Re-emerging threat of Trypanosoma cruzi vector transmission in El Salvador, update from 2018 to 2020

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 confrmation 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.

Plant virology in the 21st century in China:Recent advances and future directions

Plant viruses are a group of intracellular pathogens that persistently threaten global food security.Significant advances in plant virology have been achieved by Chinese scientists over the last 20 years,including basic research and technologies for preventing and controlling plant viral diseases.Here,we review these milestones and advances,including the identification of new crop-infecting viruses,dissection of pathogenic mechanisms of multiple viruses,examination of multilayered interactions among viruses,their host plants,and virus-transmitting arthropod vectors,and in-depth interrogation of plantencoded resistance and susceptibility determinants.Notably,various plant virus-based vectors have also been successfully developed for gene function studies and target gene expression in plants.We also recommend future plant virology studies in China.

Mathematical model of zika virus dynamics with vector control and sensitivity analysis

In this paper,we have developed and analyzed a deterministic Zika model considering both vector and sexual transmission route with the effect of human awareness and vector control in the absence of disease induce death.To formulate the model,we assume that the Zika virus is being first transmitted to human by mosquito bite,and then it is being transmitted to his or her sexual partner.The system contains at most three equilibrium points among them one is the disease free and other two are endemic equilibrium points,exists under certain conditions.The theoretical analysis shows that the diseases-free equilibrium is locally and globally asymptotically stable if the basic reproduction number is less than one.Theatrically we have established that endemic equilibrium point which is locally asymptotically stable if the basic reproduction number is greater than one.The system exhibits backward bifurcation when the transmission probability per biting of susceptible mosquito with infected humans crosses the critical value.We estimate the model parameters and validate the model by fitting the model with the reported Zika infected human data from 1 to 36 week of 2016 Zika outbreak in Colombia.Furthermore,using the normalised forward sensitivity index method we have established that the model parameter mosquito biting rate,recruitment rate of mosquito,transmission probability per biting of Susceptible(infected)humans with infected(susceptible)mosquito,rate of awareness in host population,recovery rates of infected human are most sensitive parameters of the considered Zika model.Lastly,some conclusions are given to control the spreading of the Zika disease.