Evidence of circulation of Orthobunyaviruses in diverse mosquito species in Kwale County, Kenya

Background Arbovirus surveillance and recurrence of outbreaks in Kenya continues to reveal the re-emergence of viruses of public health importance. This calls for sustained efforts in early detection and characterization of these agents to avert future potential outbreaks. Methods A larval survey was carried out in three different sites in Kwale County, Vanga, Jego and Lunga Lunga. All containers in every accessible household and compound were sampled for immature mosquitoes. In addition, adult mosquitoes were also sampled using CO2-baited CDC light traps and BG-Sentinel traps in the three sites and also in Tsuini. The mosquitoes were knocked down using trimethylamine and stored in a liquid nitrogen shipper for transportation to the laboratory where they were identified to species, pooled and homogenized ready for testing. Results A total of 366 houses and 1730 containers were inspected. The House Index (HI), Container Index (CI) and Breateau Index (BI) for Vanga Island were (3%: 0.66: 3.66) respectively. In Jego, a rural site, the HI, CI and BI were (2.4%: 0.48: 2.4) respectively. In Lunga Lunga, a site in an urban area, the HI, CI and BI were (22.03%: 3.97: 29.7) respectively. The indices suggest that this region is at risk of arbovirus transmission given they were above the WHO threshold (CI > 1, HI > 1% and BI > 5). The most productive containers were the concrete tanks (44.4%), plastic tank (22.2%), claypot (13.3%), plastic drums (8.9%), plastic basins (4%), jerricans (1.2%) and buckets (0.3%). Over 20,200 adult mosquitoes were collected using CDC light traps, and over 9,200 using BG- sentinel traps. These mosquitoes were screened for viruses by inoculating in Vero cells. Eleven Orthobunyavirus isolates were obtained from pools of Ae. pembaensis (4), Ae. tricholabis (1), Cx. quinquefasciatus (3), Culex spp. (1) and Cx. zombaensis (2). Five of the Orthobunyaviruses were sequenced and four of these were determined to be Bunyamwera viruses while one isolate was found to be Nyando virus. One isolate remained unidentified. Conclusions These results indicate circulation of Orthobunyaviruses known to cause diverse grades of febrile illness with rash in humans in this region and highlights the need for continued monitoring and surveillance to avert outbreaks.

AEDES ALBOPICTUS (SKUSE) SURVEILLANCE WITH BIOGENTS (R) MOSQUITITO TRAPS AND LARVAL INDICES- A COMPARATIVE STUDY

Effective surveillance and monitoring of Aedes albopictus is essential for the possible prediction and implementation of the preventive measures. We tested BG sentinel mosquitito traps with BG lure to collect adults as an alternative surveillance tool in relation to larval indices. Study was carried out in Calicut District, Kerala, India. Three villages in the district were selected by random sampling as study area. In each village, 50 houses were selected as study site for trap collection, larval survey and fever surveillance. Study was conducted for six months from July to December, 2017. Number of adults of Ae.albopictus collected in BG sentinel traps was only 84 in 22 collections spanning over six months (mean 3.82, 95% CI-2.57-5.06).Though the larval indices were high; no epidemic was reported from the study area. There was no correlation between adults collected and larval indices. Adult collection showed a positive correlation with most of meteorological parameters. Larval indices showed no correlation with climatic factors.BG mosquitito trap was found to be not successful for adult surveillance in the area. More studies are required using different traps to suggest adult traps as an alternative to currently used larval indices. Larval indices were high but no cases reported. Our study shows that a more reliable monitoring mechanism is required for Ae.albopictus to enable prevention, to introduce abatement and its evaluation.

