Schaumburg, Illinois, September 15, 2021 - The American Association of Veterinary Parasitologists (AAVP) recently formed a national task force to address an emerging issue in canine and human health: multi-anthelmintic drug resistant (MADR) Ancylostoma caninum, which are canine hookworms resistant to two or more drug classes of FDA-approved dewormers (benzimidazoles, macrocyclic lactones, tetrahydropyrimidines (e.g. pyrantel)). This AAVP Hookworm Task Force, which is composed of 25 members, including veterinarians and parasitologists from academia, industry and government, is developing guidance for veterinary practitioners related to the standard of care for the diagnosis and treatment of MADR A. caninum.
“Multiple anthelmintic resistance in Ancylostoma caninum is much worse than we feared,” said Dr. Ray Kaplan, Professor of Parasitology and Associate Dean for Graduate Studies at the School of Veterinary Medicine, St. George's University. “It has been found in almost every Greyhound fecal sample we recently evaluated from breeding farms and racing tracks, and clinical reports and preliminary molecular data suggest it has entered the pet dog population where we are now finding suspected cases in many non-Greyhound dogs as well.”
Key information for veterinary practitioners:
1.) MADR A. caninum was first identified in racing Greyhounds in the US, many of which have been adopted as pets. Suspected cases are now emerging in non-Greyhound pet dogs across the US. More surveillance is required to determine the geographic distribution as well as the percentage of pet dogs infected.
2.) No validated test for MADR A. caninum is currently available for clinical use. Suspected cases can be evaluated using Fecal Egg Count Reduction Tests (FECRT) which may provide some insight into product efficacy. MADR hookworm infections need to be addressed; failing to implement appropriate diagnostics and treatment could result in a standard of care deficiency.
3.) In dogs documented to have patent hookworm infections after treatment, veterinarians should perform a FECRT, comparing the fecal egg counts before treatment with those at 10 to 14 days after treatment. Dewormers most likely are not effective if hookworm fecal egg counts do not decrease by 75% or more 10–14 days after treatment. The AAVP Hookworm Task Force is developing educational materials to assist practitioners with performing a FECRT. In the meantime, most commercial and university veterinary diagnostic laboratories can provide this service or offer guidance.
4.) The single most important step to limit reinfection and spread is immediate removal of fecal material. Proper disposal of feces can protect dogs from reinfection and prevent further spread of MADR hookworms. Hookworm eggs shed in the environment develop within a few days into infective larvae that can infect other dogs and may be a source of infection to humans, potentially causing cutaneous larval migrans.
Recently published studies provide additional guidance regarding treatment of suspected MADR A. caninum, including:
a.) Hess et al. Combination Anthelmintic Treatment for Persistent Ancylostoma caninum Ova Shedding in Greyhounds. J Am Anim Hosp Assoc. 2019;55(3):160-166. DOI 10.5326/JAAHA-MS- 6904.
b.) Jimenez Castro, P.D. and R.M. Kaplan, Persistent or suspected-resistant hookworm infections. Clinician's Brief (parasitology), 2020 (August).
“MADR hookworms present an even greater need for veterinarians to counsel owners on parasite control, fecal hygiene measures, and required routine diagnostics,” said Dr. Pablo Jimenez Castro. The AAVP Task Force encourages state veterinarians to share information about drug-resistant hookworms because of the potential widespread transmission and zoonotic risk.
Veterinarians should report suspected treatment failure to the product manufacturer or to the Food and Drug Administration by calling 1-888-FDA-VETS or online at http://www.fda.gov/reportanimalae. Reporting these cases will assist in determining the extent of MADR hookworms in dogs across the country.
The information provided is current as of September 3, 2021; however, the veterinary and animal health community is rapidly moving forward to address questions such as the use of historic parasiticides, genotyping, and the geographic distribution of these MADR hookworms.
More in-depth guidance on diagnosis and management of MADR hookworms will be available soon from the AAVP Hookworm Task Force.