Bacterial Communities Associated with Angiostrongylus cantonensis Third-Stage Larvae Vary Across Different Intermediate Host Species

Host-associated microbiomes are critical to animal biology, yet those of helminthic parasites are poorly understood. We investigated the microbiome of third-stage larvae (L3) of the rat lungworm, Angiostrongylus cantonensis , isolated from two invasive slug intermediate host species in Hawaiʻi, Laevicaulis alte and Parmarion martensi . Using partial 16 S rRNA gene sequencing, we compared parasite microbiomes with those of their slug hosts. The nematodes harbored a distinct microbiome that overlapped with, but differed compositionally from, the slug microbiomes. Angiostrongylus cantonensis L3 microbiomes also differed between larvae isolated from the two slug species. Predictions of parasite microbiome functional capability identified 480 microbial gene pathways that varied in abundance between the parasite-isolate populations, including pathways related to amino acid and B-vitamin synthesis. These findings suggest that A. cantonensis L3 maintains a selective, partially host-derived, microbiome that also may have a role in nutrient provisioning for the parasite. This study provides novel insights into parasite-microbiome ecology, with implications for understanding host-parasite interactions and transmission dynamics.