Treatment and control of swine dysentery caused by Serpulina hyodysenieriae may fail due to factors such as inappropriate medication, poor hygiene, dietary factors, the development of antibiotic resistance by S. hyodysenteriae and the presence of other disease such as salmonellosis. This report relates to outbreaks of swine dysentery on seven pig finishing farms in England in 1997. Isolates of S.hyodysenteriae made from the pigs on six of these farms gave minimum inhibitory concentrations (MICs) indicative of resistance to both tiamulin and lincomycin. Some response to treatment was observed and it was not clear if these isolates were also virulent An isolate from the 7th farm gave an MIC indicative of resistance to tiamulin but of intermediate sensitivity to lincomycin. Concurrent enterocolitis associated with Salmonella typhimurium infection was identified on four of these seven farms. See Table 1 - these were all indoor straw-based finishing farms. Farm 1 was continuous flow and the remainderwere all-in and all-out. Farms 4, 5 and 7 were linked by pig movements. The level of recorded morbidity and mortality on these farms was variable as indicated in Table 1.
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