Biomedical subjects

Charles M Mbogo

Publications and source records attributed to Charles M Mbogo.

At least 19 recordsLinked to original sources

PubMed2006

Survival of immature Anopheles arabiensis (Diptera: Culicidae) in aquatic habitats in Mwea rice irrigation scheme, central Kenya.

BACKGROUND: The survivorship and distribution of Anopheles arabiensis larvae and pupae was examined in a rice agro-ecosystem in Mwea Irrigation Scheme, central Kenya, from August 2005 to April 2006, prior to implementation of larval control programme. METHODS: Horizontal life tables were constructed for immatures in semi-field condition. The time spent in the various immature stages was determined and survival established. Vertical life tables were obtained from five paddies sampled by standard dipping technique. RESULTS: Pre-adult developmental time for An. arabiensis in the trays in the experimental set up in the screen house was 11.85 days from eclosion to emergence. The mean duration of each instar stage was estimated to be 1.40 days for first instars, 2.90 days for second instars, 1.85 days for third instars, 3.80 days for fourth instars and 1.90 days for pupae. A total of 590 individuals emerged into adults, giving an overall survivorship from L1 to adult emergence of 69.4%. A total of 4,956 An. arabiensis immatures were collected in 1,400 dips throughout the sampling period. Of these, 55.9% were collected during the tillering stage, 42.5% during the transplanting period and 1.6% during the land preparation stage. There was a significant difference in the An. arabiensis larval densities among the five stages. Also there was significant variation in immature stage composition for each day's collection in each paddy. These results indicate that the survival of the immatures was higher in some paddies than others. The mortality rate during the transplanting was 99.9% and at tillering was 96.6%, while the overall mortality was 98.3%. CONCLUSION: The survival of An. arabiensis immatures was better during the tillering stage of rice growth. Further the survival of immatures in rice fields is influenced by the rice agronomic activities including addition of nitrogenous fertilizers and pesticides. For effective integrated vector management, the application of larvicides should target An. arabiensis larvae at the tillering stage (early vegetative stage of rice) when their survival in the aquatic habitats is high to significantly reduce them and the larvicides should be long-lasting to have a significant impact on the malaria vector productivity on the habitats.

Animals↗

PubMed2006

Concomitant infections of Plasmodium falciparum and Wuchereria bancrofti on the Kenyan coast.

BACKGROUND: Anopheles gambiae s.l. and An. funestus are important vectors of malaria and bancroftian filariasis, which occur as co-endemic infections along the Kenyan Coast. However, little is known about the occurrence and prevalence of concomitant infections of the two diseases in mosquito and human populations in these areas. This study reports the prevalence of concomitant infections of Plasmodium falciparum and Wuchereria bancrofti in mosquito and human populations in Jilore and Shakahola villages in Malindi, Kenya. METHODS: Mosquitoes were sampled inside houses by pyrethrum spray sheet collection (PSC) while blood samples were collected by finger prick technique at the end of entomological survey. RESULTS: A total of 1,979 female Anopheles mosquitoes comprising of 1,919 Anopheles gambiae s.l and 60 An. funestus were collected. Concomitant infections of P. falciparum sporozoites and filarial worms occurred in 1.1% and 1.6% of An. gambiae s.l collected in Jilore and Shakahola villages respectively. Wuchereria-infected mosquitoes had higher sporozoite rates compared to non-infected mosquitoes, but multiple infections appeared to reduce mosquito survivorship making transmission of such infections rare. None of the persons examined in Shakahola (n = 107) had coinfections of the two parasites, whereas in Jilore (n = 94), out of the 4.3% of individuals harbouring both parasites, 1.2% had P. falciparum gametocytes and microfilariae and could potentially infect the mosquito with both parasites simultaneously. CONCLUSION: Concerted efforts should be made to integrate the control of malaria and bancroftian filariasis in areas where they co-exist.

Journal Article↗

PubMed2006

Relationship between malaria and filariasis transmission indices in an endemic area along the Kenyan Coast.

