Application of loop mediated isothermal amplification (LAMP) assays for the detection of Onchocerca volvulus, Loa loa and Mansonella perstans in humans and vectors

Abstract

Conventional diagnosis of filarial infections is based on morphological identification of microfilariae using light microscopy and requires considerable expertise, is time-consuming, and can be subjective. Loop-mediated isothermal amplification (LAMP) has advantages over microscopy or PCR because of its operational simplicity, rapidity and versatility of readout options. LAMP assays represent a major step forward in improved filarial diagnostic tools suitable for low resource settings and field applicability. The study goal was to retrospectively evaluate the performance and suitability of the O-150, RF4, and Mp419 LAMP assays for diagnosing Onchocerca volvulus, Loa loa and Mansonella perstans infections, respectively, in humans and vectors under experimental and natural field conditions. Surveys were conducted in four health districts of Cameroon using skin snip and thick blood film methods to detect skin (O. volvulus) and blood (L. loa and M. perstans) dwelling microfilaria in humans. Engorged vectors (Simulium spp., Chrysops spp., and Culicoides spp.) were evaluated by LAMP. Dissected, wild-caught vectors were also analyzed. LAMP showed a prevalence of 40.4% (O. volvulus), 17.8% (L. loa) and 36.6% (M. perstans) versus 20.6% (O. volvulus), 17.4% (L. loa) and 33.8% (M. perstans) with microscopy. Simulium spp. were dissected for microscopy and pooled for LAMP. The O-150 LAMP assay infection rate was 4.3% versus 4.1% by microscopy. Chrysops spp. were dissected and analyzed individually in the LAMP assay. The RF4 LAMP assay infection rate was 23.5% versus 3.3% with microscopy. The RF4 LAMP assay also detected parasites in Chrysops spp. fed on low microfilaremic volunteers. The Mp419 LAMP assay infection rate was 0.2% for C. milnei and 0.04% for C. grahamii, while three other species were LAMP-negative. The sensitivity, species specificity, rapidity and ease of its use of these filarial LAMP assays, and validation of their performance in the field support use as alternatives to microscopy as diagnostic and surveillance tools in global health programs aimed to eliminate onchocerciasis.

Diversity of Culicoides in the middle belt of Ghana with Implications on the transmission of Mansonella perstans; a molecular approach

“…Using colorimetric loop-mediated isothermal amplification assay [ 17 ], this study has successfully identified C. grahamii as the potential vector for M. perstans transmission in the middle belt of Ghana. A similar finding was made in the southwest region of Cameroon where C. grahamii was identified as a potential competent vector of M. perstans [ 18 ] even though C. milnei had been identified in earlier studies [ 10 ] to be the main vector in said region. This indicates that C. grahamii is susceptible to M. perstans invasion.…”

Acceptability of test and treat with doxycycline against Onchocerciasis in an area of persistent transmission in Massangam Health District, Cameroon

“…However, it has been shown that parasitological (skin biopsy) and immunological (OV16 antigen) parameters are in moderate agreement [37]. Therefore, new diagnostics being develop such as multiplex, loop mediated isothermal amplification (LAMP) and others are of interest [38][39][40]. In any acceptability of doxycycline treatment will be much higher in a single round than when skin snip is involved as it is the main determinant of TTd acceptability.…”

Culicoides Species of the Rain Forest Belt of the Littoral Region of Cameroon: Their Incrimination in the Transmission of Mansonella perstans

“…The UV-light trap collection may be a better method for midge collection than HLC when investigating the prevalence of the infection either by microcopy or molecular assay. Indeed, LAMP was recently used to detect M. perstans , Loa loa and Onchocerca volvulus infections in both engorged and wild-caught Culicoides , Chrysops and Simulium flies, respectively [ 34 , 35 , 36 ].…”