Vector control Aedes sp. during pandemic COVID-19

During the coronavirus disease 2019 (COVID-19) outbreak in Indonesia, the government also faces another health problem, namely dengue hemorrhagic fever (DHF). The routine activities of the dengue management system have been significantly curtailed as government authorities concentrate more on containing the transmission of the COVID-19. This study aimed to describe vector control <em>Aedes sp.</em> during pandemic COVID-19, such as community activities in controlling breeding places, area risk, vector density and the determinant factors. This study was a community-based cross-sectional survey involving 136 households in the endemic area of Gondokusuman District, Yogyakarta, Indonesia using proportionate stratified random sampling. Data analysis was performed through simple and multiple logistic regression tests. Vector control for <em>Aedes sp.</em> breeding places during pandemic COVID-19 in the community are still low; the high level of vector density proves this based on House Index (HI): 44.1%, container index (CI): 57.4%, and Breteau Index (BI): 213.2%. This district is also at high risk to be the breeding places of <em>Aedes sp.</em> based on maya index (MI): 64.7%. The determinant factor that affects this condition is the lack of support by health workers/cadres during the COVID-19 pandemic.

A Report on Vector Surveillance for Zika/Dengue at CCS International Airport, Lucknow, India

In view of reports of Zika outbreak from Gujarat & Rajasthan states, an entomological surveillance of Aedes aegypti vector was carried out at Adani Chaudhary Charan Singh (CCS) International Airport, Lucknow and its adjoining areas between 2016 to 2019. The regular monitoring of the vector and effective intervention measures prevented the invasion of new pathogen of Zika and Yellow fever pathogen (virus) by bringing down the Aedes aegypti vector density at lowest level. The entomological indices worked out in 2016 as the premise index in the month of February, June and August, were remained positive for Aedes aegypti and container index (CI) was found 14.14. The House Index (HI), Container Index (CI) & Breteau Index (BI) were 24.50, 17.51 & 25.27, respectively in residential colony of Air Port Staff located at a distance of 0.50 km, whereas, indices were found very high i.e. 37.50, 25.50 & 57.62, respectively in Farrukhabad/Chillawan civil inhabitation located at a distance of 2.0 Kilometre. With the dedicated efforts of Airport Authority of India and State Health Department, Aedes aegypti indices gradually declined to very low level as the premise were positive for Aedes aegypti larvae but container index inside & outside airport premise became 2.70 & 4.37 respectively in early half of 2019. The HI, CI & BI were found 2.57, 2.69 & 3.09 in the airport residential colony and 3.15, 2.57 & 2.77, respectively in civil inhabitation i.e. Farrukhabad/Chillawan area in early half of 2019. The collateral impact of low vector density resulted drastic decline in dengue morbidity by 83.73% & 74.74% and in mortality by 88.89% & 94.44%, during 2017 & 2018 respectively in comparison to 2016 and the case fatality rate (CFR) declined from 0.65% in 2016 to 0.14% in 2018. However no death was documented due to Chikungunya in Lucknow and the morbidity though was doubled in 2017 & declined again to the level of 2016, but remained very less in comparison to dengue, as only 44, 80 & 47 cases of Chikungunya were reported during 2016, 2017 & 2018, respectively. The Airport also achieved the dividend in the form of conferring the title of Best Airport of the year 2018 in size & region managing the cleanliness in increased thrust of passengers’ load to more than double in limited resources.

Determinants of Aedes mosquito density as an indicator of arbovirus transmission risk in three sites affected by co-circulation of globally spreading arboviruses in Colombia, Ecuador and Argentina

