Another dose of dewormer may be the wrong move for a dog whose worms keep coming back. Ask your vet about a fecal egg count reduction test first. That's the most practical point for ordinary owners in a new guideline on emerging parasites in dogs and cats from the American Animal Hospital Association (AAHA). AAHA published it on October 28 for veterinary teams, and it names 12 parasites of most concern. Most are tied to a region or a habit, so we've sorted the list by who should ask about what.
Your pet's situation and what to ask
| Your situation | Parasite on the list | What to ask or do |
|---|---|---|
| Hookworms return after treatment | Multidrug-resistant hookworm | Fecal egg count reduction test |
| Tapeworm segments keep appearing | Flea tapeworm that resists praziquantel | Clear the fleas first, then ask about resistance |
| Raccoons use your yard | Raccoon roundworm | Extra fecal exams or a monthly roundworm product |
| Your dog hunts or scavenges in Alaska, the northern US or the upper Midwest | Echinococcus tapeworms | Routine fecal testing, and no raw offal or carcasses |
| Your dog wades in fresh water near the Gulf Coast | Heterobilharzia, a blood fluke | Saline sedimentation or fecal PCR test |
| Your dog lives in the southern US | Trypanosoma cruzi, spread by kissing bugs | Ask your vet about suitable protection against kissing bugs |
| You live between New York, Georgia and Missouri | Long-horned tick | Stay on regular tick prevention |
A routine fecal flotation test misses the blood fluke, which is why that row names different tests. The long-horned tick has spread to more than 20 states, but it isn't yet known to carry disease to dogs, cats or people in the US.
The list also names New World screwworm, which vets must report to state and federal animal health officials.
Hookworms that survive the usual dewormers
Some hookworms now survive all three main classes of dewormer. Cases of this multidrug-resistant strain have been reported across the US. Infected dogs can have diarrhea, weight loss and signs of anemia.
Resistance isn't the only explanation, and your vet will want to rule out the others. A new infection can start shedding eggs within two to four weeks, before the next monthly dose. Larvae stored in the body can also move back into the gut, and dogs that eat feces can reinfect themselves.
Your vet can count eggs before treatment and repeat the count 10 to 14 days afterward. AAHA recommends a combination of dewormer classes for confirmed resistant hookworms, with follow-up testing to check whether treatment worked. Do not assemble that combination yourself.
Extra dewormer can backfire
AAHA warns against adding a broad-spectrum dewormer to an overlapping monthly heartworm preventive without a clinical reason. Before buying another treatment, give your vet the names and dosing dates of everything your pet already takes. Do not stop prescribed treatment without discussing it with the vet.
Keep up planned prevention, though. The concern is treatment with no look at the pet's real risk. Dose by your pet's current weight too, because underdosing also breeds resistance.
Heartworm preventives still work for most pets
Some heartworm populations carry genetic markers linked to resistance, and they've been found in many states, especially along the Lower Mississippi River Valley. Even so, AAHA says the evidence doesn't show preventives failing widely. The most common reason one fails is a missed dose.
Keep scheduled prevention on track and ask your vet about testing appropriate to your pet. AAHA supports year-round prevention in the US and annual heartworm testing for dogs and cats. Testing a cat differs from testing a dog, so let the clinic choose and interpret the tests.
Raccoon roundworm around the home
Raccoon roundworm deserves attention around play areas used by small children. AAHA reports that up to 90% of raccoons carry it in some areas. Eggs appeared in about five of every 100,000 dog fecal samples in a large US and Canadian study. A positive sample can reflect infection or a dog eating contaminated feces, so that figure is not a direct infection rate.
The CDC says human infections are rare but can be severe, and most involve children who get dirt or animal waste in their mouths. The eggs take two to four weeks to become infectious, so remove raccoon droppings quickly and carefully, and bag your dog's waste the same day.
Keep children and pets away from a raccoon latrine while arranging safe cleanup. Follow the CDC’s precautions or ask a qualified cleanup service for help. Heat-based methods can cause burns or start fires, so they are not a casual backyard cleaning task.
One tick doesn't mean the product failed
Don't switch products because you found a tick on a treated dog. Many flea and tick products don't repel anything, and the parasite has to bite or touch the pet before the drug works. Finding one doesn't show that the product has stopped working.
The guideline's backers
Antech Diagnostics, Boehringer Ingelheim, Merck Animal Health and Zoetis supported this guideline. AAHA discloses that support on its guidelines page. The recommendations should be assessed on their evidence and your pet’s needs, rather than assuming that sponsorship proves or disproves them.
