Beware out-of-season parasites

17 September 1999

Beware out-of-season parasites

UNUSUAL weather means that sheep producers must be aware of unseasonable parasite problems in their flocks.

More cases of Haemonchus contortus infection, caused by a roundworm parasite, have been seen recently because of warm, humid weather, warns VLA vet officer Brian Preece, based at Starcross, Exeter, Devon.

"Unlike most cases of gastroenteritis, there are no signs of diarrhoea in sheep infected by this parasite, although you may see some dark, almost black faeces.

"Infected sheep tend to lose condition, become lethargic and suffer sudden deaths," he says.

This is because once the parasite is picked-up off pasture it lives in the sheeps abomasum, sucking blood and reducing the packed cell volume – a measure of red blood cells in the body.

When this drops, sheep may not be able to carry enough oxygen because they are anaemic, and so any sudden stress can result in death, he adds.

Another concern due to warm temperatures, is an increase in nematodirus. "High temperatures have encouraged a synchronised hatching of nematodirus worms." This causes scour in lambs, which will lose condition.

Mr Preece says producers should ensure they pay adequate attention to their parasite programme, and when concerned should discuss it with their vet. &#42

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