A biological agent is a microorganism or a toxin derived from it, which causes disease in humans, plants, or animals or causes deterioration of material. It produces an effect through multiplication within a target host and is intended for use in war to cause disease or death in humans, plants, or animals. (Venkatesh, Memish, 2003) In this context, the biological agents are normally divided into three categories: anti-personnel, anti-animal, and anti-plant. In addition, the use of biological agents is often classified by the manner in which they are used. For example: biological warfare has been defined as a specialized type of warfare conducted by a government against a target; bioterrorism has been defined as the threat or use of biological agents or toxins by individuals or groups motivated by political, religious, ecological, or other ideological objectives. Biological weapons are devices intended to deliberately disseminate disease-producing organisms or toxins in food, water, by insect vector, or as an aerosol. They achieve their target effects through infectivity or intoxication. The toxic substances that the agents generate can sometimes be isolated. The weapons have the capacity to initiate epidemics on a scale and with a degree of lethality unparalleled in modern history. Thousands of pathogenic microorganisms have been investigated for their potential utility as weapons, but few have been found satisfactory, and fewer have found their way into weapons. (Venkatesh, Memish, 2003) Terrorists can be distinguished from other types of criminals by their motivation and objective; criminals may also be driven by psychological pathologies and may use biological agents. When criminals use biological agents for murder, extortion, or revenge it is called a biocrime. (Anderson, Friedman, & Bendinelli, 2006)
When a bioterrorist event occurs, the clinical microbiology laboratory could be helpful in detecting and identifying the biological weapon used and alerting authorities. The term biological agent applies to a diverse group of microorganisms as well as toxins of microorganisms, plants, and animals. More specifically bioterrorism is defined as the use of biological agents to inflict disease and/or death on humans, animals or plants. Crops and livestock as well as human populations are considered possible bioterrorist targets. Bioterrorist attacks could have ideological, religious, political or criminal motivation and could be planned by groups or a single individual or be part of state-sponsored terrorist activities. The biological agents thought to be most likely weapons of bioterrorists include B. anthracis (anthrax), Francisella tularensis (tularemia), Yersinia pestis (plague), variola virus (smallpox), agents of viral hemorrhagic fevers, and botulism toxin. While some agents only harm the population exposed, infectious agents producing contagious disease could disseminate through susceptible population unaffected directly by the initial bioterrorist event. The agent must be "weaponized" or produced in sufficient quantity and in a form that would be relatively stable and easily disseminated. The attack itself would be either covert or overt. In the case of covertly disseminated infectious agents, there might be no realization that an attack had occurred until numerous victims fell ill and their common illness had been diagnosed. The most efficient method of delivering biological agents is thought to be the air-borne route, with agents dispersed in aerosols but miscalculation of wind direction could result in a missed target or worse, self-contamination with the agent being dispersed. (Wolfgang & Ruoff, 2001)
The idea of mounting some form of defensive activity against possible bioterrorist actions is appealing because although bioterrorist acts are expected to be infrequent, they are regarded as "low-probability, high-consequence events." Public feelings about bioterrorism are reminiscent of the widespread concern about nuclear weapons that arose in the post-World War II Cold War era. Fear of nuclear, chemical, and biological weapons of mass destruction is well founded and perhaps reflects an innate human revulsion, based on moral and ethical grounds, against the use of weapons producing such catastrophic suffering in fellow humans, even those construed as enemies. The bombing of the World Trade Center in New York marked the introduction of such International terrorism to U.S. territory, and there are indications that terrorists could use biological agents in the future. The U.S. Department of Health and Human Services increased the budget to prepare for bioterrorism in the fiscal year. The funds support an antibioterrorism initiative with the goal of preparing the nation to better defend itself against a potential attack with biological agents.(Wolfgang & Ruoff, 2001)
Most agents are designed to be easily breathed in and susceptible to weather which is never predictable. During dispersal, the agent could float to unintended places. For example, the anthrax attacks through the mail added another dimension to biological weaponry by not being weather dependent. Hoaxes are a risk for travelers because they have caused closure of airports, complete change of itineraries and grounding of airplanes. (Venkatesh, Memish, 2003)
Bioterrorism agents include microorganisms such as bacteria, viruses, Chlamydia, fungi and rickettsia, entering the body by inhalation or ingestion and multiplying and causing illness and death or epidemics. These agents also include toxins and chemicals that regulate biological functions. Hormones and peptides have normal physiological effects in low and moderate doses and patho-physiological effects in high doses. B. anthracis, botulinum toxin, smallpox, Yersinia pestis, ricin, staphylococcal enterotoxin B, and Venezuelan equine encephalitis virus directly affect exposed people and cannot pass from person to person. (Venkatesh, Memish, 2003)
Biological agents are categorized by several features which influence their potential use for weapons. Some of the features include infectivity, virulence, lethality, pathogenicity, incubation period, contagiousness, stability. (Venkatesh, Memish, 2003)
Robert Koch provided a basis for the development of a new generation of biological weapons. He conceptualized and provided experimental support for the germ theory of disease. Koch used microscopy during his early work with anthrax to demonstrate that the blood of animals with disease contained large numbers of a spore-forming bacterium and that the bacteria could be cultured outside the body in nutrient fluids. The organism must be isolated in pure culture to link a specific microorganism to a specific disease; towards the end Koch developed several methods to isolate the microorganisms in pure culture. Once they were available he was able to formulate the criteria, Koch's postulates, for proving that a specific type of microorganism causes a specific disease. (Anderson, Friedman, & Bendinelli, 2006)
Since 1900-2003, there have been 29 confirmed incidents in which the use of a biological agent was suspected. The majority of them were criminal type, 15 involved the use of bacteria, 10 toxins, 5 viruses, and 1 used the ova of a parasitic roundworm; 3 of the incidents were used against livestock or other animals, the remainder involved the use of biological agents or toxins against humans. (Anderson, Friedman, & Bendinelli, 2006)
The largest event deliberately infected people by Salmonella Typhimurium and involved the injection of HIV. Ricin was the most common toxin used in those incidents where toxins were used in assassination or for murder. The majority of the bacterial species that were used belonged to the Enterobacteriaceae, which is the method used to disseminate the agent that was not known in the case. In the cases that it was known, contaminated food ingestion, injection, and inhalation were used. A significant proportion of the incidents were perpetrated by individuals with scientific or medical training. (Anderson, Friedman, & Bendinelli, 2006)
For many years biological agents were used for criminal activities, warfare or terrorist attacks. Bioterrorism is a terrible threat causing many fatalities. The public health system in the United States is making many efforts to prepare and protect from bioterrorist attacks through surveillance, epidemiology and laboratory capacity, which will hopefully lead to early detection of events and minimize the number of casualties. (Anderson, Friedman, & Bendinelli, 2006)
****Listed below are several charts and tables showing characteristics, criteria, biological agents, and diagnosis of laboratory tests of several biological agents.****
