Evaluation of a Dipstick Malaria Sporozoite Panel Assay for Detection of Naturally Infected Mosquitoes

Abstract

The determination of the presence or absence of malaria sporozoites in wild-caught Anopheles mosquitoes remains an integral component to the understanding of the transmission dynamics in endemic areas. To improve that capability, there has been on-going development of a new device using dipstick immunochromatographic technology for simplifying the testing procedure and reducing the time required to obtain results. As part of a larger multi-center effort, we evaluated the sensitivity and specificity of a prototype malaria sporozoite antigen panel assay (Medical Analysis Systems, Camarillo, CA) against three human Plasmodium species/polymorphs. The wicking (dipstick) assay was compared against a standard parasite antigen capture enzyme-linked immunosorbent assay (ELISA) for the detection of human circumsporozoite protein (CSP) in wild-caught mosquitoes. Over 6,800 Anopheles mosquitoes, representing 20 species collected from malaria endemic areas of Indonesia were tested either individually or in pools of up to 10 mosquitoes each. From 1,442 pooled test strip assays and ELISA formats, nine mosquito pools were found reactive for P.falciparum, P. vivax 210, or P. vivax 247 CSP. There was complete concordance between test strip results and ELISA results. Sensitivity was 100% and given some minor problems with false positives or negatives, specificity (n = 488) was 97%. Most strips judged as false positive produced very weak signals compared with negative control blank strips and paired ELISA-negative samples. The dipstick test proved technically simpler to perform and interpret than the ELISA and results were obtained within 15 min of exposure to mosquito suspension. This qualitative assay appears an attractive alternative to the CSP ELISA for detection of sporozoites in fresh or dried mosquitoes.

Evaluation of the VecTest Malaria Antigen Panel Assay for the Detection ofPlasmodium falciparumandP. vivaxCircumsporozoite Protein in Anopheline Mosquitoes in Thailand

“…The V-MAP assay was sensitive and speciÞc for each of the parasites evaluated, simple to use, rapid (results obtained in 15 min), and could be used in the Þeld. Studies by Bangs et al (2002) in Indonesia and at a variety of other laboratories throughout the world (Ryan et al 2001 also document the excellent performance of this assay.…”

“…The V-MAP assay determines the presence or absence of speciÞc peptide epitopes of CS protein of P. falciparum and two P. vivax strains (variants 210 and 247). Bangs et al (2002) reported that the performance of the V-MAP assay was comparable to that of the CS ELISA in Indonesia and Papua New Guinea. More recently, Ryan et al (2002) analyzed data from over 40,000 assays conducted at 16 different test centers from around the world and found that performance of the V-MAP was comparable to the CS ELISA.…”

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“…The studies performed to evaluate the malaria sporozoite antigen panel assay (MRP dipstick assay or VecTest™) for detecting naturally infected mosquitoes show that it is an optimal diagnostic method for use in malaria endemic areas [13,14]. These surveys compared MRP dipstick assay with another serological diagnostic probe (ELISA assay) for detecting CSP antigen.…”

“…A test was interpreted as positive when at least two lines appeared on the strip and as negative if only the control line was present. Strips were also examined one month after testing to note retention of bands [14]. …”

“…The malaria rapid panel (MRP) dipstick uses equivalent species-specific Mabs (monoclonal antibodies) as the enzyme-linked immunosorvent assay (ELISA) to detect parasite circumsporozoite protein (CSP) [13,14]. …”