Species of Angiostrongylus (Nematoda: Metastrongyloidea) in wildlife: A review - PubMed (original) (raw)

Review

Species of Angiostrongylus (Nematoda: Metastrongyloidea) in wildlife: A review

David M Spratt. Int J Parasitol Parasites Wildl. 2015.

Abstract

Twenty-one species of Angiostrongylus plus Angiostrongylus sp. (Nematoda: Metastrongyloidea) are known currently in wildlife. These occur naturally in rodents, tupaiids, mephitids, mustelids, procyonids, felids, and canids, and aberrantly in a range of avian, marsupial and eutherian hosts including humans. Adults inhabit the pulmonary arteries and right atrium, ventricle and vena cava, bronchioles of the lung or arteries of the caecum and mesentery. All species pass first-stage larvae in the faeces of the host and all utilise slugs and/or aquatic or terrestrial snails as intermediate hosts. Gastropods are infected by ingestion or penetration of first-stage larvae; definitive hosts by ingestion of gastropods or gastropod slime. Transmission of at least one species may involve ingestion of paratenic hosts. Five developmental pathways are identified in these life cycles. Thirteen species, including Angiostrongylus sp., are known primarily from the original descriptions suggesting limited geographic distributions. The remaining species are widespread either globally or regionally, and are continuing to spread. Small experimental doses of infective larvae (ca. 20) given to normal or aberrant hosts are tolerated, although generally eliciting a granulomatous histopathological response; large doses (100-500 larvae) often result in clinical signs and/or death. Two species, A. cantonensis and A. costaricensis, are established zoonoses causing neurological and abdominal angiostrongliasis respectively. The zoonotic potential of A. mackerrasae, A. malaysiensis and A. siamensis particularly warrant investigation. Angiostrongylus cantonensis occurs in domestic animals, mammalian and avian wildlife and humans in the metropolitan areas of Brisbane and Sydney, Australia, where it has been suggested that tawny frogmouths and brushtail possums may serve as biosentinels. A major conservation issue is the devastating role A. cantonensis may play around zoos and fauna parks where captive rearing of endangered species programmes may exist and where Rattus spp. are invariably a problem.

Keywords: Angiostrongylus spp; Geographical distribution; Life cycles; Pathology; Wildlife; Zoonoses.

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Figures

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Graphical abstract

Fig. 1

Fig. 1

The life cycle of Angiostrongylus cantonensis. Rat definitive hosts acquire third-stage larvae by ingesting infected intermediate hosts, aquatic or terrestrial snails and slugs. Larvae penetrate the stomach, enter the hepatic portal and mesenteric lymphatic systems and are carried to the heart and lungs. They enter alveoli, invade the pulmonary veins, are returned to the left heart and distributed around the body by the arterial circulation. Larvae reach the CNS, predominantly the cerebrum and cerebellum, grow and moult twice in the parenchyma and young adults invade the subarachnoid space of the brain. After about two weeks they invade the cerebral vein and move to the heart and pulmonary arteries where they mature. Eggs are carried in the blood to the lungs where they embryonate. First-stage larvae escape up the bronchial escalator, are swallowed, pass out in the faeces, are ingested by intermediate hosts, snails and slugs, and develop to third-stage infective larvae. A broad spectrum of animals – planarians, prawns, crabs, frogs and lizards may serve as paratenic hosts in which infective larvae reside but undergo no further development. Humans are an accidental host and infection may occur through ingestion of intermediate or paratenic hosts, the latter often eaten raw or their juices used in preparation of local dishes. Infective larvae may also leave molluscs and contaminate vegetables such as lettuce (adapted from Wang et al., 2008, fig. 1).

Fig. 2

Fig. 2

Tawny frogmouth, Podargus strigoides, with severe posterior paresis and unable to right itself due to infection with Angiostrongylus cantonensis.

Fig. 3

Fig. 3

Immature Angiostrongylus cantonensis in the cerebellum of a brushtail possum, Trichosurus vulpecula, with extensive granulomatous and eosinophilic meningoencephalitis and malacia (adapted from Ma et al., 2013, fig. 7).

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