Chemical Control of Chagas Disease Vectors

This paper presents the reasons why countries to which Chagas disease is endemic should carry out the relevant research themselves. A local technical capability for a rational improvement in the chemical control of vectors is being developed. This research includes (1) the triatomicidal activity of chemical insecticides, (2) determination of the mechanisms of action of these chemicals, (3) search for new synergists of these insecticides, (4) development of fumigation canisters which may be more widely used, and (5) development of new chemicals with a greater potential for use as triatomicides. 1989 Academic Press, Inc.

Stochastic Investigations for the Fractional Vector-Host Diseased Based Saturated Function of Treatment Model

The goal of this research is to introduce the simulation studies of the vector-host disease nonlinear system(VHDNS)along with the numerical treatment of artificial neural networks(ANNs)techniques supported by Levenberg-Marquardt backpropagation(LMQBP),known as ANNs-LMQBP.This mechanism is physically appropriate,where the number of infected people is increasing along with the limited health services.Furthermore,the biological effects have fadingmemories and exhibit transition behavior.Initially,the model is developed by considering the two and three categories for the humans and the vector species.The VHDNS is constructed with five classes,susceptible humans Sh(t),infected humans Ih(t),recovered humans Rh(t),infected vectors Iv(t),and susceptible vector Sv(t)based system of the fractional-order nonlinear ordinary differential equations.To solve the number of variations of the VHDNS,the numerical simulations are performed using the stochastic ANNs-LMQBP.The achieved numerical solutions for solving the VHDNS using the stochastic ANNs-LMQBP have been described for training,verifying,and testing data to decrease the mean square error(MSE).An extensive analysis is provided using the correlation studies,MSE,error histograms(EHs),state transitions(STs),and regression to observe the accuracy,efficiency,expertise,and aptitude of the computing ANNs-LMQBP.

Dynamic of Non-Autonomous Vector Infectious Disease Model with Cross Infection

In the article, we established a non-autonomous vector infectious disease model, studied the long-term dynamic behavior of the system, and obtained sufficient conditions for the extinction and persistence of infectious diseases by constructing integral functions.

Scoping review on vector-borne diseases in urban areas:transmission dynamics,vectorial capacity and co-infection

Background:Transmission dynamics,vectorial capacity,and co-infections have substantial impacts on vector-borne diseases(VBDs)affecting urban and suburban populations.Reviewing key factors can provide insight into priority research areas and offer suggestions for potential interventions.Main body:Through a scoping review,we identify knowledge gaps on transmission dynamics,vectorial capacity,and co-infections regarding VBDs in urban areas.Peer-reviewed and grey literature published between 2000 and 2016 was searched.We screened abstracts and full texts to select studies.Using an extraction grid,we retrieved general data,results,lessons learned and recommendations,future research avenues,and practice implications.We classified studies by VBD and country/continent and identified relevant knowledge gaps.Of 773 articles selected for full-text screening,50 were included in the review:23 based on research in the Americas,15 in Asia,10 in Africa,and one each in Europe and Australia.The largest body of evidence concerning VBD epidemiology in urban areas concerned dengue and malaria.Other arboviruses covered included chikungunya and West Nile virus,other parasitic diseases such as leishmaniasis and trypanosomiasis,and bacterial rickettsiosis and plague.Most articles retrieved in our review combined transmission dynamics and vectorial capacity;only two combined transmission dynamics and co-infection.The review identified significant knowledge gaps on the role of asymptomatic individuals,the effects of co-infection and other host factors,and the impacts of climatic,environmental,and socioeconomic factors on VBD transmission in urban areas.Limitations included the trade-off from narrowing the search strategy(missing out on classical modelling studies),a lack of studies on co-infections,most studies being only descriptive,and few offering concrete public health recommendations.More research is needed on transmission risk in homes and workplaces,given increasingly dynamic and mobile populations.The lack of studies on co-infection hampers monitoring of infections transmitted by the same vector.Conclusions:Strengthening VBD surveillance and control,particularly in asymptomatic cases and mobile populations,as well as using early warning tools to predict increasing transmission,were key strategies identified for public health policy and practice.

Vector-borne disease and climate change adaptation in African dryland socialecological systems

Background:Drylands,which are among the biosphere's most naturally limiting and environmentally variable ecosystems,constitute three-quarters of the African continent.As a result,environmental sustainability and human development along with vector-borne disease(VBD)control historically have been especially challenging in Africa,particularly in the sub-Saharan and Sahelian drylands.Here,the VBD burden,food insecurity,environmental degradation,and social vulnerability are particularly severe.Changing climate can exacerbate the legion of environmental health threats in Africa,the social dimensions of which are now part of the international development agenda.Accordingly,the need to better understand the dynamics and complex coupling of populations and environments as exemplified by drylands is increasingly recognized as critical to the design of more sustainable interventions.Main body:This scoping review examines the challenge of vector-borne disease control in drylands with a focus on Africa,and the dramatic,ongoing environmental and social changes taking place.Dryland societies persisted and even flourished in the past despite changing climates,extreme and unpredictable weather,and marginal conditions for agriculture.Yet intrusive forces largely out of the control of traditional dryland societies,along with the negative impacts of globalization,have contributed to the erosion of dryland's cultural and natural resources.This has led to the loss of resilience underlying the adaptive capacity formerly widely exhibited among dryland societies.A growing body of evidence from studies of environmental and natural resource management demonstrates how,in light of dryland system's inherent complexity,these factors and top-down interventions can impede sustainable development and vector-borne disease control.Strengthening adaptive capacity through community-based,participatory methods that build on local knowledge and are tailored to local ecological conditions,hold the best promise of reversing current trends.Conclusions:A significant opportunity exists to simultaneously address the increasing threat of vector-borne diseases and climate change through methods aimed at strengthening adaptive capacity.The integrative framework and methods based on social-ecological systems and resilience theory offers a novel set of tools that allow multiple threats and sources of vulnerability to be addressed in combination.Integration of recent advances in vector borne disease ecology and wider deployment of these tools could help reverse the negative social and environmental trends currently seen in African drylands.

