Effectiveness of the ivermectin sustained-release bolus in the control of bovine nematodosis.
OBJECTIVE
To evaluate the nematocidal effectiveness of the ivermectin sustained-release bolus throughout its 135-day delivery period.


METHODS
Twenty-four naturally infected calves were randomly allocated to 1 of 3 equivalent experimental groups: group-T1 calves were untreated controls, group-T2 calves each received a sustained-release bolus on trial day 0, and group-T3 calves were rendered nematode-free and used at 35-day intervals during the study as tracers. One contaminated pasture was used for all principal calves for the 135-day grazing interval of the study. Calves of groups T1 and T2 were also artificially administered mixed infective nematode larvae at intervals during the grazing period, after which, all calves were confined to concrete for 21 days prior to necropsy.


METHODS
All calves were approximately 6 months old on trial day 0, weighed from 136 to 216 kg, and were of mixed breeding and sex.


METHODS
At intervals during the study, feces from all calves were analyzed for nematode egg counts, and all calves were weighed and examined for bolus retention (T2 calves only). For nematode recovery, all calves were necropsied 21 to 22 days after removal from the contaminated pasture.


RESULTS
Parasitic populations of Haemonchus, Ostertagia, Trichostrongylus, Cooperia, Bunostomum, and Oesophagostomum spp were significantly reduced in cattle treated with the ivermectin sustained-release bolus.


CONCLUSIONS
The nematocidal activity of the ivermectin sustained-release bolus proved highly effective, with > 98% efficacy for all nematode species present.
Yazwinski
T A
TA
Department of Animal Sciences, University of Arkansas, Fayetteville 72701, USA.
Featherston
H
H
Tucker
C
C
D000723:Ancylostomatoidea / Q000302:isolation & purification; D000818:Animals; D000977:Antiparasitic Agents / Q000008:administration & dosage / Q000592:standards / Q000627:therapeutic use*; D002417:Cattle; D002418:Cattle Diseases / Q000188:drug therapy* / Q000469:parasitology / Q000517:prevention & control; D003692:Delayed-Action Preparations; D005243:Feces / Q000469:parasitology; D005260:Female; D006188:Haemonchiasis / Q000188:drug therapy / Q000517:prevention & control / Q000662:veterinary; D006189:Haemonchus / Q000302:isolation & purification; D006725:Hookworm Infections / Q000188:drug therapy / Q000517:prevention & control / Q000662:veterinary; D007559:Ivermectin / Q000008:administration & dosage / Q000592:standards / Q000627:therapeutic use*; D008297:Male; D009348:Nematoda / Q000302:isolation & purification; D009349:Nematode Infections / Q000188:drug therapy / Q000517:prevention & control / Q000662:veterinary*; D010028:Ostertagia / Q000302:isolation & purification; D010029:Ostertagiasis / Q000188:drug therapy / Q000517:prevention & control / Q000662:veterinary; D010270:Parasite Egg Count / Q000662:veterinary; D011897:Random Allocation; D014253:Trichostrongylosis / Q000188:drug therapy / Q000517:prevention & control / Q000662:veterinary; D014254:Trichostrongylus / Q000302:isolation & purification
D000977:Antiparasitic Agents; D003692:Delayed-Action Preparations; D007559:Ivermectin