A lymphatic dwelling filarioid nematode, Rumenfilaria andersoni (Filarioidea; Splendidofilariinae), is an emerging parasite in Finnish cervids

Abstract

BackgroundRecent studies revealed expansion of filarioid nematodes into northern Finland. In addition to Setaria tundra, an abundant filarioid, Rumenfilaria andersoni, was found inhabiting the lymphatic vessels of reindeer. Our study explores the dynamics of the rapid geographic expansion of R. andersoni, defining prevalence and density of microfilariae among 4 new cervid host species in Finland while developing a context for host-parasite ecology in Fennoscandia and more broadly in the Arctic and boreal regions.MethodsBlood samples were evaluated for presence of microfilariae from 1576 semi-domesticated reindeer, 8 captive reindeer, and free-ranging cervids including 105 wild forest reindeer, 862 moose, 114 white tailed deer and 73 roe deer in 2003–2006 (−2010). Additionally, the prepatent period and the efficacy of ivermectin treatment were investigated.ResultsRumenfilaria andersoni was found to be a common and abundant parasite in reindeer (0-90%) and wild forest reindeer (41-100%). Also moose (0-12%), white-tailed deer (15-22%) and roe deer (3%) were revealed as definitive hosts. Ivermectin was not effective against adult parasites. The prepatent period was estimated to be about five months.ConclusionsRumenfilaria andersoni was identified in 3 endemic cervid species and the introduced white-tailed deer, all constituting previously unrecognized host species in the Palearctic. Among moose, the prevalence and intensity were substantially lower than levels observed among subspecies of reindeer. White-tailed deer had a relatively high prevalence and density of R. andersoni microfilariae (rmf), whereas our limited data for roe deer indicated that the nematode may not have been abundant. Density and prevalence of rmf in moose and white tailed deer suggests the nematode may be adapted to these species, and that these cervids may be among the primary hosts of R. andersoni and reservoirs for transmission in Finland. Our current data suggest that R. andersoni became established in Finland recently, coincidental with introduction of white-tailed deer from North America in 1935; subsequent invasion and emergence in the past 70–80 years appears driven by climate-related factors. An alternative hypothesis for a temporally deeper occurrence for R. andersoni in Fennoscandia, representing post-Pleistocene range expansion with moose tracking deglaciation, is not firmly supported.

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

“…Besides O. lupi , there have been reports of other species of Onchocerca associated with wild cervids ( Onchocerca jakutensis (Gubanov, 1964)) and suids ( Onchocerca dewittei japonica Uni, Bain & Takaoka, 2001) in humans, and therefore, other blackfly-transmitted Onchocerca species may also pose a potential zoonotic threat [ 45 – 47 ]. Climate envelopes may determine the geographical distributions of potential blackfly and related arthropod vectors, and accelerating climate warming and habitat change have considerable potential to modify the ranges of vector-borne host-parasite assemblages [ 48 , 49 ]. Habitat disruption drives changing opportunities for transmission and may result in altered patterns of exposure and infection for species of Onchocerca among otherwise naïve and potential hosts such as other ungulates and humans.…”

Bacterial Genomics Reveal the Complex Epidemiology of an Emerging Pathogen in Arctic and Boreal Ungulates

“…Northern ecosystems are changing especially rapidly, where unprecedented rates of climate change are influencing a wide range of ecological processes (Post et al, 2013; IPCC, 2014). Several recent emergence events of macroparasites in northern wildlife have been linked to climate warming (Kashivakura, 2013; Kutz et al, 2013; Laaksonen et al, 2015), whereas the role of climate change in emerging diseases caused by microparasites, including viruses, bacteria and protozoa, is not yet as clearly established (e.g., Goldstein et al, 2009; Kutz et al, 2009; Harms, 2012; Loiseau et al, 2012; Ducrocq et al, 2013; Hansen et al, 2015; but see Ytrehus et al, 2015). Pathogen emergence poses a risk to the health and sustainability of wildlife populations which, in addition to their intrinsic value and ecosystem services, continue to be an important component of community health and food security for many indigenous communities in temperate and arctic regions of North America (Inuit Circumpolar Council- Canada, 2012; Council of Canadian Academies, 2014).…”

Range expansion of muskox lungworms track rapid arctic warming: implications for geographic colonization under climate forcing

“…Habitats and host-parasite assemblages we have explored on Victoria Island are not idiosyncratic. General mechanisms are at play at high latitudes, as evidenced by similar trends in distribution, invasion, host association and explosive emergence of disease for phylogenetically distant filarioid nematodes, with arthropod and vector-borne transmission, among reindeer and other cervids across northern Finland 64 , 65 .…”