Ape Tourism and Human Diseases

Gorillas are among our closest relatives and therefore susceptible to a large number of human pathogens. Although there is little published evidence demonstrating proof of direct transmission of pathogens from humans to great apes in the wild, a number of cases have been documented providing ample evidence of definite susceptibility of apes to human diseases.
Cases of illnesses in apes that have been associated with human respiratory viruses and bacteria include influenza, Adenovirus, Thinovirus, respiratory syncitial virus (RSV), pneumococcal pneumonia, Herpes viruses, measles, mumps, and Cytomegalovirus. Enteric germs include polioviruses, coxsackie viruses, Salmonella, Shigella, Campylobacter, as well as numerous parasites. This variety of agents leaves no doubt about a widely shared susceptibility to pathogens among great apes and humans.
Even though the transmission of diseases during interaction of humans with a wild environment generally poses a greater threat for wildlife than for humans, the risks for humans to acquire a new germ to which they have not previously been exposed cannot be underestimated. HIV, Ebola and other viruses of the filovirus family are obvious examples.

Gorilla Exposure to Humans

The current trend in tourism based on "unique" adventures translates into more tourists increasingly entering remote, isolated and sometimes poorly accessible regions of the world in search of rare and meaningful encounters. Tourists visiting gorillas thus often arrive from distant and varied locations, and are likely to have travelled previously to other countries and continents. This represents, from an epidemiological point of view, a very effective means of transport for an increased number of exotic germs due to the speed and diversity of modern transport systems.
Habituating gorillas for research or tourism requires regular, continuous and close human presence near the gorillas in their natural habitat. The researchers usually spend several hours at a time with gorilla groups, and therefore represent a similar degree of exposure to gorillas as tourists, even if they may not visit gorillas as often as tourists. In addition, occasional emergency veterinary interventions are inevitable and imply staff getting in direct contact with gorillas through clothes, hair and other fomites, despite the required use of masks and gloves, thus representing an acute additional source of exposure for gorilla groups.
The area surrounding the Virungas and Bwindi is one of the most densely populated areas in Africa. Malaria, respiratory infections and diarrhoeal diseases account for the majority of illnesses among adults, and deaths among children. Some areas like Kisoro District have particularly acute water and sanitation problems due to the volcanic basaltic structure of the subsoil. These conditions, combined with poor hygiene practices, greatly favour the spread of faecal-oral germs.
Among the major respiratory pathogens prevailing in the local population, Streptococcus, influenza, tuberculosis, measles and RSV figure prominently. TB is of particular concern due to its association with the HIV, or AIDS virus, and the emergence of multi-drug resistant TB strains, which is most probably due to partial or inadequate treatment. In addition, many agents causing respiratory infections can cause bouts of diarrhoea as a result of the generalised immunosuppression suffered by people with AIDS.
Current Gorilla Tourism Rules: Sufficient Protection?

* Limiting the frequency of visits (currently 1 visit per day per habituated gorilla group). Every additional daily visit doubles the exposure time of gorillas to visitors, thus increasing the risk of disease transmission. In addition, the duration of any disturbance to the gorillas' normal activities and the amount of associated stress induced would be doubled. Since stress, especially over prolonged periods of time, has been associated with immunosuppression, it could have negative health implications for gorillas. An associated risk of increased daily visits is that each visitor group entering the forest conceivably causes additional ecological disturbance.
* Recommendation: Maintain the status quo.

* Limiting the number of visitors (currently 6 in Uganda, 8 in Rwanda and Congo). Each additional visitor represents a potential contamination source and the susceptibility of gorillas to diseases greatly affects the outcome of exposure to humans. It would only take one individual gorilla to be infected for an infection to potentially spread very rapidly to the rest of the group, and the larger the group, the larger the number of animals infected. In addition, depending on interactions with other groups in the forest, the potential for spread to other wild, and perhaps even more susceptible animals, cannot be underestimated. These facts also point out that visitor group size cannot be reviewed without considering the size of the gorilla group.
* Recommendations: No visits for gorilla groups smaller than 6 or larger than 15 animals, no more than 10 people per tourist group (including guides, trackers, rangers etc.).

* Maintaining a minimum distance between visitors and gorillas (currently 5 m). Sneeze particles can cross a distance of 6 m in the absence of any wind or ventilation factor. Very light wind can greatly increase this distance for aerosols or dust particles. Therefore this rule should be reinforced to provide a safety factor against both avoidable (intentional) and unavoidable (wind) fluctuations in effective distance. This rule should apply not only to tourists, but also to all other gorilla visitors, including researchers, veterinatians, park guides, trackers and rangers and any other forest users.
* Recommendation: Increase the minimum distance to 7.5 m.

