New AAHA guidelines warn of emerging parasites in dogs and cats. Learn what is driving them, how to spot signs, and how to protect your pet and family.

Emerging Parasites in Dogs and Cats: What Pet Owners Need to Know

Fleas, ticks and worms are nothing new, but the way they affect our pets is changing. This week, the American Animal Hospital Association (AAHA) released new guidelines that warn veterinary teams about emerging parasites in dogs and cats. The guidelines are written for vets, but the message matters to every pet owner. Here is a plain-language guide to what the guidelines say, why parasites are emerging, and what you can do to protect your pet and your family.

The Short Answer

Some parasites are becoming more common, spreading to new areas, or resisting the drugs that used to control them. The 2026 AAHA guidelines focus on 12 emerging parasites of greatest concern in dogs and cats, and a further nine of potential concern. The advice for owners comes down to this: keep up with parasite prevention, test regularly, and talk openly with your vet about your pet’s lifestyle and travel.

What Are the 2026 AAHA One Health Guidelines?

AAHA published the 2026 AAHA One Health Guidelines: Emerging Concerns in Canine and Feline Parasitology on October 29, 2026. Key facts:

• Free to read: The guidelines are available at aaha.org/one-health-parasitology and in the Journal of the American Animal Hospital Association (JAAHA).
• Aimed at vet teams: They cover how to recognise, diagnose and treat each parasite, and how to talk to pet owners about it.
• A One Health approach: This means treating parasites as a concern for pets, people and the wider environment together, because some parasites can pass between animals and humans.
• Industry support: The guidelines were supported by several animal health companies, including Boehringer Ingelheim, Antech Diagnostics, Merck Animal Health and Zoetis.

What Is an Emerging Parasite?

According to the guidelines, an emerging parasite is one that has recently become more common, or is on track to do so. The definition covers several situations:

• Infections that are newly recognised in a population
• Parasites that are new to an area or are returning to one
• Parasites that have become resistant to treatment

Why Are Parasites Emerging? Four Main Drivers

The guidelines identify four main reasons:

1. Antiparasitic use and resistance. Frequent, intensive use of parasite drugs can favour resistant parasites over time.
2. Environmental and host changes. Shifts in climate, land use and animal movement can expand where parasites live, and may affect how well treatments work.
3. More animal movement and contact. Travel, relocation, disaster sheltering, daycare and off-leash play can spread parasites, especially when animals are not screened.
4. Better detection. Improved surveillance and more sensitive tests are finding infections that went unnoticed before. So part of the rise reflects better detection rather than only more disease.

Which Parasites Are of Concern?

The full list of 12 is in the guidelines, so check the original document or your vet for the details that apply to your area. Several topics highlighted in the guidelines’ resource list give a flavour of what is emerging:

• Heartworm resistance: Research is looking at heartworm strains that resist common preventives, and at newer products designed to overcome that resistance.
• Echinococcus tapeworms: Scientists are tracking an emerging tapeworm in dogs from the United States and Canada, detected with faecal DNA tests.
• Tick-borne disease in cats: One resource focuses on preventing Cytauxzoon infection in cats, which is spread by ticks.

These are examples of the issues under study, not the guidelines’ official ranking. Which parasites matter most depends on where you live, so ask your vet about local risks.

Why This Matters for People, Too

Some parasites can spread from pets to humans, which is why the guidelines take a One Health view. The guidelines encourage vets to explain zoonotic risks and prevention options to owners. For households with young children, older adults, pregnant women or people with weakened immune systems, parasite control is part of protecting the whole family.

What Can Pet Owners Do?

There is no single solution to parasite control, as one of the guidelines’ co-chairs, parasitologist Dr. Kathryn Duncan, points out. A combination of measures works best, and good communication with your vet is part of that. Practical steps:

• Follow your vet’s prevention plan. Keep up with year-round protection as advised, and do not skip, stretch or swap products on your own.
• Test regularly. Standard US parasite guidance recommends yearly heartworm testing for dogs, and yearly testing for tick-borne infections in areas where they occur or are emerging. It also calls for several faecal tests in a puppy’s first year, and at least two a year for adult pets, depending on health and lifestyle.
• Tell your vet about travel and activities. Mention boarding, daycare, dog parks, trips abroad or moving house, because these raise exposure.
• Check for ticks and fleas. Run your hands over your pet after walks in grassy or wooded areas, especially in tick season.
• Keep your home and yard clean. Pick up pet waste promptly and wash your hands after handling pets, soil and litter.
• Raise concerns openly. If you hesitate about giving a medication, talk to your vet. The guidelines’ co-chair Dr. Jason Stull notes that open conversations about drug use and the barriers to it are an important, often overlooked part of parasite control.

Signs Your Pet May Have a Parasite

Signs vary by parasite, and some pets show none. Common warning signs include:

• Diarrhoea or vomiting that does not go away
• Weight loss despite a normal appetite
• Scratching, scooting or hair loss
• A dull coat or a pot-bellied look in young animals
• Coughing, tiredness or reduced stamina
• Visible worms in stool or around the tail

See a vet if you notice these signs. Early testing is easier and cheaper than treating a serious infection.

Frequently Asked Questions

What are emerging parasites in dogs and cats?

They are parasites that have recently become more common, appeared in new areas, or become resistant to treatment. The AAHA guidelines identify 12 of greatest concern and nine of potential concern.

Why are parasites becoming more common?

The guidelines name four main drivers: drug resistance, environmental and climate changes, increased travel and contact between animals, and better testing that finds infections more often.

Can pet parasites infect people?

Some can. That is why the guidelines take a One Health approach, and why good hygiene and regular prevention matter for the whole household.

How often should I test my pet for parasites?

Standard US guidance recommends yearly heartworm tests for dogs and several faecal tests in the first year of life, then at least twice a year for adults, depending on health and lifestyle. Your vet will tailor this to your pet.

Should I stop giving my pet parasite medicine if resistance is increasing?

No. Follow your vet’s advice. Resistance is a reason for vets to use products thoughtfully and for owners to follow the plan, not to stop prevention.

Where can I read the guidelines?

They are free at aaha.org/one-health-parasitology. They are written for vets, so you may want to discuss them with yours.

Sources

• AAHA press release via EIN Presswire: AAHA releases 2026 One Health guidelines on emerging parasites in dogs and cats
• AAHA: 2026 AAHA One Health Guidelines: Emerging Concerns in Canine and Feline Parasitology
• Pet Age: AAHA Releases 2026 One Health Guidelines on Emerging Parasites in Dogs, Cats
• Companion Animal Parasite Council: CAPC Guidelines

This article is general information and not veterinary advice. Parasite risks vary by region, so consult your vet about the best plan for your pet.