gastrointestinal nematodes, calves (exper.), efficacy of ivermectin given subcutaneously or given orally as drench or paste

The activity of ivermectin against common nematode parasites of sheep was examined in 2 experiments. In the 1st experiment, 14 sheep with naturally acquired infections were assigned to 2 groups of 7 sheep each. Sheep in 1 group were treated with 200 micrograms of ivermectin/kg of body weight and the remainder served as nontreated controls. In the 2nd experiment, 15 sheep with experimentally supplemented infections (including a benzimidazole-resistant strain of Haemonchus contortus) were assigned to 3 groups of 5 each. The 1st group was treated with 200 micrograms of ivermectin/kg, the 2nd was treated with 88 mg of thiabendazole/kg, and the 3rd served as nontreated controls. Ten to 12 days after treatment, all sheep were euthanatized and necropsied, and the parasites they harbored were recovered and identified. Efficacy of ivermectin was excellent (greater than 96%) against Dictyocaulus filaria, H contortus, Ostertagia circumcinta, Marshallagia marshalli, Trichostrongylus axei, T colubriformis, and T vitrinus. Treatment was not as uniformly effective for Nematodirus spathiger (73% to 85%), N filicollis (80% to 96%), Cooperia curticei (92% to 100%), immature nematodes (92% to 100%), and early 4th-stage larvae (46% to 100%). Efficacy of thiabendazole was poor for H contortus (42%) and early 4th-stage larvae in the abomasum (52%), but approached 100% for most of the other parasites.

Psoroptes ovis, calves, control with ivermectin, dosages and routes of administration; effect on Bovicola bovis; Otobius megnini not affected

During the United States Department of Agriculture (USDA) National Animal Health Monitoring System’s (NAHMS) 2007‐2008 beef study, producers from 24 states were offered the opportunity to evaluate their animals for internal parasites and for overall responses to treatment with anthelmintics. A lapse of 45 d was required between initial sampling and any previous treatments. Choice of anthelmintic (oral benzimidazoles, and both injectable and pour-on endectocides) was at the discretion of the producer so as not to alter the local control programs. Fresh fecal samples were collected from 20 animals, or from the entire group if less than 20, then randomly assigned to 1 of 3 participating laboratories for examination. Analyses consisted of double centrifugation flotation followed by enumeration of strongyle, Nematodirus, and Trichuris eggs (the presence of coccidian oocysts and tapeworm eggs was also noted). Where strongyle eggs per gram (epg) exceeded 30, aliquots from 2 to 6 animals were pooled for egg isolation and polymerase chain reaction (PCR) analysis for the presence of Ostertagia, Cooperia, Haemonchus, Oesophagostomum, and Trichostrongylus. Results from 72 producers (19 States) indicated that fecal egg count reductions were < 90% in 1/3 of the operations. All operations exhibiting less than a 90% reduction had used pour-on macrocyclic lactones as the anthelmintic treatment. While some of these less than expected reductions could have been the result of improper drug application, PCR analyses of the parasite populations surviving treatment, coupled with follow-up studies at a limited number of sites, indicated that less than expected reductions were most likely due to anthelmintic resistance in Cooperia spp. and possibly Haemonchus spp.

Strongylus vulgaris (larvae), Trichostrongylus axei (adults), ponies (exper.), efficacy of ivermectin, controlled tests

Dirofilaria immitis, dogs, histopathological study of host response and fate of microfilariae after treatment with ivermectin

Sarcoptes scabiei var. suis, ivermectin, single treatment of infected sows before farrowing eliminated scabies from sows and prevented its transmission to their offspring, offspring remained uninfected throughout study regardless of whether they were treated with ivermectin at weaning, infection (epizootic) in growing pigs could be controlled by single treatment of all in-contact pigs but routine treatment of all pigs at weaning does not seem justified

Ascaris suum, Trichuris suis, naturally infected 10-week-old female pigs, anthelmintic activity of ivermectin administered subcutaneously or orally

gastrointestinal parasites, horses, anthelmintic efficacy of ivermectin, adverse local or systemic reactions not observed

nematodes, dogs, ivermectin activity; no activity against cestodes