Wolbachia infection and mitochondrial diversity in the canine heartworm (Dirofilaria immitis)

Abstract

Background and aims: Many species of filarial nematodes are infected with Wolbachia pipientis, a maternally inherited endosymbiont. In addition to manipulating host reproduction, these bacteria also affect the evolution of the mitochondrial DNA with which they are transmitted. Selective sweeps can establish a single mitochondrial lineage within a Wolbachia-infected population and purge genetic diversity. While this phenomenon has been studied in insect model systems, it has not been thoroughly examined in a filarial nematode.

Materials and methods: Patterns of mitochondrial diversity were examined in Dirofilaria immitis, a Wolbachia-infected species.

Results: The levels of genetic diversity observed in canine heartworm were much lower than those in related species not known to be hosts of Wolbachia. Conclusion: Results suggest that a maternally inherited endosymbiont can depress mitochondrial diversity in a filarial host.

Keywords::

• Canine heartworm
• endosymbiont
• selective sweep
• genetic diversity

Acknowledgements

Numerous veterinarians, researchers, wildlife officials, and trappers across the country enthusiastically provided us with heartworm specimens. The authors would like to thank E. Greiner (University of Florida), T. Craig and D. McIntosh (Texas Agriculture and Mining University), T. Nolan (University of Pennsylvania), B. Sacks, J. Theis, and S. Nadler (University of California Davis), E. Howerth (University of Georgia), P. Payne (Kansas State University), J. M. Lockhart (Valdosta State University), D. Paulsen (Louisiana State University), N. Heininger (Princeton University), and the following people from USDA-APHIS: A. Piaggio, Y. Toxqui, S. Swafford, M. Pipas, M. Milleson, D. Emanueli, K. Van Why, G. Wiscomb, S. Woodruff, T. Felix, T. Puckett, B. Leland, L. Tschirhart-Hejl, W. Gaston, D. Hughes, D. LeBlanc, K. Shively, and B. Zscheile. R.F. Rockwell provided useful comments on the manuscript. Without their help, this research would not have been possible.

Declaration of interest: The authors report no conflicts of interest. The authors alone are responsible for the content and writing of the paper.