Evaluation of LAMP for the diagnosis of Loa loa infection in dried blood spots compared to PCR-based assays and microscopy

BACKGROUND Loa loa is a filarial species found exclusively in West and Central Africa. Microscopy is the traditional diagnosis method for human loiasis. Several molecular methods have developed as an alternative approach for identification of L. loa filarial parasites. OBJECTIVES The aim of this study was to evaluate a Loa-Loop-mediated isothermal amplification (LAMP) assay to diagnose loiasis disease on dried blood spots (DBS) samples, compared to microscopy, filaria-real time-polymerase chain reaction (PCR) and nested-Loa PCR. METHODS A total of 100 DBS samples and 100 blood smears were used for this study. DNA was extracted using saponin/Chelex method. DNA isolated was assayed by a Loa-LAMP assay in parallel to microscopy, filaria-real time PCR and nested-Loa PCR. The sensitivities and specificities of Loa-LAMP assay was computed comparing to each one of the reference methods. FINDINGS Loa-LAMP's sensitivity was more than 90% and specificity was nearly 100% when compared to molecular methods. On the other hand, sensitivity was decreased a bit when Loa-LAMP faced microscopy, but keeping the other statistical values high. MAIN CONCLUSIONS Loa-LAMP is an appropriate method for loiasis diagnosis in endemic areas. Though, it has disadvantages like the reagents' high price at the moment and not to be able to detect more filarial species at once.

Phosphoenolpyruvate-succinate-glyoxylate pathway in the filarial parasite Setaria digitata.

Setaria digitata, a filarial parasite of cattle possesses certain unique characteristics like cyanide insensitivity, and lack of cytochromes. In the present study, we have shown that the parasite has an incomplete tricarboxylic acid cycle with the absence of activities of isocitrate dehydrogenase, α-ketoglutarate dehydrogenase and succinyl-CoA synthase. However the parasite showed the existence of glyoxylate cycle and phosphoenolpyruvate-succinate pathway. The widely used antifilarial drug diethylcarbamazine caused general inhibition of all enzymes of phosphoenolpyruvate-succinate pathway and glyoxylate cycle except that of fumarase and isocitrate lyase. The results may pave the way for new targets for chemotherapy in the control of filarial parasites.