Volume 12, Number 7—July 2006
Peer Reviewed Report Available Online Only
Preparedness for Anthrax Epizootics in Wildlife Areas
Preparedness for Anthrax Epizootics in Wildlife Areas
October 24–28, 2005
After a year with an unusual number of anthrax outbreaks in wildlife in sub-Saharan Africa, the Malilangwe Trust in Zimbabwe hosted a workshop (2005 24–28 Oct) to formulate plans to prevent or limit anthrax in wildlife. The guidelines developed are meant for use by veterinary, public health, and wildlife personnel and provide a framework to develop formal preparedness plans specific to areas under their jurisdiction. These plans should take into account the circumstances unique to each wildlife management area (WMA).
The workshop identified key factors for management preparedness and effective action in the face of an anthrax outbreak. The relevance of each of these factors varies with the size, economic position, and conservation status of susceptible species in the WMA. Large national parks where anthrax is endemic and does not threaten wildlife population stability will view disease issues differently from small WMAs that are dependent on maintaining stable populations for economic survival, but in all cases spillover into livestock areas and public health risks present a concern.
Risk factors and warning signs must be identified. Changes in livestock vaccination programs, past local histories of anthrax, and the occurrence of cases in adjacent human and livestock areas should be monitored. Such surveillance requires links with veterinary services, public health authorities, and neighboring communities. Cause of death for carcasses detected in a WMA must be determined. Less obvious risk factors are landscape features such as habitats that support high densities of susceptible host species, alkaline soils conducive to Bacillus anthracis spore survival, or drainage sumps where spores accumulate. A dry season following above-average rainfall seasons may also increase the risk of an outbreak and recognizing when a region's primary anthrax host species has reached a high density may be important for predicting outbreaks.
Disease prevention plans begin with minimizing risk factors and responding to the warning signs listed above. Protocols appropriate to the terrain must be devised and field staff must be trained. Educational and advisory information on how to identify, respond to, and avoid anthrax should be distributed to communities within and surrounding the WMA. Culling or dispersing primary anthrax host species to prevent population densities from reaching high levels should be considered. Policies will vary with size, economic position, and conservation status of susceptible species in the WMA. Vaccination of cattle in neighboring communities should be carried out as this is a primary risk management tool.
Proactive management included planning for an outbreak. Of primary importance is halting the spread of the disease. This involves identifying and localizing the source of the outbreak by developing methods of carcass detection and disposal. Preferably, carcasses should be burned, but if local resources prohibit this, then contamination and spore formation can be substantially reduced by covering carcasses to minimize their opening by scavengers (anthrax spores form when vegetative anthrax in the blood comes into contact with air). Carcass burial is an option, but should only be considered when carcasses are fresh and intact because spores can remain virulent for years under appropriate soil conditions, and become the source of future outbreaks when exposed. In addition, controlling blowfly populations, providing scavengers with uncontaminated meat decoys, burning contaminated areas of the bush to destroy spores and disperse animals, and performing ring vaccination of rare or susceptible species are important considerations. WMA personnel should be allocated to teams to implement actions, and efforts should be coordinated. Information regarding the safe handling of carcasses, consumption of meat from animals that have died of an unknown cause, and use of potentially contaminated water should be made available to those in contact with infected animals.
Budgets need to cover the resources necessary to control an outbreak. Costs include additional personnel and longer work hours as well as increased use of transport vehicles and mechanical diggers for carcass burial when appropriate. Other costs include veterinary and medical services, vaccines and vaccination equipment, protective clothing, insecticides, disinfectants, material for covering carcasses, fuel for carcass incineration, and educational materials. Prophylactic treatment of wildlife in the face of an outbreak is costly and likely impractical for large populations of wild animals. Carcass detection is enhanced by aerial observation, but costs must be weighed against probable benefits, considering that anthrax carcasses not disposed of act as potential infection sources for future outbreaks.
Rapid diagnosis of anthrax is important. Anthrax is diagnosed easily with basic facilities and knowledge of the appropriate techniques and safety precautions. Ideally, an on-site laboratory should be established for anthrax diagnosis based on blood smear detection only. This does not require opening the carcass. Equipment should include a microscope, McFadyean stain, slides, swabs, discard containers, disinfectants, an autoclave, and a small incinerator. A list of laboratory and veterinary facilities capable of providing advanced diagnostic and scientific support for culture, serologic testing, and strain-typing should be made available.
Ideal management plans should allow for postoutbreak studies to improve understanding of the disease and assess the effectiveness of the interventions implemented. Documentation and analysis of the outbreak can help identify disease-exacerbating factors, including the role of insects and scavengers in spreading the disease, the impact of the outbreak on nearby livestock, and the potential of livestock in acting as a source of infection for wildlife. Serologic studies in collaboration with specialists could help determine the extent to which the disease was present in the area before the outbreak. Strain typing could help trace back the source of an outbreak as well as identify whether or not distinct outbreaks are independent events or caused by the spread of a defined outbreak strain.
Several issues were not resolved because of lack of consensus or insufficient data from which to draw a conclusion. From a public health perspective, outbreaks present risk communication challenges regarding treatment and safety of domestic water and the safety of utilizing apparently healthy animals and fish for human consumption. The group discussed but deferred a resolution on the need for or duration of postexposure antimicrobial drug prophylaxis for animal care workers. Finally, substantial debate occurred on the rationale on which to base pre- and postexposure vaccination and postexposure treatment to protect rare or endangered wildlife species. This workshop underscored the interrelationship between livestock, wildlife, and human health and the need for partnerships to address emerging infectious diseases.
We extend special thanks to Peter Turnbull for his assistance in organizing the workshop and in preparing this manuscript. We are grateful to the following organizations for sponsoring the workshop: The Malilangwe Trust, Anglo American Corporation, Arjemptur Technology Ltd., Unifreight, Centers for Disease Control and Prevention, Delta Corporation Ltd., Deutscher Entwicklungsdienst, Milborrow, and Triangle Ltd.
Suggested citation for this article: Clegg S, Wildlife Anthrax Epizootic Workshop Working Group. Preparedness for anthrax epizootics in wildlife areas [conference summary]. Emerg Infect Dis [serial on the Internet]. 2006 Jul [date cited]. http://dx.doi.org/10.3201/eid1207.060458
1William Amanfu, Roy Bengis, Wolfgang Beyer, Carrie Cizauskas, Bruce Clegg, Sarah Clegg, Valerius de Vos, Hym Ebedes, Christopher Foggin, Stuart Hargreaves, Markus Hofmeyr, Arnold Kaufmann, Michael Kock, Richard Kock, Fabian Leendertz, Regula Leuenberger, Pauline Lindeque, Nina Marano, Peter Morkel, Carlos Pereira, Peter Turnbull, Wendy Turner, and Colin Wenham