Table 1.

Principal field studies that have employed molecular xenomonitoring in different LF-endemic WHO regions.

WHO region & endemic countries	setting/s	purpose/s	mosquito collection methods (MCMs)	mosquito species	parasite/s	mosquito pools/infection	source
Africa (AFRO)
Ghana	rural, two communities	comparing diagnostic tools for assessing interruption of LF	GTs (outside houses for Culex) and pyrethrum knock-down collection (inside houses for Anopheles)	Culex spp., Anopheles spp.	W. bancrofti	Culex spp: 1/264 pools (4099 females in total) tested positive for W. bancrofti DNA by PCR; Anopheles spp: 13/30 pools (401 females in total) tested positive for W. bancrofti DNA by PCR	[22]
Tanzania	rural, two communities: Masaika (end of rainy season); Vyeru, Tanga Region (rainy season)	comparing MCMs	CDC LTs (inside houses) and CDC GTs (outside houses)	Cx. quinquefasciatus	W. bancrofti	masaika (individually tested)—2/150 females collected using GTs tested positive (1.3%) by PCR; Vyeru (25 females/pool)—15/110 pools collected from LTs tested positive (0.6%) by PCR; 1/115 pools collected using GTs tested positive (0.03%) by PCR	[23]
Togo	rural, 37 villages in three districts in one of four evaluation units (EUs)	post-MDA surveillance	pyrethroid spray catches inside houses (PSC) versus exit trap collection (ETC) over 5 months	Anopheles spp., Cx. quinquefasciatus	W. bancrofti	pools of 25 or less females; LAMP used to detect W. bancrofti DNA; positive pools confirmed by PCR; Anopheles spp: 0/629 pools (9191 females in total including 6992 An. gambiae) tested positive	[24]
Americas (AMR/PAH)
Brazil	urban, Olinda (RMR)	comparing MCMs	CDC LTs (inside houses) and large battery-powered aspirators (inside houses)	Cx. quinquefasciatus	W. bancrofti	0/182 pools (1556 mosquitoes) tested positive by PCR	[25]
Eastern Mediterranean (EMRO)
Egypt	rural, two communities (150–200 houses per year sampled in each study area): Giza villages (high LF prevalence) and Qalubiya villages (low LF prevalence)	post-MDA surveillance	manual aspiration (inside houses)	Cx. pipiens	W. bancrofti	pools of >25 blood-fed or gravid females; Poolscreen infection rates decreased following MDA: 3.07% pre-MDA to 0.19% post-MDA (Giz) and 4.37% pre-MDA to 0.00% post-MDA (Qal) after five annual rounds	[9]
Egypt	rural, seven districts	comparing single PCRs and multiplex PCRs	battery-powered aspiration (inside houses)	Culex spp., Anopheles spp., Aedes spp.	W. bancrofti, D. immitis, Dirofilaria repens	100 pools of 25 females/pool tested using single PCRs and mulitplex PCRs for the 3 filarial parasites; the overall estimated rate of infection using Poolscreen was 0.6%; the multiplex PCR had a higher sensitivity (100%) compared with single PCR, and 98% specificity	[19]
Egypt	rural, two villages: Samalay and Kafr El-Tarainah after 13th round of MDA	post-MDA surveillance	25 GTs (outside houses) for 6 successive nights	Cx. pipiens	W. bancrofti	pools of 25 mosquitoes were tested by a real-time PCR: 152 pools for Samalay, 167 pools for Kafr El-Tarainah; all pools were negative; all primary school children were negative by ICT	[26]
Southeast Asia (SEARO)
Sri Lanka	rural, 19 PHI areas in eight LF-endemic districts, plus two in Colombo, 6 years after MDA (conducted 2002–2006)	post-MDA surveillance	CDC GTs placed in each quadrant of each PHI for 1–4 days	Cx. quinquefasciatus	W. bancrofti	almost 3900 pools (20 females/pool) in 19 PHIs tested for filarial DNA by qPCR; filarial rates exceeded the 0.25% target in 10/19 PHIs and were >1% in Galle	[27]
Sri Lanka	two Galle EUs, one coastal/high risk and one inland/low risk, 8 years after last round of MDA in 2006	post-MDA surveillance comparing number of trap sites required/scale	CDC GTs placed in 300 trap locations per EU	Cx. quinquefasciatus	W. bancrofti	qPCR results: 28 000 females collected and tested in 1208 pools (1–25 females/pool, 89.5% contained 25 females); 92/625 positive (=0.63% Poolscreen filarial DNA rate) in high-risk EU; 8/583 positive (=0.0.6% Poolscreen filarial DNA rate) in low-risk EU; filarial DNA rates do not differ whether 75, 150 or 300 trap sites are tested	[28]
Sri Lanka	six of the 19 PHI areas previously examined [27]	post-MDA surveillance	CDC GTs placed in each quadrant of each PHI (50 trapping locations/PHI)	Cx. quinquefasciatus	W. bancrofti	four pools of 20 fed, gravid or semigravid mosquitoes were tested/PHI; filarial DNA was detected in all six PHI areas, and exceeded the target in three: two in Galle District (1.17% in Ambalangoda and 1.23 in Unawatuna), and one in Matara District (1.09% in Weligama)	[29]
