Longitudinal follow‐up of malaria transmission dynamics in two villages in a Sahelian area of Niger during a nationwide insecticide‐treated bednet distribution programme

Malaria transmission was monitored in two villages in the Sahel zone of Niger over 4 years. During this period, a nationwide vector control programme was carried out in which insecticide‐treated bednets were distributed free to mothers of children aged <5 years. Anopheles gambiae and Anopheles arabiensis (Diptera: Culicidae) were found to be the major malaria vectors. The dynamics of An. gambiae s.l. did not vary dramatically over the study period although the proportion of female mosquitoes found resting indoors decreased in both villages and, in one village, the parity rate and sporozoite index were significantly reduced after bednet distribution. By contrast with An. gambiae, the dynamics of Anopheles funestus altered greatly after the bednet distribution period, when adult density, endophagous rate and sporozoite rates decreased dramatically. Our observations highlight the importance of quantifying and monitoring the dynamics and infections of malaria vectors during large‐scale vector control interventions.     

Malaria in urban and rural Kinshasa: the entomological input

Abstract. Mosquitoes were collected on human bait over a 16-month period (September 1988 to December 1989) in an urban and a rural area of Kinshasa, Zaïre. P.falciparum malaria sporozoite rates were determined by ELISA. In the urban area Culex quinquefasciatus accounts for 96% of the 121 bites/ person/night (b/p/n). The only anopheline is Anopheles gambiae, sensu stricto, with an average of 5.1 b/p/n and a sporozoite rate of 1.86%. The entomological inoculation rate (EIR) averages 0.08 infective b/p/n. Malaria transmission is almost interrupted at the end of the dry season. In the rural area mosquito nuisance is small (20b/p/n), almost entirely due to six species of Anopheles including four vectors of malaria: An.gambiae (13.3 b/p/n), An.funestus (2.4b/p/n), An.nili (0.4b/p/n) and An.brunnipes (0.7b/p/n) with mean sporozoite rates of 7.85%, 6.60%, 6.63% and 0.53% respectively. An.paludis (0.4b/p/n) and An.hancocki (0.2b/p/n) were not found infective. Malaria transmission is intense and perennial: the overall EIR varies monthly between 0.60 and 3.29 infective b/p/n. The specific contributions of An.gambiae, An.funestus and An.nili average 1.07, 0.14 and 0.03 infective b/p/n respectively. Malaria transmission peaks during the rainy season in both study areas. The daily mean survival rates for An.gambiae were 0.91 and 0.78 in the rural and urban area, respectively. All An.gambiae examined belonged to the forest cytotype (Coluzzi et al., 1979). Through its effect on the sporozoite rate, the higher vector survival rate in the rural environment appears to be the major determinant of the greater malaria transmission rate in the rural area as compared to urban Kinshasa.     

Malaria vectors and transmission dynamics in coastal south-western Cameroon

Background

Malaria is a major public health problem in Cameroon. Unlike in the southern forested areas where the epidemiology of malaria has been better studied prior to the implementation of control activities, little is known about the distribution and role of anophelines in malaria transmission in the coastal areas.

Methods

A 12-month longitudinal entomological survey was conducted in Tiko, Limbe and Idenau from August 2001 to July 2002. Mosquitoes captured indoors on human volunteers were identified morphologically. Species of the Anopheles gambiae complex were identified using the polymerase chain reaction (PCR). Mosquito infectivity was detected by the enzyme-linked immunosorbent assay and PCR. Malariometric indices (plasmodic index, gametocytic index, parasite species prevalence) were determined in three age groups (<5 yrs, 5–15 yrs, >15 yrs) and followed-up once every three months.

Results

In all, 2,773 malaria vectors comprising Anopheles gambiae (78.2%), Anopheles funestus (17.4%) and Anopheles nili (7.4%) were captured. Anopheles melas was not anthropophagic. Anopheles gambiae had the highest infection rates. There were 287, 160 and 149 infective bites/person/year in Tiko, Limbe and Idenau, respectively. Anopheles gambiae accounted for 72.7%, An. funestus for 23% and An. nili for 4.3% of the transmission. The prevalence of malaria parasitaemia was 41.5% in children <5 years of age, 31.5% in those 5–15 years and 10.5% in those >15 years, and Plasmodium falciparum was the predominant parasite species.

