Presentations

Tularemia is an infectious disease, caused by Francisella tularensis. This bacterium has a broad host range, including vertebrate and invertebrate species, and even humans (zoonosis). The European brown hare (Lepus europaeus) plays an important role in the ecology of tularemia, and may serve as a significant source of human infection.

In the present study we examine the lesions induced by F. tularensis in 50 cases of naturally infected, seropositive European brown hares (screened by slide agglutination test) from different areas of Hungary. Macroscopic, microscopic, and immunohistochemical examinations were used to describe the lesions, and isolation and identification of the bacteria were carried out as well.

Numerous, grayish-white foci with a diameter of 0.1-1 cm in single (24 cases) or multiple organs (20 cases) in a total of 44/50 (88%) cases were found with gross pathological examination. These foci proved to be areas of granulomatous inflammation, and necrosis was often observed in the centre of these lesions, with microscopic examination. Histological lesions and F. tularensis antigen (by immunhistochemical assay) was detected in a total of 46/50 (92%) cases. F. tularensis ssp. holarctica was isolated by culture and identified by polymerase chain reaction from 35/50 cases (70%).

Infection by the respiratory route is suggested by the presence of the tissue lesions in thoracic organs (lung, pericardium, mediastinal lymph node) of 44/50 (88%) cases. The immunohistochemical assay for the diagnosis of F. tularensis infection was found to be more sensitive and had a similar specificity as bacterial culture. The combination of slide agglutination test and detection of gross pathological lesions has proved to be a very sensitive tool for preliminary diagnosis of tularemia.