Epidemiology of salmonellosis in the live sheep export industry [Australia to Middle East]
1993
Higgs, A.R.B. | Norris, R.T. | Richards, R.B. (Western Australian Dept. of Agriculture, South Perth. Animal Health Lab.)
Salmonellosis in sheep was studied on 7 commercial voyages from Australia to the Middle East and in one animal house study. Faecal excretion of salmonellas was not a good indicator of pathological changes in the gastrointestinal tract. The ratio of the proportion of sheep excreting salmonellas to the proportion with histological lesions of salmonellosis ranged from 1:1 to 23:1. Increasing excretion rates indicated that most sheep would be exposed to infection, although deaths from salmonellosis were not spatially or temporally clustered as would be expected if challenge alone was a sufficient cause. In the animal house study, histological lesions of salmonellosis were exclusively in inappetent sheep although almost all sheep excreted salmonellas in faeces. Lesions of salmonellosis were found only in sheep that were seriously ill or had died, which suggested that, under the conditions of lot-feeding and sea transport, most sheep with enteric lesions are likely to die. It was concluded that sheep were predisposed to salmonellosis by inappetence and that stress was involved in lesion development. The development of enteric lesions of salmonellosis, in the live export system, inevitably led to death.
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