In vitro efficacy of three novel compounds on development and survival of gastrointestinal nematode larvae in feces of sheep

Abstract Text:

Gastrointestinal nematode (GIN) parasites are a major constraint to profitable sheep production. The long-term use of anthelmintics has resulted in GIN populations developing resistance to those available. The objective of this study was to determine the efficacy of three novel compounds on development and survival of GIN larvae in feces of sheep. Feces were collected directly from the rectum of 10 lambs and combined to make one large sample. This sample was homogenized by thorough mixing by hand and five 2 g subsamples were randomly selected for determination of fecal egg count (FEC) using the McMaster technique. Fifty 5 g subsamples were then randomly selected and individual fecal cultures were made by mixing with an equivalent volume of vermiculite and adding water to make a soft crumbly culture composition. Three novel[BJ1]  synthetic compounds (Bedoukian Research, Inc.) similar to natural flavor/fragrance application compounds were diluted 1:10, 1:1,000 and 1:10,000. Five mL of water (control) and each dilution of the compounds were thoroughly mixed with a culture, making 5 replicates/dilution. Cultures were incubated at 27°C for 2 wk, after which, they were processed by a baermann procedure to recover infective larvae (L3). The number of L3 were counted to estimate L3/g of feces. The mean FEC (3530 ± 231) indicated that the GIN eggs were evenly distributed in the homogenized fecal mass, so all subsamples were considered to have equivalent FEC. The control larval recovery was 814 L3/g, and recovery for all the dilutions of the 3 compounds was < 10 L3/g. This indicated very high efficacy of L3 reduction (over 98.7%, P < 0.05). These novel compounds may be a viable treatment to aid in the control of GIN infection by reducing development and survival of larvae in feces, thus reducing pasture infectivity.

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Keywords: Nematodes, control, sheep