Alveolar echinococcosis in non-human primates
The fox tapeworm (Echinococcus (E.) multilocularis), widespread in Central Europe, is the agent of alveolar echinococcosis, a dangerous zoonosis. Main final host of this tapeworm measuring 2 to 4 mm is the fox. In general, intermediate hosts get infected by oral intake of eggs, which are shed by the fox with the feces. After ingestion, the larvae nearly always invades the liver of their intermediate hosts, where the larvae develop by infiltrative growth. The budding germ epithelium permeates the liver tissue leading to massive alterations. This inflammatory process, which resembles a tumor, may result in hepatomegaly, cholestasis, jaundice, cirrhosis, portal hypertension, and the Budd-Chiari-syndrome. Aberrant intermediate hosts include humans and non-human primates.
The clinical course of alveolar echinococcosis in non-human primates is highly variable. After oral intake of eggs of the small fox tapeworm, the human liver gets infected. However, this infection mostly remains subclinical for many years. The course of disease in non-human primates is considerably shorter. The larvae proliferate in the liver tissue, and an alveolar mass develops within a short time period after infection.
For years, clinical cases of echinococcosis have been regularly diagnosed in the animal population of the German Primate Center. In the last years, 25 animals died and presented the characteristic disease pattern at necropsy. Apart from lion-tailed macaques and rhesus monkeys, cynomolgus monkeys are most commonly affected. It was not possible to significantly diminish the fox population by prophylactic measures, as e. g. intense population control using live traps, approved by the authorities, since other animals follow on from the forested environments of the German Primate Center. Therefore, the deworming of foxes is currently practiced by appropriate baiting. A very effective prophylactic measure is the vaccination of the intermediate and aberrant intermediate hosts. A vaccination of primates is currently under development.