A serological survey of antibodies against Francisella tularensis in some Swedish mammals.

Tularemia occurs in Sweden as an epizootic among the mountain hare. Little is known about the occurrence of the disease in other animals in this country. For this reason serum samples from 28 cattle, 83 moose, 110 beavers and 97 mountain hares were investigated for the presence of antibodies against Francisella tularensis. The antibody levels against F. tularensis found in moose and cattle were generally low and also in a low incidence. This indicates that these species are not susceptible to tularemia and not involved in the epizootiology of this disease. Beaver titres were found to vary from 1:20 to 1:1 000. Twenty-one % of the investigated sera showed titres higher than 1:100. This indicates that infections are common in the species and that the Scandinavian beaver plays an important role in the epizootiology of tularemia. It could well act as a reservoir for the disease. Ninety-six of the 97 tested sera from the mountain hare were negative. In one serum was a titer of 1:20 seen. This low titer was regarded as non-specific. The absence of titers against F. tularensis in this species could be explained by the high susceptibility to this disease. This indicates that the mountain hare is not a reservoir for tularemia in Sweden. It is one of the most susceptible and the dominating species involved in tularemia epizootics, but it is not the normal reservoir for F. tularensis.