a1 Department of Veterinary Pathology and Public Health, Massey University, Palmerston North, New Zealand
a2 National Health Institute, kenepuru Drive, Porirua, New Zealand
In an experimental study on a piggery it was found that haemolytic Escherichia coli of O-scrotypes 138 or 139 proliferated in the intestinal tracts of pigs following weaning, with E. coli of the 0-138 typo also being occasionally recovered from unwearied pigs, and onco from a sow. Organisms of the O-138 typo produced heat labile enterotoxin and their presence in weaned pigs was associated with the development of severe post-weaning diarrhoea. E. coli of O-130 type produced a vero cell cytotoxin and were associated with a milder diarrhoea in weaned pigs. Under various managemental circumstances the O-138 type E. coli almost invariably proliferated after weaning. The O-139 strain of E. coli did however proliferate rather than the O-138 strain following the movement of weaned pigs to new accommodation, after weaned pigs were returned to their sow and then weaning again 5 days later, and very occasionally in pigs weaned at 5 weeks of ago. In all theso cases earlier proliferation of the O-138 E. coli had been detected, suggesting that this may be a prerequisite for proliferation of the O-130 strain.
(Accepted October 27 1987)
p1 Present address: Division of Veterinary Biology, School of Veterinary Studies, Murdoch University, Murdoch, Western Australia, 6150
p2 Present address: Fairfield Hospital, Melbourne, Victoria, Australia.