By Matt WalkerEditor, BBC Nature
In a bid to save wild apes from extinction, people may be unwittingly infecting them with potentially deadly diseases, new research shows.
Humans and great apes are closely related, creating the potential for diseases to jump between them.
Isolated incidents have been documented of apes and monkeys contracting measles, pneumonia, and influenza from people, as well as a range of other bacteria, viruses and parasites.
But the problem may be greater than even that, as highlighted by five recently published academic studies.
The close contact between animals and humans in research centres and sanctuaries is facilitating the spread of pathogens to apes, say scientists.
A newly published study by researchers in Japan examined blood serum from 14 captive chimpanzees in Japanese primate research institutes.
Takanori Kooriyama of the Rakuno Gakuen University in Ebetsu, and colleagues across Japan, tested for antibodies against 62 human pathogens.
The chimps had antibodies against 29 of these pathogens, showing they had been exposed to them.
"Captive chimpanzees are highly susceptible to human pathogens," the researchers write in the journal Primates.
Bad bugs
Earlier this month, Frieder Schaumberg of the Institute of Medical Microbiology in Munster, Germany, and colleagues in Germany, the US and Uganda, published a revealing study in the American Journal of Primatology.
They found a high prevalence of drug-resistant Staphylococcus aureusbacteria in sanctuary chimpanzees in Zambia and Uganda.
Helping hand or health risk?
These bacteria were likely passed to the apes by the veterinarians and staff caring for them.
The bugs are difficult to eradicate and can cause skin and tissue infections as well as severe bouts of pneumonia and septicaemia.
The study shows specifically that human pathogens can be passed to apes that are destined for release in the wild.
Researchers say that plans to reintroduce apes into the wild need to be re-evaluated to prevent drug-resistant diseases being spread through populations of rare animals.
Knowing the risks
Steve Unwin of the Animal Health Centre at Chester Zoo, UK and colleagues in the UK and US, agree that the development is "worrying".
But in the same issue of the journal, they argue that it is too soon to consider stopping reintroductions.
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Past ills
- Humans, possibly ecotourists, are thought to have passed the skin disease scabies and intestinal worms to gorillas living in Biwindi National Park, Uganda
- Human metapneumovirus is suspected to have killed mountain gorillas in Rwanda, and been responsible for chimpanzee die offs in Tai National Park in Cote D'Ivoire.
The problem has been known for a while, they say, and the International Union for the Conservation of Nature (IUCN) has developed a set of guidelines governing the release of animals and rare species back into the wild.
These guidelines recommend screening animals for health issues prior to their release and potentially placing them in quarantine.
By testing for human-borne diseases, and preventing the release of infected animals, the problem may be averted, they say.
Two researchers, Charles Nunn of Harvard University, Massachusetts, US and Brian Hare of Duke University, North Carolina, US, who are experts in the evolutionary biology of humans and other apes, also comment in the same journal.
They recommend a number of areas for future research.
For example, to better understand the risks, we need to know more about how antibiotic-strains of bacteria spread between individual apes, and whether they actually cause any greater sickness or death in these animals.
It may be that other pathogens we are unaware of can spread between humans and apes too. And young animals are more prone to infection, as they spend more time in physical contact with sanctuary workers.
Scratched and bitten
Solving the problem is difficult, in part because passing diseases to primates is a practical as well as an ethical issue.
As Prof Nunn and Prof Hare point out in their paper, the release of apes back into the wild remains an art form.
Sanctuary managers face a range of political, time and financial pressures that limit their ability to take in new apes, care for them, and then release them.
Between 2000 and 2006, for example, the chimp population living at Pan African Sanctuary Alliance sanctuaries grew 15% a year, driven by the adoption of an average of 56 new apes each year - animals that had been orphaned by the bushmeat trade.
Reintroducing these animals is important, argue Unwin and colleagues.
Not only does it help rehabilitate the lives of individual apes, and boost numbers of rare species in the wild, but the process can help educate local people about the importance of conservation.
Diseases can spread of course from primates to people: the group of HIV viruses that cause AIDS has jumped from monkeys and chimpanzees into people, seeding a global human health crisis. Ebola meanwhile is harboured by gorillas.
A study published late last year by George Engel and Lisa-Jones Engel of the University of Washington, Seattle, US, in the American Journal of Primatology, presented the results of a survey of 116 primatologists who had worked closely with non-human primate species.
Of those surveyed, almost 60% said they had been scratched by a primate and 40% had been bitten, highlighting the risk of disease transmission.
But our ability to pass novel diseases back into ape and monkey species is less well known.
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Monkey malaise
- A study presented at the 35th Meeting of the American Society of Primatologists in Sacremento, California, US in June, showed that macaques had antibodies to both human and avian influenza viruses in areas where high densities of people live.
- That reveals the macaques had been exposed to the viruses and may be susceptible to them.
- Drs Engle and Engle sampled blood serum from more than 200 macaques at sites in Singapore, Bangladesh, Gibraltar, Cambodia and Indonesia.
Wild apes are also exposed to human pathogens through a number of different routes, including when apes raid crops, when tourists encounter apes in their natural habitat and when workers go into forests to exploit resources, such as mining, logging and the hunting of bushmeat.
At the heart of the issue is a painful dilemma. Contact between humans and apes often occurs because conservationists and researchers have to get close to the apes to save them.
Scientists themselves can pass diseases to the apes they study.
In recent years, primatologists have debated the extent to which they might be threatening the wild apes they research, and what to do about it.
Many research groups now wear face masks when close to their subjects, to avoid transmitting airborne diseases.
Disinfecting boots before heading into the forest, and observing apes from predetermined safe distances, are other safeguards, ones that many feel ecotourists should also follow.
For many primatologists, it seems, they are damned if they do and damned if they don't.
Populations of great apes; gorilla, chimp and orang-utan species, and the small apes, or gibbons, are dwindling around the world, and everything possible must be done to save them, they say.
Researchers must study the animals in the wild to understand them, and find better ways to protect them.
The benefits of such research far outweighs the costs, many experts argue.
As well as providing valuable information about the size and behaviour of great ape populations, the presence of researchers can deter poachers, encourage politicians to take an interest in primate conservation and directly save or protect the lives of many rare apes.
Sanctuaries take in apes as a last resort, and their reintroduction is considered to be an important conservation tool.
However, as the latest research shows, the difficult part is finding ways to save these closest relatives of ours, without unwittingly harming them in the process.
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