Evaluating Molecular Xenomonitoring as a Tool for Lymphatic Filariasis Surveillance in Samoa, 2018–2019

McPherson, Brady; Mayfield, Helen J.; McLure, Angus; Gass, Katherine; Naseri, Take; Thomsen, Robert; Williams, Steven A.; Pilotte, Nils; Kearns, Thérèse; Graves, Patricia M.; Lau, Colleen L.

doi:10.3390/tropicalmed7080203

Cited by 12 publications

(22 citation statements)

References 23 publications

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“…Two studies from American Samoa and Samoa, comprising 11 study sites, provided comparisons for a meta-analysis of molecular xenomonitoring prevalence between Aedes and Culex mosquitoes. 40 , 45 There was no difference between the two genera (prevalence ratio: 1.07; 95% CI: 0.52–2.19).…”

Section: Resultsmentioning

confidence: 88%

The impact of mosquito sampling strategies on molecular xenomonitoring prevalence for filariasis: a systematic review

Reimer,

Pryce

2024

Bull World Health Organ

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Objective To explore the impact of mosquito collection methods, sampling intensity and target genus on molecular xenomonitoring detection of parasites causing lymphatic filariasis. Methods We systematically searched five databases for studies that used two or more collection strategies for sampling wild mosquitoes, and employed molecular methods to assess the molecular xenomonitoring prevalence of parasites responsible for lymphatic filariasis. We performed generic inverse variance meta-analyses and explored sources of heterogeneity using subgroup analyses. We assessed methodological quality and certainty of evidence. Findings We identified 25 eligible studies, with 172 083 mosquitoes analysed. We observed significantly higher molecular xenomonitoring prevalence with collection methods that target bloodfed mosquitoes compared to methods that target unfed mosquitoes (prevalence ratio: 3.53; 95% confidence interval, CI: 1.52–8.24), but no significant difference compared with gravid collection methods (prevalence ratio: 1.54; 95% CI: 0.46–5.16). Regarding genus, we observed significantly higher molecular xenomonitoring prevalence for anopheline mosquitoes compared to culicine mosquitoes in areas where Anopheles species are the primary vector (prevalence ratio: 6.91; 95% CI: 1.73–27.52). One study provided evidence that reducing the number of sampling sites did not significantly affect molecular xenomonitoring prevalence. Evidence of differences in molecular xenomonitoring prevalence between sampling strategies was considered to be of low certainty, due partly to inherent limitations of observational studies that were not explicitly designed for these comparisons. Conclusion The choice of sampling strategy can significantly affect molecular xenomonitoring results. Further research is needed to inform the optimum strategy in light of logistical constraints and epidemiological contexts.

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Section: Resultsmentioning

confidence: 88%

The impact of mosquito sampling strategies on molecular xenomonitoring prevalence for filariasis: a systematic review

Reimer,

Pryce

2024

Bull World Health Organ

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“…Detailed description of the sampling design has been previously reported [ 35 , 37 ]. In brief, participants were surveyed from 35 primary sampling units (PSUs) across Upolu, Savai’i, and Manono Islands.…”

Section: Methodsmentioning

confidence: 99%

Scabies prevalence after ivermectin-based mass drug administration for lymphatic filariasis, Samoa 2018–2019

Willis,

Kearns,

Mayfield

et al. 2023

PLoS Negl Trop Dis

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Background Scabies is a common skin infestation caused by the Sarcoptes scabei mite. Ivermectin, one of three drugs used in mass drug administration (MDA) for lymphatic filariasis, is also effective for treating scabies. Ivermectin-based MDA was first conducted in Samoa in August 2018, with ivermectin being offered to those aged ≥5 years. Here, we report scabies prevalence in Samoa after MDA. Methods We conducted household surveys 1.5–3.5 months (Survey 1) and 6–8 months (Survey 2) after the 2018 MDA in 35 primary sampling units. We conducted clinical examination for scabies-like rash and used International Alliance for the Control of Scabies classification criteria. We estimated scabies prevalence by age, gender and region. Multivariable logistic regression was used to assess factors associated with prevalence. Results We surveyed 2868 people (499 households) and 2796 people (544 households) aged 0–75 years in Surveys 1 and 2, respectively. Scabies prevalence increased from 2.4% (95% CI 2.1–2.7%) to 4.4% (95% CI 4.0–4.9%) between surveys. Scabies was associated with younger age (0–4 years: aOR 3.5 [2.9–4.2]; 5–15 years: aOR 1.6 [1.4–1.8] compared to ≥16 years), female gender (aOR 1.2 [95% CI 1.1–1.4]; region (aOR range from 1.4 [1.1–1.7] to 2.5 [2.1–3.1] between regions), large households (aOR 2.6 [2.0–3.4] households ≥13), and not taking MDA in 2018 (aOR 1.3 [95% CI 1.1–1.6]). Conclusions We found moderate prevalence of scabies in two population-representative surveys conducted within 8 months of the 2018 MDA for lymphatic filariasis. Prevalence appeared to increase between the surveys, and ongoing surveillance is recommended, particularly in young children.

