Mortality associated with Angiostrongylus cantonensis in non-human primates in Europe.

Between December 2020 and March 2022, three cases of fatal meningoencephalitis were documented in two red-fronted brown lemurs (Eulemur rufus) and a ring-tailed lemur (Lemur catta) at the Bioparc in Valencia, eastern Spain. Post-mortem analyses revealed moderate congestion in the meninges of the brain in all cases. Multifocal areas of hemorrhage were observed in one lemur, primarily in the cerebellum and brainstem. Histopathological examination showed mainly acute hemorrhagic and necrotic changes, together with moderate eosinophilic and/or histiocytic meningoencephalitis, with perivascular cuffing, and gliosis. Numerous nematode larvae were found in the meninges, brain, and spinal cord, with or without associated inflammation, hemorrhage, and necrosis. Considering the affected host species, nematode morphology, and its anatomical localization, Angiostrongylus cantonensis (Nematoda: Metastrongylidae) was suspected as the causative agent. Phylogenetic studies based on the internal transcriber spacer 1/cytochrome c oxidase subunit I (ITS1/COI) genes confirmed the initial suspicion of this zoonotic parasite and its relationship to sequences from the Balearic and Canary Islands. This is the first known detection of A. cantonensis in non-human primates in Europe and it represents one of the few occurrences reported in the Palearctic region to date. Further research on this zoonotic parasite is crucial to understanding its spread in Spain, assessing public health risks, and developing effective control measures to mitigate outbreaks and protect human and animal health.