BACKGROUND AND OBJECTIVES: An entomological survey was conducted to determine the relationship between malaria and lymphatic filariasis transmission by Anopheles gambiae s.l. and An. funestus in two inland villages along the Kenyan coast. METHODS: Mosquitoes were sampled inside houses by pyrethrum spray sheet collection (PSC). In the laboratory, the mosquitoes were sorted to species, dissected for examination of filarial infection and the anophelines later tested for Plasmodium falciparum circumsporozoite proteins by an enzyme-linked immunosorbent assay (ELISA). RESULTS: From a total of 2,032 female mosquitoes collected indoors, An. gambiae s.l constituted 94.4% while the remaining 5.6% comprised of An. funestus and Culex quinquefasciatus. None of the Cx. quinquefasciatus was positive for filarial worms. P. falciparum sporozoite rate for An. gambiae s.l. from both villages was significantly higher than Wuchereria bancrofti infectivity rate. Similarly, the entomological inoculation rate for An. gambiae s.l. was significantly higher than the corresponding W. bancrofti infective biting rate and transmission potential for both the villages. Mass treatment of people with filaricidal drugs in Shakahola in the ongoing global elimination of lymphatic filariasis campaign seemed to have reduced the indices of filariasis transmission but had no effect on malaria transmission. INTERPRETATION AND CONCLUSION: These results indicate the intensity of malaria transmission by anophelines to be much higher than that of lymphatic filariasis in areas where both diseases co-exist and re-emphasise the need to integrate the control of the two diseases in such areas.

Animals↗

PubMed2005

Self-reported malaria and mosquito avoidance in relation to household risk factors in a Kenyan coastal city.

A geographically stratified cross-sectional survey was conducted in 2002 to investigate household-level factors associated with use of mosquito control measures and self-reported malaria in Malindi, Kenya. A total of 629 households were surveyed. Logistic regressions were used to analyse the data. Half of all households (51%) reported all occupants using an insecticide-treated bed net and at least one additional mosquito control measure such as insecticides or removal of standing water. Forty-nine per cent reported a history of malaria in the household. Of the thirteen household factors analysed, low (OR=0.23, CI 0.11, 0.48) and medium (OR=0.50, CI 0.29, 0.86) education, mud--wood--coral (OR=0.0.39, CI 0.24, 0.66) and mud block--plaster (OR=0.47, CI 0.25, 0.87) wall types, farming (OR=1.38, CI 1.01, 1.90) and travel to rural areas (OR=0.48, CI 0.26, 0.91) were significantly associated with the use of mosquito control, while controlling for other covariates in the model. History of reported malaria was not associated with the use of mosquito control (OR=1.22, CI 0.79, 1.88). Of the thirteen covariates analysed in the second model, only two household factors were associated with history of malaria: being located in the well-drained stratum (OR=0.49, CI 0.26, 0.96) and being bitten while in the house (OR=1.22, CI 0.19, 0.49). These results suggest that high socioeconomic status is associated with increased household-level mosquito control use, although household-level control may not be enough, as many people are exposed to biting mosquitoes while away from the house and in areas that are more likely to harbour mosquitoes.

Animals↗

PubMed2005

Anopheles gambiae s.l. and Anopheles funestus mosquito distributions at 30 villages along the Kenyan coast.

This study investigated whether Anopheles gambiae s.l. and Anopheles funestus Giles mosquito populations were distributed randomly among houses on the coast of Kenya. Sample means and variances of mosquitoes were estimated from bimonthly pyrethrum spray collections at 30 villages from July 1997 through May 1998. In total, 5,476 An. gambiae s.l. and 3,461 An. funestus were collected. The number of An. gambiae s.l. collected was highest in November/December and lowest in May. The number of An. funestus collected was highest during September/October and lowest during May. As the density of mosquitoes decreased, there was a tendency toward randomness in the distribution. The proportion of An. gambiae s.l. and An. funestus mosquitoes collected per house for each sampling period also showed patterns of clustering, with 80% of An. gambiae s.l. collected from <30% of the houses and 80% of An. funestus collected from <20% of the total houses. The total number of mosquitoes collected from any one house ranged from 0 to 121 for An. gambiae s.l. and from 0 to 152 for An. funestus. This coupled with the results of the variance to mean ratio plots suggests extensive clustering in the distribution of An. gambiae s.l. and An. funestus mosquito populations throughout the year along the coast of Kenya.

