1 in 3 gorillas killed by Ebola over last 20 years

mountain gorilla (credit: d_proffer)

It’s easy to believe that humans pose the greatest threat to wildlife and endangered species. Poaching, bushmeat, habitat loss are all threats to rare animals. But there’s also natural threats that can devastate a species. A new study about diseases in primates show that over the last 20 years 1 in 3 gorillas have been killed by the Ebola virus.

The study published this month in PLoS ONE considered whether intervention should be undertaken to tackle infectious diseases in great apes. For conservationists it’s a difficult ethical dilemma. Should humans interfere with natural forces and treat or vaccinate wild apes against disease or should the animals fend for themselves even if it risks the extinction of the population or species.

perhaps the time has come for routine vaccinations of the most endangered apes that are at greatest risk

A third of gorillas killed by Ebola virus.

According to the study over the last 20 years a third of the world’s population of gorillas have been killed by the Zaire strain of Ebola virus and almost the same proportion of chimpanzees have also died. this can have a major impact on a population of endangered apes.

Recovery time for an outbreak in an ape population can be as little as 5 years for a minor infectious disease outbreak – where 4% of the population die – to as much as 131 years in a major outbreak killing up to 96% of the population.

The risk of a large outbreak of disease among gorillas is increasing as human population around the gorilla reserves increase and as more ecotours take adventurous travellers on gorilla viewing trips.

Recent studies show non-virulent diseases in apes impacts survival of populations.

New studies are also showing that disease once thought harmless to ape populations can have a major impact on the survival of the population. Simian immunodeficiency virus (SIV) had until recently been considered to be fairly benign in chimpanzees. Recent studies show though that chimpanzees infected with SIM have annual death rates 10 times higher than non-infected populations and birth rates that are just a third of non-infected individuals.

Is intervening in natural systems right?

Intervening in treatment and vaccination of wild apes to protect them from disease is certainly an ethical argument to have. But on a practical level there may be no argument to be had. Apes are now restricted to such a small area compared to their historic range that human intervention is needed to ensure a viable and healthy population.

Eco tourists also need to lay their part in ensuring that gorillas and other great apes do not fall victim to diseases that they are carrying. It’s important to follow the rules that are laid down and not try and get closer to the apes as allowed. Wildlife watchers also need to ensure that they wear whatever masks and clothing is required no matter how uncomfortable it may be.

No matter how many bio-security processes are put in place though eventually outbreaks will occur. Treatment is one way to ensure that an entire population will not be lost. But, as the saying goes, prevention is far better than cure.

Is it time for routine vaccination of apes to reduce infectious disease?

It may now also be necessary to look at widespread vaccination of apes in order to cut the incidence of disease. Widespread vaccination has occurred on a couple of occasions – eg. the inoculation of chimpanzees in Tanzania to combat polio – perhaps the time has come for routine vaccinations of the most endangered apes that are at greatest risk.