The American Animal Hospital Association (AAHA) has released its 2026 AAHA One Health Guidelines: Emerging Concerns in Canine and Feline Parasitology, providing veterinary professionals with practical recommendations for recognizing, diagnosing, treating, and discussing emerging parasitic threats in companion animals. The guidelines emphasize that parasite control is no longer simply about routine deworming. Instead, it requires a comprehensive One Health approach that considers animal health, human health, and environmental factors.
According to the guidelines, an emerging parasite may be a pathogen that has increased in prevalence, expanded into new geographic regions, reappeared after a period of absence, or developed resistance to available treatments. AAHA identifies four primary drivers behind parasite emergence:
- Antiparasitic drug use and resistance
- Environmental and host-related changes
- Increased animal movement and interaction
- Improved surveillance, diagnostics, and awareness
The 12 Emerging Parasites of Greatest Concern
The AAHA task force identified the following emerging parasites as the highest-priority concerns for dogs, cats, or both in North America:
- Ancylostoma caninum with multiple anthelmintic drug resistance (MADR)
- Baylisascaris procyonis (raccoon roundworm)
- Cercopithifilaria bainae (canine filarial nematode)
- Cochliomyia hominivorax (New World screwworm)
- Praziquantel-resistant Dipylidium caninum (flea tapeworm)
- Dirofilaria immitis with macrocyclic lactone loss of efficacy
- Echinococcus granulosus
- Echinococcus canadensis
- Echinococcus multilocularis
- Haemaphysalis longicornis (Asian long-horned tick)
- Heterobilharzia americana (canine schistosomiasis fluke)
- Trypanosoma cruzi (agent of Chagas disease)
Why These Guidelines Matter
Several of the parasites highlighted in the document represent challenges that many practitioners may not have encountered routinely in the past. Drug-resistant hookworms and tapeworms, heartworm strains with reduced preventive efficacy, the re-emergence of New World screwworm, and the continued spread of zoonotic parasites underscore the need for heightened vigilance. Many of these organisms also carry significant public health implications, reinforcing the importance of a One Health framework.
The guidelines encourage veterinary teams to adopt antiparasitic drug stewardship principles, including selecting the right drug for the right patient and monitoring treatment outcomes. This approach aims to preserve the effectiveness of existing therapies while limiting the development of resistance.
Strengthening Client Communication
One of the most valuable aspects of the new guidelines is the emphasis on client communication. The document recognizes that disease prevention efforts are only effective when pet caregivers understand parasite risks, zoonotic concerns, and the rationale behind preventive recommendations. Veterinary teams are encouraged to engage in open conversations about parasite control, address treatment hesitancy, and develop individualized prevention strategies that align with each animal’s lifestyle and exposure risks.
Key Takeaway for Veterinary Teams
AAHA’s 2026 guidelines send a clear message: emerging parasitic diseases demand a proactive, multifaceted response. Routine screening, accurate diagnostics, responsible antiparasitic use, ongoing surveillance, and effective client education all play critical roles in protecting companion animals and public health. As parasite distributions, resistance patterns, and environmental conditions continue to evolve, veterinary professionals must remain adaptable and informed to stay ahead of these emerging threats.
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