Animals↗

PubMed2005

Evaluation of environmental data for identification of Anopheles (Diptera: Culicidae) aquatic larval habitats in Kisumu and Malindi, Kenya.

This research evaluates the extent to which use of environmental data acquired from field and satellite surveys enhances predictions of urban mosquito counts. Mosquito larval habitats were sampled, and multispectral thermal imager (MTI) satellite data in the visible spectrum at 5-m resolution were acquired for Kisumu and Malindi, Kenya, during February and March 2001. All entomological parameters were collected from January to May 2001, June to August 2002, and June to August 2003. In a Poisson model specification, for Anopheles funestus Giles, shade was the best predictor, whereas substrate was the best predictor for Anopheles gambiae, and vegetation for Anopheles arabensis Patton. The top predictors found with a logistic regression model specification were habitat size for An. gambiae Giles, pollution for An. arabensis, and shade for An. funestus. All other coefficients for canopy, debris, habitat nature, permanency, emergent plants, algae, pollution, turbidity, organic materials, all MTI waveband frequencies, distance to the nearest house, distance to the nearest domestic animal, and all land use land cover changes were nonsignificant. MTI data at 5-m spatial resolution do not have an additional predictive value for mosquito counts when adjusted for field-based ecological data.

Animals↗

PubMed2004

A simulation model of African Anopheles ecology and population dynamics for the analysis of malaria transmission.

BACKGROUND: Malaria is one of the oldest and deadliest infectious diseases in humans. Many mathematical models of malaria have been developed during the past century, and applied to potential interventions. However, malaria remains uncontrolled and is increasing in many areas, as are vector and parasite resistance to insecticides and drugs. METHODS: This study presents a simulation model of African malaria vectors. This individual-based model incorporates current knowledge of the mechanisms underlying Anopheles population dynamics and their relations to the environment. One of its main strengths is that it is based on both biological and environmental variables. RESULTS: The model made it possible to structure existing knowledge, assembled in a comprehensive review of the literature, and also pointed out important aspects of basic Anopheles biology about which knowledge is lacking. One simulation showed several patterns similar to those seen in the field, and made it possible to examine different analyses and hypotheses for these patterns; sensitivity analyses on temperature, moisture, predation and preliminary investigations of nutrient competition were also conducted. CONCLUSIONS: Although based on some mathematical formulae and parameters, this new tool has been developed in order to be as explicit as possible, transparent in use, close to reality and amenable to direct use by field workers. It allows a better understanding of the mechanisms underlying Anopheles population dynamics in general and also a better understanding of the dynamics in specific local geographic environments. It points out many important areas for new investigations that will be critical to effective, efficient, sustainable interventions.

Animal Nutritional Physiological Phenomena↗

PubMed2004

Characterization of potential larval habitats for Anopheles mosquitoes in relation to urban land-use in Malindi, Kenya.

BACKGROUND: This study characterized Anopheles mosquito larval habitats in relation to ecological attributes about the habitat and community-level drainage potential, and investigated whether agricultural activities within or around urban households increased the probability of water body occurrence. Malindi, a city on the coast of Kenya, was mapped using global positioning system (GPS) technology, and a geographic information system (GIS) was used to overlay a measured grid, which served as a sampling frame. Grid cells were stratified according to the level of drainage in the area, and 50 cells were randomly selected for the study. Cross-sectional household and entomological surveys were conducted during November and December 2002 within the 50 grid cells. Chi-square analysis was used to test whether water bodies differed fundamentally between well and poorly drained areas, and multi-level logistic regression was used to test whether household-level agricultural activity increased the probability of water body occurrence in the grid cell. RESULTS: Interviews were conducted with one adult in 629 households. A total of 29 water bodies were identified within the sampled areas. This study found that characteristics of water bodies were fundamentally the same in well and poorly drained areas. This study also demonstrated that household-level urban agriculture was not associated with the occurrence of water bodies in the grid cell, after controlling for potential confounders associated with distance to the city center, drainage, access to resources, and population density. CONCLUSIONS: Household-level urban agricultural activity may be less important than the other types of human perturbation in terms of mosquito larval habitat creation. The fact that many larvae were coming from few sites, and few sites in general were found under relatively dry conditions suggests that mosquito habitat reduction is a reasonable and attainable goal in Malindi.

