Lungworm Heterostrongylus heterostrongylus Travassos, 1925 from the black-eared opossum in South America: Morphologic, histopathological and phylogenetic aspects

Nematode parasites of the cardiopulmonary system of livestock and pet animals have been receiving attention due to the pathogenic effects they produce in the course of the infection. However, parasitism in wild animals by metastrongilid nematodes has been neglected, resulting in potential risk to wildlife. Heterostrongylus heterostrongylus is the etiological agent of bronchial pneumonia in the black-eared opossum, Didelphis aurita, a widely distributed marsupial frequently reported to inhabit areas from wild environments to peri-urban spaces. In this study, we reassessed the taxonomy of H. heterostrongylus, describing and comparing morphology of L1 and L3 larvae and adult worms with closely related angiostrongilids, and inferring phylogenetic affinities within the family Angiostrongylidae; we also detailed histopathological reactions under natural infection. Ultrastructural morphology and light microscopy confirmed cephalic structures with well-developed trilobed lips, patterns of caudal bursa rays, spicules shape, terminal anal aperture and presence of the ventral protuberance in L3 larvae, characteristics present for the family Angiostrongylidae. Our molecular phylogenetic analyses, based on the partial small subunit (SSU) 18S rRNA gene, suggested that H. heterostrongylus and Didelphostrongylus hayesi are closely related. Pathological analyses agreed with previous findings, showing that cardiopulmonary parasitism provokes verminous pneumonia and mucous bronchiolitis with hypertrophy of the smooth bronchiolar muscle. These data confirmed that H. heterostrongylus represents a pulmonary pathogen in D. aurita, produces severe pathological effects, and may represent risk to domestic and wild animals.