bims-mosdis 2023-05-14 papers

Issue of 2023–05–14
eight papers selected by
Richard Halfpenny, Staffordshire University

Parasit Vectors. 2023 May 06. 16(1): 159

Density of Aedes aegypti (Diptera: Culicidae) in a low-income Brazilian urban community where dengue, Zika, and chikungunya viruses co-circulate.

Raquel L Souza, Romero J Nazare, Hernan D Argibay, Maysa Pellizzaro, Rosângela O Anjos, Moyra M Portilho, Leile Camila Jacob-Nascimento, Mitermayer G Reis, Uriel D Kitron, Guilherme S Ribeiro.

BACKGROUND: Low-income urban communities in the tropics often lack sanitary infrastructure and are overcrowded, favoring Aedes aegypti proliferation and arboviral transmission. However, as Ae. aegypti density is not spatially homogeneous, understanding the role of specific environmental characteristics in determining vector distribution is critical for planning control interventions. The objectives of this study were to identify the main habitat types for Ae. Aegypti, assess their spatial densities to identify major hotspots of arbovirus transmission over time and investigate underlying factors in a low-income urban community in Salvador, Brazil. We also tested the field-collected mosquitoes for arboviruses.
METHODS: A series of four entomological and socio-environmental surveys was conducted in a random sample of 149 households and their surroundings between September 2019 and April 2021. The surveys included searching for potential breeding sites (water-containing habitats) and for Ae. aegypti immatures in them, capturing adult mosquitoes and installing ovitraps. The spatial distribution of Ae. aegypti density indices were plotted using kernel density-ratio maps, and the spatial autocorrelation was assessed for each index. Visual differences on the spatial distribution of the Ae. aegypti hotspots were compared over time. The association of entomological findings with socio-ecological characteristics was examined. Pools of female Ae. aegypti were tested for dengue, Zika and chikungunya virus infection.
RESULTS: Overall, 316 potential breeding sites were found within the study households and 186 in the surrounding public spaces. Of these, 18 (5.7%) and 7 (3.7%) harbored a total of 595 and 283 Ae. aegypti immatures, respectively. The most productive breeding sites were water storage containers within the households and puddles and waste materials in public areas. Potential breeding sites without cover, surrounded by vegetation and containing organic matter were significantly associated with the presence of immatures, as were households that had water storage containers. None of the entomological indices, whether based on immatures, eggs or adults, detected a consistent pattern of vector clustering in the same areas over time. All the mosquito pools were negative for the tested arboviruses.
CONCLUSIONS: This low-income community displayed high diversity of Ae. aegypti habitats and a high degree of heterogeneity of vector abundance in both space and time, a scenario that likely reflects other low-income communities. Improving basic sanitation in low-income urban communities through the regular water supply, proper management of solid wastes and drainage may reduce water storage and the formation of puddles, minimizing opportunities for Ae. aegypti proliferation in such settings.

Keywords: Aedes aegypti; Environmental indicators; Environmental monitoring; Mosquito control; Mosquito vectors; Mosquito-borne diseases; Socioeconomic factors; Water supply

DOI: https://doi.org/10.1186/s13071-023-05766-5

J Med Entomol. 2023 May 08. pii: tjad053. [Epub ahead of print]

El Niño Southern Oscillation (ENSO) effects on local weather, arboviral diseases, and dynamics of managed and unmanaged populations of Aedes aegypti (Diptera: Culicidae) in Puerto Rico.

Roberto Barrera, Veronica Acevedo, Manuel Amador, Melissa Marzan, Laura E Adams, Gabriela Paz-Bailey.

We investigated the effects of interannual El Niño Southern Oscillation (ENSO) events on local weather, Aedes aegypti populations, and combined cases of dengue (DENV), chikungunya (CHIKV), and Zika (ZIKV) viruses in 2 communities with mass mosquito trapping and 2 communities without mosquito control in southern Puerto Rico (2013-2019). Gravid adult Ae. aegypti populations were monitored weekly using Autocidal Gravid Ovitraps (AGO traps). Managing Ae. aegypti populations was done using 3 AGO traps per home in most homes. There were drought conditions in 2014-2015 concurrent with the emergence of a strong El Niño (2014-2016), wetter conditions during La Niña (2016-2018), a major hurricane (2017), and a weaker El Niño (2018-2019). The main factor explaining differences in Ae. aegypti abundance across sites was mass trapping. Populations of Ae. aegypti reached maximum seasonal values during the wetter and warmer months of the year when arbovirus epidemics occurred. El Niño was significantly associated with severe droughts that did not impact the populations of Ae. aegypti. Arbovirus cases at the municipality level were positively correlated with lagged values (5-12 mo.) of the Oceanic El Niño Index (ONI), droughts, and abundance of Ae. aegypti. The onset of strong El Niño conditions in Puerto Rico may be useful as an early warning signal for arboviral epidemics in areas where the abundance of Ae. aegypti exceeds the mosquito density threshold value.

