Genomic and morphologic characterization of Strongyloides nasua causing fatal strongyloidiasis in coatis (Nasua nasua)

<title>Abstract</title>
<p>
The parasitic nematode
<italic>Strongyloides</italic>
sp. infects a large range of host species, including ungulates, carnivores, non-human primates, and humans, causing mostly asymptomatic chronic infections.
<italic>Strongyloides nasua</italic>
represents a previously understudied and poorly described species, which is capable of causing fatal hyperinfection in its host. We report the first genomic description and comprehensive morphological analysis of
<italic>S. nasua</italic>
, which caused fatal strongyloidiasis in two coatis (
<italic>Nasua nasua</italic>
) at a wildlife rescue centre in Peru, South America. The two animals were housed in the centre for a few months prior to clinical signs occurring, with infection ultimately leading to a fatal outcome. Post-mortem examination showed cachectic animals, inflamed intestine with enlarged Peyer’s patches and mesenteric lymph nodes. Histological analysis revealed hyperinfection, with severe parasitic enteritis with the presence of numerous nematodes at various developmental stages entrapped in the intestinal mucosa. Direct microscopic examination of the nematodes revealed key morphological characteristics of parasitic female
<italic>S. nasua</italic>
. Combining
<italic>18S rRNA</italic>
and
<italic>cox1</italic>
genotyping together with short- and long-read whole genome sequencing, our data revealed that
<italic>S. nasua</italic>
represents a member of a potentially new group in the genus
<italic>Strongyloides</italic>
, closely related to
<italic>S. stercoralis</italic>
and
<italic>S. procyonis.</italic>
The
<italic>S. nasua</italic>
genome was associated with expansion of acetylcholinesterases, embryonic development and developmental processes and contraction of orthogroups associated with immune and antimicrobial responses, indicating potential diversification or specialisation of associated processes in
<italic>S. nasua</italic>
.
</p>