Redescription, molecular characterisation and endosymbionts of () (Mullin & Orihel, 1972) (Spirurida: Onchocercidae) from the common treeshrew Diard & Duvaucel (Mammalia: Scandentia) in Peninsular Malaysia.

The genus Faust, 1929 includes 29 species, mainly parasites of platyrrhine monkeys in South America and anthropoid apes in Africa. In Malaysia, () (Mullin & Orihel, 1972) was described from the common treeshrew Diard & Duvaucel (Scandentia). In a recent classification of the genus , seven subgenera were proposed, with . (.) as a monotypic species in the subgenus . In this study, we collected new material of . (.) from common treeshrews in Peninsular Malaysia and redescribed the morphological features of this species. We found that . (.) differs from . () Uni et al., 2004 from sika deer (Cetartiodactyla) in Japan, with regards to morphological features and predilection sites in their respective hosts. Based on multi-locus sequence analyses, we examined the molecular phylogeny of . (.) and its genotype. Species of the genus grouped monophyletically in clade ONC5 and . (.) was placed in the most derived position within this genus. (.) was closely related to . (.) (Manson, 1897) from humans in Central and South America, and most distant from . (.) . The calculated p-distances between the 1 gene sequences for . (.) and its congeners were 13.09% for . () and 15.6-16.15% for . (.) . The molecular phylogeny of spp. thus corroborates their morphological differences. We determined that . (.) harbours endosymbionts of the supergroup F genotype, in keeping with all other species screened to date.