Entomological survey in two communes with residual malaria transmission in Gia Lai Province in the central highlands of Vietnam

Background In 2018, the National Malaria Control Programme in Vietnam switched from prioritizing malaria control to elimination. However, with the ongoing elimination programme, there are still areas where residual malaria transmission persists, including the central highlands. This entomological survey was conducted to evaluate Anopheles diversity and host-seeking activity of Anopheles vectors in two communes with very low malaria transmission in Gia Lai Province. Methods Anopheles species were collected in Ia DReh commune and Ia KDam commune, Gia Lai Province in the central highlands of Vietnam. Collections were conducted using human-baited double net trap, light trap and manual aspiration collections around cattle sheds, in the dry and rainy season. Mosquito specimens were identified morphologically, and members of species complexes were distinguished molecularly. Mosquito night-feeding patterns were investigated during the dry and rainy seasons. Results Overall, 18,835 specimens including 19 taxa were collected in Ia KDam and Ia DReh communes. These included the primary malaria vectors, Anopheles dirus and Anopheles minimus, and other secondary vector species. Anopheles dirus was observed to be an anthropophilic species, whereas An. minimus and a number of secondary vectors were observed to be zoophilic. Anopheles vagus was the dominant species, followed by Anopheles sinensis and Anopheles peditaeniatus. The majority of specimens were collected in the rainy season due to the relatively large number of An. vagus, while An. peditaeniatus, An. dirus, Anopheles kochi, Anopheles monstrosus and Anopheles tessellatus were collected in greater numbers during the dry season. The peak of host-seeking activity for An. dirus, An. sinensis, and An. vagus was between 18.00 and 19.00 h. Conclusion This study provided information on the diversity, seasonal prevalence and behaviour of Anopheles at the study sites. Identifying the diverse mosquito fauna in the central highlands of Vietnam allows species-specific control measures to be implemented by the National Programme to reduce malaria in areas of very low malaria transmission. The peak Anopheles host-seeking activity observed in this study was between 18.00 and 23.00 h, which highlights the need to better characterize Anopheles behaviour in this region of Vietnam to inform on vector control strategies.

Update on the mosquito fauna (Diptera: Culicidae) distribution in Cabo Verde: occurrence of the species complexes Anopheles gambiae and Culex pipiens (pipiens, quinquefasciatus and their hybrids)

In this study, we aimed to update the mosquito species composition and distribution based on a national entomological survey in all municipalities of Cabo Verde. This includes the sibling species of the Culex pipiens complex, namely Cx. pipiens , Cx. quinquefasciatus and their hybrids, in locations where information is not available. The entomological survey took place from October 2017 to September 2018, in all municipalities of Cabo Verde. Mosquito larvae and pupae were collected in breeding sites and samples were sent to the Laboratory of Medical Entomology of the National Institute of Public Health for the morphological identification of the species. The mosquitoes morphologically identified in Anopheles gambiae and Culex pipiens complexes of species were further molecular analysed to species confirmation. A total of 814 breeding sites were surveyed and 10 mosquito species of five genera were identified. The greatest number of mosquito species was reported in the island of Santiago. The most widespread species in the country were Aedes aegypti and Culex quinquefasciatus. Anopheles arabiensis was the only species identified in the Gambiae complex of species. The results of this study will assist decision makers in important health policies to control mosquitoes and vector-borne diseases towards a strategic approach by timely detection of changes in species diversity.

Entomological Survey Confirms Changes in Mosquito Composition and Abundance in Senegal and Reveals Discrepancies among Results by Different Host-Seeking Female Traps

Mosquitoes-borne diseases are major public health issues particularly in Africa. Vector control interventions and human-made environmental/climatic changes significantly affect the distribution and abundance of vector species. We carried out an entomological survey targeting host-seeking mosquitos in two different ecological contexts—coastal and inland—in Senegal, by CDC-light and BG-sentinel traps. Results show high predominance of Culex quinquefasciatus (90%) and of Anopheles arabiensis within malaria vectors (46%), with mean numbers of females/trap/nights =8 and <1, respectively, reinforcing previous evidence of changes in species composition and abundance, highlighting thus increasing risk of transmission of filariasis and emerging arboviruses in the Senegambia region. From the methodological perspective, results show a higher specificity of BG traps for Cx. quinquefasciatus and of CDC traps for An. gambiae s.l. and highlight that, despite both traps target the host-seeking fraction of the population, they provide different patterns of species abundance, temporal dynamics and host-seeking activity, leading to possible misinterpretation of the species bionomics. This draws attention to the need of taking into account trapping performance, in order to provide realistic quantification of the number of mosquitoes per units of space and time, the crucial parameter for evaluating vector–human contact, and estimating risk of pathogen transmission.

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.

Use of vector control to protect people from sleeping sickness in the focus of Bonon (Côte d’Ivoire)

