Little change in levels of abattoir zoonoses

ZOONOSES INFECTION in a survey of stock at UK abattoirs in 2003 remained relatively high, with little change in levels detected in the last survey in 2000.

Salmonella carriage in pigs was 23.4%, higher than in sheep and cattle. But levels showed no change since the last survey. Salmonella levels in cattle and sheep were 1.4% and 1.1%, respectively.

Feeding practices, hygiene and vermin control are key issues on farm to cut salmonella infection, say industry vets.

Salmonella in pigs is being tackled through the Zoonoses Action Plan (ZAP). But pig vet Adrian Cox of Larkmead Vet Group, Oxon, warns that this pig industry programme can be misleading.

“ZAP is not a test specific for pig zoonotic pathogens and just shows that at some stage the pig has been exposed to salmonella. It does not necessarily mean it is carrying or shedding salmonella at slaughter.”

But changing diets is one way pig units can cut salmonella, he advises. Wet feed finishing lowers pH which improves gut health, reduces shedding of the organism and, therefore, infection in subsequent pigs.

“It is also possible to acidify diets so over time salmonella in the environment falls, reducing the risk of shedding and contamination.”

Mr Cox suggests producers also operate sensible pig flow by moving stock – and staff – in a logical manner through the unit to reduce cross contamination.

But he questions the validity of salmonella testing at abattoir level, as he believes the risk to humans is contamination of meat after slaughter.

In cattle, flocks of starlings or other birds seeking winter feed are a problem for herds feeding maize silage, says Somerset-based Paddy Gordon of Shepton Vet Group. “They paddle between the maize clamp, through slurry and down feed passages. There is a huge opportunity for cross-contamination and spreading salmonella.

“Producers can control birds using decoy birds of prey or scarecrows, bird-proof clamps with netting, or use standard vermin control. But it is difficult, particularly when we advise opening up barns to improve ventilation,” he says.

Results for the zoonosis E coli 0157 show faecal carriage was 4.7% in cattle, 0.75% in sheep and 0.35% in pigs. This is a significant fall in infection in sheep, but the other two species are similar to the last survey.

On the campylobacter front, thermophillic species were isolated from 54.6% of cattle, 43.85% of sheep and 67.3% of pigs. “This is an increase since the last survey for cattle and sheep, but a more sensitive isolation method was used,” says a DEFRA spokesman.

“A comparison of the new test and the previous one suggested levels in cattle and sheep would probably have been lower if the original test had been applied.”