Submitted to: Meeting Abstract
Publication Type: Abstract Only
Publication Acceptance Date: June 29, 2010
Publication Date: July 31, 2010
Citation: Burke, C., Foster, J.G., Zajac, A.M. Effect of an orange oil emulsion on gastrointestinal nematodes in naturally infected sheep [abstract]. American Association of Veterinary Parasitologists, 55th Annual Meeting. July 1-August 3, 2010, Atlanta, Georgia, p. 44-45, Abstract No. 24.
Increasing levels of anthelmintic resistance in ovine gastrointestinal strongylids, especially Haemonchus contortus, have led many investigators worldwide to examine potential anthelmintic effects of naturally occurring plant products. In previous work, we have shown that 1200 mg/kg of an orange oil emulsion given daily for 5 days showed 87.8% efficacy against H. contortus in a gerbil model. In sheep experimentally infected with H. contortus a single treatment of a modified orange oil emulsion reduced fecal egg counts by 97%. Our objective in this study was to examine the effects of the orange oil emulsion on natural strongylid infection in sheep grazing contaminated pasture. Twelve mixed breed weaned lambs were exposed to naturally infected pasture at the Virginia Tech Sheep Center. Five days before treatment, the lambs were housed and strongylid fecal egg counts determined (Modified McMaster’s test). Sheep were allocated to 2 groups balanced for fecal egg count. On Day 0, 600 mg/kg of orange oil emulsion were administered orally to sheep in one of the groups. Rectal fecal samples were collected on Days 1, 2 and 4 post treatment. On Day 6, sheep were euthanized and abomasal and intestinal samples collected for determination of parasite numbers and species. Four days after treatment the mean fecal egg counts were 292 and 3425 in the treated and untreated lambs, respectively. Mean total worm burden in the treated animals was 7429 compared to 15,588 in untreated animals. The difference between worm burdens of treated and untreated animals was greater in abomasal worm counts than in intestinal counts. These results suggest that citrus oils should be further explored for activity against ovine gastrointestinal nematodes.