Efficacy of doramectin injectable against Oestrus ovis and gastrointestinal nematodes in sheep in the southwestern region of France

• Published in: Veterinary parasitology Vol. 96; no. 2; pp. 147 - 154
• Main Authors: Dorchies, Ph, Jacquiet, Ph, Bergeaud, J.P., Duranton, C., Prévot, F., Alzieu, J.P., Gossellin, J.
• Format: Journal Article
• Language: English
• Published: Netherlands Elsevier B.V 20-03-2001
• Subjects: Animals; Anthelmintics - administration & dosage; Anthelmintics - therapeutic use; Control methods; Diptera - parasitology; Doramectin; Ectoparasitic Infestations - drug therapy; Ectoparasitic Infestations - veterinary; Feces - parasitology; France; Injections, Intravenous; Insecticides - administration & dosage; Insecticides - therapeutic use; Intestinal Diseases, Parasitic - drug therapy; Intestinal Diseases, Parasitic - veterinary; Ivermectin - administration & dosage; Ivermectin - analogs & derivatives; Ivermectin - therapeutic use; Nematoda; Nematode Infections - drug therapy; Nematode Infections - veterinary; Nematodirus battus; Nematodirus filicollis; Oesophagostomum venulosum; Oestridae; Oestrus ovis; Parasite Egg Count - veterinary; Sheep; Sheep Diseases - drug therapy; Sheep-nematoda; Teladorsagia circumcincta; Trichuris; Trichuris sp; France; Nematodirus battus; Nematodirus filicollis; Control methods; Sheep-nematoda; Oesophagostomum venulosum; Doramectin; Trichuris sp; Teladorsagia circumcincta; Oestrus ovis
• ISSN: 0304-4017; 1873-2550
• DOI: 10.1016/S0304-4017(00)00429-5

A study was conducted to evaluate the therapeutic efficacy of doramectin administered intramuscularly at a dose rate of 200
μg/kg to sheep harbouring naturally acquired infections of gastrointestinal nematodes and
Oestrus ovis in the southwestern region of France. On day 0, 24 sheep were selected on the basis of positive faecal egg counts (>100 EPG) and positive assessment of
O. ovis infection (including positive
O. ovis antibody level and positive clinical score). The sheep were randomly allocated to a non-medicated control group (T1) or a doramectin-treated group (T2) of 12 animals each. On day 0, sheep in group T2 received a single intramuscular injection of doramectin (200
μg/kg), whereas those in group T1 received an intramuscular injection of saline solution (sodium chloride, 0.02
ml/kg). Individual faecal egg counts were performed on days 0, 1, 2, 3, 4, 5, 6, 7, and 14. Between days 14 and 16, all sheep were slaughtered, and worm and
O. ovis burdens were determined.
In doramectin-treated sheep, faecal egg counts had decreased to zero by day 4 for all recovered types of nematode eggs: strongyles,
Nematodirus sp.,
Trichuris sp., and
Rhabditidae sp. For strongyles,
Nematodirus sp., and
Rhabditidae, the percentage reductions in faecal egg counts (geometric means) of doramectin-treated sheep, compared to the non-medicated control sheep were 100% from days 4–7. For
Trichuris sp., they were 100, 99.7, 99.9, and 100% on days 4, 5, 6, and 7, respectively. On day 14, percentage reductions were 100% for
Nematodirus sp. and
Rhabditidae, and 99.8 and 99.1% for strongyles and
Trichuris sp., respectively.
At necropsy, only adult nematodes and mainly first-stage
O. ovis larvae were recovered. Doramectin was highly efficacious against the adult stages of
Teladorsagia circumcincta (100%),
Nematodirus battus (100%),
Nematodirus filicollis (99.9%),
Oesophagostomum venulosum (99.8%), and
Trichuris sp. (99.3%). It was also 100% efficacious against first-stage larvae of
O. ovis. No abnormal clinical signs or adverse reactions in any of the sheep treated with doramectin were observed.