Piroplasmosis in a Grey Wolf (Canis lupus) Population in Croatia

Introduction: Infection with Babesia canis is common in Croatian dogs suffering from haemolytic anaemia, but also in asymptomatic dogs. Captive wolves can develop babesiosis as well, while the role of free-ranging wolves in the piroplasms life cycle and impact on their health status hasn’t been investigated. Materials and Methods: Blood or different organ samples from one live-trapped wolf and 108 carcasses were screened for presence of Babesia/Theileria DNA. Wolf W1 was captured for movement monitoring, blood-sampled and traced for one year. Wolf W2 was euthanized after car collision. Samples from W2 were submitted for haematology, biochemistry and pathology. Results: Theileria sp. closely related to T. capreoli was confirmed in 13.8%, while B. canis was found in 5.5% of animals, which presents the first report of these pathogens in free- ranging grey wolves. Haematological and biochemical findings in W1 and W2 were within reference values although merozoites were present in 0.03% and 0.09% of erythrocytes, respectively. Majority of necropsied wolves were autolytic, but no signs of hepatosplenomegaly, jaundice, anaemia, pigmenturia or DIC were found. In W2 tissue analysis revealed discrete spleen histocytosis and merozoites within erythrocytes in brain and myocardium capillaries, without other signs specific for babesiosis. Conclusions: B. canis and Theileria sp. maintain sylvatic cycle within wolf population in Croatia. Wolves, although closely related to dogs, don’t develop disease and probably serve as asymptomatic carriers. Free-ranging wolf pups most likely have developed mechanisms for piroplasm clearance like foals infected with B. caballi in which maternal antibodies aid in protective immunity development.