An exploratory study of community factors relevant for participatory malaria control on Rusinga Island, western Kenya

<p>Abstract</p> <p>Background</p> <p>Capacity strengthening of rural communities, and the various actors that support them, is needed to enable them to lead their own malaria control programmes. Here the existing capacity of a rural community in western Kenya was evaluated in preparation for a larger intervention.</p> <p>Methods</p> <p>Focus group discussions and semi-structured individual interviews were carried out in 1,451 households to determine (1) demographics of respondent and household; (2) socio-economic status of the household; (3) knowledge and beliefs about malaria (symptoms, prevention methods, mosquito life cycle); (4) typical practices used for malaria prevention; (5) the treatment-seeking behaviour and household expenditure for malaria treatment; and (6) the willingness to prepare and implement community-based vector control.</p> <p>Results</p> <p>Malaria was considered a major threat to life but relevant knowledge was a chimera of scientific knowledge and traditional beliefs, which combined with socio-economic circumstances, leads to ineffective malaria prevention. The actual malaria prevention behaviour practiced by community members differed significantly from methods known to the respondents. Beside bednet use, the major interventions implemented were bush clearing and various hygienic measures, even though these are ineffective for malaria prevention. Encouragingly, most respondents believed malaria could be controlled and were willing to contribute to a community-based malaria control program but felt they needed outside assistance.</p> <p>Conclusion</p> <p>Culturally sensitive but evidence-based education interventions, utilizing participatory tools, are urgently required which consider traditional beliefs and enable understanding of causal connections between mosquito ecology, parasite transmission and the diagnosis, treatment and prevention of disease. Community-based organizations and schools need to be equipped with knowledge through partnerships with national and international research and tertiary education institutions so that evidence-based research can be applied at the grassroots level.</p

Variation in malaria transmission dynamics in three different sites in Western Kenya

The main objective was to investigate malaria transmission dynamics in three different sites, two highland villages (Fort Ternan and Lunyerere) and a lowland peri-urban area (Nyalenda) of Kisumu city. Adult mosquitoes were collected using PSC and CDC light trap while malaria parasite incidence data was collected from a cohort of children on monthly basis. Rainfall, humidity and temperature data were collected by automated weather stations. Negative binomial and Poisson generalized additive models were used to examine the risk of being infected, as well as the association with the weather variables. Anopheles gambiae s.s. was most abundant in Lunyerere, An. arabiensis in Nyalenda and An. funestus in Fort Ternan. The CDC light traps caught a higher proportion of mosquitoes (52.3%) than PSC (47.7%), although not significantly different (P = 0.689). The EIR's were 0, 61.79 and 6.91 bites/person/year for Fort Ternan, Lunyerere and Nyalenda. Site, month and core body temperature were all associated with the risk of having malaria parasites (P <0.0001). Rainfall was found to be significantly associated with the occurrence of P. falciparum malaria parasites, but not relative humidity and air temperature. The presence of malaria parasite-infected children in all the study sites provides evidence of local malaria transmission

Screening mosquito house entry points as a potential method for integrated control of endophagic filariasis, arbovirus and malaria vectors.

