Treatment rates for injectable tiamulin and lincomycin as an estimate of morbidity in a swine herd with endemic swine dysentery.

Treatment can be used as an indirect measure of morbidity, and treatment records can be used to describe disease patterns in a population. The aim of this study was to describe the rates of treatments with tiamulin and lincomycin by the intramuscular route in cohorts of pigs affected by swine dysentery. Data from treatment records from 19 cohorts of a 1500-head grower-finisher barn were analyzed using Poisson regression to determine factors associated with rates of treatment. Serial interval and reproductive numbers were extracted. Treatment rates displayed marked seasonality. The mean serial interval was estimated at 17 d with variability among batches. In the early period of most cohorts, the effective reproductive number did not exceed 1, and the highest estimate was 2.15 (95% CI: 1.46, 3.20). The average days-to-first treatment was 4.8 which suggests that pigs could have been infected at time of entry. The information about possible sources of infection and likely seasonality should be considered when developing disease and infection control measures in affected barns.