Conclusion

Malaria transmission is perennial, rainfall dependent and An. melas does not contribute to transmission. These findings are important in the planning and implementation of malaria control activities in coastal Cameroon and West Africa.

     

Environmental Factors Associated with the Distribution of Anopheles gambiae s.s in Ghana; an Important Vector of Lymphatic Filariasis and Malaria

Anopheles gambiae s.s mosquitoes are important vectors of lymphatic filariasis (LF) and malaria in Ghana. To better understand their ecological aspects and influence on disease transmission, we examined the spatial distribution of the An. gambiae (M and S) molecular forms and associated environmental factors, and determined their relationship with disease prevalence. Published and current data available on the An. gambiae species in Ghana were collected in a database for analysis, and the study sites were georeferenced and mapped. Using the An. gambiae s.s sites, environmental data were derived from climate, vegetation and remote-sensed satellite sources, and disease prevalence data from existing LF and malaria maps in the literature. The data showed that An. gambiae M and S forms were sympatric in most locations. However, the S form predominated in the central region, while the M form predominated in the northern and coastal savanna regions. Bivariate and multiple regression analyses identified temperature as a key factor distinguishing their distributions. An. gambiae M was significantly correlated with LF, and 2.5 to 3 times more prevalent in the high LF zone than low to medium zones. There were no significant associations between high prevalence An. gambiae s.s locations and malaria. The distribution of the An. gambiae M and S forms and the diseases they transmit in Ghana appear to be distinct, driven by different environmental factors. This study provides useful baseline information for disease control, and future work on the An. gambiae s.s in Ghana.     

Application of hydrolysis probe analysis to identify clade types of the malaria vector mosquito Anopheles funestus sensu stricto from Muheza,northeastern Tanzania

A hydrolysis probe analysis (TaqMan assay) was used to study clade types in Anopheles funestus sensu stricto Giles, a major malaria vector in sub‐Saharan Africa, with specimens collected from Muheza in Tanga, northeastern Tanzania. A total of 186 An. funestus specimens were analysed, revealing that 176 (94.6%) were of clade I and 10 (5.4%) of clade II. These findings extend the distribution of clade type II from southern Mozambique and northern Zambia to northeastern Tanzania. The technique used can also be of great value in assessing the role and contribution of these clade types in malaria transmission and insecticide resistance frequencies for An. funestus s.s.     

Shifts in malaria vector species composition and transmission dynamics along the Kenyan coast over the past 20 years

Background

Over the past 20 years, numerous studies have investigated the ecology and behaviour of malaria vectors and Plasmodium falciparum malaria transmission on the coast of Kenya. Substantial progress has been made to control vector populations and reduce high malaria prevalence and severe disease. The goal of this paper was to examine trends over the past 20 years in Anopheles species composition, density, blood-feeding behaviour, and P. falciparum sporozoite transmission along the coast of Kenya.

Methods

Using data collected from 1990 to 2010, vector density, species composition, blood-feeding patterns, and malaria transmission intensity was examined along the Kenyan coast. Mosquitoes were identified to species, based on morphological characteristics and DNA extracted from Anopheles gambiae for amplification. Using negative binomial generalized estimating equations, mosquito abundance over the period were modelled while adjusting for season. A multiple logistic regression model was used to analyse the sporozoite rates.

Results

Results show that in some areas along the Kenyan coast, Anopheles arabiensis and Anopheles merus have replaced An. gambiae sensu stricto (s.s.) and Anopheles funestus as the major mosquito species. Further, there has been a shift from human to animal feeding for both An. gambiae sensu lato (s.l.) (99% to 16%) and An. funestus (100% to 3%), and P. falciparum sporozoite rates have significantly declined over the last 20 years, with the lowest sporozoite rates being observed in 2007 (0.19%) and 2008 (0.34%). There has been, on average, a significant reduction in the abundance of An. gambiae s.l. over the years (IRR?=?0.94, 95% CI 0.90–0.98), with the density standing at low levels of an average 0.006 mosquitoes/house in the year 2010.

