Researchers have been keeping a close eye on a rising issue affecting dogs throughout the United States, drug-resistant hookworm infections.
These infections are critical to address not only because they can impact your pets but also their owner’s health! Hookworm, specifically in this case, A. Caninum is zoonotic meaning it can spread from animals to humans.
The A caninum isolate has been shown to be resistant to three of the most common antihelminthics formerly used to treat infections pyrantel pamoate, fenbendazole, and milbemycin oxime.
According to the AVMA, a study indicates that infections with drug-resistant hookworms are increasing mainly in the Southeast but have been documented in the Northeast and California.
The good thing is that not all isolates are drug resistant but if A. Caninum becomes widespread they could eventually take over.
How are hookworms spread?
Hookworms live in the intestines of dogs and cats (and other mammals as well including cattle and rodents) once shed they hatch within a day and develop into infective larvae over weeks.
The worms are spread when a dog or cat defecates and releases eggs into the environment. One dog can release hundreds to thousands of worms through their feces.
Signs that your dog has a multidrug-resistant hookworm infection
Some dogs may not exhibit any signs but the most common signs of multidrug-resistant hookworm infection are
- Bloody diarrhea
- Weight loss
- Pale gums
- Lethargy
- Weakness
The most common reason owners bring their dogs in for hookworm is that they actually see physical worms in the stool.
How did the worm become drug resistant?
Parasite researchers think the worm, Ancylostoma caninum, emerged from retired racing Greyhounds and now appears to be spreading to dogs across the United States.
In August 2020 it was noted that “most if not all” racing or retired racing Greyhounds appear to be infected with multidrug-resistant hookworms.
According to the AVMA common reasons researchers believe the issue started in the Greyhound racing population is because of the improper use of parasitic medication including misdosing, inappropriate dosing, or the off-label use of antihelminthic medication meant for livestock.
Greyhounds also may metabolize anthelmintics differently than other breeds and this may also add to the reason for the resistance.
Zoonosis: How hookworms can affect humans
An increase in hookworm shedding can also pose a risk to human health as the larvae can infect people by penetrating unbroken skin.
Once in the skin, the parasites form cutaneous larva migrans or CLM which causes creeping eruption, an infectious syndrome caused by multiple types of hookworms.
Humans normally get a self-limiting very itchy rash on their feet or in the area of initial contact. Unless the worms are eaten they are unable to reach the gastrointestinal tract (GI) and die within the host. If the worms are eaten they will end up in the small intestines and the cycle will continue.
Treatment is usually topical or oral antiparasitic medication.
What can be done?
Researchers have found the parasitic medication, emodepside, which is approved in Europe for use in dogs but this is off-label use in the United States since the product is not officially approved for them.
Emodepside is approved in the United States but only for use in cats. It is in Profender along with praziquantel to be given to cats topically. However, it does not work in dogs topically and must be given orally..
For this reason, if your veterinarian does prescribe emodepside as an off-label use for hookworms they will need to run a blood test for heartworm so be prepared for this added expense.
How to prevent your dog from being infected with worms
While it may be impossible to completely prevent your dog from being infected there are some things you can do to decrease your dog’s chances.
1. Pick up feces
Pick up feces from both your dog and other dogs in the area. While you may be averse to picking up random dog poop if it is in the vicinity of where your dog visits regularly it is a must to decrease your dog’s chances of becoming infected with worms.
The worms are spread from dog to dog via feces usually so if there is infected poop in the area it increases the chances of your dog becoming infected with hookworm.
2. Regularly check their stool for worms
While you can’t see the eggs with your bare eyes as they are microscopic and much too small, if there is an abundance of worms in your dog’s gastrointestinal system adults may begin to make their way out of your dog.
3. Get regular fecals for your dog
Regularly checking your dog’s feces for hookworm eggs is a must to alert you to a possible infection and treat it if necessary.
This should be done at least once a year during your dog’s annual checkup and vaccinations. It is a very easy process, you just collect some poop about the size of a large grape and bring it to your vet clinic. They should be able to take it from there. They will have to look under the microscope to see the hookworm eggs.
If your fecal turns out to be positive make sure you have a follow-up fecal with your vet in 10-14 days after treatment to ensure all of the worms were eliminated.
If your dog does test positive for A. Caninum you or your vet should report the status to the FDA.
References
- To read more about the drug-resistant hookworm on the AVMA website click here
- https://pubmed.ncbi.nlm.nih.gov/32403053/
- https://www.vet.cornell.edu/animal-health-diagnostic-center/news/ancylostoma-caninum-emerging-drug-resistance
- https://businesswales.gov.wales/farmingconnect/news-and-events/technical-articles/roundworms-and-anthelmintic-resistance
