Pasteurella haemolytica serotypes isolated in Northern Ireland during 1989-1991.

Pasteurella haemolytica isolates from clinical veterinary samples were serotyped over a three year period to determine the distribution of strains in Northern Ireland, to compare the results with the recorded distribution in the remainder of Great Britain and to extend information on the geographical prevalence of the serotypes. Four hundred and nine typable and 91 untypable strains were isolated from 490 animal cases. From 127 typable cattle isolates, the commonest serotype was A1, most frequently associated with calf pneumonia. Serotypes A2, T4, T10 and T15 were the commonest sheep isolates, A2 being most frequently associated with lamb pneumonia and the T-biovars more prevalent in adult pneumonia and lamb septicaemia. The isolates from approximately half the cases were evaluated in terms of the results obtained from gross and histopathological post mortem examination. Approximately two-thirds of these isolates were associated with significant pathology, including a small number of serotypes which are not included in the sheep vaccines currently used in Great Britain.