Immunoanalysis of different antigenic preparations of Angiostrongylus cantonensis for neuroangiostrongyliasis diagnosis improvement

Molecular Diagnosis of Severe Angiostrongylus cantonensis-Induced Eosinophilic Meningitis: A Case Report Emphasizing the Need for Accurate Detection Methods

BACKGROUND Angiostrongylus cantonensis, also known as the rat lungworm, is the most common parasitic cause of human eosinophilic meningitis. A. cantonensis infection is an emergent disease causing permanent neurological injury or even death when not diagnosed and treated promptly. Usually, human infection occurs through ingestion of food contaminated by intermediated hosts or the third stage larvae of A. cantonensis. Indicators for diagnosis include clinical signs of meningitis; contact history, such as that from eating raw or improperly cooked intermediated hosts or contaminated vegetables; and cerebrospinal fluid (CSF) eosinophilia. However, diagnosis is now primarily defined through polymerase chain reaction (PCR) assay of CSF or serum. CASE REPORT A 66-year-old homeless man with unclear exposure history presented with fever and conscious change. The initial hemogram showed eosinophilia without neutrophilic leukocytosis. Non-contrast computed tomography (CT) and magnetic resonance imaging (MRI) of the head revealed no evidence of stroke. A lumbar puncture was performed and showed eosinophilic meningitis. The patient was ultimately diagnosed through PCR and sequencing for A. cantonensis infection, and dexamethasone treatment was started immediately. Although his general condition improved after dexamethasone treatment, his mental status did not improve completely. CONCLUSIONS Our report highlights the importance of applying molecular techniques in diagnosis of angiostrongylosis, especially in individuals who have unknown contact history.

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

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.