Sri Lanka	hotspot with persistent LF (Balapitya PHI area in Galle EU)	post-MDA surveillance	in 2015 trapping was as previously described [29]; in 2016, CDC GTs placed in each quadrant: eight trapping locations in Balapitya PHI and 14 in coastal Galle EU	Cx. quinquefasciatus	W. bancrofti	two pools of 25 fed, gravid or semigravid mosquitoes were tested/PHI; filarial DNA was detected in all five Public Health Midwife areas within Balapitia PHI; mean prevalence rates were lower in 2016 compared with 2015 but were 3.0% overall	[30]
India	one hotspot (≥1% community microfilaria prevalence) and PHC area in Ammapettai, Thanjavur District, Tamil Nadu	post-MDA surveillance comparing number of trap sites required/scale	CDC GTs placed at 204 households (HHs) for the hotspot, and 231 HHs in the PHC in 2010 and 2012	Cx. quinquefasciatus	W. bancrofti	qPCR results: 231 pools of over 5000 mosquitoes (around 23 females/pool) were tested for each sample taken each year; the hotspot pool rates and estimated LF infection rates were higher in the hotspot than the PHC area, e.g. W. bancrofti DNA prevalence in hotspot versus PHC area was 1.1% versus 0.9% and 0.3% versus 0.2% in 2010 and 2012, respectively	[31]
India	surveyed nine districts with LF hotspots pre-MDA in two states: Maharashtra and Karnataka	post-MDA surveillance	CDC LTs on porches of HH	not specified in publication	W. bancrofti	PCR: unspecified number of pools (10 mosquitoes/pool); 6/9 districts had pools positive for Ssp1 gene specific to L3 (infective mosquitoes)	[32]
Bangladesh	rural, two districts (30 villages/EU): Panchagarh (previously endemic, stopped MDA) and Gaibandha (non-endemic)	assessing interruption of LF following 12 rounds of MDA	CDC GTs placed 180 trap sites (HH courtyards)/district	Cx. quinquefasciatus	W. bancrofti	PCR results: 0/594 pools (1–25 females, mean 16.9) tested positive for W. bancrofti DNA	[33]
Western Pacific (WPRO)
American Samoa	rural, three coastal villages of Tutuila island	comparing microscopy and PCR for parasite detection	10 BG Sentinel traps baited with BG Lure placed on ground locations in each village for 4 consecutive days; repeated to give a total of 8 trap days/village	Aedes spp.	W. bancrofti	compared microscopy (hemalum staining and dissection) with PCR (average pool size=4.9 for Aedes polynesiensis, 1.92 for Ae. aegypti and 2.10 for Ae. upolensis); overall prevalence of W. bancrofti in Aedes polynesiensis was 0.16% by microscopy, and 0.69% by PCR (Poolscreen rate)	[12]
American Samoa	rural, multiple coastal villages in five islands of Tutuila, Aunu'u, Ofu, Olosega and Ta'u	comparing diagnostic tools for assessing interruption of LF following 10 rounds of MDA	usually, 10 BG Sentinel traps baited with BG Lure placed on ground locations for 24–48 h throughout each village	Aedes spp., Cx. quinquefasciatus	W. bancrofti	females placed in pools of ≤20 prior to PCR/Poolscreen; Aedes polynesiensis most abundant (15 215 females: 42/1250 pools positive (0.28% prevalence); Cx. quinquefasciatus (4413 females) had a prevalence rate of 0.11% (5/584 positive pools); Ae. aegypti (887 females) had the highest prevalence (0.92%; 8/360 pools)	[34]
Samoa	rural, Fsitoo-Tai village on coast of Upolu island	comparing MCMs	compared BG Sentinel traps, HBCs and UV LED CDC LTs	Ae. polynesiensis. Ae. (Finlaya) spp., Ae. aegypti. Cx. quinquefasciatus	W. bancrofti	Ae. polynesiensis: 57 pools (2251 females) were analysed by PCR and four were positive for LF (4.7% prevalence); Ae. (Finlaya) spp.: 17 pools (153 females) were analysed by PCR and one was positive for LF (0.67% prevalence)	[35]
Malaysia	rural, 21 endemic implementation units (red IUs) and six non-endemic (green IUs)	investigate evidence of local transmission	human-landing catches and CDC LTs	Culex spp., Anopheles spp., Aedes spp., Armigeres spp., Coquillettidia spp., Mansonia spp.	W. bancrofti, B. malayi	0/668 pools (4738 mosquitoes) tested by PCR were positive for infection	[36]
Papua New Guinea	rural, three villages in Drekkier District (two high, one moderate transmission zones)	pre-MDA (2014) and post-MDA (2015) surveillance	human-landing catches	not specified in publication	W. bancrofti	293 samples were collected in 2014, and 448 samples were collected in 2015; DNA was run using conventional PCR and gel electrophoresis; mosquito infection rates decreased in both high (10.8% to 2.6%) and moderate (16.3% to 1.6%) transmission zones	[37]