Canine ocular onchocercosis in the United States is associated with Onchocerca lupi.

Canine ocular onchocerciasis has a worldwide distribution and has been associated in Europe with Onchocerca lupi based on morphologic and molecular analysis. In the United States, canine ocular onchocerciasis is reportedly associated with Onchocerca lienalis. This association is based solely on histopathologic examination of ocular tissues. The purpose of this study was to use molecular analysis of formalin-fixed, paraffin-embedded canine ocular tissue to determine the genetic identity of Onchocerca associated with canine ocular onchocerciasis in the United States. PCR and DNA sequencing of the mitochondrial cytochrome oxidase I (cox1) and NADH hydrogenase 5 (nd5) genes demonstrated >99% similarity between the sequences obtained from canine ocular tissues previously diagnosed with onchocerciasis. The obtained sequences were most similar to O. lupi (>99% similarity). This report confirms for the first time that O. lupi is associated with canine ocular onchocerciasis in the United States, contrary to previously published reports.