scholarly journals 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

2021 ◽  
Vol 14 (1) ◽  
Author(s):  
Benoit Talbot ◽  
Beate Sander ◽  
Varsovia Cevallos ◽  
Camila González ◽  
Denisse Benítez ◽  
...  
Keyword(s):  
Zika Virus ◽  
Ecological Factors ◽  
Household Wealth ◽  
Mitigation Strategies ◽  
Transmission Risk ◽  
Mosquito Vector ◽  
Mosquito Density ◽  
Vector Density ◽  
Entry Points ◽  
Study Sites

Abstract 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

scholarly journals Determinants of arbovirus vector density as a measure of transmission risk in regions of recent Zika virus introduction in the Americas

2021 ◽  
Author(s):  
Benoit Talbot ◽  
Beate Sander ◽  
Varsovia Cevallos ◽  
Camila González ◽  
Denisse Benítez ◽  
...  
Keyword(s):  
Zika Virus ◽  
Random Effect ◽  
Ecological Factors ◽  
Household Wealth ◽  
Mitigation Strategies ◽  
Transmission Risk ◽  
Mosquito Vector ◽  
Mosquito Abundance ◽  
Vector Density ◽  
Entry Points

Abstract Background The global impact of Zika virus in Latin America and the Caribbean 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 arboviral transmission risk in three cities of potential recent Zika virus introduction: Ibagué, Colombia; Manta, Ecuador; and Posadas, Argentina, in order to inform disease mitigation strategies. Methods We monitored Aedes mosquito populations over 12 months starting in 2018 in a total of 1,086 randomly selected households, using indoor and peridomestic mosquito collection methods. 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 3,230 female Aedes mosquitoes were collected, of which 99.8% were Ae. aegypti and 0.2% were Ae. albopictus. Mean female Aedes spp. mosquito abundance per household was 1.71. We modeled the interaction between neighborhood and household wealth profiles, and found significantly lower Aedes density in highest compared to lowest and middle wealth households, although the effect differed by level of neighborhood wealth. We used mixed-effects Poisson regression analyses to identify predictors of Aedes density, using month, neighborhood, and country as random-effect variables. Across study sites, the number of household occupants (Incidence rate ratio, IRR = 1.08), presence of entry points for mosquitoes into the household (IRR = 1.51), and presence of decorative vegetation (IRR = 1.52) were associated with higher Aedes density; while being in the highest wealth tertile of household wealth (IRR = 0.78), knowledge of how arboviruses are transmitted (IRR = 0.94) and regular emptying of water containers by occupants (IRR = 0.79) were associated with lower Aedes density. Conclusions Our study addresses the complexities of arbovirus vectors of global significance at the interface between society and the environment. Our results point to several determinants of Aedes mosquito vector density in countries with co-circulation of multiple Aedes-borne viruses, and could help us identify targets of practical intervention for disease prevention and control.

scholarly journals Global risk model for vector-borne transmission of Zika virus reveals the role of El Niño 2015

2016 ◽  
Vol 114 (1) ◽  
pp. 119-124 ◽  
Author(s):  
Cyril Caminade ◽  
Joanne Turner ◽  
Soeren Metelmann ◽  
Jenny C. Hesson ◽  
Marcus S. C. Blagrove ◽  
...  
Keyword(s):  
South America ◽  
El Niño ◽  
Zika Virus ◽  
El Nino ◽  
Southern China ◽  
Significant Risk ◽  
The United States ◽  
Transmission Risk ◽  
Boreal Summer ◽  
Mosquito Vector

Zika, a mosquito-borne viral disease that emerged in South America in 2015, was declared a Public Health Emergency of International Concern by the WHO in February of 2016. We developed a climate-driven R0 mathematical model for the transmission risk of Zika virus (ZIKV) that explicitly includes two key mosquito vector species: Aedes aegypti and Aedes albopictus. The model was parameterized and calibrated using the most up to date information from the available literature. It was then driven by observed gridded temperature and rainfall datasets for the period 1950–2015. We find that the transmission risk in South America in 2015 was the highest since 1950. This maximum is related to favoring temperature conditions that caused the simulated biting rates to be largest and mosquito mortality rates and extrinsic incubation periods to be smallest in 2015. This event followed the suspected introduction of ZIKV in Brazil in 2013. The ZIKV outbreak in Latin America has very likely been fueled by the 2015–2016 El Niño climate phenomenon affecting the region. The highest transmission risk globally is in South America and tropical countries where Ae. aegypti is abundant. Transmission risk is strongly seasonal in temperate regions where Ae. albopictus is present, with significant risk of ZIKV transmission in the southeastern states of the United States, in southern China, and to a lesser extent, over southern Europe during the boreal summer season.