* Limiting the duration of the tourist visit (currently 1 hour). The shorter the viewing time, the greater the pressure and expectations exerted from tourists anxious to capture the best photos of gorillas, which might cause challenges to any distance rule. Conversely, the longer the viewing time, the greater the exposure of gorillas to potential disease transmission. This rule must therefore balance visitor satisfaction against increased exposure time.
* Recommendation: Maintain the one-hour viewing time while allowing
a maximum 15-minute waiting period, at 20 m or more from the gorillas, before starting the clock, if the gorillas are not visible at the time of initial encounter.

* Eating before or after gorilla viewing (currently no eating "near" gorillas). Food is a source of direct exposure and several human diseases of concern for apes are transmitted via the faecal-oral route. Food can act as a strong attractant to apes and other animals in the park. Rangers and researchers, who may occasionally spend days or weeks at a time in proximity to gorillas and eat their meals there, also represent a source of food contamination to gorillas, even greater than tourists. Food scraps dropped by community and other forest users represent another substantial contamination source.
* Recommendation: A 5-minute minimum walking distance away from gorillas before eating; removal of all food remains.

* Disposal of human faeces (currently burying it 1 ft deep). The potential for transmission of human viruses or parasites through faeces is much more efficient than the airborne route and also much more dangerous than through food, due to the concentration of germs that can be found in faeces. Even significantly more park staff and local community residents deposit faeces in the park than do tourists.
* Recommendations: Promoting and allowing time for toilet use before start of tour, ensure that guides or trackers dig holes at least 0.5 m deep for tourists and themselves, treat faeces with an antiseptic solution before filling holes.

* Prohibiting littering in the park (currently carrying out all rubbish).
* Recommendation: Ensuring and monitoring safe and adequate rubbish deposits and removal around parks.

* Limiting the minimum age of eligibility to visit gorillas (currently 15 years). The health rationale of an age limit is to prevent the transmission of "childhood" diseases to gorillas. It is widely admitted that the majority of childhood disease episodes occur before puberty.
* Recommendation: Maintain the age limit of 15.

* Prohibiting access to people who are ill (currently required to self report). The greatest challenge to this rule is ist limitation in scope and enforcement. Infected people can shed viruses or bacteria before and after the appearance of symptoms and this rule does not address the situation of sick guides, trackers or rangers. Tourists may lack the motivation to self-report and guides may not be qualified to judge whether or not a tourist is ill.
* Recommendation: Immunisation of tourists and park staff against specific diseases.

* Controlling smoking, eating, sneezing, and coughing in the presence of gorillas.
* Recommendation: Include spitting and nose-blowing.
Possible Additional Measures
To further reduce the risk of disease transmission, the following measures were recommended, among others:

• Wearing protective devices during hands-on interventions by park and veterinary staff;
• Hand and boot disinfection before and after gorilla viewing;
• Proof of immunisation against yellow fever, polio, tetanus, hepatitis A, measles and influenza as well as a clear TB status;
• Regular medical checks for park staff and researchers;
• Regular information and discussion sessions for guides, trackers and rangers on disease transmission;
• Sensitisation campaigns for surrounding park communities, tourists and tour operators.

Conclusions

Rules are only meant to limit the potential damage that tourism may cause. As long as tourism will be practised, rules will have to be in place, constantly revised and refined, and enforced as well as possible. Yet, the most powerful enforcement tool is motivation and self-control. No matter the level or sophistication of punitive or coercive schemes that are used or have been articulated, rules can – and will – always be broken. The best hope for minimising the damage from a tourism program resides in the widespread sensitisation, awareness and understanding of the catastrophic consequences of unconscious gorilla tourism. This is admittedly a medium, if not long-term, goal that requires careful planning and sustained efforts and certainly cannot be considered in isolation. Other immediate actions can and should be undertaken to limit the risks in the meantime.
Eventually however, it is not the rules, but the attitude of the human community towards its non-human environment that will decide of the fate of the gorillas, and indeed of many life forms on this planet, including our own. Therefore, awareness raising, albeit a long and strenuous process, is the only sure investment. It may not be a guarantee of success, but it undoubtedly is a vital ingredient in the balance of the many choices that will have to be made.

Summary of a report by Jaco Homsy (1999), with permission of IGCP (International Gorilla Conservation Programme)

The report is also available for download as PDF file.

Tourism overview

Homepage