Interspecific Variability of Filarioid Nematodes of the Genus Setaria Viborg, 1795 Occurring in Wild Ruminants in Europe: A Review

Abstract

Nematodes of the genus Setaria (Spirurida, Filarioidea) are parasites of vertebrates except fish. Dangerous are their larvae (microfilariae) that may migrate to the central nervous system of hosts causing serious neuropathic disorders of vertebrates including human. Setaria cervi, S. labiatopapillosa, and S. tundra are potential parasites in wild ruminants in Europe. The most recent studies of variability among Setaria spp. are based on a combination of morphometric and molecular methods. Although there is no clear consistency in the morphological structures used by different authors, a morphological key was compiled based on the body length, the arrangement of peribucal crown, and the number of papillae in the caudal part of the body. The barcoding system of Setaria genus is based on sequences of conserved gene polymorphisms such as COX1 and rDNA genes. The published sequences of COX1 gene in Setaria populations were analysed using in silico phylogenetic analysis by the maximum likelihood method (Tamura-Nei model). This analysis confirmed that the COX1 nucleotide polymorphisms genes are species-specific and represent the theoretical basis for the development of markers enabling barcoding system in the genus Setaria.

Setaria cervi(Filarioidea, Onchocercidae) undressing in ungulates: altered morphology of developmental stages, their molecular detection and complete sequencecox1 gene

“…Species-specific traits of S. cervi are apparent from a comparison of three most frequent European congeners occurring in hoofed game ( S. cervi , S. labiatopapillosa and S. tundra ) made by Lanková et al . (2019). Setaria cervi females (males) are up to 142 (76) mm long, their cuticle is smooth, their cuticular peribuccal crown with four dentate elevations has an almost square shape, lateral lips have a crescentic shape; S. cervi adult males have horn-like lateral appendages, characteristically striated bands on the ventral side of the tail, four pairs precloacal papillae, one mediate papilla near the cloaca, four pairs postcloacal papillae and one pair small lateral papillae.…”

“…The third congener, S. tundra , is shorter up to 80 (37) mm in length and the cuticle is covered by numerous small papillae on each side. The lateral lips are non-cuticularized, and on the ventral side of the tail are three pairs of precloacal, one pair of ad-cloacal papillae and three pairs of postcloacal papillae (see Lanková et al ., 2019). The morphology of younger developmental stages may slightly differ; however, literature data are scarce.…”

“…It is now clear that the comprehensive approach to identifying Setaria that combines light and scanning electron microscopy with molecular data is currently the only reliable method. Regarding molecular taxonomy, one of the most commonly used tools is the sequencing of the mitochondrial cytochrome c oxidase subunit 1 gene ( cox 1); five European Setaria species, including S. cervi , have repeatedly been subjected to this procedure (for review, see Lanková et al ., 2019). Two studies of S. cervi by Alasaad et al .…”