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.

A double-blind randomized clinical trial was undertaken to determine the value of parenterally administered Streptococcus equi M-protein vaccine in foals during an epizootic of strangles. Weaned mixed-breed foals (n = 664) housed on 2 adjacent feed-lots (A and B) arrived over a 5-day period, 2 weeks before primary vaccination. Foals in lot B (n = 114) were randomly administered vaccine (n = 59) or saline solution (placebo; n = 55) on 3 occasions at biweekly intervals. Foals in lot A (n = 450) were given 1 dose of vaccine (n = 225) or placebo. The following clinical observations were scored blindly by a single observer for all foals in lot B and for 120 (randomly sampled) foals in lot A on a single day, 2 (lot B) and 6 (lot A) weeks after final vaccination: cervical lymphadenopathy, type of bilateral nasal discharge, and palpable swelling at injection site(s). Bacteriologic culture of nasal swab specimens or lymph node aspirates from selected foals with clinical disease yielded S equi. Cervical lymphadenopathy was observed in 17 of 59 (29%) vaccinates and 39 of 55 (71%) nonvaccinated controls in lot B and in 32 of 60 (53%) vaccinates and 29 of 60 (48%) controls in lot A. Contingency X2 analysis confirmed significantly lower cervical lymphadenopathy rate (X2 = 18.5; P < 0.001) and prevalence of mucopurulent nasal discharge (X2 = 11.4; P < 0.01) for vaccinates in lot B only. Swelling(s) at the vaccine injection site were palpated in 44% of lot B and 29% of lot A vaccinates vs < 2% of placebo controls. In the face of intense natural exposure, foals inoculated 3 times with M-protein vaccine were less than half as likely to have clinical signs of strangles as were nonvaccinated horses.

Strangles is an extremely contagious bacterial infection specific to&#xD;equine species( horses, mules and zebras). A nationwide screening of S. equi was conducted among horses following an isolation of Streptococcus equi subsp. equi (S. equi) from a horse. All horses were monitored for the presence of respiratory signs, nasal discharge and submandibular swelling. This paper reports the isolation of S. equi from horses during a nationwide survey from August 2010 to December 2010. From August 2010 to December 2010 our laboratory received 2,825 nasal swabs, 9 guttural pouch flushes, 1 submandibular swab and 1 submandibular abscess. The samples were subjected to conventional bacterial isolation and identification.&#xD;Streptococcus equi-positive samples were also confirmed by detecting the M-gene (SeM) of the bacteria by using PCR. Two nasal swabs from two horses and one submandibular abscess from a horse were positive for S. equi by culture and subsequently by PCR. Surveillance for S. equi should be continued for the control of the strangles. PCR can be carried out in parallel to bacterial culture to increase the&#xD;detection rate of carriers and shedders.