Hellabrunn Zoo forced to euthanize six drills due to severe illness

Hellabrunn Zoo was forced to euthanize six drills due to an incurable illness.

This decision, taken with a heavy heart by the veterinary team, was unavoidable due to animal welfare reasons. The rest of the group is medically unremarkable and is being closely monitored. Other primates at the zoo are not affected and there is no danger to visitors. Tuesday, 29 November, was a sad day for Hellabrunn Zoo. A detailed health check of all twelve drills revealed that six of the rare primates had such severe organ lesions, especially in the liver and lungs, but also in some other organs, that they had to be euthanized. These lesions are considered to be the result of a fox tapeworm infection. This diagnosis was initially made on the basis of a pathological examination of two seriously ill animals. However, the rapid course and severity of the disease took the vets and zookeepers by surprise. The rest of the group, four male and two female drills, are currently unremarkable. They are undergoing regularly checks and the zookeepers are keeping a close eye on them.

No approved vaccine against the parasite in the EU

Transmission of the fox tapeworm pathogen is not possible either from primate to primate, human to primate or primate to human. Intensive investigations are currently being carried out into how and when the animals could have been infected with the pathogen. A network of experts from test laboratories, the university and other research institutions are involved in the investigation. Their priority is to prevent further infections. At present, there is no approved vaccine against fox tapeworm available in the EU. The vaccines developed to date are experimental and have not been approved for zoos in EU countries.

"All of us, but especially the vets and zookeepers, were hit hard by the outcome of the investigation," said zoo director Rasem Baban. “As is sadly often the case with wild animals, our drills appear to have hidden their serious illness. We are currently working flat out to determine how the pathogen was transmitted to the drills. We are also discussing how to move forward with all the zookeepers regarding hygiene measures and prophylactic checks. This loss is particularly difficult for Hellabrunn, especially as we are responsible for coordinating the conservation breeding programme for this highly endangered species. After consultation with the vets, the decision to euthanize the animals affected was unavoidable in the interest of animal welfare, as the disease would have been fatal for them within a few weeks."

Fox tapeworm (Echinococcus multilocularis) in Central Europe

The pathogen is widespread in Germany, Austria, Switzerland, France and northern Italy. The eggs are microscopic and extremely resistant to cold temperatures. Transmission to susceptible animal species occurs through the consumption of food contaminated with fox tapeworm eggs. The intermediate hosts are voles in whose internal organs the larvae grow and reproduce. The latter are ingested by foxes when they eat the infected animals. The parasitic infestation manifests itself in animals as a tumour-like growth in the liver. In advanced stages, the affected organs hardly have any normal tissue left, which ultimately leads to the death of the infected animals.

Humans can also become infected by ingesting fox tapeworm eggs found in fox or dog faeces. Early detection of the infection is therefore very important.

Recommended prevention measures are:

1. Wash your hands thoroughly after collecting wild berries or mushrooms
2. Do not consume foraged fruits or mushrooms without preparing them
3. Wash fruits and mushrooms thoroughly to remove any eggs attached and then boil the berries or sear the mushrooms
4. Deworm your pets regularly