Partial molecular characterization of the mitochondrial genome of Baylisascaris columnaris and prevalence of infection in a wild population of Striped skunks

Abstract

Members of the genus Baylisascaris utilize omnivores or carnivores as their definitive hosts. The best known member of this genus is Baylisascaris procyonis, which is an intestinal parasite of raccoons. The closest relative of B. procyonis is B. columnaris, which utilizes the common skunk as its definitive host. Although B. procyonis has been extensively studied, relatively little is known of B. columnaris. For example, the mitochondrial genome of B. procyonis has been sequenced in its entirety. Conversely, the mitochondrial genome of B. columnaris remains largely unexplored. Likewise, the prevalence of this parasite in its wild host has not been documented. In this study, we collected parasites from a wild population of skunks in the state of Utah, United States. The cytochrome c oxidase subunit 1 and 2 genes, NADH dehydrogenase 2 and several tRNA genes were sequenced from the mitochondrial genome of these parasites. We also determined the prevalence of B. columnaris in a wild population of skunks. In this work we identify several novel polymorphic genetic loci between B. procyonis and B. columnaris. These findings provide additional molecular targets for the differentiation of Baylisascaris species through clarification of genetic differences between B. columnaris and B. procyonis.

Molecular phylogenetics and species-level systematics of Baylisascaris

“…Morphologically, they are almost indistinguishable, and identifying the species of larval or adult B. procyonis or B. columnaris based on morphology alone is not always possible even for specialists (Kazacos, 2001; Graeff-Teixeira et al, 2016). Previous authors have also attempted to discriminate between B. columnaris and B. procyonis based on pathogenicity in paratenic hosts, protein electrophoresis (Berry, 1985), larval excretory-secretory antigens (Dangoudoubiyam et al, 2010), and DNA sequence data (Dangoudoubiyam et al, 2009; Gatcombe et al, 2010; Franssen et al, 2013; Choi et al, 2017). The most pronounced difference between skunk- and raccoon-derived worms is in pathogenicity for paratenic hosts.…”

“…Recent attempts at using molecular data to distinguish B. columnaris and B. procyonis were conducted by Franssen et al (2013) and Choi et al (2017). Franssen et al (2013) analyzed specimens obtained from skunk hosts in the Netherlands, and from raccoon hosts in Indiana, USA and Norway, and reported a GA repeat region in ITS-2 with unique patterns for individuals of B. procyonis (nine repeats) and B. columnaris (six or seven repeats).…”

“…Choi et al (2017) obtained mitochondrial sequence data for 10 skunk-derived Baylisascaris in Salt Lake County, Utah, USA. They compared complete sequences of 11 mitochondrial genes – cox1 , cox2 , nd2 , and 8 tRNA genes – with mitochondrial genome sequences of one B. procyonis specimen (Xie et al, 2011b) and with cox1 and cox2 sequences obtained by Franssen et al (2013).…”

“…They compared complete sequences of 11 mitochondrial genes – cox1 , cox2 , nd2 , and 8 tRNA genes – with mitochondrial genome sequences of one B. procyonis specimen (Xie et al, 2011b) and with cox1 and cox2 sequences obtained by Franssen et al (2013). In total, Choi et al (2017) reported 11 SNPs that were presumed diagnostic for skunk- and raccoon-derived Baylisascaris : six SNPs in cox1 ; three SNPs in nd2 ; one SNP in tRNA-Leu; and one SNP in tRNA-Ser. In contrast to Franssen et al (2013) no diagnostic SNPs were identified in cox2 .…”

“…Genetic analyses of Baylisascaris species have been limited, but sequence data from certain species has been used to investigate: 1) phylogenetic relationships among species in order Ascaridida (Nadler, 1992; Nadler and Hudspeth, 1998, 2000; Xie et al, 2011a, 2011b, 2013; Li et al, 2012; Liu et al, 2014); 2) detection of species from fecal samples ( B. procyonis , Dangoudoubiyam et al, 2009, Gatcombe et al, 2010; B. transfuga , De Ambrogi et al, 2011; B. schroederi , Zhou et al, 2013); 3) identification of adults from different hosts ( B. devosi , Tranbenkova and Spiridonov, 2017; B. schroederi , Lin et al, 2012; Zhao et al, 2012; B. transfuga , Testini et al, 2011) or geographic areas (Davidson et al, 2013); 4) species delimitation of B. procyonis and B. columnaris (Franssen et al, 2013; Choi et al, 2017); and 5) descriptions of new species ( B. ailuri , He et al, 2008, cited in Xie et al, 2011a; B. potosis , Taira et al, 2013 and Tokiwa et al, 2014; B. venezuelensis , Pérez Mata et al, 2016).…”