Assessment of automated loop-mediated isothermal amplification-(LAMP-)based xenomonitoring for Plasmodium spp. in Anopheles mosquitoes

Abstract Background Xenomonitoring is an approach of epidemiological infection risk assessment addressing vector-transmitted infections like malaria in hematophagous arthropods. Standardization and automation can facilitate its use even in remote areas. In this study, the suitability of an automated commercial loop-mediated isothermal amplification (LAMP) assay, originally designed for the detection of malaria parasite DNA in human blood, was assessed for its applicability for xenomonitoring purposes. Methods An automated generic LAMP assay for malaria detection in human blood was applied with Anopheles spp. samples. The results were compared with commercial generic as well as species-specific real-time PCR. Results LAMP identified 15/43 (34.9%, 95% CI (20.1%; 50.9%)) mosquitoes artificially exposed to Plasmodium berghei, while this was the case for 22/43 (51.2%, 95% CI (35.5%; 66.7%)) samples applying real-time PCR. Considerably less discrepancy was observed with Anopheles spp. imported to Germany from field studies with 12/172 pools (7.0%, 95% CI (3.7%; 11.9%)) for LAMP and 13/172 pools (7.6%, 95% CI (4.1%; 12.6%)) for real-time PCR. Single testing and typing of DNA isolates indicated an overall infection rate of 1.2% (20/1711) with Plasmodium falciparum, P. malariae and P. ovale. Low rates of invalid results during a field exercise proved the general suitability of the LAMP approach for use at tropical settings. Conclusions Imperfect sensitivity in case of artificial exposure of mosquitoes to non-human plasmodial species was detected for both compared molecular approaches with slightly lower sensitivity of the LAMP approach. For Anopheles spp. infected with Plasmodium spp. causing human malaria, comparable diagnostic reliability could be shown for both approaches and the LAMP assay was shown to be suitable for application under tropical field conditions.