Status Resistensi Nyamuk Aedes aegypti dari Wilayah Kerja Puskesmas Salido terhadap Malathion 5% dan Alfa-sipermethrin 0,025%

Background: Insecticides resistance status in Aedes aegypti population is one of the factors that influence the successful control efforts of dengue vector. Objectives:To determine the resistance status of Aedes aegypti from Salido Health Center towards malathion 5% and alpha-cypermethrine 0,025%. Methods: This was a descriptive study and collected during December 2019 – June 2020. Those samples were then observed with larval survey and from the ovitrap placed in 100 houses and then maintained in laboratory of parasitology, faculty of medicine Andalas University. To determine the resistance status of Aedes aegyptiusing the bioassay method with the susceptibility test by referring to the guidance of the Ministry of Health based on the 2016 WHO standard using impregnated paper malathion 5% and alpha-sipermethrin 0.025%. Observations were made by recording the number of mosquito deaths in the 15, 30, 45, 60 and 1440 minutes. The percentage of mosquito deaths is calculated after 24 hours of maintenance it is categorized as resistant if the mortality rate is less than 90%, supected to be resistant if the mortality is between 90-97%, and categorized as vunerable if the mortality rate is between 98-100%.Result: The mortality rate of Aedes aegypti for 24 hours by malathion 5% was 95%, the LT50 and the LT90 were 624 minutes and 1.247 minutes respectively. The percentage of mosquito deaths by alpha-sipermetrin 0,025% after 24 hours was 96,25% the LT50 and the LT90 were 526 minutes and 1.163 minutes respectively.Conclusion: that the resistance status of Aedes aegypti from Salido Health Center is resistant towards malathion 5% and alpha-cypermethrine 0,025%.

Demystifying Essential Containers and Places for Aedes Mosquito Control in Thailand

Background: The strategy for prevention and control of Aedes-borne diseases relies on timely elimination of key breeding containers. There is thus a crucial need to identify key breeding containers to enhance vector control activities. The visual larval survey of wet containers has then been conducted as a routine mission of the Department of Disease Control (DDC). To facilitate this, DDC has deployed a mobile application, namely TanRabad SURVEY, since May 2016. As per an inspected place, TanRabad SURVEY supports the real-time collection of its larval survey data and processing of its larval indices and key breeding containers. Methods: Larval survey data from 2017 to 2019 were spatially and temporally collected by public health officials via TanRabad SURVEY. Several measurements were computed to identify the overall and regional key breeding containers and places; and the regional transmission potentiality of Aedes-borne diseases. The measurements for identifying essential containers were breeding potentiality, productivity, contribution and preference ratio. As for places, the larval productivity of places based on larval indices was employed. Such place productivity was also implemented for discovering the regional transmission potentiality of Aedes-borne diseases. Results: The overall essential breeding containers were water tank, unused containers, other used containers, old tyres, anti-ant bowls, drip tray of water dispensers, pet bowls and plant leaves. As for regional aspects, different regions had different essential breeding containers wherein their most common containers were unused containers, other used containers, old tyres and drip tray of water dispensers. All regions had similar experiences that villages and temples were the top two riskiest places, followed by schools, factories, hotels and hospitals. Additionally, all regions had high transmission potentiality of Aedes-borne disease as above 30 of all their places were moderate and high risk places. Conclusions: This study identified the overall and regional key breeding containers and places along with the regional transmission potentiality of Aedes-borne diseases. Beside this, the empirical evidence had shown that the breeding productivity of most containers and places in each type was gradually decreased from time to time. This was mainly because TanRabad SURVEY supported real-time risk communication to community participants and effective prevention and control program development.

Habitats Characteristic and the Resistance Status of Aedes sp. Larvae in the Endemic Areas of Dengue Haemorrhagic Fever in Sewon Subdistrict, Bantul Regency, Special Region of Yogyakarta

