A virus that normally only infects humans has caused the deaths of wild mountain gorillas in Africa, reported a team of researchers from the U.S. and several African countries.
The researchers are from the UC Davis nonprofit Mountain Gorilla Veterinary Project, the UC Davis Wildlife Health Center, the Center for Infection and Immunity (CII) at Columbia University and the Rwanda Development Board.
The virus, called human metapneumovirus (HMPV), causes mild respiratory tract infection in humans. In 2008 and 2009, a group of mountain gorillas living in Rwanda experienced an outbreak of respiratory disease that resulted in the deaths of a female gorilla and her infant.
“Diseases can flow from humans to animals and from animals to humans,” said Linda Lowenstine, a veterinary pathologist with the UC Davis Mountain Gorilla One Health Program. “The more closely related the species, the more likely they are to share diseases, including viral diseases.”
When Lowenstine looked at the tissues of the gorillas under the microscope, she found bacterial pneumonia that often occurs after a viral infection weakens the immune system. The infant showed signs of poor nutrition and umbilical infections, likely due to the mother feeling too ill to properly care for her young.
Lowenstine worked with collaborators in New York to detect and identify a virus in the gorillas. One of the collaborators was Gustavo Palacios, a virologist at the Center for Infection and Immunity at Columbia University in New York.
“One of the concerns at the start was to know if it was a new virus or if it was an unknown virus,” Palacios said.
Technician Nazir Sajvi and his colleagues from CII used a test called polymerase chain reaction (PCR), which amplified the available amount of gorillas’ DNA so that the molecular biologists could compare the unknown disease samples with known DNA sequences.
“We did phylogenetic analysis to identify the virus’s evolutionary history and quantified the viral load in all samples,” Sajvi said.
Palacios said the researchers found that the closest relative was to human cases of pneumonia in South Africa.
“[The virus] is not necessarily from there,” Palacios said, “but it is a close neighbor.”
Mountain gorillas are protected in national parks in Rwanda, Uganda and the Democratic Republic of Congo; however, according to the Mountain Gorilla Veterinary Project, the densest human populations in continental Africa surround them. Since gorillas share 98.5 percent of their DNA with humans, this could put them at risk for human-borne infectious diseases.
“Gorillas and other great apes … are susceptible to many human viruses, including chicken pox, measles and, as was demonstrated in the paper, HMPV,” Lowenstine said.
So far, researchers are unsure if HMPV infection in mountain gorillas is a recent species jump or if mountain gorillas have always been susceptible due to the genetic similarity.
“HMPV has been confirmed in chimpanzees, but how frequent this jump occurs is the question,” Palacios said. “If we explore other ecological niches like non-human primates, bats and rodents that have close contact with humans, we can try to predict what are the mechanisms that guide species jumps.”
Mountain gorillas are a severely endangered species with fewer than 800 individuals in the world. About 480 individuals live in an area called the Virunga Volcanoes Massif, which combines national parks in Rwanda, Uganda and the Democratic Republic of Congo. The rest of the individuals live inside the Bwindi Impenetrable National Park in Uganda.
Stricter rules for tourists visiting the mountain gorillas’ habitats are needed in order to protect the apes from infectious disease, Sajvi said.
“[Protective] masks are a must,” Sajvi said.
Though both the public and researchers pay a great deal of attention to the possibility of animal viruses infecting humans – such as the swine flu outbreak in 2009 – this study focused on human-to-ape transmission.
“One of the messages that we like to emphasize is that normally we only think of transmissions of species infections from other animals to humans,” Palacios said. “There is increasing research that it isn’t a one-way road but a two-way highway of transmission between species.”
AMY STEWART can be reached at email@example.com.