3.4 Detection of the parasite from intermediate and paratenic hosts

Surveys of known definitive, intermediate, and paratenic hosts are instrumental in the tracking and quantifying of Angiostrongylus cantonensis prevalence in the environment, and also to develop an accurate risk assessment. Currently, surveys have been known to employ visual methods for detection in hosts (Xie et al., 2023), as well as molecular methods (Gamiette et al., 2023). Molecular tools such as PCR-based detection and analysis are accurate and have the additional benefit of being effective with both fresh and frozen snail tissue, and with low parasite numbers (high ct value in qPCR) (Qvarnstrom et al., 2010). The assay developed by Qvarnstrom et al. (2010) demonstrated specificity of detection when tested against Angiostrongylus costaricensis and A. vasorum , both known mammalian parasites, and was thus a commonly used protocol in many subsequent studies. However, a relatively cheaper and more accessible qPCR assay using SYBR green was more recently developed by Jakkul et al. (2021), which bypasses the need for probes. Apart from PCR, loop-mediated isothermal amplification (LAMP) assays have been developed for providing low-cost and sensitive detection of Angiostrongylus cantonensis from invasive P. canaliculata hosts, which is an effective strategy for large scale prevalence detection (Chen et al., 2011). However, the specificity of this protocol against other species ofAngiostrongylus remains to be tested.
Rapid and accurate methods of identifying Angiostrongylus cantonensis larvae within mollusk hosts as well as patient samples have gained a substantial amount of interest as the number of outbreaks of eosinophilic meningitis continues to rise (Rollins et al., 2021). Furthermore, newly developed environmental DNA (eDNA) based methods may be applied to detect many infectious diseases from environmental samples (eg: standing water from paddy fields) which could also be applied forAngiostrongylus cantonensis detection and quantification (Bass et al., 2023).