Veterinary use
Ivermectin is routinely used to control parasitic worms in the gastrointestinal tract of
ruminant animals. These parasites normally enter the animal when it is grazing, pass the bowel, and set and mature in the intestines, after which they produce eggs that leave the animal via its droppings and can infest new pastures. Ivermectin is only effective in killing some of these parasites, this is because of an increase in anthelmintic resistance.
[114] This resistance has arisen from the persistent use of the same anthelmintic drugs for the past 40 years.
[115][116]
In dogs, ivermectin is routinely used as prophylaxis against
heartworm.[117] Dogs with defects in the
P-glycoprotein gene (
MDR1), often collie-like herding dogs, can be severely poisoned by ivermectin. The mnemonic "white feet, don't treat" refers to Scotch collies that are vulnerable to ivermectin.
[118] Some other dog breeds (especially the
Rough Collie, the
Smooth Collie, the
Shetland Sheepdog, and the
Australian Shepherd), also have a high incidence of mutation within the
MDR1 gene (coding for P-glycoprotein) and are sensitive to the toxic effects of ivermectin.
[119][120] Clinical evidence suggests kittens are susceptible to ivermectin toxicity.
[121] A 0.01% ivermectin topical preparation for treating
ear mites in cats is available.
[122]
Ivermectin is sometimes used as an
acaricide in reptiles, both by injection and as a diluted spray. While this works well in some cases, care must be taken, as several species of reptiles are very sensitive to ivermectin. Use in turtles is particularly contraindicated.
[123]
A characteristic of the antinematodal action of ivermectin is its potency: for instance, to combat
Dirofilaria immitis in dogs, ivermectin is effective at 0.001 milligram per kilogram of body weight when administered orally.
[76]
For dogs, the insecticide
spinosad may have the effect of increasing the toxicity of ivermectin.
[124][125]
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