The relationship between house height and mosquito house entry: an experimental study in rural Gambia.
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ABSTRACT:
SUBMITTER: Carrasco-Tenezaca M
PROVIDER: S-EPMC8150013 | biostudies-literature | 2021 May
REPOSITORIES: biostudies-literature
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The relationship between house height and mosquito house entry: an experimental study in rural Gambia.
Carrasco-Tenezaca Majo M Jawara Musa M Abdi Mahamed Y MY Bradley John J Brittain Otis Sloan OS Ceesay Sainey S D'Alessandro Umberto U Jeffries David D Pinder Margaret M Wood Hannah H Knudsen Jakob B JB Lindsay Steve W SW
Journal of the Royal Society, Interface 20210526 178
Most malaria infections in sub-Saharan Africa are acquired indoors, thus finding effective ways of preventing mosquito house entry should reduce transmission. Since most malaria mosquitoes fly less than 1 m from the ground, we tested whether raising buildings off the ground would prevent the entry of <i>Anopheles gambiae</i>, the principal African malaria vector, in rural Gambia. Nightly collections of mosquitoes were made using light traps from four inhabited experimental huts, each of which co ...[more]
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Project description:BackgroundAnopheles gambiae, the major malaria mosquito in sub-Saharan Africa, feed largely indoors at night. Raising a house off the ground with no barriers underneath reduces mosquito-house entry. This experiment tested whether walling off the space under an elevated hut affects mosquito-hut entry.MethodsFour inhabited experimental huts, each of which could be moved up and down, were used in rural Gambia. Nightly collections of mosquitoes were made using light traps and temperature and carbon dioxide levels monitored indoors and outdoors using loggers. Each night, a reference hut was kept at ground level and three huts raised 2 m above the ground; with the space under the hut left open, walled with air-permeable walls or solid walls. Treatments were rotated every four nights using a randomized block design. The experiment was conducted for 32 nights. Primary measurements were mosquito numbers and indoor temperature in each hut.ResultsA total of 1,259 female Anopheles gambiae sensu lato were collected in the hut at ground level, 655 in the hut with an open ground floor, 981 in the hut with air-permeable walls underneath and 873 in the hut with solid walls underneath. Multivariate analysis, adjusting for confounders, showed that a raised hut open underneath had 53% fewer mosquitoes (95% CI 47-58%), those with air-permeable walls underneath 24% fewer (95% CI 9-36%) and huts with solid walls underneath 31% fewer (95% CI 24-37%) compared with a hut on the ground. Similar results were found for Mansonia spp. and total number of female mosquitoes, but not for Culex mosquitoes where hut entry was unaffected by height or barriers. Indoor temperature and carbon dioxide levels were similar in all huts.ConclusionRaising a house 2 m from the ground reduces the entry of An. gambiae and Mansonia mosquitoes, but not Culex species. The protective effect of height is reduced if the space underneath the hut is walled off.
| S-EPMC11003187 | biostudies-literature
Project description:UnlabelledBackgroundScreening doors, windows and eaves of houses should reduce house entry by eusynanthropic insects, including the common African house mosquito Culex pipiens quinquefasciatus and other culicines. In the pre-intervention year of a randomized controlled trial investigating the protective effects of house screening against mosquito house entry, a multi-factorial risk factor analysis study was used to identify factors influencing house entry by culicines of nuisance biting and medical importance. These factors were house location, architecture, human occupancy and their mosquito control activities, and the number and type of domestic animals within the compound.Results40,407 culicines were caught; the dominant species were Culex thalassius, Cx. pipiens s.l., Mansonia africanus, M. uniformis and Aedes aegypti. There were four times more Cx. pipiens s.l. in Farafenni town (geometric mean/trap/night = 8.1, 95% confidence intervals, CIs = 7.2-9.1) than in surrounding villages (2.1, 1.9-2.3), but over five times more other culicines in the villages (25.1, 22.1-28.7) than in town (4.6, 4.2-5.2). The presence of Cx. pipiens s.l. was reduced in both settings if the house had closed eaves (odds ratios, OR town = 0.62, 95% CIs = 0.49-0.77; OR village = 0.49, 0.33-0.73), but increased per additional person in the trapping room (OR town = 1.16, 1.09-1.24; OR village = 1.10, 1.02-1.18). In the town only, Cx. pipiens s.l. numbers were reduced if houses had a thatched roof (OR = 0.70, 0.51-0.96), for each additional cow tethered near the house (OR = 0.73, 0.65-0.82) and with increasing distance from a pit latrine (OR = 0.97, 0.95-0.99). In the villages a reduction in Cx. pipiens s.l. numbers correlated with increased horses in the compound (OR = 0.90, 0.82-0.99). The presence of all other culicines was reduced in houses with closed eaves (both locations), with horses tethered outside (village only) and with increasing room height (town only), but increased with additional people in the trapping room and where cows were tethered outside (both locations).ConclusionThe findings of this study advocate eave closure and pit latrine treatment in all locations, and zooprophylaxis using horses in rural areas, as simple control measures that could reduce the number of culicines found indoors.
