Efficacy of an orange oil emulsion as an anthelmintic against Haemonchus contortus in gerbils (Meriones unguiculatus) and in sheep

Haemonchus contortus is a blood-sucking abomasal parasite responsible for major losses to small ruminant producers worldwide The recent increase in populations of anthelmintic resistant parasites has produced a demand for alternative control methods An orange oil emulsion that has shown activity against plant parasitic nematodes and H contortus in vitro was assessed for activity against H contortus in a gerbil model and in the natural ovine host In gerbil experiments animals were infected with 600 infective third stage (13) H contortus larvae In one experiment gerbils were treated with 600 milligrams per kilogram bodyweight (mg/kg BW) orange oil once or daily for 5 days In a second experiment gerbils were treated with 1200 mg/kg BW orange oil once or daily for 5 days On Day 9 post-infection gerbils were killed their stomachs removed and the worms counted The 600 mg/kg BW dosage caused 7% and 62 6% parasite reduction compared to a control group when given once or daily for 5 days respectively The 1200 mg/kg BW dosage of orange oil caused 25% and 87 8% parasite reduction compared to a control group when given once or daily for 5 days respectively The difference between the multiple treatment and control group were significant at both dosages (P< 0 005) In the sheep trial 18 lambs were orally inoculated with 10 000 13 H contortus One month later two groups of six lambs each were dosed with 600 mg/kg BW orange oil either once or daily for 3 days Fecal egg counts were monitored daily starting on the first day of treatment (Day 0) and continuing for 14 days Results showed that a single dose of the product caused high fecal egg count reduction (97 4%) compared to control sheep Egg counts were significantly reduced by Day 2 (P< 0 0001) Thus the orange oil emulsion may potentially be useful in the control of ovine haemonchosis (C) 2010 Elsevier B V All rights reserved