Current issues in heartworm chemotherapy.

Area of Science:

• Veterinary Parasitology
• Molecular Biology
• Epidemiology

Background:

• Heartworm infection incidence is increasing in the USA, with contributing factors like climate change, vector range, and parasite resistance poorly understood.
• Macrocyclic lactone resistance (MLR) in heartworms is a growing concern, with genomic markers indicating rising resistance allele frequencies, though causative mechanisms remain elusive.
• Extra-label use of emodepside for treating drug-resistant hookworms (Ancylostoma caninum) in dogs presents a potential safety concern, as its efficacy and safety in heartworm-infected dogs are unreported.

Purpose of the Study:

• To highlight critical research needs in heartworm prevention and treatment.
• To investigate the factors contributing to the increasing incidence of heartworm infections.
• To address concerns regarding macrocyclic lactone resistance and the extra-label use of emodepside in canine parasitic infections.

Main Methods:

• Review of current literature on heartworm epidemiology and resistance mechanisms.
• Analysis of genomic markers associated with macrocyclic lactone resistance.
• Assessment of the implications of extra-label drug use in veterinary medicine.

Main Results:

• Factors like climate change, vector expansion, compliance, and macrocyclic lactone resistance (MLR) are likely interrelated drivers of increased heartworm incidence.
• Genomic markers for MLR are increasingly prevalent, but their phenotypic relevance and the specific genes involved require further investigation.
• Emodepside, used off-label for resistant hookworms, has potential activity against filarial parasites, but its safety in heartworm-coinfected dogs is unknown.

Conclusions:

• Urgent research is needed to understand and combat rising heartworm incidence and MLR.
• Phenotypic validation of MLR markers and identification of resistance genes are critical.
• Veterinarians should assess heartworm status before treating dogs with emodepside for resistant hookworms due to unknown safety profiles.