Clinical bacteriological and epidemiological observations on infectious atrophic rhinitis of pigs in southern England.

Three distinct patterns of infection with Bordetella (Alcaligenes) bronchiseptica were found in groups of 12 to 24 pigs born in 1977-78 in 12 herds in southern England. In five of these, heavy bordetella infection of a substantial proportion of unweaned piglets persisted to a variable extent until slaughter. Clinical disease and severely atrophied turbinates were most marked in these groups. In three other herds the infection first appeared soon after weaning and occasionally persisted until slaughter. Clinical disease occurred in only one of these other groups and conchal atrophy at slaughter was moderate. In the groups of the four remaining herds there was no clinical disease and conchal atrophy at slaughter was slight, infection appearing only late in the weaning, or even the fattening, stages. These varying patterns suggest that immunological phenomena were involved in the infection in the least affected herds and that such responses might, if reproducible artificially, provide a better means of control of this disease in badly affected herds than the available forms of chemotherapy.