Letter to dvm360: More options for intestinal parasite control

dvm360dvm360 April 2019
Volume 50
Issue 4

A reader responds to Dr. Gerholds January Just Ask the Expert column with suggestions.

In the January edition of dvm360 magazine, “Just Ask the Expert” by Dr. Richard Gerhold discussed the problem of hookworm re-infestation of dogs receiving a monthly heartworm preventive. I would add to the discussion the option of giving the dog the heartworm preventive every two weeks instead of once a month. The environment of these animals is hopelessly contaminated with hundreds of thousands-or millions-of hookworm, roundworm and whipworm eggs that will survive for years. Dr. Gerhold neglected to mention this option, and I would propose that it is the best option for dogs with these parasites.

-Rocky Deutsch, DVM Manassas, Virginia

Dr. Gerhold responds

Although it is doable (and extralabel use) to give two doses of a heartworm preventive that's also effective against intestinal parasites (such as hookworms) in one month to help control this problem, alternatively you could give an appropriate dose of pyrantel pamoate or fenbendazole in the middle of month. Also, alternatively, if you're using imidacloprid-moxidectin (Advantage Multi for Dogs-Bayer), the drug reaches a steady-state plasma concentration after administration for five consecutive months.1 This would help, especially if larval leak is occurring.

Larval leak occurs when the larvae of hookworms arrest in dog muscle; they are activated once the adult parasites in the intestines are expelled due either to drug administration or worm death by other means. The larvae can continue to “leak” from muscle to the gastrointestinal lumen for some time, depending on the larval burden level in the muscle.

-Richard Gerhold, DVM, MS, PhD Department of Biomedical and Diagnostic Sciences, College of Veterinary Medicine University of Tennessee


  1. von Samson-Himmelstjerna G, Epe C, Schimmel A, et al. Larvicidal and persistent efficacy of an imidacloprid and moxidectin topical formulation against endoparasites in cats and dogs. Parasitol Res 2003;90(Suppl 1):114-115.
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