| S-EPMC2584634 | biostudies-literature
Project description:Sustained malaria control is underway using a combination of vector control, prompt diagnosis and treatment of malaria cases. Progress is excellent, but for long-term control, low-cost, sustainable tools that supplement existing control programs are needed. Conventional vector control tools such as indoor residual spraying and house screening are highly effective, but difficult to deliver in rural areas. Therefore, an additional means of reducing mosquito house entry was evaluated: the screening of mosquito house entry points by planting the tall and densely foliated repellent plant Lantana camara L. around houses. A pilot efficacy study was performed in Kagera Region, Tanzania in an area of high seasonal malaria transmission, where consenting families within the study village planted L. camara (Lantana) around their homes and were responsible for maintaining the plants. Questionnaire data on house design, socioeconomic status, malaria prevention knowledge, attitude and practices was collected from 231 houses with Lantana planted around them 90 houses without repellent plants. Mosquitoes were collected using CDC Light Traps between September 2008 and July 2009. Data were analysed with generalised negative binomial regression, controlling for the effect of sampling period. Indoor catches of mosquitoes in houses with Lantana were compared using the Incidence Rate Ratio (IRR) relative to houses without plants in an adjusted analysis. There were 56% fewer Anopheles gambiae s.s. (IRR 0.44, 95% CI 0.28-0.68, p<0.0001); 83% fewer Anopheles funestus s.s. (IRR 0.17, 95% CI 0.09-0.32, p<0.0001), and 50% fewer mosquitoes of any kind (IRR 0.50, 95% CI 0.38-0.67, p<0.0001) in houses with Lantana relative to controls. House screening using Lantana reduced indoor densities of malaria vectors and nuisance mosquitoes with broad community acceptance. Providing sufficient plants for one home costs US $1.50 including maintenance and labour costs, (30 cents per person). L. camara mode of action and suitability for mosquito control is discussed.
| S-EPMC3192125 | biostudies-literature
Project description:Recent human history is marked by demographic transitions characterized by declines in mortality and fertility. By influencing the variance in those fitness components, demographic transitions can affect selection on other traits. Parallel to changes in selection triggered by demography per se, relationships between fitness and anthropometric traits are also expected to change due to modification of the environment. Here we explore for the first time these two main evolutionary consequences of demographic transitions using a unique data set containing survival, fertility, and anthropometric data for thousands of women in rural Gambia from 1956-2010. We show how the demographic transition influenced directional selection on height and body mass index (BMI). We observed a change in selection for both traits mediated by variation in fertility: selection initially favored short females with high BMI values but shifted across the demographic transition to favor tall females with low BMI values. We demonstrate that these differences resulted both from changes in fitness variance that shape the strength of selection and from shifts in selective pressures triggered by environmental changes. These results suggest that demographic and environmental trends encountered by current human populations worldwide are likely to modify, but not stop, natural selection in humans.
