Horrific scenes of the stricken great apes slumped on the forest floor coughing and sneezing have been witnessed by researchers studying the effects of human diseases on our closest primate relatives. A chimpanzee community suffered a 44 percent hit rate from a respiratory illness believed to be of human origin. One baby chimp cried for hours clinging to its dead mother after she fell victim to a flu-like virus.
Two years ago reports emerged of chimpanzees in Uganda dying from a human “common cold” virus and now a new study has identified two other respiratory viruses hitting the apes living in the same forest.
Professor Tony Goldberg, an expert on emerging pathogens in animals at the University of Wisconsin-Madison’s school of veterinary medicine, led the team looking at two simultaneous outbreaks of respiratory illness in the chimpanzees, one of which proved fatal. The team’s research was published this week in the journal, Emerging Microbes and Infections.
One group of 205 chimps known as the Ngogo community living in Uganda’s Kibale National Park saw almost half the animals affected, with 25 dying. The other 55-strong group, known as the Kanyawara community, witnessed a 69 percent infection rate but no fatalities.
By being able to recover chimpanzee bodies for post mortems, the veterinary experts were able to gather key evidence.
While genetic material gathered from the Ngogo chimps revealed infection by metapneumovirus, the teams also collected evidence of parainfluenza virus 3 in the the Kanyawara group.
Parainfluenza virus 3 is a common cause of croup in pre-school children. In people, metapneumovirus (MPV) is a common cause of “wheezing illnesses” in infants, explained James Gern, co-author of the new study and professor of allergy and immunology in the UW School of Medicine and Public Health as well as an authority on human respiratory viruses.
He explained: “Mortality rates for MPV are very low in humans, so the chimps clearly had more severe illnesses than what is observed in humans. The parainfluenza virus 3 illnesses in chimps, while not associated with mortality, were on average more severe than what would generally be observed in humans.
“It is also remarkable that the majority of the chimp population was affected, suggesting that there was no pre-existing immunity and that this virus was newly introduced, perhaps from a human source.”
For the reseach team, there was also the awful spectre of watching the chimpanzees suffering. One infant chimp cried for hours clinging to its mother’s body before wandering off to find the rest of the group.
Professor Goldberg said: “It’s a horrible thing to see. It’s heart-breaking to watch these animals suffer, not only from the disease but also from grief over the loss of members of their society.
“These are very common human viruses that circulate worldwide and cause ‘the sniffles’ in kids. In people, they are no big deal unless the patient has asthma or another underlying condition.
“The chimps cough and sneeze and lie on the forest floor looking miserable. And they lose a lot of weight.”
It was a team led by Professor Goldberg which was the first to identify a human cold virus – rhinovirus 3 – killing Ugandan chimpanzees six years ago. He believes a human origin responsible for the latest outbreaks.
Government authorities and conservation organisations are working to avoid infections, introducing quarantine periods for people entering the forest, using face masks and sanitisers and imposing strict rules on the distance tourists must keep from the apes.
Professor Goldberg continued. “The viruses responsible this time aren’t even remotely related to rhinoviruses.
“So, it seems like a plethora of common and mostly benign respiratory viruses of people can be transmitted to chimps in this part of the world, causing disease and sometimes death.
“It could happen in any number of ways. Local villagers, researchers, tourists, and many other people visit forests where apes live. All it takes is one person unwittingly carrying a ‘common cold’ virus to spark a deadly outbreak in apes.
“The more we can learn about these outbreaks, the better prepared we will be to prevent them and to protect the health of apes.”