BACKGROUND: Partial mosquito-proofing of houses with screens and ceilings has the potential to reduce indoor densities of malaria mosquitoes. We wish to measure whether it will also reduce indoor densities of vectors of neglected tropical diseases. METHODOLOGY: The main house entry points preferred by anopheline and culicine vectors were determined through controlled experiments using specially designed experimental huts and village houses in Lupiro village, southern Tanzania. The benefit of screening different entry points (eaves, windows and doors) using PVC-coated fibre glass netting material in terms of reduced indoor densities of mosquitoes was evaluated compared to the control. FINDINGS: 23,027 mosquitoes were caught with CDC light traps; 77.9% (17,929) were Anopheles gambiae sensu lato, of which 66.2% were An. arabiensis and 33.8% An. gambiae sensu stricto. The remainder comprised 0.2% (50) An. funestus, 10.2% (2359) Culex spp. and 11.6% (2664) Mansonia spp. Screening eaves reduced densities of Anopheles gambiae s. l. (Relative ratio (RR) = 0.91; 95% CI = 0.84, 0.98; P = 0.01); Mansonia africana (RR = 0.43; 95% CI = 0.26, 0.76; P<0.001) and Mansonia uniformis (RR = 0.37; 95% CI = 0.25, 0.56; P<0.001) but not Culex quinquefasciatus, Cx. univittatus or Cx. theileri. Numbers of these species were reduced by screening windows and doors but this was not significant. SIGNIFICANCE: This study confirms that across Africa, screening eaves protects households against important mosquito vectors of filariasis, Rift Valley Fever and O'Nyong nyong as well as malaria. While full house screening is required to exclude Culex species mosquitoes, screening of eaves alone or fitting ceilings has considerable potential for integrated control of other vectors of filariasis, arbovirus and malaria

Extent of digestion affects the success of amplifying human DNA from blood meals of Anopheles gambiae (Diptera: Culicidae)

The success of distinguishing blood meal sources of Anopheles gambiae Giles through deoxyribonucleic acid (DNA) profiling was investigated by polymerase chain reaction (PCR) amplification at the TC-11 and VWA human short tandem repeats (STR) loci. Blood meal size and locus had no significant effect on the success of amplifying human DNA from blood meals digested for 0, 8, 16, 24 and 32 h (P = 0.85 and 0.26 respectively). However, logistic regression found a significant negative relationship between time since ingestion and the success probability of obtaining positive PCR products among meals digested for between 8 and 32 h (P = 0.001). Approximately 80 f fresh blood meals were successfully profiled. After 8 h, the proportion of blood meals that could be successfully profiled decreased slowly with time after ingestion, dropping to below 50 fter approximately 15 h. There was no significant difference in the success of amplifying human DNA from blood meals of mosquitoes killed at time 0 and 8 h after ingestion (P = 0.272)

Comparative evaluation of four mosquitoes sampling methods in rice irrigation schemes of lower Moshi, northern Tanzania

Adult malaria vector sampling is the most important parameter for setting up an intervention and understanding disease dynamics in malaria endemic areas. The intervention will ideally be species-specific according to sampling output. It was the objective of this study to evaluate four sampling techniques, namely human landing catch, pit shelter, indoor resting collection and odour-baited entry trap. These four sampling methods were evaluated simultaneously for thirty days during October 2008, a season of low mosquitoes density and malaria transmission. These trapping methods were performed in one village for maximizing homogeneity in mosquito density. The cattle and man used in odour-baited entry trap were rotated between the chambers to avoid bias. A total of 3,074 mosquitoes were collected. Among these 1,780 (57.9%) were Anopheles arabiensis and 1,294 (42.1%) were Culex quinquefasciatus. Each trap sampled different number of mosquitoes, Indoor resting collection collected 335 (10.9%), Odour-baited entry trap-cow 1,404 (45.7%), Odour-baited entry trap-human 378 (12.3%), Pit shelter 562 (18.3%) and HLC 395 (12.8%). General linear model univariate analysis method was used, position of the trapping method had no effect on mosquito density catch (DF = 4, F = 35.596, P = 0.78). Days variation had no effect on the collected density too (DF = 29, F = 4.789, P = 0.09). The sampling techniques had significant impact on the caught mosquito densities (DF = 4, F = 34.636, P < 0.0001). The Wilcoxon pair-wise comparison between mosquitoes collected in human landing catch and pit shelter was significant (Z = -3.849, P < 0.0001), human landing catch versus Indoor resting collection was not significant (Z = -0.502, P = 0.615), human landing catch versus odour-baited entry trap-man was significant (Z = -2.687, P = 0.007), human landing catch versus odour-baited entry trap-cow was significant (Z = -3.127, P = 0.002). Odour-baited traps with different baits and pit shelter have shown high productivity in collecting higher densities of mosquitoes than human landing catch. These abilities are the possibilities of replacing the human landing catch practices for sampling malaria vectors in areas with An. arabiensis as malaria vectors. Further evaluations of these sampling methods need to be investigated is other areas with different species

Evaluation of low density polyethylene and nylon for delivery of synthetic mosquito attractants.