| S-EPMC3668323 | biostudies-literature
Project description:BackgroundRural communities in low- and middle-income countries, such as The Gambia, often experience water insecurity periodically due to climate drivers such as heavy rainfall and reduced rainfall, as well as non-climate drivers such as infrastructural issues and seasonal workloads. When facing these challenges households use a variety of coping mechanisms that could pose a risk to health. We aimed to understand the drivers of water insecurity (climate and non-climate), the behavioural responses to water insecurity and the risks these responses pose to the health of communities in rural Gambia and map these findings onto a conceptual framework.MethodsWe interviewed 46 participants using multiple qualitative methods. This included in-depth interviews and transect walks. A subset of 27 participants took part in three participatory pile-sorting activities. In these activities participants were asked to rank water-related activities, intrahousehold prioritisation of water, and the coping strategies utilised when facing water insecurity.ResultsMultiple strategies were identified that people used to cope with water shortages, including: reductions in hygiene, changes to food consumption, and storing water for long periods. Many of these could inadvertently introduce risks for health. For example, limiting handwashing increases the risk of water-washed diseases. Deprioritising cooking foods such as millet, which is a nutrient-dense staple food, due to the high water requirements during preparation, could impact nutritional status. Additionally, storing water for long periods could erode water quality. Social factors appeared to play an important role in the prioritisation of domestic water-use when faced with water shortages. For example, face-washing was often maintained for social reasons. Health and religion were also key influencing factors. People often tried to protect children from the effects of water insecurity, particularly school-aged children, but given the communal nature of many activities this was not always possible. Many people associated water insecurity with poor health.ConclusionsTo reduce the risks to health, interventions need to address the drivers of water insecurity to reduce the need for these risky coping behaviours. In the short term, the promotion of behavioural adaptations that can help buffer health risks, such as water treatment, may be beneficial.
| S-EPMC11562698 | biostudies-literature
Project description:We aimed to estimate the relationship between height (a measure of early-life cumulative net nutrition) and later-life cognitive function among older rural South African adults, and whether education modified this relationship. Data were from baseline in-person interviews with 5059 adults ≥ 40 years in the population-based "Health and Aging in Africa: A Longitudinal Study of an INDEPTH Community in South Africa" (HAALSI) study in Agincourt sub-district, South Africa, in 2015. Linear regression was used to estimate the relationship between height quintile and latent cognitive function z-score (representing episodic memory, time orientation, and numeracy), with adjustment for life course covariates and a height-by-education interaction. Mean (SD) height was 162.7 (8.9) cm. Nearly half the sample had no formal education (46%; 2307/5059). Mean age- and sex-adjusted cognitive z-scores increased from - 0.68 (95% CI: - 0.76 to - 0.61) in those with no education in the shortest height quintile to 0.62 (95% CI: 0.52-0.71) in those with at least 8 years of education in the tallest height quintile. There was a linear height disparity in cognitive z-scores for those with no formal education (adjusted β = 0.10; 95% CI: 0.08-0.13 per height quintile), but no height disparity in cognitive z-scores in those with any level of education. Short stature is associated with poor cognitive function and may be a risk factor for cognitive impairment among older adults living in rural South Africa. The height disparity in cognitive function was negated for older adults who had any level of education.
| S-EPMC6370512 | biostudies-literature
Project description:The relationship between anosmia and anthropometric factor has not been investigated sufficiently yet. Thus, the purpose of this study was to evaluate anthropometric risk factors of anosmia in an Asian population. Claims data of subjects over 20 years old who underwent a national health examination conducted by the Korean National Insurance Program between 2005 and 2008 were analyzed. They were followed up through the Korean National Insurance Service database. Individuals newly diagnosed with anosmia were identified after the initial health examination until the last follow-up date (December 31, 2016). The incidence of anosmia was high in females younger than 70 years old. The hazard ratio of anosmia was found to be higher in taller groups. The tallest quintile had higher risk than the shortest quintile (hazard ratio = 1.185, 95% confidence interval: 1.147-1.225) after adjusting for age, sex, BMI, income, smoking status, alcohol consumption, regular physical activity, hypertension, diabetes mellitus, and dyslipidemia. This study showed that the incidence of anosmia had a positive association with height. However, careful interpretation is needed to generalize our result because of the limitation of the study population. Further studies are needed to clarify the genetic or environmental causes of anosmia.
