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国際共同研究グループは、シャーガス病の原因である媒介昆虫による感染リスクを評価するため、2年間にわたり中米エルサルバドル全域にて調査を行いました。シャーガス病は、WHOが定義する顧みられない熱帯病(Neglected Tropical Diseases, NTDs)の一つであり、クルーズトリパノソーマ(Trypanosoma cruzi)と呼ばれる原虫に感染している媒介昆虫によりヒトに感染します。主にラテンアメリカで猛威をふるう感染症で、エルサルバドルは流行国の中でも特に感染者が多く深刻な状況であるにもかかわらず、媒介昆虫がどの程度、病原体に寄生されておりヒトへの感染源となっているかについて、十分な調査や報告がなされていませんでした。そこで本研究グループは、エルサルバドル全域で同国保健省や地方自治体等と協力し家屋への立ち入り調査を行い、媒介昆虫の侵入状況や感染率をもとに、リスクの高い地域を層別することができました。本研究成果により、今後特に感染リスクの高い地域を対象とした対策の効率化が期待できます。, Background: Since the late twentieth century, Chagas disease gained global attention to suppress the vector burden as a main control strategy in endemic countries. In Central America, multi-national initiative successfully achieved significant reduction in the estimated disease prevalence as well as elimination of the region's principal vector species at the time in 2012. While the last decade has witnessed significant changes in ecosystem-such as urbanization and replacement of the main vector species-that can possibly affect the vector's habitation and residual transmission, the up-to-date vector burden in the region has not been evaluated thoroughly due to the cessation of active vector surveillance. The aim of this study was to update the risk of vector-borne Trypanosoma cruzi infection in El Salvador, the top Chagas disease-endemic country in Central America. / Methods: A nationwide vector survey was conducted in the domestic environment of El Salvador from September 2018 to November 2020. The selection of the houses for inspection was based on expert purposeful sampling. Infection for T. cruzi was examined by microscopic observation of the insects' feces, followed by a species confirmation using PCR. The data were analyzed using R software version 4.1.3. Proportion estimates with 95% confidence intervals were inferred using the Jeffrey's method provided under the epiR package. / Results: A total of 1529 Triatoma dimidiata was captured from 107 houses (infestation rate, 34.4%; 107/311) in all the fourteen departments of the country visited within the period; prevalence of T. cruzi infection was as high as 10% (153/1529). In the country, domestic T. dimidiata infestation was distributed ubiquitously, while T. cruzi infection rates varied across the departments. Five out of fourteen departments showed higher infection rates than the average, suggesting sporadic high-risk areas in the country. / Conclusions: Our comprehensive study revealed substantial T. cruzi infection of T. dimidiata across the country, indicating potential active transmission of the disease. Therefore, strengthened surveillance for both vector and human infection is required to truly eliminate the risk of T. cruzi transmission in Central America.