BACKGROUND: Synthetic odour baits present an unexploited potential for sampling, surveillance and control of malaria and other mosquito vectors. However, application of such baits is impeded by the unavailability of robust odour delivery devices that perform reliably under field conditions. In the present study the suitability of low density polyethylene (LDPE) and nylon strips for dispensing synthetic attractants of host-seeking Anopheles gambiae mosquitoes was evaluated. METHODS: Baseline experiments assessed the numbers of An. gambiae mosquitoes caught in response to low density polyethylene (LDPE) sachets filled with attractants, attractant-treated nylon strips, control LDPE sachets, and control nylon strips placed in separate MM-X traps. Residual attraction of An. gambiae to attractant-treated nylon strips was determined subsequently. The effects of sheet thickness and surface area on numbers of mosquitoes caught in MM-X traps containing the synthetic kairomone blend dispensed from LDPE sachets and nylon strips were also evaluated. Various treatments were tested through randomized 4¿×¿4 Latin Square experimental designs under semi-field conditions in western Kenya. RESULTS: Attractant-treated nylon strips collected 5.6 times more An. gambiae mosquitoes than LDPE sachets filled with the same attractants. The attractant-impregnated nylon strips were consistently more attractive (76.95%; n¿=¿9,120) than sachets containing the same attractants (18.59%; n¿=¿2,203), control nylon strips (2.17%; n¿=¿257) and control LDPE sachets (2.29%; n¿=¿271) up to 40¿days post-treatment (P

Using a New Odour-Baited Device to Explore Options for Luring and Killing Outdoor-Biting Malaria Vectors: A Report on Design and Field Evaluation of the Mosquito Landing Box.

Mosquitoes that bite people outdoors can sustain malaria transmission even where effective indoor interventions such as bednets or indoor residual spraying are already widely used. Outdoor tools may therefore complement current indoor measures and improve control. We developed and evaluated a prototype mosquito control device, the 'Mosquito Landing Box' (MLB), which is baited with human odours and treated with mosquitocidal agents. The findings are used to explore technical options and challenges relevant to luring and killing outdoor-biting malaria vectors in endemic settings. Field experiments were conducted in Tanzania to assess if wild host-seeking mosquitoes 1) visited the MLBs, 2) stayed long or left shortly after arrival at the device, 3) visited the devices at times when humans were also outdoors, and 4) could be killed by contaminants applied on the devices. Odours suctioned from volunteer-occupied tents were also evaluated as a potential low-cost bait, by comparing baited and unbaited MLBs. There were significantly more Anopheles arabiensis, An. funestus, Culex and Mansonia mosquitoes visiting baited MLB than unbaited controls (P<=0.028). Increasing sampling frequency from every 120 min to 60 and 30 min led to an increase in vector catches of up to 3.6 fold (P<=0.002), indicating that many mosquitoes visited the device but left shortly afterwards. Outdoor host-seeking activity of malaria vectors peaked between 7:30 and 10:30pm, and between 4:30 and 6:00am, matching durations when locals were also outdoors. Maximum mortality of mosquitoes visiting MLBs sprayed or painted with formulations of candidate mosquitocidal agent (pirimiphos-methyl) was 51%. Odours from volunteer occupied tents attracted significantly more mosquitoes to MLBs than controls (P<0.001). While odour-baited devices such as the MLBs clearly have potential against outdoor-biting mosquitoes in communities where LLINs are used, candidate contaminants must be those that are effective at ultra-low doses even after short contact periods, since important vector species such as An. arabiensis make only brief visits to such devices. Natural human odours suctioned from occupied dwellings could constitute affordable sources of attractants to supplement odour baits for the devices. The killing agents used should be environmentally safe, long lasting, and have different modes of action (other than pyrethroids as used on LLINs), to curb the risk of physiological insecticide resistance

A Push-Pull System to Reduce House Entry of Malaria Mosquitoes.