Keywords: Aedes aegypti ; ENSO; El Niño; Zika; dengue

DOI: https://doi.org/10.1093/jme/tjad053

J Arthropod Borne Dis. 2022 Dec;16(4): 350-363

Biodiversity and Spatial Distribution of Mosquitoes (Diptera: Culicidae) in Kurdistan Province, Western Iran.

Farid Sharifi, Omid Banafshi, Ali Rasouli, Shadi Ghoreishi, Samrand Saeedi, Mahmood Khalesi, Afshar Rezai, Eslam Moradi Asl, Bushra Zareie, Nasrollah Veisi Khodlan, Arshad Veysi.

Background: Mosquitoes (Diptera: Culicidae) have always been considered as the vector/s of viral and parasitic diseases. This study aimed to conduct a comprehensive survey on the species composition, spatial distribution, and biodiversity indices of mosquitoes in Kurdistan Province, western Iran.
Methods: This study was carried out in 10 counties of Kurdistan Province. The immature stages of mosquitoes were collected monthly from June to September. ArcGIS software was used to spatial analysis and create maps. Alpha diversity indices were calculated using the related formula.
Results: Totally, 5831 larvae belonging to the family Culicidae were collected. Twelve species were identified including: Anopheles claviger, An. maculipennis s.l, An. superpictus s.l, Culiseta. longiareolata, Cs. subochrea, Culex hortensis, Cx. mimeticus, Cx. perexiguus, Cx. pipiens, Cx. theileri, Cx. modestus and Cx. territans. Based on this analysis, the high-risk areas of the province are determined as Anopheles in the west, Culex in the north, and the Culiseta in the south of the province. Analyzing the Alpha biodiversity indices showed Baneh and Sarabad had the maximum and Bijar had the minimum mosquito biodiversity.
Conclusion: The western counties of the province are regarded as the hotspots for anopheline mosquitos. Moreover, reporting of malaria cases in the past, bordering with Iraq and the high traffic of travelers have made these areas as potential foci for malaria transmission. So that, routine entomological inspections are proposed to detect any suspicious vector or case entrance.

Keywords: Diptera; Diversity; GIS; Larvae; Mosquitoes

DOI: https://doi.org/10.18502/jad.v16i4.12194

BMC Zool. 2022 Apr 29. 7(1): 21

Confirmed presence of aedes (rusticoidus) refiki Medschid, 1928 in a continental dry Mediterranean peri-urban environment in south-central Spain.

Laia Casades-Martí, Mario Frías, Sarah Delacour, Francisco Ruiz-Fons.

BACKGROUND: The 'snow-melt mosquito' aedes (rusticoidus) refiki is a rare species with a wide distribution in Europe that is usually defined as an aggressive mosquito for mammals, including humans. During a mosquito survey in a peri-urban area in south-central mainland Spain, adult Ae. refiki females were captured and identified by morphological traits. The presence of this species of mosquito has never been molecularly confirmed under continental dry Mediterranean climatic influence with scarce number of days with snow on soil. The aim of this study was to confirm by amplification and sequencing of mitochondrial cytochrome c oxidase subunit I (COI) and internal transcribed spacer 2 (ITS2) region.
RESULTS: We also successfully amplified and typed the species molecularly by COI and ITS2 regions. The peri-urban area where Ae. refiki was found contrasts with the reported cold, humid and snowy environments required by the species to breed.
CONCLUSIONS: This finding suggests that the species is already adapted to continental dry Mediterranean environments, questioning whether it is a truly stenotopic species of cold snowy environments.

Keywords: Aedes; Barcoding; Mediterranean; Peri-urban; Scarce

DOI: https://doi.org/10.1186/s40850-022-00124-x

IJID Reg. 2023 Jun;7 230-232

First introduction of dengue virus type 3 in Niger, 2022.

Adamou Lagare, Martin Faye, Gbaguidi Fintan, Gamou Fall, Hadiza Ousmane, Elh Tassiou Ibrahim, Moussa Moise Diagne, Soumana Amadou, Safietou Sankhe, Laminou Ibrahim, Haoua Seini, Ousmane Faye, Ronan Jambou.

