When the polar bears started dying, nobody suspected the zebras.
Jerka was the first. The 20-year-old polar bear was born in captivity, and had lived in Germany’s Wuppertal Zoo since the age of two. In the summer of 2010, she started suffering from epileptic seizures and eight days later, on the 16th of June, she finally passed away. Lars, a male bear who lived in the same enclosure, also became seriously ill. He was hooked up to an IV drip and treated with anti-seizure medicine. It took several weeks, but he eventually made a full recovery.
When the zookeepers dissected Jerka’s body, they found signs of inflammation in her brain. The pattern of damage pointed to a viral infection, but no one knew which virus was responsible. A team of scientists led by Alex Greenwood from the Leibniz-Institute for Zoo and Wildlife Research searched Jerka’s brain tissue for the genetic material of many possible viruses, from rabies to canine distemper virus. They found only one hit, and it looked a lot like EHV1 – a virus that infects horses.