Prevalence and genetic characterization of Dirofilaria lutrae Orihle, 1965 in North American river otters (Lontra canadensis)

Dirofilaria lutrae Orihle, 1965 is a subcutaneous filarial worm found in North American river otters (Lontra canadensis). Previous studies reported the geographical range of this worm to include Louisiana, Florida, and North Carolina, USA. Although D. lutrae does not cause disease in otters, it must be distinguished from Dirofilaria immitis (Leidy, 1856), which causes heartworm disease in otters. The goal of this study was to determine the prevalence of D. lutrae in several states and to investigate the phylogenetic relationship of D. lutrae and other Dirofilaria species. Adult D. lutrae were collected from 32 of 40 (80%) otters from North Carolina (n = 38), South Carolina (n = 1), and Kentucky (n = 1), whereas all otters from Georgia (n = 1), Pennsylvania (n = 2), Arkansas (n = 184) and California (n = 1) were negative for D. lutrae. A portion of the cytochrome c oxidase I (COI) was amplified from nine North Carolina specimens and one South Carolina specimen. Sequence analysis indicated that all but one were identical to each other and D. lutrae was phylogenetically most closely related to D. immitis; however, few Dirofilaria sequences are available for comparison. Because other subcutaneous parasites may be detected in otters, parasites should be carefully examined to confirm their identity. Finally, given the high prevalence of D. lutrae in otters in some southeastern states, microfilaria found in blood samples of otters must be correctly identified because treatment for D. lutrae is generally not warranted and some pharmaceutical treatments can cause mortality in otters.