Conclusion

Reductions in the densities of the major malaria vectors and a shift from human to animal feeding have contributed to the decreased burden of malaria along the Kenyan coast. Vector species composition remains heterogeneous but in many areas An. arabiensis has replaced An. gambiae as the major malaria vector. This has important implications for malaria epidemiology and control given that this vector predominately rests and feeds on humans outdoors. Strategies for vector control need to continue focusing on tools for protecting residents inside houses but additionally employ outdoor control tools because these are essential for further reducing the levels of malaria transmission.     

Shift in species composition in the Anopheles gambiae complex after implementation of long‐lasting insecticidal nets in Dielmo,Senegal

Long‐lasting insecticidal nets (LLINs) and indoor residual spraying (IRS) are the cornerstones of malaria vector control. However, the effectiveness of these control tools depends on vector ecology and behaviour, which also largely determine the efficacy of certain Anopheles mosquitoes (Diptera: Culicidae) as vectors. Malaria vectors in sub‐Saharan Africa are primarily species of the Anopheles gambiae complex, which present intraspecific differences in behaviour that affect how they respond to vector control tools. The focus of this study is the change in species composition in the An. gambiae complex after the implementation of LLINs in Dielmo, Senegal. The main findings referred to dramatic decreases in the proportions of Anopheles coluzzii and An. gambiae after the introduction of LLINs, and an increase in the proportion of Anopheles arabiensis. Two years after LLINs were first introduced, An. arabiensis remained the most prevalent species and An. gambiae had begun to rebound. This indicated a need to develop additional vector control tools that can target the full range of malaria vectors.     

Malaria vector composition and insecticide susceptibility status in Guinea Conakry,West Africa

This study provides data on malaria vector species composition and insecticide susceptibility status from three localities in Guinea Conakry. A total of 497 mosquitoes were collected resting indoors and morphologically identified as belonging to the Anopheles gambiae complex. The majority of these were An. gambiae s.s. (99.6%), but a small percentage (0.4%) were identified as Anopheles arabiensis. Thirty‐four Anopheles funestus s.s. were also collected. The molecular S form of An. gambiae s.s. was predominant over the M form in Siguiri (95%) and Boffa (97.4%), whereas at Mt Nimba the M form was more abundant (61.4%) than the S form (38.1%). One hybrid M/S specimen was recorded from Mt Nimba. Siguiri populations showed high levels of resistance to DDT, dieldrin and bendiocarb. Anopheles gambiae from Boffa were largely susceptible to the insecticides tested. At Mt Nimba, resistance to DDT and bendicocarb was detected. Biochemical enzyme analysis showed that an altered acetylcholinesterase is operating in the field at low levels. The frequency of the 1014F kdr allele in the An. gambiae S form was 0.24 at Siguiri and 0.14 at Mt Nimba. A single RR specimen was found in the M form. The heterogeneity in species composition and resistance profiles between sites requires vector control interventions to be tailored to each site based on the data collected from ongoing monitoring and surveillance.     

Permethrin-impregnated bednet effects on resting and feeding behaviour of lymphatic filariasis vector mosquitoes in Kenya

