshwater Ecosystems.
Psychrophilic Bacteria: Isolation and Characterization.
Pulp and Paper Industry: Microbiological Aspects of.
Quantification of Microbial Biomass.
Radioactive Waste Disposal.
Red Tides and other Harmful Algal Blooms.
Regulation of the Commercial use of Microorganisms.
Ribotyping Methods for Assessment of in situ Microbial Community Structure.
Risk assessment of environmental exposure to viruses.
Salinity Effects on the Physiology of Soil Microorganisms.
Salmonella in Aquatic Environments.
Sampling Techniques for Environmental Microbiology.
Sea Ice Microorganisms.
Sediments: Sulfate Reduction in Marine Sediments.
Snow and Ice Environments.
Soil and Soil Microorganisms.
Soil distribution of microorganisms.
Soil Fungi: Nature's Nutritional Network.
Soil Genetic Ecology.
Soil Nitrogen Cycle.
Soil quality: the role of microorganisms.
Sorption properties of biofilms.
Source water Protection: Microbiology of Source Water.
Space Microbiology - Microgravity Effects.
Space Microbiology: Effects of Ironizing Radiation on Microorganisms in Space.
Spas and Hot Tubs Microbiology.
Storage Polymers and their Role in the Ecology of Activated Sludge.
Stress response in Archaea.
Stress Response in Bacteria: Heat Shock.
Stress response, in bacteria.
Subsurface Microbial Communities: Diversity of Culturable Microorganisms.
Subsurface Samples: Collection and Processing.
Sulfate reducing bacteria: Technological and environmental application.
Sulfur Bacteria in Drinking Water.
Sulfur Cycle in Soils.
Sustainable Agriculture: Role of Microorganisms.
Thermophiles, Diversity of.
Thermophiles: Anaerobic Alkalithermophiles.
Toxicity of Organic Solvents in Microorganisms.
Toxicity testing in soils: use of microbial and enzymatic tests.
Toxicity Testing in Wastewater Treatment.
Trace gases, soil.
Tracers in Groundwater: Use of Microorganisms and Microspheres.
Use of Capillary Electrophoresis in Ribotyping of Microbial Communities.
Use of Cold Adapted Microorganisms in Biotechnology.
Use of microscopic algae in toxicity testing.
UV Disinfection- Theory to Practice.
VIABLE BUT NOT CULTURABLE (VBNC) MICROORGANISMS.
Virus Survival in Soils.
VIRUS TRANSPORT and Modeling IN THE SUBSURFACE (saturated zone).
Viruses and protozoan parasites in food including methodology.
Viruses in Drinking Water and Ground water.
Viruses in the Marine Environment.
Volcanic Tuffs: Deep Subsurface Microbiology of.
Wastewater and Biosolids as Sources of Airborne Microorganisms.
Wastewater Microbiology - Biofiltration and Bioodor Removal.
Wastewater Treatment - Septic Tank Systems.
Wastewater Treatment - Stabilization Ponds.
Wastewater Treatment Microbiology - Growth Kinetics of Microbes In Situ.
Water fungi as decomposers in freshwater ecosystems.
Weathering: Mineral Weathering and Microbial Metabolism.
Wetlands and Reedbeds for Wastewater Treatment.
Wetlands: Biodegradation of Organic Pollutants.