Hookworms evolved to evade all the FDA-approved drugs vets use to kill them – sciencedaily

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Hookworms are one of the most common parasites in the pet world.

They use their hook-shaped mouths to cling to an animal’s intestines, where they feast on tissue fluids and blood. Infected animals can experience dramatic weight loss, bloody stools, anemia, and lethargy, among other problems.

Now, they’ve become multidrug resistant, according to a new study from the University of Georgia.

Right now, American vets use three types of drugs to kill hookworms, but the parasites seem to be becoming resistant to all of them. Researchers at the UGA College of Veterinary Medicine first reported this development regarding development in 2019 and new research, recently published in the International Journal of Parasitology: Drugs and Drug Resistance, provides a deeper insight into the origin of the problem and its severity since.

For the present study, the researchers focused on current and former racing greyhounds. Dog racetracks are particularly conducive to the spread of the parasite because of the sandy soil in the facilities, ideal breeding ground for hookworms. Due to the conditions, all dogs are dewormed approximately every three to four weeks.

After analyzing stool samples from adopted greyhound kennels, three veterinary offices working with adoption groups, and an active racing kennel, the researchers found that the parasites were very common in the breed. Four out of five greyhounds tested tested positive for hookworms. And those who tested negative are likely infected as well, said Ray Kaplan, study correspondent author and former UGA professor of veterinary parasitology. Hookworms can sometimes “hide” in the tissues, where they will not reproduce and egg until the infection worsens and seeps into the dog’s intestines.

But perhaps more alarmingly, the team found that the dogs still had high levels of hookworm infection even after being treated for them.

The study marks the first demonstration of widespread drug resistance in a dog parasite reported worldwide.

Parasitic mutations

In situations where there are a lot of dogs infected with a lot of parasites, such as in racing dog breeding farms and kennels, there are many more opportunities for the parasites to develop rare mutations allowing them to survive deworming treatments. If dewormers are applied frequently, the new resistant worms that emerge will survive and pass on the mutation that helped them pass the drug to their offspring.

With repeated treatments over time, most drug-sensitive worms on the farm or kennel will be killed, and resistant worms will predominate.

To make the problem worse, vets usually don’t test animals after treatment to make sure the worms are gone, so drug-resistant worms go undetected until the dog has a serious infection and begins to show signs of hookworm.

The researchers found that almost all of the stool samples were positive for the mutation that allows hookworms to survive treatment with benzimidazoles, a class of broad-spectrum dewormers used in both animals and humans. While there is no molecular test yet to test for resistance to the other two types of drugs, other types of tests the team performed have shown that hookworms are resistant to these drugs as well.

“There is a very engaged greyhound adoption industry because they are beautiful dogs,” Kaplan said. “I used to own one. But as these dogs are adopted, drug resistant hookworms will appear in other companion dogs.”

A breeding ground for a possible drug-resistant hookworm outbreak is also the place many dog ​​owners use to exercise their pets: dog parks.

“Personally, I wouldn’t take my dog ​​to a dog park,” Kaplan said. “If your dog gets these resistant hookworms, it’s not as easy as just treating them with medication. Until new types of medication become available, taking your dog to a dog park should be considered. a risky activity. “

The results

Dogs do not need to ingest the worms to be infected. Hookworm larvae live in the soil and can also burrow into the skin and paws of the dog. And female dogs can pass the parasite on to their puppies through their milk.

If that’s not scary enough, hookworms in dogs can infect humans as well.

The infection does not manifest itself in the same way in humans, but once the worms enter the skin, they cause a red, very itchy rash when they move under the skin. As the number of drug resistant worms increases, they will also pose a risk to humans.

Previously, doctors treated patients with an ointment containing a dewormer and a corticosteroid. “Unfortunately, it won’t work against these drug-resistant hookworms,” Kaplan said.

But hope is not entirely lost.

Kaplan and Pablo Jimenez Castro, lead author of the study and recent PhD from Kaplan’s lab, found in another recent study that these multi-drug resistant dog hookworms appear to be susceptible to emodepside, a dewormer currently approved only for use in cats. in the United States, but the use of this cat medicine on dogs should only be done by a veterinarian, as it requires veterinary expertise and supervision.

Based in part on Castro’s work, the American Association of Veterinary Parasitologists recently formed a national task force to address the problem of drug resistance in canine hookworms.

The co-authors of this study include Abigail Malatesta, a veterinary student at Tuskegee University, Hannah Huff, currently a veterinary student at the University of Georgia, and researchers at the University of Calgary in Canada.


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