Hookworms are one of the most common parasites plaguing the companion animal world. Now they’ve become multiple-drug resistant, according to new research from the US.
Right now, veterinarians rely on three types of drugs to kill the hookworms, but the parasites appear to be becoming resistant to all of them.
Researchers from the University of Georgia College of Veterinary Medicine first reported this concerning development in 2019, and new research, published recently in the International Journal for Parasitology: Drugs and Drug Resistance, provides deeper insight into where the problem started and how bad it’s since become.
For the present study, the researchers focused on current and former racing greyhounds. Dog racetracks are particularly conducive to spreading the parasite due to the sandy ground of the facilities, an ideal breeding ground for hookworms. Because of the conditions, all the dogs are dewormed about every three to four weeks.
After analysing fecal samples from greyhound adoption kennels, three veterinary practices that work with adoption groups and an active racing kennel, the researchers found the parasites were highly prevalent in the breed. Four out of every five greyhounds tested came up positive for hookworms. And the ones that tested negative are probably also infected, as hookworms can sometimes ‘hide’ in tissues, where they won’t reproduce and shed eggs until the infection worsens and leaks into the dog’s intestines.
But perhaps more alarming, the team saw that the dogs still had high levels of infection with hookworms even after they were treated for them.
The study marks the first demonstration of widespread multiple-drug resistance in a dog parasite reported in the world.
The researchers found that almost all the fecal samples tested positive for the mutation that enables hookworms to survive treatment with benzimidazoles, a broad-spectrum class of dewormers used in both animals and humans. Although a molecular test does not yet exist to test for the resistance to the other two types of drugs, other types of testing by the team showed that the hookworms were resistant to those drugs as well.
“There’s a very committed greyhound adoption industry because they are lovely dogs,” Professor Ray Kaplan said. “I used to own one. But as those dogs are adopted, the drug-resistant hookworms are going to show up in other pet dogs.”
One possible breeding ground for a potential drug-resistant hookworm outbreak is also the place many dog owners use to exercise their animals: dog parks.
“Personally, I would not take my dog to a dog park,” Professor Kaplan said. “If your dog picks up these resistant hookworms, it’s not as easy as just treating them with medication anymore. Until new types of drugs are available, taking your dog to a dog park has to be considered a risky activity.”