| S-EPMC7991667 | biostudies-literature
Project description:BackgroundIn sub-Saharan Africa, house design and ventilation affects the number of malaria mosquito vectors entering houses. This study hypothesized that indoor light from a CDC-light trap, visible from outside a hut, would increase entry of Anopheles arabiensis, an important malaria vector, and examined whether ventilation modifies this effect.MethodsFour inhabited experimental huts, each situated within a large chamber, were used to assess how light and ventilation affect the number of hut-entering mosquitoes in Tanzania. Each night, 300 female laboratory-reared An. arabiensis were released inside each chamber for 72 nights. Nightly mosquito collections were made using light traps placed indoors. Temperature and carbon dioxide concentrations were measured using data loggers. Treatments and sleepers were rotated between huts using a randomized block design.ResultsWhen indoor light was visible outside the huts, there was an 84% increase in the odds of collecting mosquitoes indoors (Odds ratio, OR = 1.84, 95% confidence intervals, 95% CI 1.74-1.95, p < 0.001) compared with when it was not. Although the odds of collecting mosquitoes in huts with closed eaves (OR = 0.54, 95% CI 0.41-0.72, p < 0.001) was less than those with open eaves, few mosquitoes entered either type of well-ventilated hut. The odds of collecting mosquitoes was 99% less in well-ventilated huts, compared with poorly-ventilated traditional huts (OR = 0.01, 95% CI 0.01-0.03, p < 0.001). In well-ventilated huts, indoor temperatures were 1.3 °C (95% CI 0.9-1.7, p < 0.001) cooler, with lower carbon dioxide (CO2) levels (mean difference = 97 ppm, 77.8-116.2, p < 0.001) than in poorly-ventilated huts.ConclusionAlthough light visible from outside a hut increased mosquito house entry, good natural ventilation reduces indoor carbon dioxide concentrations, a major mosquito attractant, thereby reducing mosquito-hut entry.
| S-EPMC8818140 | biostudies-literature
Project description:ObjectiveThe main objective was to assess the risk factors for infant mortality among children living in the Health and Demographic Surveillance System (HDSS) in Farafenni, The Gambia. Our secondary objective was to assess these risks separately in the neonatal and postneonatal (>28 days) period.DesignRetrospective cohort study.SettingHDSS in an urban centre and surrounding area in The Gambia.Patients7365 infants (47% female) born between 2014 and 2018, of which 126 (1.71%) died in the first year.Main outcome measuresInfant mortality.ResultsRisk factors for mortality were death of any sibling (HR 2.78, 95% CI 1.54 to 5.00), having a twin (HR 1.96, 95% CI 1.01 to 3.80), being born in the harvest season (HR 1.55, 95% CI 1.07 to 2.24), living in a rural village (HR 4.34, 95% CI 2.03 to 9.29) and longer distance to the nearest village with a public health centre (HR 1.33, 95% CI 1.11 to 1.59). In addition, no breast feeding (HR 10.73, 95% CI 6.83 to 16.86) and no BCG vaccination in the first week of life (HR 3.47, 95% CI 1.07 to 11.24) were associated with infant mortality. Similar risk factors were found in the neonatal and postneonatal periods.ConclusionMost risk factors associated with infant mortality (neonatal and postneonatal) are not easily modifiable at the individual level and would require programmatic approaches to target vulnerable infants and facilitate access to health services.
| S-EPMC8461724 | biostudies-literature
Project description:BackgroundClose contact between an infectious and susceptible person is an important factor in respiratory disease transmission. Information on social contacts and mixing patterns in a population is crucial to understanding transmission patterns and informing transmission models of respiratory infections. Although West Africa has one of the highest burdens of respiratory infections, there is a lack of data on interpersonal contact and mixing patterns in this region.MethodsBetween January and November 2022, we conducted a cross-sectional, social contact survey within the population of the Central and Upper River Regions of The Gambia. Selected participants completed a questionnaire about their travel history and social contacts, detailing the number, intensity, location, frequency, duration, and age of contacts. We calculated age-standardized contact matrices to determine contact patterns in the population.ResultsOverall, individuals made an average of 12.7 (95% CI: 12.4-13.0) contacts per day. Contact patterns were mostly age-assortative and 84.5% of all contacts were physical. School-aged children (5-14 years) had the highest mean number of physical contacts (11.3, 95% CI: 10.9-11.8) while the < 1-year age group had the fewest contacts (9.4, 95% CI: 9.1-9.8). A large proportion of contacts (78%) occurred at home. Daily number of contacts increased with household size. While we did not observe any effect of gender on contact patterns, there were seasonal variations in contact type. Non-physical contacts were higher during the dry season compared to the rainy season. In contrast, there were more physical contacts in the rainy season compared to the dry season.ConclusionsIn rural Gambia, social contact patterns were primarily driven by household mixing. Most contacts were physical and mostly age-assortative, particularly among school-aged children. Our data can improve infectious disease transmission models of respiratory pathogens in high-transmission settings, which are valuable for optimizing the delivery of different interventions.
| S-EPMC11844039 | biostudies-literature