scholarly journals An Investigation of Human–Mosquito Contact Using Surveys and Its Application in Assessing Dengue Viral Transmission Risk

2020 ◽  
Vol 57 (6) ◽  
pp. 1942-1954
Author(s):  
Panpim Thongsripong ◽  
Zhuolin Qu ◽  
Joshua O Yukich ◽  
James M Hyman ◽  
Dawn M Wesson
Keyword(s):  
Virus Transmission ◽  
Viral Transmission ◽  
Transmission Risk ◽  
Transmission Model ◽  
Field Methods ◽  
Vector Density ◽  
Mosquito Bite ◽  
Transmission Parameters ◽  
Human Landing ◽  
Study Sites

Abstract Aedes-borne viral diseases such as dengue fever are surging in incidence in recent years. To investigate viral transmission risks, the availability of local transmission parameters is essential. One of the most important factors directly determining infection risk is human–mosquito contact. Yet the contact rate is not often characterized, compared with other risk metrics such as vector density, because of the limited research tool options. In this study, human–mosquito contact was assessed in two study sites in the Southern United States using self-administered standardized survey instruments. The fraction of mosquito bites attributed to important vector species was estimated by human landing sampling. The survey participants reported a significantly higher outdoor mosquito bite exposure than indoor. The reported bite number was positively correlated with outdoor time during at-risk periods. There was also a significant effect of the study site on outdoor bite exposure, possibly due to the differing vector density. Thus, the levels of human–mosquito contact in this study were influenced both by the mosquito density and human behaviors. A dengue virus transmission model demonstrated that the observed difference in the contact rates results in differential virus transmission risks. Our findings highlight the practicality of using surveys to investigate human–mosquito contact in a setting where bite exposure levels differ substantially, and serve as a basis for further evaluations. This study underscores a new avenue that can be used in combination with other field methods to understand how changes in human behavior may influence mosquito bite exposure which drives mosquito-borne virus transmission.

Investigating Male Aedes aegypti (Diptera: Culicidae) Attraction to Different Oviposition Containers Using Various Configurations of the Sound Gravid Aedes Trap

2019 ◽  
Vol 57 (3) ◽  
pp. 957-961
Author(s):  
Kyran M Staunton ◽  
Barukh B Rohde ◽  
Michael Townsend ◽  
Jianyi Liu ◽  
Mark Desnoyer ◽  
...  
Keyword(s):  
Aedes Aegypti ◽  
Zika Virus ◽  
Disease Transmission ◽  
Urban Landscape ◽  
Mosquito Control ◽  
Transmission Risk ◽  
Northern Australia ◽  
Control Programs ◽  
Male Dispersal ◽  
Olfactory Attractant

Abstract Aedes aegypti (Linnaeus), the primary vectors of the arboviruses dengue virus and Zika virus, continue to expand their global distributions. In efforts to better control such species, several mosquito control programs are investigating the efficacy of rearing and releasing millions of altered male Aedes throughout landscapes to reduce populations and disease transmission risk. Unfortunately, little is known about Ae. aegypti, especially male, dispersal behaviors within urban habitats. We deployed Sound-producing Gravid Aedes Traps (SGATs) in Cairns, northern Australia, to investigate male Ae. aegypti attraction to various oviposition container configurations. The traps were arranged to include: 1) water only, 2) organically infused water, 3) infused water and L3 larvae, 4) infused water and a human-scented lure, and lastly 5) no water or olfactory attractant (dry). Our data suggest that males were more attracted to SGATs representing active larval sites than potential larval sites, but were equally attracted to dry SGATs relative to those containing water and/or infusion. Additionally, we found that female Ae. aegypti were equally attracted to wet SGATs, with or without infusion, but not dry ones. These results suggest that male Ae. aegypti within northern Australia are more attracted to active larval sites and equally attracted to dry containers as wet or infused ones. Additionally, female Ae. aegypti are unlikely to enter dry containers. Such findings contribute to our understanding of potentially attractive features for local and released Ae. aegypti throughout the northern Australian urban landscape.

