Anopheles salivary biomarker as a proxy for estimating plasmodium falciparum malaria exposure on the Thailand-Myanmar border

Timely identification and treatment of malaria transmission “hot spots” is essential to achieve malaria elimination. Here we investigate the relevance of using an Anopheles salivary biomarker to estimate Plasmodium falciparum malaria exposure risk along the Thailand–Myanmar border to guide malaria control. Between May 2013 and December 2014, > 9,000 blood samples collected in a cluster randomized control trial were screened with serological assays to measure the antibody responses to Anopheles salivary antigen (gSG6-P1) and P. falciparum malaria antigens (circumsporozoite protein, merozoite surface protein 119 [MSP-119]). Plasmodium falciparum infections were monitored through passive and active case detection. Seroprevalence to gSG6-P1, MSP-119, and CSP were 71.8% (95% Confidence interval [CI]: 70.9, 72.7), 68.6% (95% CI: 67.7, 69.5), and 8.6% (95% CI: 8.0, 9.2), respectively. Multivariate analysis showed that individuals with the highest Ab response to gSG6-P1 had six times the odds of being positive to CSP antigens (P < 0.001) and two times the odds of P. falciparum infection compared with low gSG6-P1 responders (P = 0.004). Spatial scan statistics revealed the presence of clusters of gSG6-P1 that partially overlapped P. falciparum infections. The gSG6-P1 salivary biomarker represents a good proxy for estimating P. falciparum malaria risk and could serve to implement hot spot–targeted vector control interventions to achieve malaria elimination

Anopheles salivary biomarker as a proxy for estimating Plasmodium falciparum malaria exposure on the Thailand-Myanmar border

Timely identification and treatment of malaria transmission "hot spots" is essential to achieve malaria elimination. Here we investigate the relevance of using an Anopheles salivary biomarker to estimate Plasmodium falciparum malaria exposure risk along the Thailand-Myanmar border to guide malaria control. Between May 2013 and December 2014, > 9,000 blood samples collected in a cluster randomized control trial were screened with serological assays to measure the antibody responses to Anopheles salivary antigen (gSG6-P1) and P. falciparum malaria antigens (circumsporozoite protein, merozoite surface protein 119 [MSP-1(19)]). Plasmodium falciparum infections were monitored through passive and active case detection. Seroprevalence to gSG6-P1, MSP-1(19), and CSP were 71.8% (95% Confidence interval [CI]: 70.9, 72.7), 68.6% (95% CI: 67.7, 69.5), and 8.6% (95% CI: 8.0, 9.2), respectively. Multivariate analysis showed that individuals with the highest Ab response to gSG6-P1 had six times the odds of being positive to CSP antigens (P< 0.001) and two times the odds of P. falciparum infection compared with low gSG6-P1 responders (P= 0.004). Spatial scan statistics revealed the presence of clusters of gSG6-P1 that partially overlapped P. falciparum infections. The gSG6-P1 salivary biomarker represents a good proxy for estimating P. falciparum malaria risk and could serve to implement hot spot-targeted vector control interventions to achieve malaria elimination

Use of an anopheles salivary biomarker to assess malaria transmission risk along the Thailand-Myanmar border

Background. The modalities of malaria transmission along the Thailand-Myanmar border are poorly understood. Here we address the relevance of using a specific Anopheles salivary biomarker to measure the risk of human exposure to anopheles bites. Methods. Serologic surveys were conducted from May 2013 to December 2014 in 4 sentinel villages. Dried blood spots (n&gt;9,400) were collected in filter papers among all inhabitants at baseline and then every three months up to 18 months. The relationship between the intensity of human antibody response and entomological indicators of transmission (Human biting rates and Entomological Inoculation rates or EIR) was studied using a multivariate three-level mixed model analysis. “Heatmaps” for human IgG responses for each village and survey time point were created using QGIS 2.4. Results. The levels of IgG response of participants significantly varied according to the village, season and age (P&lt;0.001) and were positively associated with the abundance of total Anopheles spp. and primary malaria vectors and EIR (P&lt;0.001). Spatial clusters of high IgG responders were identified across space and time within study villages. Conclusions. The gSG6-P1 biomarker has great potential to address the risk of transmission along the Thailand-Myanmar border and represents a promising tool to guide malaria intervention

Use of an anopheles salivary biomarker to assess malaria transmission risk along the Thailand-Myanmar border

Background. The modalities of malaria transmission along the Thailand-Myanmar border are poorly understood. Here we address the relevance of using a specific Anopheles salivary biomarker to measure the risk of human exposure to anopheles bites. Methods. Serologic surveys were conducted from May 2013 to December 2014 in 4 sentinel villages. Dried blood spots (n>9,400) were collected in filter papers among all inhabitants at baseline and then every three months up to 18 months. The relationship between the intensity of human antibody response and entomological indicators of transmission (Human biting rates and Entomological Inoculation rates or EIR) was studied using a multivariate three-level mixed model analysis. “Heatmaps” for human IgG responses for each village and survey time point were created using QGIS 2.4. Results. The levels of IgG response of participants significantly varied according to the village, season and age (P<0.001) and were positively associated with the abundance of total Anopheles spp. and primary malaria vectors and EIR (P<0.001). Spatial clusters of high IgG responders were identified across space and time within study villages. Conclusions. The gSG6-P1 biomarker has great potential to address the risk of transmission along the Thailand-Myanmar border and represents a promising tool to guide malaria intervention

Scale up of a Plasmodium falciparum elimination program and surveillance system in Kayin State, Myanmar

Background Myanmar has one of the largest malaria burdens in the Greater Mekong Subregion (GMS). Throughout the GMS, Plasmodium falciparum parasites are increasingly resistant to artemisinin combination therapies. Given that there are no current alternative treatment therapies, one proposed solution to the threat of untreatable P. falciparum malaria is to eliminate the parasite from the region. Several small-scale elimination projects have been piloted in the GMS, including along the Myanmar-Thailand border. Following the success of the pilot elimination project along the Myanmar-Thailand border, there was a scale up to a broad area of Eastern Kayin State, Myanmar. Here we describe the establishment of the scale up elimination project in Easter Kayin State. Methods The scale up relied on geographic reconnaissance and a geographic information system, community engagement, generalized access to community-based early diagnosis and treatment, near real-time epidemiological surveillance, cross sectional malaria prevalence surveys and targeted mass drug administration in villages with high prevalence of P. falciparum malaria. Molecular markers of drug resistance were also monitored in individuals with symptomatic and asymptomatic infections. Discussion This protocol illustrates the establishment of an elimination project and operational research in a remote, rural area encompassing several armed groups, multiple political organizations and a near-absent health care infrastructure. The establishment of the project relied on a strong rapport with the target community, on-the-ground knowledge (through geographic surveys and community engagement), rapid decision making and an approach that was flexible enough to quickly adapt to a complex landscape. The elimination project is ongoing, now over three years in operation, and assessment of the impact of this operational research will follow. This project has relevance not only for other malaria elimination projects but also for operational research aimed at eliminating other diseases.</p