Prevalence of anthelmintic resistant nematodes in sheep in south-east England.

The prevalence of anthelmintic resistant nematodes among 52 commercial flocks in south-east England was investigated by comparing the faecal egg counts of groups of lambs before, and seven days after, treatment with thiabendazole and levamisole. Evidence of thiabendazole resistance was found on seven farms. in each case Haemonchus contortus was the only species of nematode involved. In vitro egg hatch assays carried out for isolates from these farms gave ED50 estimates of 0.065 to 0.332 micrograms thiabendazole/ml compared with estimates of 0.027 to 0.031 micrograms thiabendazole/ml for a known susceptible strain of H contortus assayed at the same time. In a series of slaughter trials, there was a 17 to 85 per cent reduction, as compared with controls, in the mean worm burdens of groups of lambs infected with these isolates and killed seven days after treatment with thiabendazole, confirming their resistance to this anthelmintic.

In-vitro studies on intestinal malabsorption of amino-acids in young chicks infected with Eimeria acervulina.

In vitro uptake of L. histidine by intestinal tissue from chicks infected with E. acervulina was slightly reduced. This was confirmed using radio-actively labelled mixed amino-acid substrates in the form of a Chlorella protein hydrolysate.

Amino-acid malabsorption and intestinal leakage of plasma-proteins in young chicks infected with Eimeria acervulina.

The in vivo absorption of 14C-labelled amino-acids and the leakage of radioactive plasma proteins into the gut of infected birds were measured together with their food-intake and growth. The results suggested that anorexia and protein leakage from the gut are major factors in the pathogenesis of E. acervulina infection.