Background The global impact of Zika virus in Latin America has drawn renewed attention to circulating mosquito-borne viruses in this region, such as dengue and chikungunya. Our objective was to assess socio-ecological factors associated with Aedes mosquito vector density as a measure of arbovirus transmission risk in three cities of potentially recent Zika virus introduction: Ibagué, Colombia; Manta, Ecuador; and Posadas, Argentina, in order to inform disease mitigation strategies. Methods We sampled Aedes mosquito populations in a total of 1086 households, using indoor and peridomestic mosquito collection methods, including light traps, resting traps, traps equipped with chemical attractant and aspirators. For each sampled household, we collected socio-economic data using structured questionnaires and data on microenvironmental conditions using iButton data loggers. Results A total of 3230 female Aedes mosquitoes were collected, of which 99.8% were Aedes aegypti and 0.2% were Aedes albopictus. Mean female Aedes mosquito density per household was 1.71 (standard deviation: 2.84). We used mixed-effects generalized linear Poisson regression analyses to identify predictors of Aedes density, using month, neighborhood and country as random-effects variables. Across study sites, the number of household occupants [incidence rate ratio (IRR): 1.08, 95% confidence interval (CI): 1.01–1.14], presence of entry points for mosquitoes into the household (IRR: 1.51, 95% CI: 1.30–1.76) and presence of decorative vegetation (IRR: 1.52, 95% CI: 1.22–1.88) were associated with higher Aedes density; while being in the highest wealth tertile of household wealth (IRR: 0.78, 95% CI: 0.66–0.92), knowledge of how arboviruses are transmitted (IRR: 0.94, 95% CI: 0.89–1.00) and regular emptying of water containers by occupants (IRR: 0.79, 95% CI: 0.67–0.92) were associated with lower Aedes density. Conclusions Our study addresses the complexities of arbovirus vectors of global significance at the interface between human and mosquito populations. Our results point to several predictors of Aedes mosquito vector density in countries with co-circulation of multiple Aedes-borne viruses, and point to modifiable risk factors that may be useful for disease prevention and control. Graphical Abstract

The potential impact of Anopheles stephensi establishment on the transmission of Plasmodium falciparum in Ethiopia and prospective control measures

Anopheles stephensi, the primary urban malaria vector in Asia, was first detected in Africa during 2012 in Djibouti and was subsequently identified in Ethiopia in 2016, and later in Sudan and Somalia. In Djibouti, malaria cases have increased 30-fold from 2012 to 2019 though the impact in the wider region remains unclear. A mechanistic model of malaria transmission was used to estimate the increase in vector density required to explain the trends in malaria cases seen in Djibouti. Applying this vector density to Ethiopia, we assess the potential impact of An. stephensi establishment on Plasmodium falciparum transmission, accounting for pre-existing transmission and control interventions. We estimate that annual P. falciparum malaria cases could increase by 50% (95% CI 14-90) if no additional interventions are implemented. Substantial heterogeneity across the country is predicted and large increases in vector control interventions could be needed to prevent a major public health emergency.

Situating the Vector Density Approach Among Contemporary Continuum Theories of Dislocation Dynamics

For the past century, dislocations have been understood to be the carriers of plastic deformation in crystalline solids. However, their collective behavior is still poorly understood. Progress in understanding the collective behavior of dislocations has primarily come in one of two modes: the simulation of systems of interacting discrete dislocations and the treatment of density measures of varying complexity which are considered as continuum fields. A summary of contemporary models of continuum dislocation dynamics is presented. This includes, in order of complexity, the two-dimensional statistical theory of dislocations, the field dislocation mechanics treating the total Kroner-Nye tensor, vector density approaches which treat geometrically necessary dislocations on each slip system of a crystal, and high-order theories which examine the effect of dislocation curvature and distribution over orientation. Each of theories contain common themes, including statistical closure of the kinetic dislocation transport equations and treatment of dislocation reactions such as junction formation. An emphasis is placed on how these common themes rely on closure relations obtained by analysis of discrete dislocation dynamics experiments. The outlook of these various continuum theories of dislocation motion is then discussed.

