Abstract

Nematode parasitic disease, attributed mainly Haemonchus contortus, is the greatest disease problem of small ruminants in Malaysia. This thesis comprises 6 studies on the emergence of anthelmintic resistance in these parasites, and how control may be managed by exploiting the nematophagous fungus Duddingtonia flagrans. A survey of the prevalence of anthelmintic resistance (AR) on Peninsular Malaysia revealed 50% of the sheep (n=39) and 75 % of the goat farms (n=9) were infected with nematode parasites that were resistant to the benzimidazoles. Resistance to levamisole, closantel and ivermectin was also detected. Another study on a government sheep breeding farm, showed multiple AR involving the benzimidazoles, levamisole and ivermectin (plus suspect moxidectin resistance). Continuing these investigations to eastern Malaysia, showed anthelmintic failure to all the broad-spectrum groups on all the government small ruminant breeding farms. New approaches to worm control were urgently required. Studies on the potential of biological control by the use of nematophagous fungi against the free-living stages on pasture, were carried out to assess its suitability and efficacy for use in the tropical environment that is typical for Malaysia. In a survey for the presence of nematode trapping fungi from faecal samples of livestock, several nematophagous species including D. flagrans and Arthrobotrys oligospora were identified. Mass production of D. flagrans spores on various local media was attempted, and the product was also tested in pen trials where sheep were fed the spores at different dose rates, either as a supplement, or in feed blocks. Daily fungal feeding by both means resulted in an 80-95% reduction in infective larvae in faecal cultures. Similar results were found in small scale grazing experiments, where sheep were fed daily with fungal spores for 3 consecutive months. Pen trials comparing goats and sheep, showed no difference between the two livestock species. Larger scale field trials where D. flagrans was combined with rapid rotational grazing, showed excellent parasite control. This indicates that the integration of biological control with measures such as rotational grazing provides viable options for sustainable production of small ruminants in the tropics, where AR is becoming a major threat to livestock production.