The ecology of an Australian reptile icon: how do blue-tongued lizards (Tiliqua scincoides) survive in suburbia?

2001 ◽  
Vol 28 (3) ◽  
pp. 214 ◽  
Author(s):  
Jennifer Koenig ◽  
Richard Shine ◽  
Glenn Shea
Keyword(s):  
Ecological Factors ◽  
Home Ranges ◽  
Minimal Risk ◽  
Body Temperatures ◽  
Avoided Crossing ◽  
In Captivity ◽  
Radio Transmitters ◽  
Core Areas ◽  
Study Sites ◽  
Gravid Females

Although most species of large reptiles in the Sydney region are now restricted to remnant bushland, the blue-tongued lizard (Tiliqua scincoides) remains abundant. How has this large, slow-moving reptile managed to persist in the suburbs? We implanted radio-transmitters into 17 adult blue-tongued lizards and tracked them for six months (October 1998 to March 1999). Radio-tracked animals utilised 5–17 suburban backyards, but each lizard spent most of its time in a few ‘core’ areas near 2–7 shelter sites. Males had larger home ranges than females (mean of 12700 v. 5100 m 2 ) and moved further between shelter sites. Gravid females (mean home range 1000 m 2 ) were more sedentary. Lizards used corridors of dense vegetation to move between retreat sites, and actively avoided crossing roads. In sunny weather, lizards typically basked close to their overnight shelter for 1–4 h each morning until they obtained body temperatures of approximately 32°C. They maintained high body temperatures while moving about in the afternoon. In combination, the following ecological factors may facilitate persistence of blue-tongued lizards at our suburban study sites. (i) The most important subgroup of the population in terms of conservation are gravid females, which are highly sedentary and, thus, less likely to encounter the dangers of suburbia. (ii) The more ‘expendable’ males move about much more, but mostly in times and places that involve minimal risk from humans and their domestic pets. (iii) Lizards show strong site fidelity, spending up to 70% of their time in ‘safe’ locations; importantly, they avoid roads. (iv) Blue-tongued lizards readily utilise ‘artificial’ shelter sites and the commensal prey species (e.g. snails) found in most gardens. (v) These lizards can grow rapidly, mature early, and produce large litters. Because blue-tongued lizards have a long life span (over 30 years in captivity), populations of adults may persist for many years in the absence of recruitment.

Rubber specialization vs crop diversification: the roles of perceived risks

2017 ◽  
Vol 9 (2) ◽  
pp. 188-210 ◽  
Author(s):  
Shi Min ◽  
Jikun Huang ◽  
Hermann Waibel
Keyword(s):  
Land Use ◽  
Land Tenure ◽  
Risk Perceptions ◽  
Household Wealth ◽  
Environmental Conservation ◽  
Crop Diversification ◽  
Cross Sectional Survey ◽  
Content Type ◽  
Entry Points ◽  
The Impact

Purpose The purpose of this paper is to examine the impact of farmers’ risk perceptions regarding rubber farming on their land use choices, including rubber specialization and crop diversification. Design/methodology/approach A cross-sectional survey data of some 600 smallholder rubber farmers in Xishuangbanna in Southwest China is employed. This paper develops a general conceptual framework that incorporates a subjective risk item into a model of farmers’ land use choices, thereby developing four econometric models to estimate the role of risk perceptions, and applies instrumental variables to control for the endogeneity of risk perceptions. Findings The results demonstrate that risk perceptions play an important role in smallholders’ decision-making regarding land use strategies to address potential risks in rubber farming. Smallholders with higher risk perceptions specialize in rubber farming less often and are more likely to diversify their land use, thereby contributing to local environmental conservation in terms of agrobiodiversity. The land use choices of smallholder rubber farmers are also associated with ethnicity, household wealth, off-farm employment, land tenure status, altitude and rubber farming experience. Originality/value This study contributes to a better understanding of the implications of farmers’ risk perceptions and shows entry points for improving the sustainability of rubber-based land use systems.

