Angiostrongylus cantonensis: a review of its distribution, molecular biology and clinical significance as a human pathogen

Abstract

Angiostrongylus cantonensis is a metastrongyloid nematode found widely in the Asia-Pacific region, and the aetiological agent of angiostrongyliasis; a disease characterized by eosinophilic meningitis. Rattus rats are definitive hosts of A. cantonensis, while intermediate hosts include terrestrial and aquatic molluscs. Humans are dead-end hosts that usually become infected upon ingestion of infected molluscs. A presumptive diagnosis is often made based on clinical features, a history of mollusc consumption, eosinophilic pleocytosis in cerebral spinal fluid, and advanced imaging such as computed tomography. Serological tests are available for angiostrongyliasis, though many tests are still under development. While there is no treatment consensus, therapy often includes a combination of anthelmintics and corticosteroids. Angiostrongyliasis is relatively rare, but is often associated with morbidity and sometimes mortality. Recent reports suggest the parasites' range is increasing, leading to fatalities in regions previously considered Angiostrongylus-free, and sometimes, delayed diagnosis in newly invaded regions. Increased awareness of angiostrongyliasis would facilitate rapid diagnosis and improved clinical outcomes. This paper summarizes knowledge on the parasites' life cycle, clinical aspects and epidemiology. The molecular biology of Angiostrongylus spp. is also discussed. Attention is paid to the significance of angiostrongyliasis in Australia, given the recent severe cases reported from the Sydney region.

Hurdles in the evolutionary epidemiology of Angiostrongylus cantonensis: Pseudogenes, incongruence between taxonomy and DNA sequence variants, and cryptic lineages

“…Eosinophilic meningitis has only been attributed to A. cantonensis (Barratt et al., 2016), and Spratt (2015) indicates there has not been unequivocal evidence to show that A. mackerrasae or A. malaysiensis are zoonotics. However, as discussed above, morphological identifications of these species are difficult due to their similarities.…”

“…Angiostrongylus cantonensis , the rat lungworm, is a zoonotic pathogen that is one of the leading causes of eosinophilic meningitis worldwide (Barratt et al., 2016). This parasite is regarded as an emerging pathogen with a global range expansion out of southeastern Asia post‐WWII (Kliks & Palumbo, 1992; Wang, Lai, Zhu, Chen, & Lun, 2008).…”

Improving the specific diagnosis of trematode, cestode and nematode infections by a multiplex single-tube real-time PCR assay

“…Two recent reports similarly described the presence of A. cantonensis DNA in the cerebrospinal fluid of patients with eosinophilic meningitis using A. cantonensis –specific PCR reactions 17 18. If the use of NAAT for A. cantonensis is further validated in future studies, this could substantially improve the diagnosis of A. cantonensis infection since detection of larvae in the cerebrospinal fluid is very insensitive and specific serology is not widely available 19. The broad-range PCR reaction, although potentially less sensitive than a specific PCR for A. cantonensis , offers the advantage of detecting other parasites causing eosinophilic meningitis and meningoencephalitis, such as Gnathostoma , Baylisascaris , Toxocara and other helminths.…”

Clinical Reasoning: A 22-year-old man with diplopia

“…Its larva can be ingested by mollusks, particularly snails, and then transferred to humans via direct ingestion of the uncooked or undercooked mollusk or ingestion of fresh produce with the mollusk's slime or larvae. 7 It is typically found in Southeast Asia, with the greatest prevalence of disease in Taiwan, but there are reported cases originating in the main island of Hawaii. 7 The incubation period can range from days to several months.…”

“…7 It is typically found in Southeast Asia, with the greatest prevalence of disease in Taiwan, but there are reported cases originating in the main island of Hawaii. 7 The incubation period can range from days to several months. 8 Clinical manifestations are typically headache, neck stiffness, paresthesias, increased intracranial pressure, nausea, and cranial nerve deficits.…”