Dengue Hemorrhagic Fever (DHF) is caused by Dengue Virus and transmitted by female Aedes mosquito which spread almost all over the world. Aedes sp. mosquito lives cosmopolitan and breeds in wet environments. Panggungharjo and Bangunharjo villages were categorized as endemic and non-endemic DHF areas, respectively. The aims of this research were to study the characteristics of Aedes sp. mosquito breeding sites, the identity of presence species found in the sites, and the resistance status of Aedes sp. mosquitoes against organophosphate insecticide. The method was using a larval survey which consists of 200 houses as respondents located in Panggungharjo and Bangunharjo villages. The larval resistance was tested by a biochemical method since resistance could be associated with esterase enzyme activity. The characteristics of mosquito breeding sites that found were open containers, filled with clear and calm water, dark and rough wall surfaces, the bottom surface was not directly in contact with the ground, the water temperature was 27-29 °C, pH 6.5-7, and not directly exposed to sunlight. There was only one species of mosquito was found, Aedes aegypti. The resistance test of Aedes sp. larvae showed that Aedes sp. larvae population from Panggungharjo village were susceptible, and Aedes sp. larvae from Bangunharjo village were in moderate resistant against organophosphate insecticide.

A study to assess the impact of health education on larval indices in the rural areas of Ballari: a southern district of India

Background: Awareness regarding dengue through health education is one of the important components of Integrated vector control which can bring about reduction in mosquito density and thereby reduction in morbidity and mortality. The objectives of this study to assess the impact of health education on larval indices in the study area.Methods: This was a community based interventional study was conducted between August to September 2017 at rural field practice area of Vijayanagar Institute of Medical Sciences, Ballari. Three villages with a population of more than 2000 were selected randomly. A total of 100 households were surveyed for Aedes larvae in all the three villages. Baseline information and larval indices like house index (HI), container index (CI) and Breteau index (BI) were calculated as per the procedure of WHO. Health education regarding potential breeding sites of Aedes mosquito and importance and methods of eliminating them through demonstration at household level and street play at community level was done. Post intervention larval survey was done.Results: There was 31.7% reduction in container index (pre-CI: 14.2% to post-CI: 9.7%) and 40.1% reduction in Breteau index (pre-BI: 76.3 to post-BI: 45.7%) and this reduction in the larval indices was found to be statistically significant.Conclusions: Based on the high larval indices, the study areas were prone for dengue transmission. There was significant reduction in the larval indices after the educational intervention.

Infestation measured by Aedes aegypti larval surveys as an indication of future dengue epidemics: an evaluation for Brazil

Background Aedes aegypti rapid larval surveys are mandatory in Brazil. Here, we retrospectively examined whether the house index estimated by larval surveys served as a useful tool in anticipating epidemics within Brazilian municipalities from 2009–2015. Methods We used correlation indices and classification analysis stratified by year, region, population size and time after the national larval survey. Results We found no association between the house index and the proportion of municipalities experiencing an epidemic. The sensitivity of a high score house index in predicting an epidemic was 7.20% (95% CI 6.22 to 8.33%) for all years combined. The positive predictive value of a high score house index to predict a ‘true epidemic’ was 38.96%, lower than the negative predictive values of a low score house index for predicting ‘no epidemic’ (56.96%). The highest overall sensitivity was observed in the North region (20.15%; 95% CI 17.14 to 23.53%). The sensitivity of a high score house index demonstrated a monotonic decrease with increasing time from larval collection. Conclusions Larval surveys are surveillance tools with the potential to risk-stratify and guide dengue control programs towards judicious resource allocation. However, the national rapid larval survey performed in Brazil, in its present form, consistently underpredicts dengue epidemics.

Prevalence of Stegomyia albopicta in Dakshina Kannada district of Karnataka, India

Dengue is one of the rapidly spreading mosquito-borne diseases transmitted worldwide by the bites of infected Stegomyia aegypti and St. albopicta mosquito. Both species are adapted for human habitation and breeds mainly in temporary water bodies. In the present study, a preliminary larval survey was carriedout in four different localities of Dakshina Kannada District. Of the 1094 suspected water bodies, 496 sites showed the presence of St. albopicta larvae and none of them showed the presence of St. aegypti indicating the dominance of the former species. The occurrence of St. albopicta was significantly higher in natural phytotelmata compared to artificial containers. Among the different breeding sites, receptacles contributed 24.5% of larval positivity. The receptacles also showed a higher breeding preference ratio (1.56) indicating that abandoned waste thrashes when receives water may act as the most preferred breeding sites for dengue vector species.

