Shaking the Tree: Multi-locus Sequence Typing Usurps Current Onchocercid (Filarial Nematode) Phylogeny

Abstract

During the past twenty years, a number of molecular analyses have been performed to determine the evolutionary relationships of Onchocercidae, a family of filarial nematodes encompassing several species of medical or veterinary importance. However, opportunities for broad taxonomic sampling have been scarce, and analyses were based mainly on 12S rDNA and coxI gene sequences. While being suitable for species differentiation, these mitochondrial genes cannot be used to infer phylogenetic hypotheses at higher taxonomic levels. In the present study, 48 species, representing seven of eight subfamilies within the Onchocercidae, were sampled and sequences of seven gene loci (nuclear and mitochondrial) analysed, resulting in the hitherto largest molecular phylogenetic investigation into this family. Although our data support the current hypothesis that the Oswaldofilariinae, Waltonellinae and Icosiellinae subfamilies separated early from the remaining onchocercids, Setariinae was recovered as a well separated clade. Dirofilaria, Loxodontofilaria and Onchocerca constituted a strongly supported clade despite belonging to different subfamilies (Onchocercinae and Dirofilariinae). Finally, the separation between Splendidofilariinae, Dirofilariinae and Onchocercinae will have to be reconsidered.

Temporal and demographic blood parasite dynamics in two free-ranging neotropical primates

“…We reliably detected continued M. mariae infection in all animals harboring infections the previous year, so temporal sampling bias would not explain differences in prevalence from Dipetalonema spp. Given the relatively stable climate between years and that both parasites are vectored by ceratopogonid biting midges (Shelley and Coscarón, 2001, Lefoulon et al., 2015), we suspect that within-host dynamics are responsible for the variation observed between these two filarids, although the physiological consequences of these species on wild hosts remain unknown (Strait et al., 2012). It is worth mentioning that Dipetalonema spp.…”

“…likely represents two species, D. gracile and D. graciliformis , and our study does not differentiate whether one or both are responsible for the increase in prevalence. Phylogenetic relationships within the Dipetalonema clade of the Onchocercidae are an area of active research that is beyond the scope of this study (Lefoulon et al., 2015), and since mixed infections are common in nature (Sato et al., 2008, Strait et al., 2012), we do not know if parasite-host relationships would vary at sub-genus levels. The prevalence of T. minasense did change significantly across the study period, and most dramatic was the 2014 spike to 100% of S. imperator individuals and close to 100% among L. weddelli .…”

An isothermal DNA amplification method for detection of Onchocerca volvulus infection in skin biopsies

“…Although the O-150 qPCR assay has the advantage of targeting a repeat sequence that is present multiple times in the O. volvulus genome, the cox 1 LAMP assay has a comparable clinical sensitivity of 88.2%. A likely explanation for this high sensitivity is the fact that the cox 1 gene is located in the mitochondrial genome, while O-150 is located in the nuclear genome [39, 40]. Since every cell contains hundreds of mitochondrial DNA copies, it makes mitochondrial encoded sequences ideal targets for molecular detection requiring high sensitivity, as is the case for O. volvulus detection in skin biopsies [41].…”

Culex pipiens as a potential vector for transmission of Dirofilaria immitis and other unclassified Filarioidea in Southwest Spain

“…Because filarioid nematodes are difficult to collect, their diversity is mostly unknown, with only a few relatively recent studies reporting new species such as Pelecitus nematides from the Tehuantepec jackrabbit (Lepus flavigularis) ( Jiménez-Ruiz et al, 2004) and Diplotriaena railliet in birds such as Passer domesticus and P. pyrhonotus from Pakistan ( Chandio et al, 2015). Genetic studies were conducted for Micipsella numidica in the hare Lepus europaeus from Italy ( Gabrielli et al, 2015) and Rumenfilaria andersoni along with other 48 species of onchocercid subfamilies of filarial nematodes ( Lefoulon et al, 2012 andLefoulon et al, 2015). Regardless of our ability to assign the obtained filarioid DNA sequences to a given species or genus, reports such as these do suggest that diverse Filarioidea nematodes may be widely distributed in Europe, in a large range of hosts.…”