Endoparasites of the European beaver (Castor fiber L. 1758) in north-eastern Poland

Parasitological examination after necropsies of 48 European beavers from Podlaskie and Warmisko-Mazurskie provinces were performed between April 2011 and November 2012. All helminthes were isolated from the contents of the gastro-intestinal tract and their species were determined. In addition, blood samples and faeces were examined. All beavers were infected with six species of parasites. Stichorchis subtriqetrus trematodes were found in 93.7% of animals. They were localized mainly in the caecum, less in the colon, and single juvenile parasites were found in the small intestine. The intensity of infection ranged from two to 893 parasites. Travassosius rufus nematodes (10-4336 specimens) were present in the stomach of 68.7% of the beavers. In the small intestine of four (8.3%) beavers, two-six specimens of Psilotrema castoris were found. This is the first record of this species in Poland and the third of its discovery in the world. Furthermore, in the small intestine of one beaver, two Trichostrongylus capricola nematodes were detected. In the liver of one beaver, pathological changes caused by hydatid cestode Echinococus granulosus occurred. Inflammatory changes of the gastric mucosa caused by Travassosius rufus and of caecum caused by Stichorchis subtriquertus, were observed. Coproscopy was performed with the use of Baermann, flotation, and decantation methods. All results of Baermann method were negative. Examinations with flotation and decantation methods confirmed necropsy findings. Using the flotation method, single oocysts of Eimeria sprehni in one beaver were detected. A blood test conducted by Kingston and Morton method did not reveal the presence of protozoa or microfilariae.