The impact of permethrin-impregnated bednets on resting and feeding behaviour of mosquito vectors of Wuchereria bancrofti, causing human lymphatic filariasis was studied in six pairs of villages (treated and untreated) before and after intervention. The study villages were in Kwale District, near the coast of Kenya, where Bancroftian filariasis is highly endemic, transmitted by a combination of both anopheline and culicine mosquito vectors. Mosquitoes were collected weekly in each village, indoors (using pyrethrum spray catches) and outdoors (using pit traps) during 3–4 months following the long rainy season. Of the filariasis vector species of mosquitoes collected in 1994 before intervention, 33.6% were members of the Anopheles gambiae complex, 30% were An. funestus and 36.4% were Culex quinquefasciatus. PCR analysis of the An. gambiae complex species collected in 1995 demonstrated that 98.5% were An. gambiae sensu stricto, 1% An. arabiensis and 0.5% An. merus. Introduction of impregnated bednets in 1995 significantly reduced the number of indoor-resting An. gambiae s.l. by 94.6% and An. funestus by 96.7%, but there was no change in the number of Cx quinquefasciatus collected indoors. The number of outdoor-resting An. gambiae s.l. was significantly reduced, whereas densities of An. funestus and Cx quinquefasciatus remained unaffected outdoors. ELISA analysis of mosquito bloodmeals showed a shift from human to animal feeding after the introduction of treated nets. The human blood index (HBI) for indoor resting Cx quinquefasciatus was reduced from 93.1% to 14.4%. Vector potential based on the HBI and mosquito density was estimated to be reduced by 99% for An. gambiae s.l., 98% for An. funestus and 97% for Cx quinquefasciatus and vectorial capacity would be suppressed even more by the impact on the vector survival rates (not measured). These results suggest that permethrin-impregnated bednets give effective personal protection against transmission of W. bancrofti by An. gambiae, An. funestus and Cx quinquefasciatus in East Africa.     

Bacterial communities associated with the midgut microbiota of wild Anopheles gambiae complex in Burkina Faso

Plasmodium falciparum is transmitted by mosquitoes from the Anopheles gambiae sensu lato (s.l) species complex and is responsible for severe forms of malaria. The composition of the mosquitoes’ microbiota plays a role in P. falciparum transmission, so we studied midgut bacterial communities of An. gambiae s.l from Burkina Faso. DNA was extracted from 17 pools of midgut of mosquitoes from the Anopheles gambiae complex from six localities in three climatic areas, including cotton-growing and cotton-free localities to include potential differences in insecticide selection pressure. The v3–v4 region of the 16S rRNA gene was targeted and sequenced using Illumina Miseq (2?×?250 nt). Diversity analysis was performed using QIIME and R software programs. The major bacterial phylum was Proteobacteria (97.2%) in all samples. The most abundant genera were Enterobacter (32.8%) and Aeromonas (29.8%), followed by Pseudomonas (11.8%), Acinetobacter (5.9%) and Thorsellia (2.2%). No statistical difference in operational taxonomic units (OTUs) was found (Kruskal–Wallis FDR—p?>?0.05) among the different areas, fields or localities. Richness and diversity indexes (observed OTUs, Chao1, Simpson and Shannon indexes) showed significant differences in the cotton-growing fields and in the agroclimatic zones, mainly in the Sudano-Sahelian area. OTUs from seven bacterial species that mediate refractoriness to Plasmodium infection in An. gambiae s.l were detected. The beta diversity analysis did not show any significant difference. Therefore, a same control strategy of using bacterial species refractoriness to Plasmodium to target mosquito midgut bacterial community and affect their fitness in malaria transmission may be valuable tool for future malaria control efforts in Burkina Faso.

     

Behavioural and insecticidal effects of organophosphate‐, carbamate‐ and pyrethroid‐treated mosquito nets against African malaria vectors