Journal Article↗

PubMed2004

Relationships between body size of anopheles mosquitoes and Plasmodium falciparum sporozoite rates along the Kenya coast.

The influence of body size of Anopheles gambiae s.s., Anopheles arabiensis, Anopheles merus, and Anopheles funestus on the transmission of Plasmodium falciparum was studied at 3 sites along the Kenyan coast. Adult mosquitoes were collected inside houses by pyrethrum spray collection (PSC) from April to September 2001. Wing length was measured microscopically to the nearest 0.01 mm as an index of mosquito body size. The P. falciparum circumsporozoite protein (CSP) was detected by enzyme-linked immunosorbent assay technique. A total of 1715 anopheline mosquitoes were collected, of which 785 (45.77%) were An. gambiae s.s., 54 (3.15%) An. arabiensis, An. merus 27 (1.57%), and 849 (49.5%) were An. funestus. The mean wing length for An. gambiae s.s. was 2.94 mm and that of An. funestus was 2.50 mm. There was no site-to-site variation in the body size of An. gambiae or An. funestus. There was no significant difference in wing length between sporozoite-infected and uninfected An. gambiae s.s., and the same was found for An. funestus. At the 3 rural coastal sites in Kenya, the efficiency of malaria parasite transmission does not appear to be influenced by variation in vector body size.

Animals↗

PubMed2004

Ecological limitations on aquatic mosquito predator colonization in the urban environment.

Urban malaria cases are becoming common in Africa as more people move into cities and industrialization proceeds. While many species of Anopheles mosquitoes vector malaria in rural areas, only a few are found within cities. The success of anthropophilic species in cities, such as members of the An. gambiae complex, may be explained by limitations on colonization by predator species in urban environments. Habitats that are temporal or structurally simple have lower predator survivorship in a variety of ecosystems, but these have not been investigated previously in an urban area. Areas within and around the Kenyan coastal town of Malindi were previously sampled for the presence of standing water using a geographic sampling strategy with probability proportional to size sampling of planned well-drained, unplanned poorly-drained, planned poorly-drained, unplanned well-drained, and peri-urban locations. Standing aquatic habitats in these areas were reassessed. During monthly sampling, presence/absence of mosquitoes and predator taxa were noted, as were ecological habitat variables: structural complexity and presence of water. Lambda statistics were calculated to associate predator guilds, habitat types, location variables, and ecological variables. All predator guilds found in habitats were strongly associated with habitat type, as were the structural complexity and temporal nature of the habitats. Types of habitat were heterogeneously distributed throughout Malindi, with swimming pools as a common habitat type in planned urban areas and tire track pools a common habitat type in peri-urban areas of Malindi. Predator colonization of aquatic habitats in Malindi was strongly influenced by habitat type, and not associated with location characteristics. Ecological variables were affected by the type of habitats, which are co-associated with planning and drainage in Malindi. While habitat types are distributed heterogeneously within Malindi, habitats with low predation pressure are available for mosquito colonization in both urban and peri-urban areas. The temporal, peri-urban tire track pools and the structural simplicity of urban swimming pools may discourage predator colonization, thereby increasing the probability of malaria vectors in these areas of Malindi. Future studies should evaluate habitats for use in malaria surveillance and experimentally test the effects of structural complexity and temporal nature of urban habitats on the densities of mosquito larvae and their aquatic predators.

Animals↗

PubMed2003

Linking field-based ecological data with remotely sensed data using a geographic information system in two malaria endemic urban areas of Kenya.

