Case report: First documented case of cerebral angiostrongyliasis caused by Angiostrongylus costaricensis in a free-ranging opossum

Abstract

Angiostrongylus costaricensis is a metastrongyloid nematode that primarily infects the mesenteric arteries of wild rodents. This parasite is endemic in several regions of the American continent, and in humans, causes a disease known as abdominal angiostrongyliasis. Despite the important health implications of this nematode, there are limited studies investigating the involvement of wild animals in its life cycle. In this study, we present the clinical manifestations, pathologic findings, and molecular diagnosis, to the best of our current knowledge, of the first documented onset of cerebral angiostrongyliasis because of A. costaricensis infection in a juvenile free-ranging opossum (Didelphis marsupialis). Histopathological findings stress the presence of eosinophilic meningoencephalitis with nematodes present within the lesions, and PCR was positive for cox1 and ITS1 reactions. The obtained sequences for a 279 bp fragment of ITS1 were 100% identical to A. costaricensis from Costa Rica. This case highlights the substantial difficulties in diagnosing neuroangiostrongyliasis, yet underscores the importance of considering A. costaricensis as a potential culprit behind neurological conditions in wild marsupials. It acts as an urgent call to action to improve surveillance programs tracking infectious and parasitic diseases causing mortality in wildlife populations.

Keywords: angiostrongyliasis; case report; parasitic diseases; wildlife reservoir; zoonosis.

Figure 1

Post-mortem analysis findings. (A) Juvenile opossum (Didelphis marsupialis). (B) Multifocal areas of variable sizes, slightly raised and whitish in color, observed in the parietal lobes and occipital lobe of the brain, as well as in the cerebellar vermis (arrowhead). (C) Nematodes located in the leptomeninges above the cerebellar vermis and the occipital lobe (arrowhead).

Figure 2

Morphological characteristics of nematodes collected from the neuroparenchyma. (A) The anterior end of the nematode possesses a rounded shape with a circular mouth opening. The cuticle of the nematode exhibits' transverse striations, as indicated by the arrowhead. (B) The posterior segment of a male nematode reveals the presence of the copulatory bursa, bursal rays (arrowhead), and the spicule (S). These images were captured using at a magnification of 100x, and the scale bar represents a length of 200 μm.

Figure 3

Histopathology of the cerebellum in juvenile opossum (D. marsupialis). (A) Lesions in the cerebellum: showing transverse sections of fully developed nematodes in the neuroparenchyma, affecting both gray matter and white matter, and surrounded by a mild mixed inflammatory infiltrate (arrowhead). H&E, magnification: 400x. (B) Lesions in pia mater: presenting a moderate inflammatory infiltrate, primarily composed of eosinophils, with a mild number of macrophages and lymphocytes (arrowhead). H&E, magnification: 200x. (C) The mature nematode: measuring approximately 250 μm in size, was characterized by a smooth cuticle (c), coelomyarian musculature (m), lateral cords (LC) and an intestine containing multinucleated cells (I). Encircling the nematode, a mixed inflammatory infiltrate comprising eosinophils, macrophages, and lymphocytes was discerned (arrowhead). H&E, magnification: 200x, scale bar: 250 μm.