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“…Monitoring of MDA performance is mainly achieved through microscopic examination of microfilariae in night time blood and detection of circulating filarial antigens. Although microscopic examinations provides the most reliable estimates, night time sampling is a major challenge and also infections may be missed in presence of unmated adult worms (17) .While monitoring of CFA can provide information about prevalence of W. bancrofti infection and antibody testing can provide a sensitive indicator of exposure levels, antibody testing cannot distinguish previous from current infectious leading to an over estimation of the true burden of infection. Molecular xenomontoring (MX) that relies on polymerase chain reaction (PCR) has been suggested by WHO as an important non-invasive surveillance tool to complement human surveys (17,18).…”

Section: Introductionmentioning

confidence: 99%

“…Although microscopic examinations provides the most reliable estimates, night time sampling is a major challenge and also infections may be missed in presence of unmated adult worms (17) .While monitoring of CFA can provide information about prevalence of W. bancrofti infection and antibody testing can provide a sensitive indicator of exposure levels, antibody testing cannot distinguish previous from current infectious leading to an over estimation of the true burden of infection. Molecular xenomontoring (MX) that relies on polymerase chain reaction (PCR) has been suggested by WHO as an important non-invasive surveillance tool to complement human surveys (17,18). MX provides a platform for monitoring infection in known vectors and also provides an opportunity to incriminate new vectors involved in the transmission of W. bancrofti (19).…”

Section: Introductionmentioning

confidence: 99%

Xenomonitoring of Lymphatic filariasis and risk factors for transmission on the Kenyan coast

Bartilol,

Babu,

Garama

et al. 2024

Preprint

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Lymphatic filariasis (LF) is an infectious neglected tropical disease caused by a mosquito-borne nematode and is a major cause of disability. In 2022, it was estimated that 51 million people were infected with LF. In Kenya filariasis is endemic along the entire coastal strip. The main vectors are Anopheles funestus and Anopheles gambiae in rural areas and Culex quinquefaciatus mosquitoes in urban areas. In 2022, mosquitoes were collected from Kilifi, Kwale and Taita-Taveta counties which are located within the LF endemic region in Kenya. Subsequently, genomic Deoxyribonucleic acid (DNA) was then extracted from these mosquitoes for speciation and analysis of W. bancrofti infection rates. The impact of sociodemographic and household attributes on infection rates were assessed using generalized estimating equations. A total of 18,121 mosquitoes belonging to Culex (n = 11,414) and Anopheles (n = 6,707) genera were collected. Morphological identification revealed that Anopheline mosquito were dominated by An. funestus (n = 3,045) and An. gambiae (n = 2,873). Wuchereria bancrofti infection rates were highest in Kilifi (35.4%; 95% CI 28%-43.3%, n = 57/161) and lowest in Taita Taveta (5.3%; 95% CI 3.3%-8.0%, n = 22/412). The major vectors incriminated are An. rivulorum, An. funestus sensu stricto and An. arabiensis. The risk of W. bancrofti infection was significantly higher in An. funestus complex (OR = 18.0; 95% CI 1.80180; p = 0.014) compared to An. gambiae (OR = 1.54; 95% CI 0.16-15.10; p = 0.7). Additionally, higher risk was observed in outdoor resting mosquitoes (OR = 1.72; 95% CI 1.06-2.78; p = 0.027) and in homesteads that owned livestock (OR = 2.05; 95% CI 1.11-3.73; p = 0.021). Bednet (OR = 0.39; 95% CI 0.12-1.32; p = 0.13) and poultry ownership (OR = 0.52; 95% CI 0.30-0.89, p = 0.018) seems to provide protection. Anopheles funestus complex emerged as the primary vectors of lymphatic filariasis along the Kenyan coast. These findings also highlight that a significant portion of disease transmission potentially occurs outdoors. Therefore, control measures targeting outdoor resting mosquitoes such as zooprophylaxis, larval source management and attractive sugar baits may have potential for LF transmission reduction.

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Evaluating Molecular Xenomonitoring as a Tool for Lymphatic Filariasis Surveillance in Samoa, 2018–2019

Cited by 12 publications

References 23 publications

The impact of mosquito sampling strategies on molecular xenomonitoring prevalence for filariasis: a systematic review

The impact of mosquito sampling strategies on molecular xenomonitoring prevalence for filariasis: a systematic review

Scabies prevalence after ivermectin-based mass drug administration for lymphatic filariasis, Samoa 2018–2019

Xenomonitoring of Lymphatic filariasis and risk factors for transmission on the Kenyan coast

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