BACKGROUND: Remote sensing technology provides detailed spectral and thermal images of the earth's surface from which surrogate ecological indicators of complex processes can be measured. METHODS: Remote sensing data were overlaid onto georeferenced entomological and human ecological data randomly sampled during April and May 2001 in the cities of Kisumu (population asymptotically equal to 320,000) and Malindi (population asymptotically equal to 81,000), Kenya. Grid cells of 270 meters x 270 meters were used to generate spatial sampling units for each city for the collection of entomological and human ecological field-based data. Multispectral Thermal Imager (MTI) satellite data in the visible spectrum at five meter resolution were acquired for Kisumu and Malindi during February and March 2001, respectively. The MTI data were fit and aggregated to the 270 meter x 270 meter grid cells used in field-based sampling using a geographic information system. The normalized difference vegetation index (NDVI) was calculated and scaled from MTI data for selected grid cells. Regression analysis was used to assess associations between NDVI values and entomological and human ecological variables at the grid cell level. RESULTS: Multivariate linear regression showed that as household density increased, mean grid cell NDVI decreased (global F-test = 9.81, df 3,72, P-value = <0.01; adjusted R2 = 0.26). Given household density, the number of potential anopheline larval habitats per grid cell also increased with increasing values of mean grid cell NDVI (global F-test = 14.29, df 3,36, P-value = <0.01; adjusted R2 = 0.51). CONCLUSIONS: NDVI values obtained from MTI data were successfully overlaid onto georeferenced entomological and human ecological data spatially sampled at a scale of 270 meters x 270 meters. Results demonstrate that NDVI at such a scale was sufficient to describe variations in entomological and human ecological parameters across both cities.

Journal Article↗

PubMed2003

Low recovery rates stabilize malaria endemicity in areas of low transmission in coastal Kenya.

The prevalence of Plasmodium falciparum malaria in African communities can be high and stable even in areas of relatively low transmission where people expose to only a few infectious bites per year. We show in this field study conducted in 30 sites along the coastal Kenya that prevalence in school children was consistently high, although there were many sites where transmission intensity measured by exposure to infectious bites was less than 10 per year. Statistical analyses revealed that prevalence was significantly correlated with the infectious exposure occurring 10-11 months previously, suggesting that long-lived infections were commonplace and one of the major contributors for the stability of malaria in these sites. Using mechanistic models of malaria transmission, we found that the association of high prevalence and low transmission could be due to low recovery rates. Therefore, significant reductions of malaria prevalence and burden require substantial reductions of the duration of acquired infections, even in areas that have quite low transmission intensities by the standards of sub-Saharan Africa. Infection control featured by active detection and drug treatment as well as vector control is critical to combat malaria in areas of relatively low transmission intensity.

Animals↗

PubMed2003

Occurrence and distribution of Anopheles (Diptera: Culicidae) larval habitats on land cover change sites in urban Kisumu and urban Malindi, Kenya.

A multitemporal, land use land cover (LULC) classification dataset incorporating distributions of mosquito larval habitats was produced in ERDAS Imagine using the combined images from the Multispectral Thermal Imager (MTI) at 5 m spatial resolution from 2001 with Thematic Mapper-classification data at 28.5 m spatial resolution from 1987 and 1989 for Kisumu and Malindi, Kenya. Total LULC change for Kisumu over 14 yr was 30.2%. Total LULC change for Malindi over 12 yr was 30.6%. Of those areas in which change was detected, the LULC change for Kisumu was 72.5% for nonurban to urban, 21.7% urban to nonurban, 0.4% urban to water, 4.5% water to urban, and 0.9% water to nonurban. The proportion of LULC change for Malindi was 93.5% for nonurban to urban, 5.9% urban to nonurban, 0.2% urban to water, 0.3% nonurban to water, and 0.1% water to urban. A grid (270 m x 270 m cells) was overlaid over the maps stratifying grid cells based on drainage and planning. Of 84 aquatic habitats in Kisumu, 32.1% were located in LULC change sites and 67.9% were located in LULC nonchange sites. Of 170 aquatic habitats in Malindi, 26.5% were located in LULC change sites and 73.5% were located in LULC nonchange sites. The most abundant LULC change per strata with anopheline habitats was unplanned and poorly drained. Ditches and puddles in Kisumu and car tracks in Malindi displayed the highest number of anopheline larval habitats for all LULC change sites. The proportion of site positive aquatic habitats for anopheline larvae was higher in LULC change sites than for LULC nonchange sites for Kisumu. This evidence suggests LULC change can influence anopheline larval habitat distribution.

