Maximum Parsimony tree depicting phylogenetic relationships among species of Onchocerca inferred from the NADH dehydrogenase subunit 5 (nad5) mitochondrial gene. Branches with less than 70% bootstrap support were collapsed. Bootstrap support shown besides branches are based on 2000 replicates. All sequences labeled as Onchocerca sp. followed by the codes Sv or St were obtained from blackflies from the Los Angeles County, southern California, and have been accessioned at GenBank (MH370252-MH370264). Sv and St refer to Simulium vittatum (s.l.), and S. tescorum, respectively, from which each DNA sequence was obtained. The code SvP23B refers to a pool of S. vittatum (s.l.) bodies. Sequences labeled as Onchocerca sp. followed by GenBank accession numbers JX075232, JX075233, JX075235 and JX075237 originated from upstate New York, and were made available through McFrederick et al.