Background Gambian human African trypanosomiasis (gHAT) is a neglected tropical disease caused by Trypanosoma brucei gambiense transmitted by tsetse flies (Glossina). In Côte d’Ivoire, Bonon is the most important focus of gHAT, with 325 cases diagnosed from 2000 to 2015 and efforts against gHAT have relied largely on mass screening and treatment of human cases. We assessed whether the addition of tsetse control by deploying Tiny Targets offers benefit to sole reliance on the screen-and-treat strategy. Methodology and principal findings In 2015, we performed a census of the human population of the Bonon focus, followed by an exhaustive entomological survey at 278 sites. After a public sensitization campaign, ~2000 Tiny Targets were deployed across an area of 130 km2 in February of 2016, deployment was repeated annually in the same month of 2017 and 2018. The intervention’s impact on tsetse was evaluated using a network of 30 traps which were operated for 48 hours at three-month intervals from March 2016 to December 2018. A second comprehensive entomological survey was performed in December 2018 with traps deployed at 274 of the sites used in 2015. Sub-samples of tsetse were dissected and examined microscopically for presence of trypanosomes. The census recorded 26,697 inhabitants residing in 331 settlements. Prior to the deployment of targets, the mean catch of tsetse from the 30 monitoring traps was 12.75 tsetse/trap (5.047–32.203, 95%CI), i.e. 6.4 tsetse/trap/day. Following the deployment of Tiny Targets, mean catches ranged between 0.06 (0.016–0.260, 95%CI) and 0.55 (0.166–1.794, 95%CI) tsetse/trap, i.e. 0.03–0.28 tsetse/trap/day. During the final extensive survey performed in December 2018, 52 tsetse were caught compared to 1,909 in 2015, with 11.6% (5/43) and 23.1% (101/437) infected with Trypanosoma respectively. Conclusions The annual deployment of Tiny Targets in the gHAT focus of Bonon reduced the density of Glossina palpalis palpalis by >95%. Tiny Targets offer a powerful addition to current strategies towards eliminating gHAT from Côte d’Ivoire.

Entomological survey for identification of Aedes larval breeding sites and their distribution in Chattogram, Bangladesh

Background Studying the characteristics of Aedes mosquito habitats is essential to control the mosquito population. The objective of this study was to identify the breeding sites of Aedes larvae and their distribution in Chattogram, Bangladesh. We conducted an entomological survey in 12 different sub-districts (Thana) under Chattogram City, during the late monsoon (August to November) 2019. The presence of different wet containers along with their characteristics and immature mosquitoes was recorded in field survey data form. Larvae and/or pupae were collected and brought to the laboratory for identification. Results Different indices like house index, container index, and the Breteau index were estimated. The multiple logistic regression analysis was applied to identify habitats that were more likely to be positive for Aedes larvae/pupae. A total of 704 wet containers of 37 different types from 216 properties were examined, where 52 (7.39%) were positive for Aedes larvae or pupae. Tire, plastic buckets, plastic drums, and coconut shells were the most prevalent container types. The plastic group possessed the highest container productivity (50%) whereas the vehicle and machinery group was found as most efficient (1.83) in terms of immature Aedes production. Among the total positive properties, 8% were infested with Aedes aegypti, 2% with Aedes albopictus, and 1% contained both species Ae. aegypti and A. albopictus. The overall house index was 17.35%, the container index was 7%, and the Breteau index was 24.49. Containers in multistoried houses had significantly lower positivity compared to independent houses. Binary logistic regression represented that containers having shade were 6.7 times more likely to be positive than the containers without shade (p< 0.01). Conclusions These findings might assist the authorities to identify the properties, containers, and geographical areas with different degrees of risk for mosquito control interventions to prevent dengue and other Aedes-borne disease transmissions.

Entomological Survey for Identification of Aedes Larval Breeding Sites and Their Distribution in Chattogram, Bangladesh

Background: Studying the characteristics of Aedes mosquito habitats is essential to control the mosquito population. The objective of this study was to identify the breeding sites of Aedes larvae and their distribution in the Chattogram. We conducted an entomological survey in 12 different sub-district (Thana) under Chattogram city, Bangladesh, during the late monsoon (August to November) 2019. The presence of different wet containers along with their characteristics and the existence of immature mosquitoes were recorded in field survey data-form. Larvae and/or pupae were collected and brought to the laboratory for identification. Results: We estimated the overall house index, container index, and the Breteau index and performed multiple logistic regression analyses to identify habitats more likely to be positive for Aedes larvae/pupae. Out of a total of 704 wet containers of 37 different types from 216 properties where 52 (7.39%) containers were positive for Aedes larvae or pupae. Tire, plastic buckets, plastic drums, and coconut shells were the most prevalent container types. The plastic group possessed highest container productivity (n=50) whereas vehicle and machinery group was the highest efficient (1.83). Among the total positive properties, 8% were infested with Aedes aegypti, 2% were Aedes albopictus and 1% contains both species Ae. aegypti and A. albopictus. The overall house index was 17.35%, container index was 7% and the Breteau index was 24.49. Containers in multistoried House had significantly lower positivity in compare to independent house. Binary logistic regression represented that containers having shade were 6.7 times more likely to be positive than the containers without shade (p< 0.01). Conclusions: These findings might assist the authorities to identify the properties, containers, and geographical areas with different degrees of risk for mosquito control interventions to prevent dengue and other Aedes-borne diseases transmissions.

Entomological Survey for Aedes Species at Deendayal Seaport, Kandla, Gujarat India during Pre-Monsoon Period, 2018

Entomological survey was conducted at Kandla international seaport, Kandla, Gujarat, India during pre-monsoon season of 2018 for immature Aedes mosquitoes. Standard entomological techniques were used for survey. All approachable larval breeding habitats were inspected. Inside seaport area, a total of 45 premises were searched for Aedes breeding out of which 02 premises were found inside area of seaport with 4.44 Premises Index (PI), 1.77 Container Index (CI) and 4.44 Breteau Index (BI). Out-side area of seaport (non-residential), none of premises/ containers were found positive for breeding while in out-side residential area 27 were searched out of which 02 houses were found positive for Aedes breeding with 7.4 House Index (HI), 8.10 Container Index (CI) and 11.11 Breteau Index (BI). Intermittent supply of water was the main reason for Aedes breeding in residential colony. From this study it is evident that inside port area and outside port area provided ample habitats for the mosquitoes to breed and thrive in wet season. Regular entomological surveillance is needed not only to monitor the Aedesmosquito breeding in and around port area including residential areas nearby but also to prevent the transportation and establishment of mosquito species in newer areas. Community awareness is also equally important to prevent entry of vector mosquito species in new areas.