Animals↗

PubMed2003

Determination of Anopheles gambiae larval DNA in the gut of insectivorous dragonfly (Libellulidae) nymphs by polymerase chain reaction.

We examined the predator-prey relationship between larvae of the malaria mosquito Anopheles gambiae and nymphs of the dragonfly (Libellulidae). Studies were conducted to determine whether polymerase chain reaction (PCR) can be used to detect DNA of An. gambiae in the gut of libellulid nymphs, and to determine how long after feeding on An. gambiae that mosquito DNA remains detectable by PCR. Total DNA was extracted from the gut contents of libellulid nymphs by using 2 types of DNA extraction methods. The target sequence for the diagnostic PCR was the intergenic spacer regions of the ribosomal DNA gene locus. These sequences were analyzed by using An. gambiae complex-specific primers. After analyzing nymphal gut contents with PCR at regular postfeed intervals, a 390-base pair product could be amplified. The presence of mosquito larvae was visually confirmed for up to 40 min after feeding. Regardless of the number of mosquito larvae ingested, libellulid gut contents could be amplified or visually seen up to 1 h of digestion. This result indicates the nymphs have a high rate of digestion and that PCR with An. gambiae complex primers will be best utilized within 1 h after feeding as a detection system. This study confirmed that dragonfly nymphs feed well on anopheline larvae, and that mosquito DNA, although rapidly digested, can be successfully recovered and detected from within nymphal digestive tracts.

Animals↗

PubMed2003

Spatial and temporal heterogeneity of Anopheles mosquitoes and Plasmodium falciparum transmission along the Kenyan coast.

The seasonal dynamics and spatial distributions of Anopheles mosquitoes and Plasmodium falciparum parasites were studied for one year at 30 villages in Malindi, Kilifi, and Kwale Districts along the coast of Kenya. Anopheline mosquitoes were sampled inside houses at each site once every two months and malaria parasite prevalence in local school children was determined at the end of the entomologic survey. A total of 5,476 Anopheles gambiae s.l. and 3,461 An. funestus were collected. Species in the An. gambiae complex, identified by a polymerase chain reaction, included 81.9% An. gambiae s.s., 12.8% An. arabiensis, and 5.3% An. merus. Anopheles gambiae s.s. contributed most to the transmission of P. falciparum along the coast as a whole, while An. funestus accounted for more than 50% of all transmission in Kwale District. Large spatial heterogeneity of transmission intensity (< 1 up to 120 infective bites per person per year) resulted in correspondingly large and significantly related variations in parasite prevalence (range = 38-83%). Thirty-two percent of the sites (7 of 22 sites) with malaria prevalences ranging from 38% to 70% had annual entomologic inoculation rates (EIR) less than five infective bites per person per year. Anopheles gambiae s.l. and An. funestus densities in Kwale were not significantly influenced by rainfall. However, both were positively correlated with rainfall one and three months previously in Malindi and Kilifi Districts, respectively. These unexpected variations in the relationship between mosquito populations and rainfall suggest environmental heterogeneity in the predominant aquatic habitats in each district. One important conclusion is that the highly non-linear relationship between EIRs and prevalence indicates that the consistent pattern of high prevalence might be governed by substantial variation in transmission intensity measured by entomologic surveys. The field-based estimate of entomologic parameters on a district level does not provide a sensitive indicator of transmission intensity in this study.

Animals↗

PubMed2003

Population genetic structure of the African malaria mosquito Anopheles funestus in Kenya.

