Blackflies in the ointment: O. volvulus vector biting can be significantly reduced by the skin-application of mineral oil during human landing catches

Abstract

Background Standard human landing catches (sHLCs) have historically been a key component of Onchocerca volvulus transmission monitoring, but expose health-workers to potentially hazardous vector bites. Novel human-bait-free trapping methods have been developed, but do not always work where they are needed and may not generate O . volvulus surveillance data that is directly comparable with historic data. Methodology Simuliid sHLCs and mineral-oil protected HLCs (mopHLCs) were performed in a rural village of Amazonas state, Brazil. A four-hour direct comparisons of sHLCs and mopHLCs was carried-out using six vector collectors, each of whom used one leg for a sHLC and one for a mopHLC. Two-person collection teams then exclusively performed either mopHLCs or sHLCs for a further set of 12 four-hour collections. Following the completion of all collections, simuliid-bite mark estimates were made from legs used exclusively in sHLCs and legs used exclusively in mopHLCs. Principal findings All of the 1669 captured simuliids were identified as the O . volvulus vector Simulium oyapockense . Overall, mopHLC simuliids captured per hour (S/H) rates were lower than those obtained with sHLC trapping (15.5 S/H versus 20 S/H). Direct comparisons of simuliid capture rates found that vector-collectors captured simuliids significantly more efficiently ( : 20.5 S/H) with mopHLC trapping than with sHLC trapping ( : 16.4 S/H): P-value = 0.002. MopHLCs performed in isolation were, however, observed to capture vectors less efficiently ( : 13.4 S/H) than sHLCs performed under similar conditions ( : 19.98 S/H). All six vector collectors had significantly higher simuliid capture per counted bite mark (SC/CBM) rates using mopHLCs than they were observe to have using sHLCs ( : 21 SC/CBM versus : 1 SC/CBM; p-value = 0.03125). Conclusions Vector collectors captured significantly more simuliids per counted bite mark with mopHLCs than with sHLCs. Further investigations into the utility of mopHLCs for onchocerciasis xenomonitoring and beyond are merited.

An Overview of the Management of Mansonellosis

“…48,63 Similarly, although novel methods for mansonellosis vector trapping, which could be used to investigate a link between infectious bites and disease pathology, have been developed, they have still not yet been deployed for any type of mansonellosis epidemiological study. 94 Similarly, although techniques for the isolation and genotyping of individual filarial individual microfilariae, which could improve our understanding of mansonellosis parasite population dynamics enormously, have developed, they have not yet been used in epidemiological studies of mansonellosis. 95 Of course, as discussed above, the public health importance of mansonellosis is not limited to its directly attributed disease burden.…”