ENTOMOLOGICAL INDEX AND INSECTICIDE SUSCEPTIBILITY STATUS IN DENGUE-ENDEMIC AREAS YOGYAKARTA

Backgrounds: Dengue Hemorrhagic Fever (DHF) is a disease that receives special attention because of causing outbreaks in some countries, including Indonesia. The problems that often emerge on the DHF Control Program are the high vector density (Aedes aegypti) and the vector resistance resulting from continuous insecticide use. This study describes the entomological index and susceptibility status of Aedes aegypti against malathion and permethrin insecticides in Sorosutan, Umbulharjo, Yogyakarta.Methods: This study used a descriptive observational method with a cross-sectional design. An entomological survey is done at 354 houses in Sorosutan, which is randomly selected. The sample of Aedes aegypti was obtained through the larval collection and ovitrap installation in 100 places. Susceptibility tests performed using the bioassay method with impregnated paper were based on the WHO standard. This study was conducted from December 2018 – February 2019. The data were analyzed using univariate analysisResults: The entomological survey in Sorosutan showed the House Index value was 35.03%; Container Index was 16.68%; Breteau Index was 46.33; Density Figure was 5.00, and Larva Free Rate was 64.97%; meaning that Sorosutan had a high level of vector density. So, the risk of DHF transmission was high. The population of Aedes aegypti in Sorosutan has been tolerant against Malathion, with 87.83% mosquito mortality.Conclusion: Sorosutan was an area with high DHF transmission risk. Aedes aegypti population in Sorosutan has been tolerant against Malathion.

Are Dawn Collections of Anopheles stephensi a Better Method To Estimate the Resting Vector Density? A Study from Chennai, India

The study was an attempt to capture Anopheles stephensi from cattle sheds during dawn to understand the realistic density of the resting mosquitoes. A 2-year longitudinal study was carried out in cattle sheds in close proximity to the human dwellings to collect the resting vector mosquitoes. The man-hour density of A. stephensi ranged from 24.7 to 206.5. The vector incrimination results indicated 0.15% of A. stephensi infected with Pv210 in 2015 and 0.09% in 2016. The current study has revealed that cattle sheds are the preferred resting place of A. stephensi and that dawn is the perfect time to collect and estimate its densities. Hence, adult vector control may also be given due importance in addition to the routine larval source management measures to curb malaria transmission in an urban setting.

Deforestation effects on Attalea palms and their resident Rhodnius, vectors of Chagas disease, in eastern Amazonia

Attalea palms provide primary habitat to Rhodnius spp., vectors of Trypanosoma cruzi. Flying from palms, these blood-sucking bugs often invade houses and can infect people directly or via food contamination. Chagas disease (CD) risk may therefore increase when Attalea palms thrive near houses. For example, Attalea dominate many deforested landscapes of eastern Amazonia, where acute-CD outbreaks are disturbingly frequent. Despite this possible link between deforestation and CD risk, the population-level responses of Amazonian Attalea and their resident Rhodnius to anthropogenic landscape disturbance remain largely uncharted. We studied adult Attalea palms in old-growth forest (OGF), young secondary forest (YSF), and cattle pasture (CP) in two localities of eastern Amazonia. We recorded 1856 Attalea along 10 transects (153.6 ha), and detected infestation by Rhodnius spp. in 18 of 280 systematically-sampled palms (33 bugs caught). Distance-sampling models suggest that, relative to OGF, adult Attalea density declined by 70–80% in CP and then recovered in YSF. Site-occupancy models estimate a strong positive effect of deforestation on palm-infestation odds (βCP-infestation = 4.82±1.14 SE), with a moderate decline in recovering YSF (βYSF-infestation = 2.66±1.10 SE). Similarly, N-mixture models suggest that, relative to OGF, mean vector density sharply increased in CP palms (βCP-density = 3.20±0.62 SE) and then tapered in YSF (βYSF-density = 1.61±0.76 SE). Together, these results indicate that disturbed landscapes may support between ~2.5 (YSF) and ~5.1 (CP) times more Attalea-dwelling Rhodnius spp. per unit area than OGF. We provide evidence that deforestation may favor palm-dwelling CD vectors in eastern Amazonia. Importantly, our landscape-disturbance effect estimates explicitly take account of (i) imperfect palm and bug detection and (ii) the uncertainties about infestation and vector density arising from sparse bug data. These results suggest that incorporating landscape-disturbance metrics into the spatial stratification of transmission risk could help enhance CD surveillance and prevention in Amazonia.