Serotypes of Pasteurella haemolytica in ovine pasteurellosis

The serotypes of 406 strains of Pasteurella haemolytica were determined. These came from cases of pasteurellosis in sheep of all ages. Serotype A2 was the most frequent and comprised 33 per cent of all strains recovered. Serotypes T3, T4 and T10 comprised 16, 14 and 12 per cent of the total respectively. Serotypes A1 and A6 contributed 5 per cent each, A7, 18, A9, A11 and A12 a total of 8 per cent collectively, serotype A5 was not isolated at all while 6 per cent of strains were serologically untypable. More strains were received during September, October and November than at any other three-month period and in these months the T biotype predominated.