Three insecticides – the pyrethroid deltamethrin, the carbamate carbosulfan and the organophosphate chlorpyrifos‐methyl – were tested on mosquito nets in experimental huts to determine their potential for introduction as malaria control measures. Their behavioural effects and efficacy were examined in Anopheles gambiae Giles s.s. (Diptera: Culicidae) and Anopheles funestus Giles s.s. in Muheza, Tanzania, and in Anopheles arabiensis Patton and Culex quinquefasciatus Say in Moshi, Tanzania. A standardized dosage of 25 mg/m² plus high dosages of carbosulfan (50 mg/m², 100 mg/m² and 200 mg/m²) and chlorpyrifos‐methyl (100 mg/m²) were used to compare the three types of insecticide. At 25 mg/m², the rank order of the insecticides for insecticide‐induced mortality in wild An. gambiae and An. funestus was, respectively, carbosulfan (88%, 86%) > deltamethrin (79%, 78%) > chlorpyrifos‐methyl (35%, 53%). The rank order of the insecticides for blood‐feeding inhibition (reduction in the number of blood‐fed mosquitoes compared with control) in wild An. gambiae and An. funestus was deltamethrin > chlorpyrifos‐methyl > carbosulfan. Carbosulfan was particularly toxic to endophilic anophelines at 200 mg/m², killing 100% of An. gambiae and 98% of An. funestus that entered the huts. It was less effective against the more exophilic An. arabiensis (67% mortality) and carbamate‐resistant Cx quinquefasciatus (36% mortality). Carbosulfan deterred anophelines from entering huts, but did not deter carbamate‐resistant Cx quinquefasciatus. Deltamethrin reduced the proportion of insects engaged in blood‐feeding, probably as a consequence of contact irritancy, whereas carbosulfan seemed to provide personal protection through deterred entry or perhaps a spatial repellent action. Any deployment of carbosulfan as an individual treatment on nets should be carried out on a large scale to reduce the risk of diverting mosquitoes to unprotected individuals. Chlorpyrifos‐methyl was inferior to deltamethrin in terms of mortality and blood‐feeding inhibition and would be better deployed on a net in combination with a pyrethroid to control insecticide‐resistant mosquitoes.     

Wild Anopheles funestus Mosquito Genotypes Are Permissive for Infection with the Rodent Malaria Parasite,Plasmodium berghei

Background

Malaria parasites undergo complex developmental transitions within the mosquito vector. A commonly used laboratory model for studies of mosquito-malaria interaction is the rodent parasite, P. berghei. Anopheles funestus is a major malaria vector in sub-Saharan Africa but has received less attention than the sympatric species, Anopheles gambiae. The imminent completion of the A. funestus genome sequence will provide currently lacking molecular tools to describe malaria parasite interactions in this mosquito, but previous reports suggested that A. funestus is not permissive for P. berghei development.

Methods

An A. funestus population was generated in the laboratory by capturing female wild mosquitoes in Mali, allowing them to oviposit, and rearing the eggs to adults. These F1 progeny of wild mosquitoes were allowed to feed on mice infected with a fluorescent P. berghei strain. Fluorescence microscopy was used to track parasite development inside the mosquito, salivary gland sporozoites were tested for infectivity to mice, and parasite development in A. funestus was compared to A. gambiae.

Results

P. berghei oocysts were detectable on A. funestus midguts by 7 days post-infection. By 18–20 days post-infection, sporozoites had invaded the median and distal lateral lobes of the salivary glands, and hemocoel sporozoites were observed in the hemolymph. Mosquitoes were capable of infecting mice via bite, demonstrating that A. funestus supports the complete life cycle of P. berghei. In a random sample of wild mosquito genotypes, A. funestus prevalence of infection and the characteristics of parasite development were similar to that observed in A. gambiae-P. berghei infections.

Conclusions

The data presented in this study establish an experimental laboratory model for Plasmodium infection of A. funestus, an important vector of human malaria. Studying A. funestus-Plasmodium interactions is now feasible in a laboratory setting. This information lays the groundwork for exploitation of the awaited genome sequence of A. funestus.     

Reproductive Isolation among Sympatric Molecular Forms of An. gambiae from Inland Areas of South-Eastern Senegal

The Anopheles gambiae species complex includes at least seven morphologically indistinguishable species, one of which, Anopheles gambiae sensu stricto, is the primary mosquito vector responsible for the transmission of malaria across sub-Saharan Africa. Sympatric ecological diversification of An. gambiae s.s. is in progress within this complex, leading to the emergence of at least two incipient species (the M and S molecular forms now recognized as good species and named An. coluzzii and An. gambiae respectively) that show heterogeneous levels of divergence in most parts of Africa. However, this process seems to have broken down in coastal areas of West Africa at the extreme edge of the distribution. We undertook a longitudinal study to describe An. gambiae s.s. populations collected from two inland transects with different ecological characteristics in south-eastern Senegal. Analysis of samples collected from 20 sites across these two transects showed the M and S molecular forms coexisted at almost all sampled sites. Overall, similar hybridization rates (2.16% and 1.86%) were recorded in the two transects; sites with relatively high frequencies of M/S hybrids (up to 7%) were clustered toward the north-western part of both transects, often near urban settings. Estimated inbreeding indices for this putative speciation event varied spatially (range: 0.52–1), with hybridization rates being generally lower than expected under panmictic conditions. Such observations suggest substantial reproductive isolation between the M and S molecular forms, and further support the ongoing process of speciation in these inland areas. According to a recent reclassification of the An. gambiae complex, the M and S molecular forms from this zone correspond to An. coluzzii and An. gambiae, respectively. There is considerable evidence that these molecular forms differ in their behavioural and ecological characteristics. Detailed study of these characteristics will allow the development and implementation of better insect control strategies for combating malaria.     

