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SECTION I

MEDICAL DEFENSE AGAINST BIOLOGICAL MATERIAL

INTRODUCTION

Biological warfare is the use of microorganisms or toxins derived from living organisms to produce death or disease in humans, animals, or plants. In spite of the 1972 Biological Weapons Convention prohibiting the use of biological warfare agents, concern over compliance remains. It is possible that allied forces may be exposed to biological weapons. Characteristics of many live agents and toxins make them potentially effective for offensive military use. These agents can provide a readily available and effective weapon in the hands of terrorists as well as assassins.

Delivery systems for biological warfare agents most commonly generate invisible aerosol clouds with particles or droplets of greater than 10 microns (m). They can remain suspended for extensive periods. The major risk is pulmonary retention of inhaled particles. To a much lesser extent, particles may adhere to an individual or his clothing. The effective area covered varies with many factors, including wind speed, humidity, and sunlight. In the absence of direct evidence of an attack, the first clue would be mass casualties fitting a clinical pattern compatible with one of the biological agents. This may occur hours or days after the attack. Toxins may cause direct pulmonary toxicity or be absorbed and cause systemic toxicity. Toxins are frequently as potent or more potent by inhalation than by any other route. A unique clinical picture may sometimes be seen which is not observed by other routes (e.g. pulmonary edema after staphylococcal enterotoxin B (SEB) exposure). Mucous membranes, including conjunctivae, are also vulnerable to many biological warfare agents. Physical protection is then quite important and use of full-face masks equipped with small-particle filters assumes a high degree of importance.

Oral: Other routes for delivery of biological weapons are thought to be less important, but are nonetheless potentially significant. Contamination of food and water supplies, either directly or secondarily after an aerosol biological warfare attack, represents a hazard for infection or intoxication by ingestion. Assurance that food and water supplies are free from contamination should be provided by appropriate preventive-medicine authorities in the event of an attack.

Dermal: Intact skin provides an excellent barrier for many but not all biological agents. Mucous membranes and abraded, or otherwise damaged, integument can, however, allow for passage of some bacteria and toxins, and should be protected in the event of an attack.

Physical Protection: The most effective and singularly most important prophylaxis in defense against biological warfare agents is physical protection. Preventing exposure of the respiratory tract and mucous membranes (to include conjunctivae} to infectious and/or toxic aerosols through use of a full-face respirator will prevent exposure, and should, theoretically, obviate the need for additional measures-Chemical protective masks effectively filter biological hazards.

Decontamination, Protection of Health Care Personnel: Any dermal exposure should be treated by soap and water decontamination. This can follow any needed use of chemical decontaminants but should be prompt. Secondary contamination from clothing, etc. of exposed soldiers to medical care personnel may be important, particularly from those individuals exposed near the dissemination source where large particle deposition may occur. Since it will be difficult to distinguish those soldiers exposed near the source from those contaminated some distance away, proper physical protection of health care providers or other persons handling exposed personnel should be maintained until decontamination is complete. This applies to chemical exposure as well. Clinical laboratory samples for toxin-exposed subjects can be dealt with routinely. Patients showing signs of pneumonic plague generally should be considered hazardous, as some will disperse plague bacilli by aerosol- Anthrax could present a risk from open lesions or blood which could result in cutaneous anthrax. Anthrax does not pose a threat of aerosol dissemination from blood or during autopsy procedures, but sporulation of bacilli exposed to air theoretically could occur, with subsequent inhalation. On the other hand, plague and tularemia bacilli may be dangerous, since, under some circumstances, they are known to cause aerosol infections. Therefore, postmortem examinations of suspected anthrax, plague, and tularemia victims should be performed with strict mask, gown, and glove precautions because of the large numbers of organisms present in body fluids.

Prophylaxis and Therapy: All medical prophylactic modalities described should be viewed only as secondary (i.e., backup), and are not to be relied upon as primary protective measures. Agent exposures near the source of dissemination will be high, and likely to overwhelm any medical protective measure. The precise efficacy of available medical countermeasures has, of course, never been evaluated in actual field circumstances, but is largely inferred from laboratory studies on nonhuman primates. While these extrapolations may be inexact, they strongly support the efficacy of vaccines and drugs at some agent dose.

Outlined in Section IX is an assessment of our current capability to respond to several of the biological agents. A common format is used to enable rapid consolidation of capabilities by response area (e.g., specific laboratory diagnosis, therapy, prophylaxis). Section III provides a review of clinical features distinguishing chemical neurointoxications from botulism.