The role of Wolbachia species

Wolbachia species bacteria have an endosymbiotic relationship with D. immitis.⁴² This rickettsial organism reportedly plays a role in larval embryogenesis, fertility, and maturation of D. immitis.⁴² The bacteria are found in all the larval stages and are released in considerable amounts during worm molts, microfilariae production, and worm death.⁴³ Researchers have shown that 25 days of tetracycline therapy inhibits Wolbachia species multiplication, thus inhibiting embryogenesis and the maturation of L3 larvae into adult heartworms.⁴² It has been hypothesized that treating heartworm-positive patients with a 25-day tetracycline course before the adulticide treatment may lessen patients' inflammatory responses to the dying worms. This is strictly hypothetical. Future studies are required to determine the true biology of the gram-negative, rickettsial, endosymbiotic Wolbachia species and its role in heartworm disease.

Kevin J. Christiansen, DVM
Meg M. Sleeper, VMD, DACVIM (cardiology)
Matthew J. Ryan Veterinary Hospital
School of Veterinary Medicine
University of Pennsylvania
Philadelphia, PA 19104-6010

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