Larval salinity tolerance of two members of the Anopheles funestus group

The Anopheles funestus group (Diptera: Culicidae) is one of the main species groups involved in malaria transmission in the Afrotropical regions. Basic research into this group has been limited because its members are eurygamic (they tend not to mate in confined spaces), which makes laboratory colonization difficult. Currently, only a few An. funestus Giles colonies are available and no colonies of other members of the group have been established. As information on the larval biology of members of the An. funestus group is limited, the present study aims to determine the effects of different salt concentrations on survival rates of the aquatic stages of two members of the An. funestus group, Anopheles funestus and Anopheles rivulorum Leeson. There were statistically significant negative trends in hatch rate and larval survival rate in An. funestus with increasing salt concentrations, with no larvae surviving to pupae at concentrations that included > 15% seawater. Anopheles rivulorum, by contrast, showed no significant trends in hatch rate or larval survival with increasing salt concentrations. This is the first report on salinity tolerance in An. rivulorum. A basic understanding of these variations in salinity tolerance provides vital information on the biology, ecology and colony rearing of members of the An. funestus group.     

Polymorphic chromosomal inversions in Anopheles moucheti,a major malaria vector in Central Africa

Anopheles moucheti Evans (Diptera: Culicidae) is a major vector of malaria in forested areas of Central Africa. However, few genetic tools are available for this species. The present study represents the first attempt to characterize chromosomes in An. moucheti females collected in Cameroon. Ovarian nurse cells contained polytene chromosomes, which were suitable for standard cytogenetic applications. The presence of three polymorphic chromosomal inversions in An. moucheti was revealed. Two of these inversions were located on the 2R chromosome arm. The homology between the 2R chromosome arms of An. moucheti and Anopheles gambiae Giles was established by fluorescent in situ hybridization of six An. gambiae genic sequences. Mapping of the probes on chromosomes of An. moucheti detected substantial gene order reshuffling between the two species. The presence of polytene chromosomes and polymorphic inversions in An. moucheti provides a new basis for further population genetic, taxonomic and ecological studies of this neglected malaria vector.     

Optimized Pan-species and Speciation Duplex Real-time PCR Assays for Plasmodium Parasites Detection in Malaria Vectors

Background

An accurate method for detecting malaria parasites in the mosquito’s vector remains an essential component in the vector control. The Enzyme linked immunosorbent assay specific for circumsporozoite protein (ELISA-CSP) is the gold standard method for the detection of malaria parasites in the vector even if it presents some limitations. Here, we optimized multiplex real-time PCR assays to accurately detect minor populations in mixed infection with multiple Plasmodium species in the African malaria vectors Anopheles gambiae and Anopheles funestus.

Methods

Complementary TaqMan-based real-time PCR assays that detect Plasmodium species using specific primers and probes were first evaluated on artificial mixtures of different targets inserted in plasmid constructs. The assays were further validated in comparison with the ELISA-CSP on 200 field caught Anopheles gambiae and Anopheles funestus mosquitoes collected in two localities in southern Benin.

