Onchocerca lupi Nematodes in Dogs Exported from the United States into Canada

Abstract

The Onchocerca lupi nematode is an emerging helminth capable of infecting pets and humans. We detected this parasite in 2 dogs that were imported into Canada from the southwestern United States, a region to which this nematode is endemic. We discuss risk for establishment of O. lupi in Canada.

Keywords: Canada; Onchocerca lupi; United States; canine ocular onchocerciasis; dogs; importation; nematode; parasites; vector-borne infections; zoonoses.

Figure 1

Histologic section of the eye of a dog infected with Onchocerca lupi nematodes, Summerside, Prince Edward Island, Canada. The typical O. lupi nematode cuticular pattern is shown, with 2 inner transverse striae (dashed arrows) within the interval between 2 outer cuticular ridges (solid arrows). Hematoxylin and eosin stain, original magnification ×100. Scale bar indicates 20 μm.

Figure 2

Phylogenetic relationship among the Onchocerca lupi nematode isolates from a dog in Calgary, Alberta, Canada (GeneBank accession nos. KT833351 and KT833352), and other filarial nematodes in the family Onchocercidae on the basis of the mitochondrial NADH dehydrogenase subunit 5 gene. The parsimonious tree depicts reciprocal monophyly of gene sequence derived from O. lupi nematodes from North America and Europe. Bootstrap consensus was inferred from 1,000 replicates. Values along branches are bootstrap values. Branches corresponding to <50% bootstrap replicates are collapsed. GenBank accession numbers are shown for all isolates. Analysis was performed by using MEGA 6 (http://www.megasoftware.net/). Canine heartworm (Dirofilaria immitis) was used as an outgroup.