An Overview of Angiostrongylus cantonensis (Nematoda: Angiostrongylidae), an Emerging Cause of Human Angiostrongylosis on the Indian Subcontinent

Abstract

Human angiostrongylosis is an emerging zoonosis caused by the larvae of three species of metastrongyloid nematodes of the genus Angiostrongylus, with Angiostrongylus cantonensis (Chen, 1935) being dominant across the world. Its obligatory heteroxenous life cycle includes rats as definitive hosts, mollusks as intermediate hosts, and amphibians and reptiles as paratenic hosts. In humans, the infection manifests as Angiostrongylus eosinophilic meningitis (AEM) or ocular form. Since there is no comprehensive study on the disease in the Indian subcontinent, our study aims at the growing incidence of angiostrongylosis in humans, alongside its clinical course and possible causes. A systematic literature search revealed 28 reports of 45 human cases from 1966 to 2022; eosinophilic meningitis accounted for 33 cases (75.5%), 12 cases were reported as ocular, 1 case was combined, and 1 case was unspecified. The presumed source of infection was reported in 5 cases only. Importantly, 22 AEM patients reported a history of eating raw monitor lizard (Varanus spp.) tissues in the past. As apex predators, monitor lizards accumulate high numbers of L3 responsible for acute illness in humans. For ocular cases, the source was not identified. Most cases were diagnosed based on nematode findings and clinical pathology (primarily eosinophilia in the cerebrospinal fluid). Only two cases were confirmed to be A. cantonensis, one by immunoblot and the other by q-PCR. Cases of angiostrongylosis have been reported in Delhi, Karnataka, Kerala, Maharashtra, Madhya Pradesh, Puducherry, Telangana, and West Bengal. With a population of more than 1.4 billion, India is one of the least studied areas for A. cantonensis. It is likely that many cases remain undetected/unreported. Since most cases have been reported from the state of Kerala, further research may focus on this region. Gastropods, amphibians, and reptiles are commonly consumed in India; however, typical preparation methods involve cooking, which kills the nematode larvae. In addition to studying rodent and mollusk hosts, monitor lizards can be used as effective sentinels. Sequence data are urgently needed to answer the question of the identity of Angiostrongylus-like metastrongylid nematodes isolated from all types of hosts. DNA-based diagnostic methods such as q-PCR and LAMP should be included in clinical diagnosis of suspected cases and in studies of genetic diversity and species identity of nematodes tentatively identified as A. cantonensis.

Nematodes associated with terrestrial gastropod molluscs in Belgium and additional characterisation of Pellioditis californica and P. hermaphrodita

“…It is estimated that more than 300 million people suffer from diseases caused by gastropod-borne helminths (Giannelli et al 2016). For instance, the gastropod nematode Angiostrongylus cantonensis Chen, 1935, is the primary cause of human eosinophilic meningoencephalitis in many parts of the Indo-Pacific region (Barratt et al 2016; Pandian et al 2023).…”

Molecular insights versus morphological traits: rethinking identification of the closely related Angiostrongylus cantonensis and Angiostrongylus malaysiensis

“…In Thailand, three Angiostrongylus species have been reported, namely A. cantonensis , A. malaysiensis , and A. siamensis. Accurate identification is essential, as misidentification can lead to improper diagnosis and treatment, thereby exacerbating public health issues [ 6 , 7 ]. The morphological similarities and the overlapping habitats of A. cantonensis and A. malaysiensis have complicated the accurate identification of these species.…”

Revealing the Impact of Selected Weed Plants on Larval Mortality of Culex Quinquefasciatus (say) Diptera: Culicidae Juveniles

“…Among these infected people, approximately 25 million men suffer from genital diseases, most commonly hydrocele, and 15 million (mostly women) suffer from lymphedema or elephantiasis of the leg. In 2023, con rmed cases of Tropical Pulmonary Eosinophilia (TPE) were reported in indigenous patients; however, this disease is rare in Pakistan (Pandian et al 2023) (Fig. 1).…”