A serological survey on strangles disease in horses of some areas in Khuzestan province by ELISA

BACKGROUND: Strangles is caused by Streptococcus equi subspecies equi. The bacteria typically infect the upper respiratory system and lymph nodes of the head and neck in equidae. OBJECTIVES: The aim of this study was to evaluate the prevalence of strangles and association of this infection with host age and geographical determinants in horses in Khuzestan province. METHODS: Serum samples from 184 horses were randomly collected in Ahvaz, Shoushtar, Baghmalek, Shoush, Abadan, Ramhormoz and Dezfool cities and were examined by ELISA assay. Also, 85 swab samples were randomly taken from nasal swab of horse and evaluated for Streptococcus equi subspecies equi by bacterial culture. RESULTS: Seroprevalence rate of strangle was 37.5% (95% CI: 30.5-44.5%). Logistic regression showed that the odds of infection between the age based on year and disease was 1.1 (95% CI: 1.04-1.17) (p<0.001), and with increase of 1 year-old, odds of infection increase 10%. Relative frequency of infection in male and female horses was 32.73 and 39.53%, respectively (p>0.05) and odds of infection in female compared with male horses was 1.34 (95% CI: 0.69-2.61). Prevalence rate in horses with and without history of respiratory disease was 94.1% and 31.74%, respectively (p<0.001). The odds of infection in horses with history of respiratory disease compared with  healthy horses was 34.42 (95%CI: 4.45-266.37). Prevalence rate in  Ahvaz, Shoushtar, Baghmalek, Shoush, Abadan, Ramhormoz and Dezfool  was 33.3%, 34.62%, 5.26%, 69.23%, 13.04, 22.22% and 75%,  respectively (p<0.001). Geographical location explained 29.6% of infection’s fluctuations. No isolate of Streptococcus equi subsp. equi was obtained in culture of nasal swab samples. CONCLUSIONS: This study determined that seroprevalence of strangles should be deleted in khuzestan province is high and Prevention and control measurements should be considered by health authorities.