TRAVELLING FRONT SOLUTIONS IN A DIFFUSIVE VECTOR DISEASE MODEL WITH SPATIO-TEMPORAL DELAY

This paper is concerned with travelling front solutions to a vector disease model with a spatio-temporal delay incorporated as an integral convolution over all the past time up to now and the whole one-dimensional spatial domain R.When the delay kernel is assumed to be the strong generic kernel,using the linear chain techniques and the geometric singular perturbation theory,the existence of travelling front solutions is shown for small delay.

A study of the correlation between dengue and weather in Kandy City, Sri Lanka (2003 -2012) and lessons learned

Background:Weather variables affect dengue transmission.This study aimed to identify a dengue weather correlation pattern in Kandy,Sri Lanka,compare the results with results of similar studies,and establish ways for better control and prevention of dengue.Method:We collected data on reported dengue cases in Kandy and mid-year population data from 2003 to 2012,and calculated weekly incidences.We obtained daily weather data from two weather stations and converted it into weekly data.We studied correlation patterns between dengue incidence and weather variables using the wavelet time series analysis,and then calculated cross-correlation coefficients to find magnitudes of correlations.Results:We found a positive correlation between dengue incidence and rainfall in millimeters,the number of rainy and wet days,the minimum temperature,and the night and daytime,as well as average,humidity,mostly with a five-to seven-week lag.Additionally,we found correlations between dengue incidence and maximum and average temperatures,hours of sunshine,and wind,with longer lag periods.Dengue incidences showed a negative correlation with wind run.Conclusion:Our results showed that rainfall,temperature,humidity,hours of sunshine,and wind are correlated with local dengue incidence.We have suggested ways to improve dengue management routines and to control it in these times of global warming.We also noticed that the results of dengue weather correlation studies can vary depending on the data analysis.

Invasion of the raccoon dog Nyctereutes procyonoides in Europe： History of colonization, features behind its success, and threats to native fauna

We aimed to review the history of the introduction and colonization of the raccoon dog Nyctereutes procyonoides in Europe, the features behind its successful expansion and its impact on native fauna. The raccoon dog quickly colonized new areas after being introduced to the European part of the former Soviet Union. Today it is widespread in Northern and Eastern Europe and is still spreading in Central Europe. Features behind its success include its adaptability, high reproductive potential, omnivory, hibernation in northem areas, multiple introductions with 〉 9000 individuals from different localities, and tendency to wander enabling gene flow between populations. Firm evidence of the raccoon dog＇s negative impact on native fauna, such as a reduction in bird populations, is still scarce. Raccoon dogs may destroy waterfowl nests, although a nest predation study in Latvia did not confirm this. Predator removal studies in Finland suggested that the raccoon dog＇s impact on game birds is smaller than expected. However, raccoon dogs may have caused local extinction of frog populations, especially on islands. Raccoon dogs may compete with other carnivores for food, for example for carrion in winter, or for the best habitat patches. In northern Europe potential competitors include the red fox Vulpes vulpes and the badger Meles meles, but studies of their diets or habitat preferences do not indicate severe competition. The raccoon dog is an important vector of diseases and parasites, such as rabies, Echinococcus mul-tilocularis and Trichinella spp. and this is no doubt the most severe consequence arising from the spread of this alien species in Europe [Current Zoology 57 （5）： 584-598, 2011].

Hidden heterogeneity and its influence on dengue vaccination impact

The CYD-TDV vaccine was recently developed to combat dengue,a mosquito-borne viral disease that afflicts millions of people each year throughout the tropical and subtropical world.Its rollout has been complicated by recent findings that vaccinees with no prior exposure to dengue virus(DENV)experience an elevated risk of severe disease in response to their first DENV infection subsequent to vaccination.As a result of these findings,guidelines for use of CYD-TDV now require serological screening prior to vaccination to establish that an individual does not fall into this high-risk category.These complications mean that the public health impact of CYD-TDV vaccination is expected to be higher in areas with higher transmission.One important practical difficulty with tailoring vaccination policy to local transmission contexts is that DENV transmission is spatially heterogeneous,even at the scale of neighborhoods or blocks within a city.This raises the question of whether models based on data that average over spatial heterogeneity in transmission could fail to capture important aspects of CYD-TDV impact in spatially heterogeneous populations.We explored this question with a deterministic model of DENV transmission and CYD-TDV vaccination in a population comprised of two communities with differing transmission intensities.Compared to the full model,a version of the model based on the average of the two communities failed to capture benefits of targeting the intervention to the high-transmission community,which resulted in greater impact in both communities than we observed under even coverage.In addition,the model based on the average of the two communities substantially overestimated impact among vaccinated individuals in the low-transmission community.In the event that the specificity of serological screening is not high,this result suggests that models that ignore spatial heterogeneity could overlook the potential for harm to this segment of the population.