New hosts for a snake's helminth: First report of intermediate and definitive hosts naturally infected by Ophidascaris arndti (Ascarididae) in the wild

We wish to report the occurrence of adult nematodes Ophidascaris arndti (Ascarididae) naturally infecting a new definitive host, the Fonseca's lancehead Bothrops fonsecai (Viperidae), and third-stage larvae of O. arndti parasitizing a new intermediate host, the montane grass mouse Akodon montensis (Cricetidae), both found in the Atlantic Forest of the state of Rio de Janeiro, Brazil. We elucidated the morphological characteristics of both adults and larvae using light and scanning electron microscopy (SEM). Taxonomic affinities between larvae and adult worms were assessed using MT-CO1 gene sequences. Adult and larval gene sequences formed a well-supported clade and had low pairwise p-distances, suggesting that they are conspecific. Our phylogenies also supported the ‘arndti’, ‘filaria’, and ‘obconica’ groups as independent lineages and confirmed the allocation of Ophidascaris within the family Ascarididae, although as an early offshoot. This is the first report of natural infection of this helminth's larvae in a wild intermediate host. [Display omitted] •Ophidascaris arndti found infecting new rodent and snake species in the wild.•L3 larvae found in a grass mouse pointing to its role as an intermediate host.•Adult worms found in a Fonseca's Lancehead, adding a new definitive host species.•Molecular analyses confirmed the closeness between mouse and snake helminths.•Phylogenies supported ‘arndti’, ‘filaria’, and ‘obconica’ groups as independent.