Abstract

There is an increasing number of free-ranging chimpanzee groups in Uganda habituated for tourism. Due to the close taxonomic relationship between humans and great apes, there exists the potential for disease transmission to chimpanzees from visiting tourists. In order to ensure the development of successful ecotourism programs with minimal effect on the health of endangered primates, measures must be established to prevent the transmission of disease. The aim of this study was to determine the potential risk for anthropozoonotic disease transmission by surveying the medical histories of human visitors to chimpanzees at Kibale National Park, Uganda. Medical histories were taken by using a consent form to ensure confidentiality, and a questionnaire to gather information on vaccination and disease histories as well as any recent occurrence of disease symptoms. Approval for this study was obtained from the human subjects review committee of the University of Tennessee.

A total of 43 surveys were completed from July to November 1998, with a predominance of European tourists 30/43 (70%), followed by tourists from Australia 6/43 (14%), the United States of America 4/43 (9%), and Africa 3/43 (7%). Although many individuals had been vaccinated against the diseases included in the questionnaire, not all were current on their vaccines. For example, 84% of those surveyed were vaccinated against hepatitis A, of which only 56% were current for the vaccination. Of those individuals diagnosed with a disease listed in the questionnaire, five cases of herpes virus infection, four cases of influenza, one case of chicken pox, and two cases of tuberculosis were still considered to be infectious at the time of visitation. When asked if they had been tested for tuberculosis, 44% answered no, and 10% were unsure about whether or not they had been tested. Of the 46% who answered yes to being tested, two individuals (11%) tested positive for tuberculosis.

The most common symptoms of disease or illness reported by foreign tourists during their stay in Africa were diarrhea (53%), coughing (23%), and vomiting (13%). If these symptoms were in fact due to some infectious agent, and were ongoing during the visit to Kibale National Park, the possibility of disease transmission to the chimpanzees is evident. Seventy percent of those surveyed indicated that they had either already visited another group of habituated chimps or gorillas prior to the Kibale visit, or they intended to upon leaving Kibale. Therefore, humans should be considered as potential sources of disease, both as carriers of infectious agents as well as fomites or vehicles of disease. These infectious diseases could then be transmitted from habituated animals to more isolated populations, further endangering the species. Of those individuals informed of the viewing regulations prior to their visit to the chimpanzees, 100% replied that they understood the need and rationale for these regulations. This is encouraging and suggests that proper education of all visitors to Kibale is an effective means of ensuring visitor compliance to regulations.

Results from these surveys should assist the Uganda Wildlife Authority to develop appropriate regulations to prevent disease transmission. This will contribute to the health management of the chimpanzees as well as to help develop a sustainable primate ecotourism program. For example, current park regulations for viewing chimpanzees include a maximum number of six tourists per visit, with a minimum distance of 5 m between the chimpanzees and the human visitors. Based on these results, regulations could be extended to include the use of face masks to reduce or prevent the transmission of airborne disease agents, and the enforcement of the right to refuse a visitor if he/she is ill. Other possible regulations to consider include the mandatory washing of hands and the use of disinfectant foot baths for all tourists prior to the visit. Further measures to minimize the potential for disease transmission could involve the provision of adequate pit latrines to ensure proper disposal of human waste. These facilities should remain at a safe distance from areas occupied by chimpanzee groups. Provision of regular health examinations and vaccination of park staff and field researchers would minimize disease risk from those in frequent contact with the chimpanzees.

The risk for disease transmission warrants further investigation. Future surveys of tourists could include serologic surveys for common infectious diseases, throat culture swabs to isolate potential aerosolized pathogens, and testing for tuberculosis. Lastly, development of non-invasive monitoring of chimpanzee health status via opportunistic blood, skin, urine, or fecal sampling, and necropsies, would further document the impacts of disease on chimpanzee populations, as well as indicate to which human diseases the chimpanzees are susceptible.

Acknowledgments

We thank the Uganda Wildlife Authority, particularly Mr. Samson Werikhe, Research Coordinator, for granting permission to conduct this study. Valuable assistance was provided by the Chief Warden of Kibale National Park, Mr. Keith Musana, the Warden of Tourism at Kibale, Mr. Aggrey Rwetsiba, the Veterinary Officer, Dr. Gladys Kalema, and Debby Cox of the Jane Goodall Institute. Special thanks to Julia Lloyd and Daniela Pezzato of The Kibale Primate Habituation Project for assistance with the administration of the surveys, and to Dr. Antoine Mudakikwa and Dr. Juergen Schumacher for language translation of the questionnaire and consent form. This project was partially funded by the Center for Conservation Medicine, Tufts University.