Dengue fever is the most important mosquito-borne viral disease of humans, with a significant disease burden in tropical and subtropical countries. The disease is caused by four distinct dengue virus (DENV) serotypes, DENV-1 to -4, all of which belong to the family Flaviviridae, genus Flavivirus. Approximately 3.6 billion people live in areas where they are at risk of transmission of DENVs, resulting in up to 390 million infections and 96 million symptomatic cases annually. Although the disease is highly endemic in the West Africa region, little is known about the prevalence and distribution of DENVs in Niger. We hereby report the first laboratory-confirmed case of dengue in Niger.

Keywords: Niger; dengue virus

DOI: https://doi.org/10.1016/j.ijregi.2023.04.001

Malar J. 2023 May 06. 22(1): 149

Spatio-temporal analysis of malaria incidence and its risk factors in North Namibia.

Remember Ndahalashili Katale, Dibaba Bayisa Gemechu.

BACKGROUND: Millions of dollars have been spent in fighting malaria in Namibia. However, malaria remains a major public health concern in Namibia, mostly in Kavango West and East, Ohangwena and Zambezi region. The primary goal of this study was to fit a spatio-temporal model that profiles spatial variation in malaria risk areas and investigate possible associations between disease risk and environmental factors at the constituency level in highly risk northern regions of Namibia.
METHODS: Malaria data, climatic data, and population data were merged and Global spatial autocorrelation statistics (Moran's I) was used to detect the spatial autocorrelation of malaria cases while malaria occurrence clusters were identified using local Moran statistics. A hierarchical Bayesian CAR model (Besag, York and Mollie's model "BYM") known to be the best model for modelling the spatial and temporal effects was then fitted to examine climatic factors that might explain spatial/temporal variation of malaria infection in Namibia.
RESULTS: Average rainfall received on an annual basis and maximum temperature were found to have a significant spatial and temporal variation on malaria infection. Every mm increase in annual rainfall in a specific constituency in each year increases annual mean malaria cases by 0.6%, same to average maximum temperature. The posterior means of the time main effect (year t) showed a visible slightly increase in global trend from 2018 to 2020.
CONCLUSION: The study discovered that the spatial temporal model with both random and fixed effects best fit the model, which demonstrated a strong spatial and temporal heterogeneity distribution of malaria cases (spatial pattern) with high risk in most of the Kavango West and East outskirt constituencies, posterior relative risk (RR: 1.57 to 1.78).

Keywords: Heterogeneity; Hierarchical Bayesian CAR model; Malaria incidence; Posterior mean; Spatiotemporal

DOI: https://doi.org/10.1186/s12936-023-04577-4

Lancet Microbe. 2023 May;pii: S2666-5247(23)00120-9. [Epub ahead of print]4(5): e284

Chikungunya in Brazil … and beyond?

The Lancet Microbe.

DOI: https://doi.org/10.1016/S2666-5247(23)00120-9

GeoJournal. 2023 ;88(2): 1769-1783

Spatial modelling of malaria prevalence associated with geographical factors in Houet province of Burkina Faso, West Africa.

Abdoul Azize Millogo, Lassane Yaméogo, Daouda Kassié, François de Charles Ouédraogo, Charles Guissou, Abdoulaye Diabaté.

Malaria is a permanent threat to health in western Burkina Faso. Research has shown that geographical variables contribute to the spatial distribution in its transmission. The objective of this study is to assess the relationship between malaria prevalence and potential explanatory geographical variables in the Houet province in Burkina Faso. Statistics on malaria prevalence registered by health centres in the Houet province in 2017 and potential geographical variables identified through a literature review were collected. An Ordinary Least Squares (OLS) regression was used to identify key geographical variables and to measure their association with malaria while the Getis Ord Gi* index was used to locate malaria hotspots. The results showed that average annual temperature, vegetation density, percentage of clay in the soil, total annual rainfall and distance to the nearest waterbody are the main variables associated with malaria prevalence. These variables account for two-thirds of the spatial variability of malaria prevalence observed in Houet province. The intensity and direction of the relationship between malaria prevalence and geographical factors vary according to the variable. Hence, only vegetation density is positively correlated with malaria prevalence. Average temperature, for soil clay content, annual rainfall and for distance to the nearest water body are negatively correlated with the disease prevalence. These results show that even in an endemic area, malaria prevalence has significant spatial variation. The results could contribute to the choice of intervention sites, as this choice is crucial for reducing the malaria burden.
Supplementary Information: The online version contains supplementary material available at 10.1007/s10708-022-10692-7.

Keywords: Burkina Faso; Distance to water; Malaria; Ordinary least squares (OLS); Rainfall; Soil permeability; Temperature; Vegetation

DOI: https://doi.org/10.1007/s10708-022-10692-7