Peer-reviewed veterinary case report
Heartworm preventives failing in dogs due to drug-resistant parasites
By Bourguinat, Catherine et al.·Published in Veterinary parasitology·2015·Institute of Parasitology, Canada·View original on PubMed →
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Original publication title: Macrocyclic lactone resistance in Dirofilaria immitis: Failure of heartworm preventives and investigation of genetic markers for resistance.
- Species:
- dog
Plain-English summary
A study found that some heartworms (Dirofilaria immitis) in dogs are becoming resistant to common preventives like ivermectin and moxidectin. This means that even when dogs are given these medications, the heartworms can still survive and cause infections. Researchers identified specific genetic markers that could help predict which heartworms are resistant to these treatments. This information is important for veterinarians to monitor and manage heartworm prevention effectively.
People also search for: dog heartworm preventive failure · heartworm resistance ivermectin · moxidectin heartworm treatment issues
Abstract
Macrocyclic lactone (ML) endectocides are used as chemoprophylaxis for heartworm infection (Dirofilaria immitis) in dogs and cats. Claims of loss of efficacy (LOE) of ML heartworm preventives have become common in some locations in the USA. We directly tested whether resistance to MLs exists in LOE isolates of D. immitis and identified genetic markers that are correlated with, and therefore can predict ML resistance. ML controlled studies showed that LOE strains of D. immitis established infections in dogs despite chemoprophylaxis with oral ivermectin or injectable moxidectin. A whole genome approach was used to search for loci associated with the resistance phenotype. Many loci showed highly significant differences between pools of susceptible and LOE D. immitis. Based on 186 potential marker loci, Sequenom(®) SNP frequency analyses were conducted on 663 individual parasites (adult worms and microfilariae) which were phenotypically characterized as susceptible (SUS), confirmed ML treatment survivors/resistant (RES), or suspected resistant/loss of efficacy (LOE) parasites. There was a subset of SNP loci which appears to be promising markers for predicting ML resistance, including SNPs in some genes that have been associated with ML resistance in other parasites. These data provide unequivocal proof of ML resistance in D. immitis and identify genetic markers that could be used to monitor for ML resistance in heartworms.
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Search related cases →Original publication on PubMed: https://pubmed.ncbi.nlm.nih.gov/25936435/