Isolation of toxigenic Pasteurella multocida type D from pigs in a herd free from progressive atrophic rhinitis in Ireland
Kavanagh, N.T.
Veterinary Record 134(9): 218-219
1994
ISSN/ISBN: 0042-4900 PMID: 8171810 Document Number: 435076
During routine health monitoring of an integrated, minimal-disease unit of 300 sows, 2 of 16 nasal swabs collected randomly from the herd in 1991 and examined by ELISA were positive for toxigenic P. multocida type D. Since the herd, which was established in 1990, and the herd of origin were both free of progressive atrophic rhinitis further investigations of the positive samples were made. Both isolates were positive for toxin production in embryonic bovine lung cells and for mouse lethality. Comparison of cultures of the two isolates showed them to be identical but to differ from P. multocida LFB 3 (the UK reference pig strain) in 4 biochemical reactions and from an atypical bovine strain in 7 reactions. After the identification of toxigenic type D in the herd nasal swabs were taken, from 16 growing and fattening pigs and tonsilar swabs from adult breeding stock, one positive sow was removed from the herd; all other swabs were negatives. When the herd was retested 30 days later all swabs were negative. Monitoring of the herd and of herds receiving breeding stock from the unit which has continued for 2 years failed to show any evidence for the presence of toxigenic P. multocida type D or progressive atrophic rhinitis. It is suggested that the pig may not be the natural host for these particular toxigenic type D isolates; this could explain why the organism did not spread and cause disease but seemed to have spontaneously disappeared from the herd.