The presence of malignant ovine babesiosis in Bosnia and Herzegovina indicates a possible emerging risk for Balkan region.

Malignant ovine babesiosis or ovine babesiosis caused by Babesia ovis is an important hemoprotozoan tick-borne disease of sheep. After 70 years, a study was conducted in Bosnia and Herzegovina, in the geographical areas of Podrinje and Eastern Herzegovina, aiming to molecularly identify and determine the presence of B. ovis infection in the sheep population. From 2019-2021, a clinical and molecular study was conducted in 53 flocks, and 192 sheep were examined, divided into two groups: clinically suspected and asymptomatic sheep. The presence of B. ovis was confirmed by PCR in blood samples of 75 % and 11.21 % of clinically affected and asymptomatic sheep, respectively. The majority of clinical cases of malignant ovine babesiosis were confirmed in the Rudo epidemiological unit (78.78 %) within the Podrinje region indicating typical seasonal pattern of disease occurrence and endemic focus. Rhipicephalus bursa was only tick species identified in Podrinje and Eastern Herzegovina. Acute form of disease was observed with dominant clinical signs of depression, fever, loss of appetite and respiratory distress. Fatal outcome was recorded in 12.28 % of cases. This study describes the molecular detection of B. ovis in sheep in Bosnia and Herzegovina for the first time. To the authors knowledge, this survey represents a report of the highest number of clinical cases of malignant ovine babesiosis in Europe. Since the disease has been recorded in the south-eastern border of Bosnia and Herzegovina, there is a high risk of disease transmission to a wider area of the Balkan region.