A bacteria found in heartworms makes the worms more vulnerable to treatment
Heartworm infections are a serious problem for dogs living in or traveling to certain regions of the United States. For more than 100 years, veterinarians have known that heartworm disease is caused by a type of long, threadlike parasitic worm called Dirofilaria immitis. The parasite is transmitted by mosquitos, and can be fatal if not treated. Interestingly, D. immitis has its own parasite, the bacteria Wolbachia, and these microbial hitchhikers appear to contribute to heartworm disease.
In the 1970s, using sophisticated electron microscopes, scientists detected bacteria living in the body of both adult and immature heartworms. It took another 20 years for veterinarians to understand that Wolbachia are not just passive passengers in the worm, but play a crucial role in the worm’s survival and in pathogenesis of filarial disease.
Because of this relationship, the discovery of Wolbachia changed how veterinarians treat heartworm disease. The American Heartworm Society recommends that doxycycline, an antibiotic that kills Wolbachia, be given for one month prior to treatment for adult heartworms. Antibiotic therapy directed against Wolbachia leads to decreases in all stages of immature heartworms and might decrease numbers of adult heartworms as well. Because Wolbachia also may contribute to a significant, and often dangerous, inflammatory response seen in some dogs, researchers believe treating with doxycycline might decrease complications associated with heartworm disease both pre- and post-treatment.
Treatment of heartworm infection has improved over the years, but it’s always preferable to protect your dog from heartworm, as well as check your dog for heartworm as recommended by your veterinarian. Testing can vary by region but, regardless of where you live, it’s important to know about heartworm prevalence in your area. Heartworm disease can be deadly but also is preventable, and many excellent heartworm preventive medications are available. Ask your veterinarian which is right for your dog.
Morris Animal Foundation has a long history of funding canine health research into important parasite infections, including heartworm disease. Learn more about our canine health research as well as our commitment to improving animal health around the world. You can learn more about heartworm by visiting the American Heartworm Society.