Animal Health & Welfare

Many sheep that appear outwardly healthy can carry worm burdens which they are able to cope with through the processes of immunity. However, this requires adequate protein nutrition and a healthy immune system.

Sheep with subclinical infections, whilst still appearing healthy, have a reduction in their voluntary feed intake and utilise nutrients less efficiently than non-parasitised animals. This can result in reduced growth rates, reductions in wool production, increased mortality, especially in young sheep, reductions in milk production and reproductive success. Sheep with subclinical infections are more likely to have dirty rumps and thus more likely to succumb to fly strike. 

Stress, either physical or psychological, can affect immune responses in sheep, thus any period of prolonged or extreme stress will make it more difficult for a sheep to mount a defence against worm burdens. Stressed sheep, therefore, will be more likely to suffer acute or chronic disease associated with worm burdens.  

The clinical signs of parasite infections are diarrhoea, dehydration, loss of appetite, failure to gain weight and anaemia in Haemonchus infections.

SAC has produced two technical notes on the control of worms (see the links to the right).