INVESTIGATIONS INTO FIELD CASES OF PORCINE COLITIS WITH PARTICULAR REFERENCE TO INFECTION WITH SERPULINA-PILOSICOLI

Investigations into the possible causes of colitis and typhlocolitis w ere carried out on 85 pig units in the United Kingdom between 1992 and 1996, Serpulina pilosicoli was identified most commonly, occurring as the suggested primary agent on 21 (25 per cent) of the units but form ing part of mixed infections on another 23 (27 per cent) of the units, the main co-infections being Yersinia pseudotuberculosis (eight units ), proliferative enteropathy (six units), Salmonella species (four uni ts) or Serpulina hyodysenteriae (two units). 'Atypical' Serpulina spec ies, S hyodysenteriae, Salmonella typhimurium, Y pseudotuberculosis an d Lawsonia intracellularis (proliferative enteropathy) were the sugges ted primary agents on seven, six, four, four and three units, respecti vely, Various combinations of mixed infections involving the latter or ganisms and other possibly incidental agents were recorded on another 10 units, Investigations on a further six units failed to detect any r ecognised pathogens, On units where S pilosicoli was the suggested pri mary agent, pigs ranging between 20 to 40 kg (eight to 16 weeks of age ), but occasionally up to 50 kg, had diarrhoea and grew poorly over a period of two to three weeks, The prevalence was estimated to be betwe en 5 and 15 per cent in affected batches, with a mortality of approxim ately 1 per cent. The clinical signs usually developed seven to 14 day s after the moving and mixing of pigs, At postmortem examination, affe cted pigs had liquid contents in their colon, which contained accumula tions of mucus in some chronic cases, Gross and histological lesions o f colitis were prominent in the mid-spiral region of the colon, In mix ed infections with Y pseudotuberculosis, Salmonella typhimurium or S h yodysenteriae, lesions were more extensive and affected the caecum as well as the colon, In the colon, lesions of proliferative enteropathy were usually confined to the proximal half of the ascending spiral but mixed infection with S pilosicoli caused more extensive colitis, Mixe d infections were reported to prolong the time taken for pigs to recov er naturally and to have a more detrimental effect on growth rates tha n S pilosicoli infection alone, Despite the successful treatment of ba tches of pigs with tiamulin or lincomycin, S pilosicoli infection pers isted as a chronic problem on many units, with diarrhoea and colitis i n successive batches of pigs unless prophylactic medication was used.