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Campylobacter in cattle and sheep
Campylobacter is the leading bacterial cause of acute gastrointestinal disease in many western countries including Australia. The disease is characterised by the usual symptoms of foodborne illness including diarrhea, vomiting and cramping. Recovery is usually complete in 4-5 days but a small proportion of subjects may suffer longer-term consequences.
Campylobacter species including C. jejuni, the most common species associated with gastrointestinal illness, are part of the natural intestinal flora of a wide range of birds and animals. Transmission to humans is usually by contamination of food or water although in some countries unpasteurised milk is also implicated. Chicken, poultry and other foods are thought to be the most likely sources of infection in developed countries (Food and Agriculture Organization / World Health Organization, 2003) although epidemiological data to support this view in Australia is lacking. During 2002, Communicable Diseases Intelligence commenced a multistate study into risk factors for Campylobacter infection. Preliminary results indicate that one of the major risk factors for illness is consumption of chicken (Communicable Diseases Intelligence 27 2003 37).
While Campylobacter spp. are relatively easily killed by heat and proper cooking of flesh foods will always destroy them, much of the foodborne illness associated with Campylobacter is thought to stem from cross-contamination from uncooked to cooked food. It is therefore of interest to note the results of a study published in Communicable Diseases Intelligence 27 2003 249 which reports on the incidence of Campylobacter and the other potential pathogens, Listeria and Yersinia, in faeces of slaughter-age cattle and sheep in Australia. The study was a subset of a much larger study on the incidence of pathogenic Escherichia coli and Salmonella in cattle and sheep. Nineteen commercial cattle and sheep properties in New South Wales and Queensland were selected to cover all production systems for red meat: six dairy cattle properties, four feedlot beef cattle properties, four pasture beef cattle properties, two prime lamb properties and three mutton-sheep properties.
Campylobacter spp. were found in all production systems and 14 of the 19 herds or flocks tested. Within individual properties there was an apparent higher prevalence in cattle than in sheep with Campylobacter being most frequently isolated from feedlot cattle. The median prevalences were: for dairy cattle 6 per cent, feedlot beef cattle 58 per cent, pasture beef cattle 2 per cent, mutton sheep 0 per cent and prime lambs 8 per cent.
For the four feedlots sampled, stocking density and weather conditions were identified from questionnaires as possible contributors to the number of animals shedding Campylobacter. The feedlot which had the lowest prevalence of Campylobacter (12 per cent) also had the lowest cattle density and was the only feedlot where dry weather conditions prevailed. Of the pastured animals, dairy cattle had the highest stocking rates and also the highest prevalence of Campylobacter.
The authors of this study note that studies from other countries report a wide variation of Campylobacter carriage rates in domestic food-producing animals. Their results agree with an earlier Australian study by Grau (Journal of Food Protection 51 1988 857), which found C. jejuni in 54 per cent of calf faecal samples and 12.5 per cent of cow faecal samples. It was also found that feedlot cattle were more likely to have C. jejuni in their intestinal tracts and on their carcasses than were pasture-fed cattle.
They conclude that this study within a study was too small to demonstrate statistically significant differences between production systems but the trends observed indicate that cattle and in particular feedlot cattle must be considered a potential source of Campylobacter for humans.
No L. monocytogenes or Yersinia enterocolitica, both important agents of human foodborne disease, were isolated from any of the properties.
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