Serotypes of Pasteurella anatipestifer isolated from commercial White Pekin ducks in the United States.

Pasteurella anatipestifer isolates from commercially raised, clinically diseased White Pekin ducks were serotyped by agglutination and agar-gel precipitin methods. Plate agglutination was found to be the most suitable test for preliminary classification. Based on National Animal Disease Center (Ames, Iowa) nomenclature, six serotypes were classified as types 1, 2, 3, 5, 7, and 8. These were compared with strains held by Houghton Poultry Research Station (Houghton, Huntingdon, England), at present constituting 15 serotypes (A to O), isolated in England and other countries. Serotype 1 was found to be identical to serotype A, the strain most commonly associated with outbreaks of the disease in England. Serotype 3 was found to be identical to serotype L, which was isolated from an outbreak of the disease in swans in Tasmania. Types 5, 7, and 8 did not react with any of the typing sera available, but serotype 7 was found to be identical to a strain (type N) isolated subsequently in England. More than 95% of field isolations made from 1975 to 1979 belonged to serotypes 1, 2, and 5.