Seroprevalence of antibotulinum neurotoxin type C antibodies in horses in Israel

Reasons for performing study: Clostridium botulinum type C is prevalent in Israel and outbreaks recorded in many species, other than horses. Association between levels of anti-BoNT/C antibodies and equine grass sickness (EGS) have been demonstrated but seroprevalence of anti-BoNT/C antibodies in horses has not been reported nor has EGS been reported in Israel. Objectives: To determine the seroprevalence of specific anti-BoNT/C antibodies in horses in Israel and to determine whether age, breed and gender, or geographical region of farms are potential risk factors for exposure to BoNT/C. Hypothesis: Anti-BoNT/C antibodies are prevalent among horses in Israel and farm and horse-level variables are associated with increased risk for exposure. Methods: Serum samples from 198 horses were collected and the levels of specific anti-BoNT/C antibodies were determined using enzyme-linked immunosorbent assay (ELISA). For each categorical variable indicator variables were created and the odds ratio (OR) and 95% confidence intervals (95% CI) for the outcome variable were calculated using a univariable and multivariable logistic regression models. Results: A total of 61 (30.8%) horses were ELISA positive for anti-BoNT/C IgG antibodies. The farm and its geographical region were associated significantly with seropositivity, horse-level variables, such as gender and breed, were also associated with seropositivity. Quarter Horse and Warmblood mares placed in the southern region of Israel had the highest odds to be tested positive for anti-BoNT/C IgG antibodies. Conclusions and potential relevance: Several farm and various horse-level risk factors for exposure to BoNT/C, found in this study, could be correlated to previously reported risk factors of EGS. Studies are required to determine the predisposing factors that cause EGS, which is apparently not present in Israel.