Humans are increasingly passing pathogens to animal populations

Humans are increasingly passing pathogens to animal populations

Nature reports:

There was something wrong with the chimpanzees. For weeks, a community of 205 animals in Uganda’s Kibale National Park had been coughing, sneezing and looking generally miserable. But no one could say for sure what ailed them, even as the animals began to die.

Necropsies can help to identify a cause of death, but normally, the bodies of chimps that succumb to disease are found long after decomposition has set in, if at all. So when Tony Goldberg, a US wildlife epidemiologist visiting Kibale, got word that an adult female named Stella had been found freshly dead, Goldberg knew this was a rare opportunity to look for an answer.

Goldberg and two Ugandan veterinary colleagues drove for two hours to a remote part of the park, then lugged their gear for another hour by foot through the hilly, forested terrain to where Stella’s body lay in the underbrush. They lifted the 45-kilogram animal onto a tarpaulin, and got to work. As they crouched over the chimp, sweat pooled beneath their full-body protective suits and their goggles fogged in the humid air. They meticulously worked their way through Stella’s organ systems, collecting samples and recording data on visible pathology. Not knowing what had killed her was “unnerving”, Goldberg recalls. “It could have been Ebola.”

As the necropsy progressed, however, Goldberg began to see telltale signs of a familiar disease: fluid build-up in Stella’s chest cavity and around her heart. Lung tissue that was dark red, consolidated and marked with lesions. It looked, in other words, like the chimp had died of severe pneumonia.

Months later, molecular testing revealed the culprit behind the outbreak: human metapneumovirus, which causes run-of-the-mill respiratory infections in people but is “a well-known killer” in our closest primate relatives, says Goldberg, a researcher at the University of Wisconsin–Madison. More than 12% of the community that Stella belonged to ended up dying in the outbreak, which occurred in 2017. More animals were indirectly lost as a result of being orphaned. “Stella had a baby that was clinging to her body for a while after she died,” Goldberg says. “The baby subsequently died.”

This phenomenon of animals catching diseases from humans, called reverse zoonoses, affects species around the world — from mussels contaminated with hepatitis A virus and cheetahs that come down with influenza A, to the parasite Giardia duodenalis passed on to African painted dogs (Lycaon pictus) and tuberculosis transmitted to Asian elephants. But because of their evolutionary closeness to humans, great apes tend to be most vulnerable to our diseases. “We share over 98% of our genetic material with gorillas and chimpanzees, so we can easily make them sick,” says Gladys Kalema-Zikusoka, a wildlife veterinarian and founder of Conservation Through Public Health, a non-profit group in Entebbe, Uganda, dedicated to promoting the coexistence of people and animals. [Continue reading…]

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