scholarly journals Sequential Infection of Aedes aegypti Mosquitoes with Chikungunya Virus and Zika Virus Enhances Early Zika Virus Transmission

Insects ◽  
2018 ◽  
Vol 9 (4) ◽  
pp. 177 ◽  
Author(s):  
Tereza Magalhaes ◽  
Alexis Robison ◽  
Michael Young ◽  
William Black ◽  
Brian Foy ◽  
...  
Keyword(s):  
Aedes Aegypti ◽  
Blood Meal ◽  
Zika Virus ◽  
Chikungunya Virus ◽  
Vector Competence ◽  
Virus Transmission ◽  
Mosquito Vector ◽  
Molecular Aspects ◽  
Virus Interactions ◽  
Sequential Infection

In urban settings, chikungunya, Zika, and dengue viruses are transmitted by Aedes aegypti mosquitoes. Since these viruses co-circulate in several regions, coinfection in humans and vectors may occur, and human coinfections have been frequently reported. Yet, little is known about the molecular aspects of virus interactions within hosts and how they contribute to arbovirus transmission dynamics. We have previously shown that Aedes aegypti exposed to chikungunya and Zika viruses in the same blood meal can become coinfected and transmit both viruses simultaneously. However, mosquitoes may also become coinfected by multiple, sequential feeds on single infected hosts. Therefore, we tested whether sequential infection with chikungunya and Zika viruses impacts mosquito vector competence. We exposed Ae. aegypti mosquitoes first to one virus and 7 days later to the other virus and compared infection, dissemination, and transmission rates between sequentially and single infected groups. We found that coinfection rates were high after sequential exposure and that mosquitoes were able to co-transmit both viruses. Surprisingly, chikungunya virus coinfection enhanced Zika virus transmission 7 days after the second blood meal. Our data demonstrate heterologous arbovirus synergism within mosquitoes, by unknown mechanisms, leading to enhancement of transmission under certain conditions.

scholarly journals Clinical, virological and epidemiological characterization of dengue outbreak in Myanmar, 2015

2017 ◽  
Vol 145 (9) ◽  
pp. 1886-1897 ◽  
Author(s):  
A. K. KYAW ◽  
M. M. NGWE TUN ◽  
M. L. MOI ◽  
T. NABESHIMA ◽  
K. T. SOE ◽  
...  
Keyword(s):  
Primary Infection ◽  
Phylogenetic Analyses ◽  
Molecular Techniques ◽  
Severe Dengue ◽  
Envelope Gene ◽  
Mosquito Vector ◽  
Serum Samples ◽  
Denv Serotypes ◽  
Significant Difference ◽  
Study Sites

SUMMARYHospital-based surveillance was conducted at two widely separated regions in Myanmar during the 2015 dengue epidemic. Acute phase serum samples were collected from 332 clinically diagnosed dengue patients during the peak season of dengue cases. Viremia levels were measured by quantitative real-time PCR and plaque assays using FcγRIIA-expressing and non-FcγRIIA-expressing BHK cells to specifically determine the infectious virus particles. By serology and molecular techniques, 280/332 (84·3%) were confirmed as dengue patients. All four serotypes of dengue virus (DENV) were isolated from among 104 laboratory-confirmed patients including two cases infected with two DENV serotypes. High percentage of primary infection was noted among the severe dengue patients. Patients with primary infection or DENV IgM negative demonstrated significantly higher viral loads but there was no significant difference among the severity groups. Viremia levels among dengue patients were notably high for a long period which was assumed to support the spread of the virus by the mosquito vector during epidemic. Phylogenetic analyses of the envelope gene of the epidemic strains revealed close similarity with the strains previously isolated in Myanmar and neighboring countries. DENV-1 dominated the epidemic in 2015 and the serotype (except DENV-3) and genotype distributions were similar in both study sites.

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