Content area
Full Text
(ProQuest: ... denotes non-US-ASCII text omitted.)
Research Papers
Introduction
Angiostrongylus cantonensis-associated eosinophilic meningitis/meningoencephalitis is a worldwide food-borne helminthic zoonosis. Humans acquire the infection by consuming the infective larval stage in the raw or poorly cooked intermediate snail host or other paratenic animal hosts, e.g. crustaceans, frogs, shrimps and monitor lizards, or ingesting fresh/raw vegetables contaminated with the infective larvae (Eamsobhana, 2006; Cross & Chen, 2007). The migration of larvae through the brain results in cerebral haemorrhage and eosinophilic meningitis, which can be fatal.
Definitive diagnosis of angiostrongyliasis relies on detection of the fifth-stage or juvenile parasitic worms in the cerebrospinal fluid (CSF), and occasionally from the eyes of patients (Wang et al., 2008; Graeff-Teixeira et al., 2009). Because of the frequent difficulty in obtaining a parasitological diagnosis, immunological means based on enzyme immunoassay format, namely standard enzyme-linked immunosorbent assay (ELISA) and immunoblotting, to detect the parasite-specific antibodies/antigens, have been used to support clinical diagnosis (Eamsobhana & Yong, 2009). A simpler version, dot-blot ELISA, has been applied in community-based studies of human angiostrongyliasis in endemic areas of north-east Thailand (Eamsobhana, 2010). However, the currently available enzyme-based tests are time-consuming and the procedure is complicated. A simpler, rapid and non-instrumented test format which is specific and sensitive is needed in a basic diagnostic laboratory or field setting - where proper facilities and highly trained personnel are limited.
A colloid gold dot-immunobinding assay on nitrocellulose membrane (NCM) developed in the late 1980 s is a simple, visually read, rapid test that uses colloidal gold conjugated antibody or antigen, for the detection of corresponding antigen or antibody, instead of enzyme conjugates as in ELISA (Chun & Chu, 1989; Spielberg et al., 1989). The current version of the dot immunogold filtration assay (DIGFA), or flow-through immunoassay, uses NCM as a solid-phase support for the antigen and colloidal gold-labelled antibody/protein A as a probe. By visual examination, the immobilized colloidal gold particles appear as pinkish dots. The test usually gives a diagnostic result within 3-5 min.
In the past decade, this rapid DIGFA format has been used increasingly in clinical laboratories and field settings to detect pathogenic organisms, including a few parasites. The DIGFA test has been adopted successfully for the serodetection of helminth infections with schistosomiasis (Xiao