Abundance and Updated Distribution of Aedes aegypti (Diptera: Culicidae) in Cabo Verde Archipelago: A Neglected Threat to Public Health

Background: Mosquito-borne viruses, such as Zika, dengue, yellow fever, and chikungunya, are important causes of human diseases nearly worldwide. The greatest health risk for arboviral disease outbreaks is the presence of the most competent and highly invasive domestic mosquito, Aedes aegypti. In Cabo Verde, two recent arbovirus outbreaks were reported, a dengue outbreak in 2009, followed by a Zika outbreak in 2015. This study is the first entomological survey for Ae. aegypti that includes all islands of Cabo Verde archipelago, in which we aim to evaluate the actual risk of vector-borne arboviruses as a continuous update of the geographical distribution of this species. Methods: In order to assess its current distribution and abundance, we undertook a mosquito larval survey in the nine inhabited islands of Cabo Verde from November 2018 to May 2019. Entomological larval survey indices were calculated, and the abundance analyzed. We collected and identified 4045 Ae. aegypti mosquitoes from 264 positive breeding sites in 22 municipalities and confirmed the presence of Ae. aegypti in every inhabited island. Results: Water drums were found to be the most prevalent containers (n = 3843; 62.9%), but puddles (n = 27; 0.4%) were the most productive habitats found. The overall average of the House, Container, and Breteau larval indices were 8.4%, 4.4%, and 10.9, respectively. However, 15 out of the 22 municipalities showed that the Breteau Index was above the epidemic risk threshold. Conclusion: These results suggest that if no vector control measures are considered to be in place, the risk of new arboviral outbreaks in Cabo Verde is high. The vector control strategy adopted must include measures of public health directed to domestic water storage and management.

Comparison Between Larval Survey Index and Positive Ovitrap Index in the Evaluation of Populations of Aedes (Stegomyia) aegypti (Linnaeus, 1762) North of Paraná, Brazil

Aedes ( Stegomyia) aegypti (Linnaeus, 1762) is one of the world’s most widely distributed mosquitoes and is the vector of the dengue virus, one of the most important reemerging diseases. Besides dengue, A. aegypti can also transmit urban yellow fever, chikungunya, and Zika virus, making it of great medical importance. Thus, it is of extreme importance to find reliable methods to evaluate the presence of A. aegypti in urban areas. In Brazil, rapid index surveys of Aedes aegypti by means of larval survey (LIRAa) is the official method to estimate the Breteau (BI) and property infestation (PII) indexes, which indicates how many infested containers with larvae of A. aegypti were found by the total number of properties surveyed and the proportion of houses infested, respectively. As the LIRAa requires access to private residences and trained personal to find breeding sites and do not reveal the mosquito’s presence when in low density, it has not demonstrated efficacy in determining the presence of A. aegypti. To evaluate an alternative method, the LIRAa method was compared with an oviposition trap, made with hay infusion and a hardboard pallet, to evaluate the BI and the PII. The 2 methods were carried out simultaneously through 4 surveys, sampling 60 homes per survey. To evaluate the best configuration of ovitraps for surveillance of A. aegypti, the ovitraps were installed in intradomicile and peridomicile areas, with 1 to 5 traps per residence and with 1 to 3 pallets per trap, and these different configurations were compared using the positive ovitrap index (POI) and egg density index (EDI). The ovitraps showed greater sensitivity for detecting the presence of A. aegypti, with a BI of 72.5% and PII of 54.2%, whereas the LIRAa revealed only 2.1% for the BI and 1.3% for the PII. Therefore, the use of sentinel traps can provide information in a more rapid and precise manner. As there were no differences in the ovitraps distributions patterns, the ovitraps can be installed in the peridomicile area, with 2 traps per surveillance point and 1 pallet per trap, making their installation easier and more cost-efficient, facilitating the work of health agents in future surveillances complementing LIRAa’s actions for efficient monitoring.