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.

Immunoglobulin reactions to Salmonella dublin in serum and milk from 4 groups of lactating cows were measured by an indirect ELISA. The groups consisted of (1) cows that were natural carriers of S dublin in the mammary gland, (2) experimentally infected cows that did not become carriers, (3) cows inoculated with a commercial S dublin bacterin, and (4) cows used as S dublin-negative controls. Milk and serum samples were obtained at monthly intervals. Models for predicting carrier status were developed by use of stepwise logistic regression. Independent variables consisted of serum and milk IgG and IgM titers to S dublin lipopolysaccharide and a ratio of IgG to IgM. The utility of a single sample vs multiple samples obtained at 1-month or 2-month intervals was tested by comparison of goodness-of-fit X2 P values for 8 models predicting carrier status. Immunoglobulin reactions specific to S dublin were a significant predictor of carrier status (P < 0.001). Serum IgG titers specific for S dublin were the most important variable for predicting carrier status. Two serum IgG titers to S dublin obtained 2 months apart was a better predictor of carrier status than measurement of the IgG:IgM ratio from a single serum sample. Immunoglobulin recognizing S dublin epitopes also were detected in milk samples. In milk, performing 2 ELISA 60 days apart to determine IgG and IgM reactions to S dublin appeared to be useful for the prediction of carrier status, but was not as accurate as models for serum immunoglobulin reactions.

Four shed-lambing operations in western Colorado were monitored during the 1984 spring lambing season to determine the causes and rates of perinatal lamb mortality. The number of lambing ewes per flock ranged from 513 to 1,712, and lambing percentages ranged from 131 to 180%. Overall perinatal lamb mortality ranged from 8.2 to 12.2%. Most lamb deaths occurred during parturition or within 24 hours after parturition. More than 85% of all lamb deaths were in lambs born to ewes having 2 or more lambs. The leading causes of lamb death were starvation, dystocia, stillbirth (unknown cause), and infectious diseases. A wheel model was used to categorize factors causing lamb deaths into 4 groups: physical, social, host, and biological, and to present data on perinatal lamb mortality in a simple visual model. In all flocks, social and biological factors resulted in most of the lamb deaths. On the basis of our findings, we suggest that interventions designed to improve ewe-lamb bonding and to reduce infectious agents and the incidence of prolonged parturition may reduce lamb mortality.

Pilus-mediated adherence is a virulence attribute of Moraxella bovis. Several pilus types have been shown to exist among strains of this bacterium, but correlation between pilus type and specific field cases of the disease has not been done. During the summer of 1987, an epizootic of infectious bovine keratoconjunctivitis was reported in 7 Iowa counties. Eight isolates of M bovis were secured from 12 episodes studied. All 8 of the isolates were nearly homogeneous in biochemical properties and had the same plasmid biotype. Pilus typing performed by immunofluorescence and immunogold electron microscopy identified a single new pilus type among 5 of the 8 isolates. This pilus type was identified in field cases that developed within a narrow time frame and over large distances. The implication of these findings is that infectious bovine keratoconjunctivitis epizootics may be associated with emergence of a novel pilus type, and that rapid dissemination over wide distances can occur, presumably by transportation of carrier cattle.