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Efficacy of ivermectin controlled-release capsules for the control and prevention of nasal bot infestations in sheep |
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| Authors: | D RUGG RP GOGOLEWSKI RA BARRICK JS EAGLESON |
| Institution: | Merck Sharp and Dohme Veterinary Research and Development Laboratory. PO Box 135, Inglebum, NSW 2565;Current address: Merck &Co Inc, Branchburg Farm, 203 River Rd, Somerville NJ 08876 USA;Merck &Co Inc, P.O. Box 2000, Rahway, NJ 07065 USA |
| Abstract: | Objective To investigate the therapeutic and prophylactic efficacy of an ivermectin controlled-release capsule against nasal bots (Oestrus ovis) in sheep. Design Trial 1 – A pen study with controls. Trial 2 – A field study with controls. Animals Trial 1 – Forty Merino wethers with natural infestations of nasal bot were used. Trial 2 – One hundred nasal bot-free wethers were used. Procedure Trial 1 – Ten randomly selected animals were slaughtered and the heads split and examined to confirm bot infestation. Fifteen animals were allocated to untreated controls and 15 to treatment with a controlled-release capsule delivering ivermectin at ≥ 20 μg/kg/day for 100 days. Twenty-nine days after treatment the sheep were killed and examined for nasal bots. Trial 2 – Nasal bot-free sheep were allocated to two groups of 45 animals. One group was untreated the other sheep were treated with capsules as above. The sheep were grazed as a single group exposed to natural challenge from O ovis . Ninety days after treatment the animals were slaughtered and examined for nasal bot infestation. Results Trial 1 – Live O ovis larvae were recovered from 60% of control sheep. No live larvae were collected from treated sheep. Trial 2 – Forty-one percent of untreated sheep harbored nasal bot infestations. No live larvae were collected from any treated animal. Conclusion Treatment with a single ivermectin controlled-release capsule was 100% effective against existing infestations of O ovis and as a prophylactic treatment for this parasite. |
| Keywords: | Nasal bot Oestrus ovis ivermectin controlled-release capsule |