Mosquitoes are the dominant vectors of pathogens that cause infectious diseases such as malaria, dengue, yellow fever and filariasis. Current vector control strategies often rely on the use of pyrethroids against which mosquitoes are increasingly developing resistance. Here, a push-pull system is presented, that operates by the simultaneous use of repellent and attractive volatile odorants. Experiments were carried out in a semi-field set-up: a traditional house which was constructed inside a screenhouse. The release of different repellent compounds, para-menthane-3,8-diol (PMD), catnip oil e.o. and delta-undecalactone, from the four corners of the house resulted in significant reductions of 45% to 81.5% in house entry of host-seeking malaria mosquitoes. The highest reductions in house entry (up to 95.5%), were achieved by simultaneously repelling mosquitoes from the house (push) and removing them from the experimental set-up using attractant-baited traps (pull). The outcome of this study suggests that a push-pull system based on attractive and repellent volatiles may successfully be employed to target mosquito vectors of human disease. Reductions in house entry of malaria vectors, of the magnitude that was achieved in these experiments, would likely affect malaria transmission. The repellents used are non-toxic and can be used safely in a human environment. Delta-undecalactone is a novel repellent that showed higher effectiveness than the established repellent PMD. These results encourage further development of the system for practical implementation in the field

Spatial heterogeneity of malaria vectors and malaria transmission risk estimated using odour-baited mosquito traps

Background Prior to the commencement of a large-scale malaria intervention study on Rusinga Island, western Kenya, intensive baseline surveillance of the mosquito population was performed using odour-baited traps. The survey aimed to determine the relative abundance and species composition of malaria vectors, and to measure seasonal and spatial heterogeneity in populations. Human malaria prevalence was combined with entomological data to provide information about malaria transmission risk before the intervention began. Materials and methods From September 2012 until June 2013, mosquito monitoring took place over successive six-week sampling periods. MM-X traps baited with attractant lures and carbon dioxide were used to collect mosquitoes from inside and outside houses, and a new random sample of 80 households was drawn for each sampling round. During the baseline period, malaria prevalence was measured twice in a randomly selected 10% of the human population. A QuickBird satellite image and digital elevation map were used to describe environmental features of the island. Mosquitoes were initially identified on the basis of morphology and anophelines were processed by PCR to confirm species identifications. Results Odour-baited MM-X traps proved to be a good tool for monitoring malaria vectors inside and outside houses. Using this tool a marked temporal and spatial heterogeneity was described for the malaria vector species Anopheles gambiae s.s., An. arabiensis and An. funestus. Regions of potentially high malaria transmission intensity were identified after mapping the distributions of malaria mosquitoes and Plasmodium-positive persons. Despite studying a range of environmental and topographical features, no strong associations were found between environmental variables and the presence or absence of adult Anopheles. Conclusions Malaria vectors and malaria prevalence are not homogeneously distributed across Rusinga Island; the risk of malaria transmission is therefore greater in some areas than others. The finding that environmental features were not closely associated with adult malaria vector distribution, indicates that other factors, such as house construction or the presence of livestock, may play a more important role in the decision of a female anopheline to approach the domestic environment of a particular house in search of a blood meal. The findings of this study demonstrate how trans-disciplinary data can be integrated to provide a better understanding of mosquito population dynamics and malaria transmission risk. Intensive mosquito monitoring before the commencement of, as well as during, a large-scale malaria intervention study, contributes valuable information which will be used in describing the eventual impact of the intervention