First molecular detection of Francisella tularensis and investigation of Coxiella burnetii in horse sera in Iran

Infections caused by <i>Francisella tularensis</i> and <i>Coxiella burnetii</i>, as zoonotic diseases, pose a serious threat to the health of humans and animals. To date, there is limited information regarding these diseases in horses. This study aimed to evaluate the prevalence of <i>F. tularensis</i> and <i>C. burnetii</i> in the serum of racehorses in Iran (Golestan province). 350 blood samples were collected from racehorses in four regions of Golestan province, and demographic data (sex, age, and sampling location) were recorded. The collected serum samples were examined by PCR to identify the genomes of <i>F. tularensis</i> and <i>C. burnetii</i>. The results showed that 3.4 % (P < 0.05, 95 % CI: 1.97 % - 5.9 %) of the serum samples were positive for <i>F. tularensis</i> genome, while no positive cases for <i>C. burnetii</i> genome were detected. Additionally, a significant relationship was observed between horse age and <i>F. tularensis</i> infection, with the highest prevalence (3.93 %) detected in animals younger than five years (P < 0.05, 95 % CI: 2.21 % - 6.9 %). Moreover, the study revealed a significant difference in <i>F. tularensis</i> prevalence between sexes, with infection rates of 5.84 % in stallions and 1.88 % in mares. Statistical analysis showed no significant difference between the regions studied and the prevalence of <i>F. tularensis</i>. According to our knowledge, this is the first report of tularemia prevalence in horses in Iran. This study indicates that horses can be considered a potential weak reservoir for <i>F. tularensis</i>.