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Canine Parasite Has Evolved Resistance to All Treatments 

When it comes to parasites in the companion animal world, hookworms are one of the most prevalent.

They latch onto an animal's intestines with their hook-like mouths, where they feed on fluids and blood from the tissue and blood vessels. Animals infected with the virus can suffer from severe weight loss, bloody stool, anemia, and lethargy, among other symptoms.

In recent years, according to new research from the University of Georgia, they have evolved into multidrug resistant organisms.

Currently, veterinarians in the United States rely on three different types of drugs to kill hookworms, but the parasites appear to be becoming resistant to all of them. Initially reported in 2019, this concerning development was confirmed by researchers from the University of Georgia College of Veterinary Medicine. More recent research, published recently in the International Journal for Parasitology: Drugs and Drug Resistance, provides more insight into how the problem began and how severe it has become since then.

The researchers concentrated their attention on current and former racing greyhounds for the current study. Hookworms thrive in sandy soil, which makes dog racetracks a prime breeding ground for the parasite. Because of this, hookworms are particularly prevalent at these facilities. Given the circumstances, deworming is performed approximately every three to four weeks on all dogs.

In their study, which included fecal samples collected from three veterinary practices that work with adoption groups, as well as from an active racing kennel, the researchers discovered that parasitic infections were extremely common in the greyhound breed. Hookworms were found in four out of every five greyhounds who were tested for them. And, according to Ray Kaplan, the study's corresponding author and a former professor of veterinary parasitology at the University of Georgia, the animals that tested negative are almost certainly infected as well.

Occasionally, hookworms can "hide" in tissues, where they will not reproduce or shed eggs until the infection becomes severe enough to leak into the dog's intestines, at which point the infection will be fatal.

But, perhaps more concerning, the team discovered that the dogs continued to have high levels of hookworm infection even after they had been treated for the parasite.

The findings of this study represent the first documented demonstration of widespread multiple-drug resistance in a canine parasite anywhere in the world.

Mutations in Parasites

In environments where there are a large number of dogs infected with a large number of parasites, such as racing dog breeding farms and kennels, there are many more opportunities for parasites to develop rare mutations that allow them to survive dewormer treatments than in other environments. The newly emerging resistant worms will survive if dewormers are applied on a regular basis, and they will pass on the mutation that allowed them to sneak past the drug to their offspring.

If you treat your farm or kennel repeatedly over time, the majority of the drug-sensitive worms will be eliminated, and the resistant worms will take over as the dominant species.

A further complication is that veterinarians do not typically test animals after treatment to ensure that the worms have been eliminated, which means that the drug-resistant worms go undetected until the dog has a severe infection and begins to show signs of hookworm disease.

A mutation in hookworms that allows them to survive treatment with benzimidazoles, which are a broad-spectrum class of dewormers used in both animals and humans, were discovered by the researchers in almost all of the fecal samples tested. Despite the fact that a molecular test for resistance to the other two types of drugs does not yet exist, other types of testing performed by the team revealed that the hookworms were also resistant to those drugs.

The adoption industry for greyhounds is extremely active, largely due to the fact that they are lovely dogs, according to Kaplan. "I used to have one of these." However, as those dogs are adopted, the drug-resistant hookworms will begin to appear in other dogs, including pet dogs."

In addition to being a potential breeding ground for a drug-resistant hookworm outbreak, dog parks are a popular place for dog owners to take their animals for exercise.

I wouldn't bring my dog to a dog park, personally," Kaplan asserted. "If your dog becomes infected with these resistant hookworms, it is no longer as simple as simply treating them with medication." Until new types of drugs become available, taking your dog to a dog park must be considered a potentially dangerous activity."

The consequences

It is not necessary for dogs to ingest the worms in order to become infected. Despite the fact that hookworm larvae live in the soil, they can burrow through the skin and paws of dogs. In addition, female dogs can pass the parasite on to their puppies through their milk if they are pregnant.

Not only that, but dog hookworms can also infect humans, which is extremely frightening.

Although the infection does not manifest itself in the same way in humans, once the worms have penetrated the skin, they cause a red, extremely itchy rash as they travel beneath the surface of the skin. As the number of drug-resistant worms increases, they will become a greater threat to humans.

Previously, doctors would prescribe an ointment that contained both a dewormer and a corticosteroid to treat patients with ringworm. In the case of drug-resistant hookworms, Kaplan explained that "unfortunately" this approach would be ineffective.

However, all hope is not completely lost.

Kaplan and Pablo Jimenez Castro, the study's lead author and a recent doctoral graduate from Kaplan's lab, discovered in another recent study that these multiple-drug resistant dog hookworms do appear to be susceptible to emodepside, a dewormer that is currently only approved for use in cats in the United States, according to the study. However, the administration of this cat medication to dogs should only be done under the supervision and guidance of a veterinarian, as it necessitates veterinary expertise and supervision.

The American Association of Veterinary Parasitologists (AAVP) recently established a national task force to address the issue of drug resistance in canine hookworms, which was inspired in part by Castro's research.

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