Efficacy of ivermectin controlled-release capsules for the control and prevention of nasal bot infestations in sheep.
OBJECTIVE
To investigate the therapeutic and prophylactic efficacy of an ivermectin controlled-release capsule against nasal bots (Oestrus ovis) in sheep.


METHODS
Trial 1--A pen study with controls. Trial 2--A field study with controls.


METHODS
Trial 1--Forty Merino wethers with natural infestations of nasal bot were used. Trial 2--One hundred nasal bot-free wethers were used.


METHODS
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 > or = 20 micrograms/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.


CONCLUSIONS
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.
Rugg
D
D
Merck Sharp and Dohme Veterinary Research and Development Laboratory, Ingleburn, NSW.
Gogolewski
R P
RP
Barrick
R A
RA
Eagleson
J S
JS
D000818:Animals; D002214:Capsules; D003692:Delayed-Action Preparations; D004175:Diptera; D007306:Insecticides / Q000008:administration & dosage / Q000627:therapeutic use*; D007559:Ivermectin / Q000008:administration & dosage / Q000627:therapeutic use*; D008297:Male; D009198:Myiasis / Q000188:drug therapy / Q000517:prevention & control / Q000662:veterinary*; D009517:New South Wales / Q000453:epidemiology; D009666:Nose / Q000469:parasitology; D010272:Parasitic Diseases / Q000188:drug therapy / Q000517:prevention & control; D010273:Parasitic Diseases, Animal; D012756:Sheep; D012757:Sheep Diseases / Q000188:drug therapy* / Q000453:epidemiology / Q000517:prevention & control
D002214:Capsules; D003692:Delayed-Action Preparations; D007306:Insecticides; D007559:Ivermectin