This is a time of crisis in human health and naturally, our focus has been on human illness during the Covid-19 pandemic. There is speculation regarding the zoonotic origin of the virus from bats and possibly pangolins or racoon dogs in wild food markets in China. However, we are warned about another possible tragic outcome of this scenario by primate scientists and conservationists: a reverse zoonotic (anthroponotic) transfer of COVID-19 to the already endangered great apes.
Great ape populations exist in Asia and Africa: Gorillas, Chimpanzees and Bonobos in Africa and Orangutans in Sumatra and Borneo. These primates share a significant proportion of their DNA with humans; they are our closest living relatives.
As such they are susceptible to many human diseases. There have been reported lethal outbreaks of respiratory disease in wild habituated apes in the past: Human Respiratory Syncytial Virus and Rhinovirus C being 2 commonly implicated pathogens.
Our closest living relatives are at risk to many of our diseases.
In humans, these cause common colds, croup and bronchiolitis. An outbreak of Human Rhinovirus C killed 5 of 40 infected chimpanzees in Kibale National Park Uganda in 2013, and human respiratory viruses are thought to be the leading cause of mortality in the chimpanzee populations of Kibale and Gombe Stream National Park (1). In mountain Gorillas, respiratory infections are responsible for 20% of sudden deaths.
Great apes are also susceptible to similar zoonoses as humans; in 2006 it was reported that half of the Central African population of Gorillas was lost to Ebola, a virus whose natural host is bats, but is seen in a range of animals and has high fatality rates in humans and apes (2).
The populations of all the great apes are threatened by loss of forest habitats through illegal logging, deforestation for large scale agriculture and other development. Poaching and the effect of local civil wars have also had negative effects. All are classified as at least endangered by the IUCN.
The law of the jungle #keepwildlifewild
The awareness of anthroponosis is one of the reasons why, in regions of wildlife tourism, there have been rules developed to mitigate against disaster. Where human habituation of wild ape populations occurs it is mandatory to maintain a significant distance from the animals, to not enter their territory if you are sick, and not leave food or rubbish in the forest.
So naturally, with the outbreak of COVID-19 (SARSCov-2) there was some serious concern regarding the susceptibility of the great apes to this coronavirus.
In 2016 a study of a respiratory outbreak of chimpanzees in Cote d’Ivoire confirmed for the first time, the transfer of a human coronavirus infection to these apes (3). The HVC_OC43 infection was thought to arise from asymptomatic researchers visiting and studying the chimpanzee population, although poachers could have been implicated. This virus causes, like most human coronaviruses a mild cold-like illness. Similar mild symptoms were seen among the chimpanzees with sneezing and coughing.
Most human Coronavirus infections are in fact mild illnesses, but the advent of novel zoonotic infections such as SARS, MERS and now COVID-19 has changed our perception of these.
The COVID-19 virus enters human pulmonary cells via the ACE2 receptor, a receptor which is identical in great apes. Pathologically, the virus is likely to be as infectious as in humans and of course, habituated apes will not demonstrate any form of social distancing.
Humans, Great Apes and Social Distancing
Some apes are by nature very social in the wild, others such as orangutans less so. Either way, the vector to these populations would be human transfer and so measures are being put in place to protect the remaining populations.
A study from Bwindi Impenetrable National Park in Uganda in 2017 found that more than 98% of the observed tourist groups violated a rule to stay 7 meters from the gorillas, and that sick tourist tried to hide their illnesses (1).
Where Intrepid Medical Conferences visits for trekking in Sumatra, the team at Green Hill Bukit Lawang are always campaigning for tourists to #keepwildlifewild, desist from getting too close to the apes such as taking selfies with Orangutans and to observe the rules of the park.
Gunung Leuser National Park is the last stronghold of the Sumatran Orangutan. The total Sumatran population is thought to be around 13,000 and is falling.
Local Tourism and the Great Apes: A double-edged sword
In Sumatra, the latest communication suggests that Gunung Leuser National Park has been closed for overnight trekking. Many of the tourist providers are not offering any trekking, and the standard rules of the park require all people to be accompanied by a guide.
Half a world away in Africa in response to the threat, governments have closed access by tourists to all gorilla and chimpanzee sites. Researchers are still allowed but require a 14 day quarantine period before entering the region, then wear facemasks, change clothing and get temperature checked before entering the forests.
Obviously the closures to tourism are a 2 edged sword. The short term protection of the apes from a devastating viral epidemic is key, but of course, responsible eco-tourism supports and educates the forest edge people in preserving the ecosystem.
Without tourism, these people will need to look for alternative income sources. The temptation for illegal logging, poaching and expanding agriculture into the jungle fringe would be a natural progression for these impoverished communities. Increasing the long term threat to the ape populations.
Back in Sumatra, local businesses are looking at alternative ways to support the operators through this period. Green Hill Guest House in Bukit Lawang has offered “Virtual Treks” whereby donation people get some exclusive images from jungle patrols in the region, a digital certificate, and the knowledge they have supported either a jungle patrol by the local guides or purchased an educational pack for the local youth for their nature club.
The nature club is an educational resource which provides appreciation and ownership of the local ecology among the children of the region. Initiatives such as these and their support will be vital in the protection of these endangered animals.
2. Ebola Outbreak Killed 5000 Gorillas
Magdalena Bermejo et al Science 08 Dec 2006:Vol. 314, Issue 5805, pp. 1564 DOI: 10.1126/science.113310
3. Livia V. Patrono et al (2018) Human coronavirus OC43 outbreak in wild chimpanzees, Côte d´Ivoire, 2016, Emerging Microbes & Infections, 7:1, 1-4, DOI: 10.1038/s41426-018-0121-2