Presence of Francisella tularensis in Apodemus spp. on the Edges of Forest Areas in Belgrade, Serbia.

Tularemia, a zoonosis caused by Francisella tularensis, is considered endemic to the Balkan Peninsula. The main reservoirs of this disease are rodents and lagomorphs, which usually show no clinical signs and are a potential disease source for other animals and humans. The presence of F. tularensis in the tissues of rodents in Serbia was examined for the first time. The animals were collected near walking tracks and places for recreation in forest areas in Belgrade. A total of 96 mice were collected in three forest locations in the autumn of 2023. Tissue samples of lungs, liver, spleen, and kidneys were taken by autopsy, and pool samples were made for all captured animals, that is, 71 striped field mice (SFM), 13 wood mice (WM), and 12 yellow-necked mice (YNM). The bacterium F. tularensis was detected by PCR, using primers that target the tul4 gene, which codes 17-kDa lipoprotein and amplifies the 400-bp product. Thirteen samples tested positive by PCR, seven of which were confirmed by sequencing to belong to F. tularensis. F. tularensis was detected in SFM animals collected from all investigated forest areas. Based on the observed results, we can conclude that F. tularensis is present in the tissues of SFM animals captured in Belgrade's forest areas.