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Macrocyclic lactones and Dirofilaria immitis microfilariae
Dwight D Bowman1, Claire Mannella
1Department of Microbiology and Immunology, Veterinary Medical Center, Cornell University College of Veterinary Medicine, Ithaca, NY 14853-6401, USA. ddb3@cornell.edu
Topics in Companion Animal Medicine
|December 14, 2011
Summary
Macrocyclic lactones kill heartworm microfilariae but may not fully clear them, potentially leading to resistance. Veterinarians must understand these effects and complications when treating infected dogs.
Area of Science:
- Veterinary Parasitology
- Companion Animal Medicine
Background:
- Extensive research exists on macrocyclic lactones for heartworm prevention and adulticidal effects in dogs.
- Limited attention has been given to the impact of these drugs on heartworm microfilariae.
Purpose of the Study:
- To review the biology and diagnostic testing of heartworm microfilariae.
- To discuss the effects of macrocyclic lactones on microfilariae in infected dogs, with or without adulticide treatment.
- To highlight potential complications and the risk of developing resistance.
Main Methods:
- Review of veterinary literature on macrocyclic lactones and heartworm microfilariae.
- Discussion of drug mechanisms, efficacy, and safety in microfilaremic dogs.
- Exploration of diagnostic testing and resistance markers.
Main Results:
- Macrocyclic lactones possess microfilaricidal properties, but clearance can be slow and incomplete in some dogs.
- 10-20% of treated dogs may retain circulating microfilariae, raising concerns about resistance.
- Evidence suggests potential selection for macrocyclic lactone resistance in heartworms.
Conclusions:
- Veterinarians should be aware of the benefits and complications of using macrocyclic lactones in microfilaremic dogs.
- Preserving the effectiveness of macrocyclic lactones is critical due to their unique role in prevention.
- Further research is needed to fully elucidate microfilarial clearance mechanisms and manage resistance.
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