In low-resource settings, resilience to infectious disease outbreaks can be hindered by limited access to diagnostic tests. Here we report the results of double-blinded studies of the performance of paper-based diagnostic tests for the Zika and chikungunya viruses in a field setting in Latin America. The tests involved a cell-free expression system relying on isothermal amplification and toehold-switch reactions, a purpose-built portable reader and onboard software for computer vision-enabled image analysis. In patients suspected of infection, the accuracies and sensitivities of the tests for the Zika and chikungunya viruses were, respectively, 98.5% (95% confidence interval, 96.2–99.6%, 268 serum samples) and 98.5% (95% confidence interval, 91.7–100%, 65 serum samples) and approximately 2 aM and 5 fM (both concentrations are within clinically relevant ranges). The analytical specificities and sensitivities of the tests for cultured samples of the viruses were equivalent to those of the real-time quantitative PCR. Cell-free synthetic biology tools and companion hardware can provide de-centralized, high-capacity and low-cost diagnostics for use in low-resource settings.
In Ecuador, the status of insecticide resistance for Aedes aegypti, the principal arboviral vector in the country, has not been previously evaluated. The aim of this research was to describe the resistance status of Ae. aegypti to the principal insecticides used for vector control in provinces with high reports of arboviral clinical cases. This was a descriptive study performed on Ae. aegypti collected from 2016 to 2017 in 14 localities of Ecuador. The larvae were reared and tested using bioassays applying the adulticides malathion and deltamethrin, and the larvicide temephos. The lethal concentrations were obtained for field-collected specimens and compared to the susceptible reference strain ROCK, MRA-734. Mosquitoes from all the localities showed resistance to deltamethrin and susceptibility to malathion. On the other hand, mosquitoes demonstrated resistance to the larvicide temephos in 5 of the 14 localities analyzed. The results obtained in this research may be used by healthcare decision-makers to improve vector control in Ecuador. Rotation of insecticides and alternative biological vector control strategies should be considered to manage the resistance observed in Ae. aegypti to deltamethrin and temephos. New strategies to use insecticides should also be aimed to prevent selective pressure with malathion.
Continued waves, new variants, and limited vaccine deployment mean that SARS-CoV-2 tests remain vital to constrain the coronavirus disease 2019 (COVID-19) pandemic. Affordable, point-of-care (PoC) tests allow rapid screening in non-medical settings. Reverse-transcription loop-mediated isothermal amplification (RT-LAMP) is an appealing approach. A crucial step is to optimize testing in low/medium resource settings. Here, we optimized RT-LAMP for SARS-CoV-2 and human β-actin, and tested clinical samples in multiple countries. “TTTT” linker primers did not improve performance, and while guanidine hydrochloride, betaine and/or Igepal-CA-630 enhanced detection of synthetic RNA, only the latter two improved direct assays on nasopharygeal samples. With extracted clinical RNA, a 20 min RT-LAMP assay was essentially as sensitive as RT-PCR. With raw Canadian nasopharygeal samples, sensitivity was 100% (95% CI: 67.6% - 100%) for those with RT-qPCR Ct values ≤ 25, and 80% (95% CI: 58.4% - 91.9%) for those with 25 < Ct ≤ 27.2. Highly infectious, high titer cases were also detected in Colombian and Ecuadorian labs. We further demonstrate the utility of replacing thermocyclers with a portable PoC device (FluoroPLUM). These combined PoC molecular and hardware tools may help to limit community transmission of SARS-CoV-2.
Aedes (Stegomyia) albopictus (Skuse), (Diptera: Culicidae), the Asian tiger mosquito, is one of the most widespread invasive vector-borne disease insect in tropical and temperate zones. This species has invaded the Americas over the past 3 decades and has spread to six countries. We report Ae. albopictus in Guayaquil city, the first time it has been identified in Ecuador. Outdoor BG-Sentinel traps without lures collected a total of 21 Ae. albopictus.
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