A cryptic species of Onchocerca (Nematoda: Onchocercidae) in blackflies (Simulium spp.) from southern California, USA

• Published in: Parasites & vectors 2018-10, Vol.11 (1), p.547-547, Article 547
• Main Authors: Verocai, Guilherme G, Nelson, Kimberly J, Callahan, R Trey, Wekesa, Joseph Wakoli, Hassan, Hassan K, Hoberg, Eric P
• Format: Article
• Language: English
• Subjects: Animals; Aquatic insects; Biodiversity; California - epidemiology; Carbon dioxide; Cervidae; Cryptic species; Current data; Cytochrome; Cytochrome-c oxidase; Cytochromes; Deer; Deer - parasitology; Deoxyribonucleic acid; Disease Vectors; DNA; DNA, Mitochondrial - genetics; Electron Transport Complex IV - genetics; Female; Filarial parasites; Filarioidea; Geographical distribution; Hosts; Insect Vectors - parasitology; Mitochondrial DNA; NADH; NADH dehydrogenase; NADH Dehydrogenase - genetics; Nematodes; Nicotinamide adenine dinucleotide; Nucleotide sequence; Odocoileus hemionus; Odocoileus virginianus; Onchocerca - classification; Onchocerca - genetics; Onchocerca - isolation & purification; Onchocerciasis; Onchocerciasis - epidemiology; Onchocerciasis - transmission; Parasite biodiversity; Parasites; Pathogens; PCR; Phylogeny; Polymerase Chain Reaction; Simuliidae - parasitology; Simulium tescorum; Species diversity; Species richness; Surveillance; Vector-borne diseases; Vectors
• ISSN: 1756-3305; 1756-3305
• DOI: 10.1186/s13071-018-3133-9

Entomological surveillance for pathogens based on molecular screening of putative arthropod vectors such as blackflies (Diptera: Simuliidae) is becoming increasingly important. Surveillance provides a means to understand host and geographical patterns of underestimated biodiversity among North American species of Onchocerca and a pathway to identify and track expanding emergence of the zoonotic Onchocerca lupi. Herein, we have screened two blackfly species, Simulium tescorum and Simulium vittatum (s.l.), from Los Angeles County, southern California, USA for DNA of filarioid nematodes to better understand species richness and limits within the genus Onchocerca. A total of 1056 and 378 female blackflies was collected using CO -baited mosquito traps from March to November of 2015 and 2016, respectively. All blackflies during 2015 were individually processed for DNA extraction and PCR targeting of the cytochrome c oxidase subunit 1 (cox1) of the mitochondrial DNA (mtDNA). Specimens of S. tescorum collected in 2016 were processed individually with heads and bodies extracted separately, whereas those of S. vittatum (s.l.) were processed in pooled samples with heads and bodies extracted separately. A subset of filarioid-positive samples from 2015 and all samples from 2016 were screened using a PCR targeting the NADH dehydrogenase subunit 5 (nad5) gene (mtDNA). In 2015, 356 S. tescorum (33.7%) and 683 S. vittatum (s.l.) (64.7%) were collected, and an additional 17 specimens were not assessed morphologically. In 2016, a total of 378 blackflies was collected. Of these, 43 (11.6%) were S. tescorum and 327 (88.4%) were S. vittatum (s.l.), and an additional 8 specimens were not assessed morphologically. In 2015, Onchocerca sequences were detected in 4.8% (n = 17) of S. tescorum samples, and only one S. vittatum (0.15%). In 2016, only a single S. vittatum pool was positive for the same cryptic Onchocerca species. In phylogenetic comparisons based on nad5, the Onchocerca sequences from California formed a clade with those isolates in white-tailed deer from upstate New York, suggesting these belong to a single widespread cryptic species. An uncharacterized species of Onchocerca associated with cervid hosts was found in blackflies from southern California. Sequence data demonstrated it is likely conspecific with an unnamed species of Onchocerca previously found in white-tailed deer from upstate New York. Current data support recognition of a broad geographical distribution