Results

The validation of the duplex real-time PCR assays on the plasmid mixtures demonstrated robust specificity and sensitivity for detecting distinct targets. Using a panel of mosquito specimen, the real-time PCR showed a relatively high sensitivity (88.6%) and specificity (98%), compared to ELISA-CSP as the referent standard. The agreement between both methods was “excellent” (κ = 0.8, P<0.05). The relative quantification of Plasmodium DNA between the two Anopheles species analyzed showed no significant difference (P = 0, 2). All infected mosquito samples contained Plasmodium falciparum DNA and mixed infections with P. malariae and/or P. ovale were observed in 18.6% and 13.6% of An. gambiae and An. funestus respectively. Plasmodium vivax was found in none of the mosquito samples analyzed.

Conclusion

This study presents an optimized method for detecting the four Plasmodium species in the African malaria vectors. The study highlights substantial discordance with traditional ELISA-CSP pointing out the utility of employing an accurate molecular diagnostic tool for detecting malaria parasites in field mosquito populations.     

Simple flow cytometric detection of haemozoin containing leukocytes and erythrocytes for research on diagnosis, immunology and drug sensitivity testing

Background

Plasmodium falciparum malaria remains endemic in sub-Saharan Africa including Ghana. The epidemiology of malaria in special areas, such as mining areas needs to be monitored and controlled. Newmont Ghana Gold Limited is conducting mining activities in the Brong Ahafo Region of Ghana that may have an impact on the diseases such as malaria in the mining area.

Methods

Prior to the start of mining activities, a cross-sectional survey was conducted in 2006/2007 to determine malaria epidemiology, including malaria parasitaemia and anaemia among children < 5 years and monthly malaria transmission in a mining area of Ghana.

Results

A total of 1,671 households with a child less than five years were selected. About 50% of the household heads were males. The prevalence of any malaria parasitaemia was 22.8% (95% CI 20.8 - 24.9). Plasmodium falciparum represented 98.1% (95% CI 96.2 - 99.2) of parasitaemia. The geometric mean P. falciparum asexual parasite count was 1,602 (95% CI 1,140 - 2,252) and 1,195 (95% CI 985 - 1,449) among children < 24 months and ≥ 24 months respectively. Health insurance membership (OR 0.60, 95% CI 0.45 - 0.80, p = 0.001) and the least poor (OR 0.57, 95% CI 0.37 - 0.90, p = 0.001) were protected against malaria parasitaemia. The prevalence of anaemia was high among children < 24 months compared to children ≥ 24 months (44.1% (95% CI 40.0 - 48.3) and 23.8% (95% CI 21.2 - 26.5) respectively. About 69% (95% CI 66.3 - 70.9) of households own at least one ITN. The highest EIRs were record in May 2007 (669 ib/p/m) and June 2007 (826 ib/p/m). The EIR of Anopheles gambiae were generally higher than Anopheles funestus.

Conclusion

The baseline malaria epidemiology suggests a high malaria transmission in the mining area prior to the start of mining activities. Efforts at controlling malaria in this mining area have been intensified but could be enhanced with increased resources and partnerships between the government and the private sector.     

Spatio‐temporal variations of Anopheles coluzzii and An. gambiae and their Plasmodium infectivity rates in Lobito,Angola

From 2003 to 2007, entomological surveys were conducted in Lobito town (Benguela Province, Angola) to determine which Anopheles species were present and to identify the vectors responsible for malaria transmission in areas where workers of the Sonamet Company live. Two types of surveys were conducted: (1) time and space surveys in the low and upper parts of Lobito during the rainy and dry periods; (2) a two‐year longitudinal study in Sonamet workers' houses provided with long‐lasting insecticide‐treated nets (LLIN), “PermaNet,” along with the neighboring community. Both species, An. coluzzii (M molecular form) and An. gambiae (S molecular form), were collected. Anopheles coluzzii was predominant during the dry season in the low part of Lobito where larvae develop in natural ponds and temporary pools. However, during the rainy season, An. gambiae was found in higher proportions in the upper part of the town where larvae were collected in domestic water tanks built near houses. Anopheles melas and An. listeri were captured in higher numbers during the dry season and in the low part of Lobito where larvae develop in stagnant brackish water pools. The infectivity rates of An. gambiae s.l. varied from 0.90% to 3.41%.