Phylogenetics of Dracunculus Nematodes in North America

Madeline Giner, from the University of Texas at San Antonio, studied the phylogenetics of Dracunculus in the lab of Dr. Christopher Cleveland.

The Dracunculus genus contains parasitic nematodes that infect a variety of hosts, including reptiles and mammals. Dracunculus medinensis, the Guinea worm, has gained much attention due to its history of infecting humans. Less studied are other dracunculids, including Dracunculus insignis and D. lutrae which are native to North America. D. insignis can infect a variety of mammalian hosts, whereas D. lutrae specifically infects North American river otters (Lontra canadensis). The goal of this project was to investigate the genetic diversity of Dracunculus in wildlife species from the Eastern USA and investigate spatial and host patterns of infection. Phylogenetic relationships were examined using the cytochrome c oxidase I (COI) gene targets. We hypothesized otters would predominantly have D. lutrae, and D. insignis would be identified from other hosts. Our experimental methods included DNA extraction, gene-specific amplification (PCR), Sanger sequencing, and phylogenetic analysis using the software Geneious. Our results indicate that a majority of worms from otters (19/65), raccoons (Procyon lotor, 22/22), and Virginia opossums (Didelphis virginiana, 2/2) were D. insignis. However, a worm from an otter from Florida had 100% identity to a novel Dracunculus sp. previously detected in Georgia, and a Georgia otter worm is closely related to another novel dracunculid species from Florida. In conclusion, D. insignis was present in most locations and hosts, D. lutrae is absent, and an additional host is now known for two novel Dracunculus species. These data provide new information about Dracunculus diversity in US wildlife, but additional investigation is required.