Abstract

Reintroduction processes carry a risk of introducing disease to release areas. This risk is significant for great apes who share many common diseases with human beings. Potential exposure of great apes to pathogens during captivity makes understanding and managing this risk critical. In addition, released animals can be affected by an endemic disease for which they are not prepared.

This paper highlights a flexible risk-analysis approach to the veterinary requirements adopted by the International Union for Conservation of Nature (IUCN) Best Practice Guidelines for the Re-Introduction of Great Apes. It combines science and policy to address two major issues:

• The likelihood of individuals or groups surviving in the new habitat.
• Minimizing pathogen spread in new environments.

Specifically, this approach uses a logical framework to determine the following:

• Adverse health events and means of introduction and spread (hazard identification).
• Likelihood of such events occurring. Methodologies, assumptions, and uncertainties need to be commonly understood by stakeholders (risk assessment).
• Strategies to reduce the likelihood of an adverse outcome.
• Strategies to manage the consequences of such an outcome occurring (risk management).

Four underlying principles of this approach are: (1) no situation is without risk, (2) socio-ecological variables make health assessment an adaptive process, (3) introduced and recipient populations need to be assessed, and (4) all stakeholders should be involved in identifying mitigation strategies.

Wildlife rehabilitation and release back to the wild are complex processes. Successful great ape reintroduction is possible^5,11 but disease investigation associated with this process must be thorough.

The potential for transmission of diseases is increased during the re-introduction process as animals and humans have frequent close contact with conspecifics and with one another under increasingly stressful conditions. Animals held in captivity or transported, even for a short period of time, may be exposed to a variety of pathogens for which they have no immunologic experience. This may result in disease, with resultant effects on fecundity, death, and/or an increase in the number of carriers of infectious organisms. Thus, releasing apes to the wild may result in the introduction of disease to conspecifics or unrelated taxa with potentially severe effects.^2,3,7-10,12

There are many established protocols for moving nonhuman primates between captive facilities around the world. In these cases, veterinary protocols are designed with a great deal of historical knowledge about the relevant facilities and animals and are fairly straightforward. In contrast, there are no standard protocols for movement of nonhuman primates for the purpose of reintroduction, supplementation, or translocation. In these cases, there are many more variables to be considered and much more uncertainty. Emerging infectious diseases have been shown to significantly adversely affect biodiversity in general⁴ and primates in particular.¹³ Wild and recently wild primate populations remain a largely unexplored source of information regarding disease and may hold clues to the origins and evolution of some important pathogens. Primates can act as reservoirs for human pathogens and vice versa. Since infectious diseases pose serious risk to threatened primate species,³ studies of these diseases in primate populations can benefit conservation efforts and may provide the missing link between laboratory studies and the well-recognized needs of early disease detection, identification, and surveillance.

Removal into captivity, such as into sanctuaries, may result in nonhuman primates becoming infected with agents to which they were not exposed in their natural habitats. For example, many helminth parasites have poorly developed host specificity, some affecting both primates and species widely separated from primates.²

As projects move towards reintroduction programs, or in some instances, continue to monitor the health of animals already released, screening for “normal (endemic) diseases” would ideally be done in both introduced animals and the recipient population (if there is one). Those diseases present in both populations or those that are not pathogenic may be of lower concern. This is difficult to interpret because relatively common diseases in one population may be emerging diseases to another. As a minimum, apes to be introduced are being screened for infectious agents not found naturally in wild populations of the taxon of concern (such as pathogens acquired from people or other apes) and agents that may result in the introduction or spread of potentially dangerous diseases.^3,10 The basic process is as follows.

Hazard Identification and Risk Assessment

A list of potential diseases of concern is drawn up after a comprehensive literature search based on susceptibility and historical findings in the species, as well as field data collected from the relevant field site. A qualitative ranking of these diseases based on epidemiologic, pathologic, and social parameters results in a “traffic light protocol” where those diseases highlighted in red and yellow are thought to be of highest risk and, therefore, must be screened for and/or prevented.

This rough assessment is adapted from work developed by the Conservation Breeding Specialist Group (CBSG) of the IUCN.¹ The reliability and certainty of the information gathered is also highlighted so future research into the diseases can be directed to any knowledge gaps. Diseases of concern will rank higher if there is certainty that a disease is detrimental to the species, or if there is a high level of uncertainty about the known effects, both to the individual and to the population. The diseases of concern list is not meant to be comprehensive, but rather reflect those that pose the greatest risk to potential release. Thus, the testing regime in this case is viewed as an absolute minimum requirement for pre-release disease monitoring and is specific to each release program.

Risk Management

Once the hazard identification and risk assessment phases establish the level of risk (qualitatively or quantitatively) associated with each disease, risk mitigation strategies and associated costs are described. Specific recommendations can then be included in the overall veterinary recommendations for the importation of animals into the release site.

Risk Communication

Vitally, all stakeholders are to be made aware of the findings of the assessment including updated information. This is part of a communication network that must be in place for any release program.

Literature Cited

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