Abstract

Physical, biologic, and chemical agents or combinations of the three can be used in a bioterrorist attack on zoos. Risk assessment and wildlife forensics can serve as initial robust lines of defense in quantifying the risk, characterizing the hazard, and enabling risk management. Computer assisted medical decision making and scientific reasoning are essential. In an era of Info-Medicine, the foiling of a bioterrorist attack requires an interdisciplinary task force. One key member of the task force should be an expert in biowarfare. The combative motivations and skills of bioterrorists should never be underestimated. A response to an attack on any zoo must be at the state and national levels due to the nature of bio-pathogens used as weapons and medico-legal factors. Maintaining optimal animal health and a highly reliable surveillance system are paramount components for countermeasures.

Introduction

The high technology advances in communication and travel in the current Information Age have magnified the ease of asymmetric warfare. It is an unconventional warfare which is trans-global and includes macro-ecological niches and micro-ecological niches. Zoological parks, gardens or zoos as micro-ecological niches are susceptible to bioterrorist attacks.

Though in-house expertise should be utilized in foiling a bioterrorist attack on a zoo, the counterattack or preventive action has to be a well-coordinated national and international effort. Though a zoo cannot afford a multi-disciplinary team of biomedical scientists and clinicians, the in-house veterinary staff can serve as coordinators for a team of specialists. The team members can consist of a toxicologist and risk assessor, a wildlife forensic pathologist, a zoo-veterinarian and a veterinary clinical bioinformatician. One significant member of the counter bio-warfare team will be an expert in counter-terrorism or asymmetric warfare with skills in chemical and biologic warfare.¹ The combative objectives of a bioterrorist attack should never be underestimated.³ Animals at a zoo can be used as reservoirs for acute bio-pathogens or chronic bio-pathogens. For example, a number of mammals, including elephants and rhinoceroses can be inoculated with weaponized strains of the anthrax organism. Reptiles and birds can be inoculated with weaponized strains of Salmonella typhimurium.

The zoo veterinarian, the toxicologist and risk assessor, the wildlife forensic pathologist, the veterinary clinical bioinformatician and bio-warfare expert can, as an effective coordinated team, develop a robust plan to foil a terrorist attack on a zoo. The 1986 thallotoxicosis at the Guyana Zoo example illustrates methods for improving approaches for nullifying bioterrorist attacks on zoos.

Modes of Attacks

The agents used by bioterrorists to attack humans and animals at a zoo can be categorized as physical, chemical and biologic agents. Combinations of these agents can be employed to induce an epidemic in a zoo community and surrounding environment. For instance, the aerosol inoculation of captive and free ranging birds and reptiles with the highly pathogenic strains of Salmonella or E. coli 0157:H7organism can be conducted covertly, and visitors to the zoo can be exposed to the organism from the body fluids and excrements of infected birds and reptiles. Feral rats and mice can be inoculated with the weaponized strains of the Leptospira organism and surreptitiously released in a zoo compound. Unless there is a successful rodent control program at the zoo or zoological park, susceptible humans and animals can be infected, and an epidemic can occur.

The bioterrorist can also use chemical agents to induce an epidemic with high mortality and low morbidity in a zoo population.² Thallium sulfate is colorless, odorless and tasteless. Depending on the exposure dose, the toxic effects can be acute, sub-acute, chronic or sub-chronic. The effective dose varies by species. During the 1986 thallotoxicosis at the Guyana Zoo, 75% of the animal population sampled were thallium positive. A forensic investigation by the author indicated that thallium was introduced into the foods of the animals when the foods were transported from the zoo kitchen to the animal enclosures. There were also animals with acute and chronic signs of thallium poisoning. One toucan and peacock exhibited paraesthesia, hind leg paralysis and diarrhea. A margay with ante-mortem signs of hemorrhagic diarrhea, epilation and shock was on necropsy examination found to have diffuse gastric and duodenal ulcers, hydrothorax, and ascites.¹³ Thallium sulfate a homicidal agent has been used during the Saddam Hussein regime against dissidents and in the Warsaw Pact countries during the Cold War.⁷ More effective than ricin, thallium toxicosis has only been detected in victims via meticulous diagnostic work-up. The bioterrorists have a variety of methods of delivering the chemical, biochemical or biologic agents to target species in a zoo.⁴ Migratory birds using the zoo grounds as a resting stop can be used as biologic or mechanical vectors. Arthropods such as ticks and mosquitoes can also be used as mechanical or biologic vectors.⁵ Bioterrorists can also infiltrate the zoo staff and covertly expose target species to a combination of chemical or bio-pathogen agents.¹² Kites, balloons or remote-controlled vehicles flown over a zoological park can be used to remotely release aerosols, powders or smoke containing bio-pathogens or toxic chemicals. How can these varied modes be foiled?

Counter Measures

From the perspective of the art of warfare, each attack, including the best attack has weaknesses or faults. These are weaknesses or faults which the defender can exploit to nullify the effectiveness of the attack. A robust surveillance program at a zoo can detect an increase in the rodent population and unusual pathogens transmitted by the rodents.¹¹ Maintaining an effective prophylactic program, including an optimal plane of nutrition for all animals can act as a buffer against the stress induced in an ecological niche due to the introduction of new pathogens or physical and chemical agents. Adequate preparation and an alert, highly trained technical zoo staff can take away the element of surprise used by many bioterrorists.

The role of each member of the team countering the potential bio-warfare attack begins prior to any emergency event. A preventive plan is developed and implemented. Drills and bio-war games are periodically conducted and the skills of the participating teams are honed.¹⁰

The toxicologist and risk assessor identifies, characterizes and analyzes the risk of the bioterrorist attack. Risk management advisories are also prepared. Dose-response curves and models of chronic and acute effects are also examined. The toxicologist and risk assessor along with the veterinary clinical bioinformatician and zoo veterinarian can develop or use software on medical decision-making to reduce error in diagnosis and therapeutic management.⁹ The wildlife forensic pathologist can provide in-depth analyses and interpretations on risk reduction and pathogen detection.⁸ The expert on bio-warfare can play a role in the development of counter tactics and strategies. The bio-warfare expert should be able to assess the combative skills and potentials of the bioterrorists and the impacts of their attacks on the health of animals in the zoo and animals and humans in neighboring communities.

Discussion and Conclusions

A bioterrorist attack on a zoo has the potential for a bio-hazard or chemical hazard at a state or a national level. It can be conducted by a group of highly skilled, highly motivated, cunning and fanatic individuals. Counter measures to foil a bio-warfare attack must be robust from a military and medical sciences perspective. Lack of funding or poor funding along with ineffective communication by a variety of experts and/or specialists can be weak links in a coordinated effort to neutralize a bioterrorist attack on a zoo.¹⁴

Habitat destruction and over-population have been some factors contributing to the increased importance of zoos. There has also been a merging of the theatres of asymmetric warfare, in which all ecosystems are part of the theatre. In the current era of Info-Medicine, the veterinary and human medical community must cooperate in their effort to prevent and combat epidemics in which domestic and non-domestic animals are abused as biochemical factories for deadly pathogens.⁶

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