Exotic animals in Germany’s Wuppertal Zoo aren’t just sharing smiles and admiration from visitors. They are sharing deadly viruses, too.
When the zoo’s polar bears began dying and coming down with fevers that sent them spiraling into near-death seizures in 2010, the zookeepers didn’t know what to make of it. One dissection revealed that a female polar bear named Jerka suffered from brain inflammation before she died, pointing to a possible viral culprit. The zookeepers sent the brain samples to a team of scientists who began poking around for viral traces.
In one sample, they got a hit. They found traces of EHV1, a virus that normally infects horses. Ed Yong of Not Exactly Rocket Science describes this microscopic culprit:
EHV1, or equine abortion virus, is a herpesvirus that’s related to the ones that cause herpes and chickenpox in humans. It affects the lungs, airways and brains of horses and donkeys, and it’s widespread among zoo zebras. Greenwood thinks that the virus probably jumped into Jerka from Wuppertal’s zebras, but it’s not clear how this happened since the zebras live 68 metres away from the bears and never came into direct contact. Maybe the zookeepers ferried the virus between them, or perhaps rodents did by sneaking in and out of the two enclosures.
The virus that killed Jerka wasn’t a pure strain of EHV1. One of its genes contained DNA from a close relative called EHV9. It’s what is known as a “recombinant virus”. At some point, EHV1 and EHV9 infected the same zebra and fused to form a hybrid virus that went on to infect both Jerka and Lars.
EHV1 has wreaked havoc in the past on other zoos, too, taking down black bears, Thomson’s gazelles, guinea pigs and other species it came into contact with. To make things even more difficult virus is often cryptic; another polar bear who died of kidney failure turned out to carry EHV1 in his bloodstream.
Unfortunately, zoo keepers and scientists have no idea how common EHV1 is in their animals, or when the next recombination event might create a deadly pathogen. Bringing together so many different animals from all corners of the earth creates a melting pot of disease potential for an entrepreneurial virus looking to conquer a new host.
As one of the scientists working the case told the BBC, “The visitors to the zoo want to see as many different animals from different places as possible, which is good but there has to be control. Knowledge is the best weapon.”
Whether knowledge is enough to save the polar bears and other animals, however, is yet to be seen.
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