PSEUDOTUBERCULOSIS CAUSING DEATH IN A EUROPEAN BROWN HARE

An adult wild male hare was found lying in sternal recumbency and exhibiting labored breathing. The animal died shortly thereafter and was submitted for necropsy to the WHG necropsy service through the disease surveillance program of the Agency for Nature and Forests.

The hare was in poor body condition and had a heavy ectoparasite burden, including mites and ticks. Necropsy revealed multiple yellow-white, bulging nodular lesions in the lungs, kidneys, liver, and spleen. Cytological examination of these lesions showed a mixed inflammatory infiltrate with abundant colonies of small, basophilic rod-shaped bacteria.

Multiple bulging pyogranulomatous lesions observed throughout the lungs and liver (arrow).

Cytology of a hepatic pyogranuloma showing mixed inflammation and abundant numbers of small, basophilic bacteria.

Bacteriological examination of the liver, spleen, and spinal cord confirmed the presence of Yersinia pseudotuberculosis infection. Histopathological examination revealed a subacute, multinodular, necrotizing pyogranulomatous hepatitis, splenitis, and nephritis, with intralesional bacterial colonies present in all affected tissues.

Yersinia pseudotuberculosis is a zoonotic, Gram-negative bacterium belonging to the family Enterobacteriaceae. Transmission occurs primarily via the fecal–oral route, with wild rodents and birds serving as important reservoir hosts. The bacterium has a worldwide distribution and may cause subclinical enteric infections in wild and domestic animals, as well as abortions in livestock. It has also been associated with fatal outbreaks in captive zoo animals, for example non-human primates.

Pseudotuberculosis, the septicemic form of infection caused by Y. pseudotuberculosis, occurs mainly in rodents, lagomorphs, and captive birds. In the European brown hare (Lepus europaeus), outbreaks of pseudotuberculosis have been reported in several European countries, including Italy and Germany. Sudden death is a common clinical presentation of the disease.

As Y. pseudotuberculosis is a potential zoonotic pathogen, appropriate hygiene practices are recommended for people handling wild lagomorphs, such as wildlife caretakers and hunters. 

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