Research Article

Cryptic Onchocerca species infecting North American cervids, with implications for the evolutionary history of host associations in Onchocerca


a1 Department of Biology, University of Rochester, Rochester, NY 14627, USA

a2 Department of Ecosystem and Public Health, Faculty of Veterinary Medicine, University of Calgary, 3330 Hospital Drive NW, Calgary AB, Canada T2N 4N1


Parasites in the genus Onchocerca infect humans, ruminants, camels, horses, suids, and canids, with effects ranging from relatively benign to debilitating. In North America, Onchocerca cervipedis is the sole species known to infect cervids, while at least 5 Onchocerca species infect Eurasian cervids. In this study, we report the discovery of a cervid-parasitizing Onchocerca only distantly related to O. cervipedis. To reconstruct the phylogenetic history of the genus Onchocerca, we used newly acquired DNA sequence from O. cervipedis (from moose in Northwest Territories, Canada) and from the newly discovered species (from white-tailed deer in upstate New York), as well as previously published sequences. Ancestral host reconstructions suggest that host switches have been common throughout the evolutionary history of Onchocerca, and that bovid- and cervid-parasitizing species have been particularly important sources of descendant species. North America cervids might therefore serve as a source for Onchocerca invasions into new hosts. Given the high density of deer populations, the potential for zoonotic infections may also exist. Our discovery of a new Onchocerca species with relatively limited sampling suggests that the diversity of Onchocerca associated with cervids in North America may be greater than previously thought, and surveys utilizing molecules and morphology are necessary.

(Received June 27 2012)

(Revised August 30 2012)

(Revised September 18 2012)

(Accepted September 19 2012)

(Online publication November 06 2012)

Key words

  • Alces alces ;
  • ancestral hosts;
  • Filarioidea;
  • Odocoileus virginianus ;
  • Onchocerca cervipedis ;
  • phylogeny;
  • Wolbachia


c1 Corresponding author: Department of Biology, University of Rochester, Rochester, NY 14627, USA. Tel: +011 1 512 471 7619. Fax: +011 1 512 471 3878. E-mail:

p1 Present address: Section of Integrative Biology, University of Texas at Austin, 2401 Speedway Drive #C0930, Austin, TX 78712, USA.