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

Author
item SQUIRES, JILL - Virginia-Maryland Regional College Of Veterinary Medicine (VMRCVM)
item Foster, Joyce
item LINDSAY, DAVID - Virginia-Maryland Regional College Of Veterinary Medicine (VMRCVM)
item DAUDELL, DAVID - Virginia-Maryland Regional College Of Veterinary Medicine (VMRCVM)
item ZAJAC, ANNE - Virginia-Maryland Regional College Of Veterinary Medicine (VMRCVM)

Submitted to: Veterinary Parasitology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 4/12/2010
Publication Date: 8/9/2010
Citation: Squires, J.M., Foster, J.G., Lindsay, D.S., Daudell, D., Zajac, A.M. 2010. Efficacy of an orange oil emulsion as an anthelmintic against Haemonchus contortus in gerbils (Meriones unguiculatus) and in sheep (Ovis aries). Veterinary Parasitology. 172(1-2):95-99.

Interpretive Summary: The barber pole worm, Haemonchus contortus, is a gastrointestinal parasitic nematode that infects sheep and goats, causing significant economic losses annually for producers worldwide. Dewormers have been used extensively to control this worm. Now, resistance of barber pole worms to available dewormers is widespread, creating a demand for alternative control methods and interest in plant chemicals that can disrupt the life cycle of this worm. Oil derived from orange peels is effective against plant parasitic nematodes, and laboratory experiments revealed sensitivity of barberpole worm eggs and third-stage larvae to orange oil emulsions. Therefore, we investigated the deworming activity of orange oil in gerbils and sheep that had been infected with third stage barber pole worm larvae. Barber pole worm infections in gerbils progress to the fourth larval stage, allowing this model to be used effectively in preliminary testing of potential deworming products. Dosing with an orange oil emulsion significantly reduced the number of worms in gerbils. The number of barber pole worm eggs in feces from infected sheep was reduced by more than 95% two days after a single dose of orange oil emulsion, and the effect continued throughout our 2-week observation period. These results indicate that orange oil emulsions may be useful in the control of barber pole worms in sheep and other small ruminants.

Technical Abstract: 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 (L3) H. contortus larvae, then treated with either 600 or 1200 mg of orange oil/kg body weight (BW) 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 caused 25% and 87.8% parasite reduction compared to a control group when given once or daily for 5 days, respectively. Differences from the control group were significant at both dosages (P < 0.005). In the sheep trial, 18 lambs were orally inoculated with 10,000 L3 H. contortus. One month later, 2 groups of 6 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. The single dose of the orange oil emulsion caused a 97.4% reduction in fecal egg count 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.