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.