Anopheles funestus Giles is a major malaria vector in Africa, but little is known about the genetic structure of natural populations. In this study, microsatellite markers were used to investigate the genetic structure of A. funestus populations from Kenya. Two populations from western Kenya 80 km apart and two from coastal Kenya 50 km apart were collected and examined for allelic variation at five trinucleotide microsatellite loci. We found A. funestus Giles was the predominant species (> 98%) in the A. funestus group in these populations. The western Kenya populations exhibited higher genetic diversity than the coastal populations. No significant genetic structure for populations within the coastal or western Kenya regions was detected. However, population genetic differentiation between the two regions was high (F(ST) = 0.208, R(ST) = 0.158), approximately two-fold higher than A. gambiae populations from the same area. The results suggest that the minimum area associated with a deme of A. funestus in western or coastal Kenya is larger than 50 km in diameter. The Great Rift Valley in east Africa, high-elevation mountains in western Kenya, and the vast arid area east to the Great Rift Valley may all play a role in restricting A. funestus gene flow between coastal and western Kenya.

Alleles↗

PubMed2003

Blood-meal analysis for anopheline mosquitoes sampled along the Kenyan coast.

A total of 1,480 Anopheles gambiae sensu lato and 439 An. funestus, collected from 30 sites along the Kenyan coast, were tested by direct enzyme-linked immunosorbent assay (ELISA) for blood-meal identification. Overall, the enzyme-linked immunosorbent assay (ELISA) identified 92 and 87% of the samples tested in An. gambiae s.l. and An. funestus, respectively. Of these, human IgG was detected in 98.97% (n = 1,347) of An. gambiae s.l. and 99.48% (n = 379) of An. funestus. Only 14 (1.03%) of the An. gambiae s.l. had fed on other vertebrate hosts tested, which were bovines, chickens, and goats. Additionally, only 2 An. funestus had fed on goats. In all the 28 sites that had bloodfed mosquitoes, An. gambiae s.l. had a human blood index greater than 0.9. Twenty-five of these sites had a human blood index greater than 0.9 for An. funestus, while the other 3 sites had no bloodfed mosquitoes. The An. gambiae s.l. were tested by polymerase chain reaction (PCR) for species identification. A total of 338 were An. gambiae s.s., 79 were An. arabiensis, and 12 were An. merus. The human blood index was 0.96, 0.91, and 1.0 for An. gambiae s.s., An. arabiensis, and An. merus, respectively. The Plasmodium falciparum sporozoite infection rates were 6.2% for species in the An. gambiae complex and 3.7% for An. funestus. These results emphasize that An. funestus and members of the An. gambiae complex on the Kenyan coast are highly anthropophilic, with nearly all specimens feeding on humans during every blood meal. The results further demonstrated active transmission of P. falciparum sporozoites by the primary vector species. This study suggests that the use of insecticide-treated nets will be effective for controlling biting mosquitoes inside houses along the coast of Kenya.

Animals↗

PubMed2002

Examining the determinants of mosquito-avoidance practices in two Kenyan cities.

BACKGROUND: This study assesses the behavioural and socio-economic factors associated with avoiding mosquitoes and preventing malaria in urban environments in Kenya. METHODS: Data from two cities in Kenya were gathered using a household survey and a two-stage cluster sample design. The cities were stratified based on planning and drainage observed across the urban areas. This helped control for the strong environmental and topographical variation that we assumed influences mosquito ecology. Individual interviews given to each household included questions on socio-economic status, education, housing type, water source, rubbish disposal, mosquito-prevention practices and knowledge of mosquitoes. In multivariate regression, factors measuring wealth, education level, and the communities' level of planning and drainage were used to estimate the probability that a household engages in multiple mosquito-avoidance activities, or has all members sleeping under a bed net. RESULTS: Our analysis shows that people from wealthier, more educated households were more likely to sleep under a net, in Kisumu (OR = 6.88; 95% CI = 2.56,18.49) and Malindi (OR = 3.80; 95% CI = 1.91,7.55). Similarly, the probability that households use several mosquito-prevention activities was highest among the wealthiest, best-educated households in Kisumu (OR = 5.15; 95% CI = 2.04,12.98), while in Malindi household wealth alone is the major determinant. CONCLUSION: We demonstrate the importance of examining human-mosquito interaction in terms of how access to resources may enhance human activities. The findings illustrate that the poorest segments of society are already doing many things to protect themselves from being bitten, but they are doing less than their richer neighbours.

Animals↗