Risk Factors For Malaria Transmission Research Articles

Clinical burden of Plasmodium infection and associated risk factors among the local population of Chakwal, Punjab, Pakistan (2019–2023)

BackgroundThis study aimed to determine the clinical burden, spatial dynamics, and associated risk factors of Plasmodium infection among the natives of Chakwal, Punjab Pakistan from 2019 to 2023 to guide targeted screening and treatment interventions.MethodA community-based cross-sectional study was conducted using primary and secondary data sources. Participants were recruited using a multi-stage cluster sampling by taking informed consent for the primary data sources. Whereas a secondary dataset of Plasmodium infection was obtained from the database of surveyed hospitals after ethical consideration. All the participants living in the study area for at least 3 months were included, while patients with chronic illness were excluded. Sociodemographic and environmental data were collected using a structured questionnaire. Plasmodium infection was diagnosed using microscopy, rapid diagnostic tests (RDTs), and nested polymerase chain reaction (PCR) as the reference standard. A Zero-inflated negative binomial logistic regression model and interpolation of malaria distribution to environmental variables were employed to determine the association and spatiotemporal patterns of malaria in Chakwal.ResultsAmong the 2457 participants, the prevalence of Plasmodium vivax infection (99%) was significantly higher than P. falciparum (0.8%) and mixed infection (0.2%). Females had a higher infection rate than males and the infection rate was higher in adults (21–40 years) and children (0–20 years). Age category (61–100), P. vivax species, temperature, rainfall, monsoon season, and mixed infection factors were significantly associated (p < 0.05) with increased Plasmodium infection risk. Geospatial mapping indicated potential malaria hotspots in Sarkal Kasar, Chak Baili, Mulkwal, Chohan, and other close areas of the Potohar region.ConclusionThe clinical burden of P. vivax was the highest during monsoon season in Chakwal. Age, gender, climatic factors, and mixed infection were significant risk factors for malaria transmission in this region. Targeted screening and treatment strategies should prioritize identified hotspots and high-risk groups to effectively control malaria in Potohar region of Pakistan.

Risk factors of malaria transmission in mining workers in Muara Enim, South Sumatra, Indonesia

Eliminating malaria by 2030 is stated as goal three in the UN’s Sustainable Development Goals (SDGs). However, malaria still remains a significant public health problem. This study aims to identify the factors determining malaria transmission in artisanal or small-scale miner (ASM) communities in three villages: Tanjung Agung, Tanjung Lalang, and Penyandingan, located in the Tanjung Enim District, Muara Enim, South Sumatra, Indonesia. Researchers conducted a cross-sectional study involving 92 participants from the study area. They used a logistic regression model to investigate the risk factors related to malaria occurrence. The multivariable analysis revealed that age (Adjusted Prevalence Ratio (APR) = 7.989 with 95% CI 1.724–37.002) and mosquito breeding (APR = 7.685 with 95% CI 1.502–39.309) were risk factors for malaria. On the other hand, higher education (APR = 0.104 with 95% CI 0.027–0.403), the use of mosquito repellent (APR = 0.138 with 95% CI 0.035–0.549), and the condition of house walls (APR = 0.145 with 95% CI 0.0414–0.511) were identified as protective factors. The current study highlights age and mosquito breeding sites as risk factors for malaria. Additionally, higher education, insect repellent use, and the condition of house walls are protective factors against malaria. Therefore, reducing risk factors and increasing protective measures through effective communication, information, and education are highly recommended to eliminate malaria in mining areas.

A Cross-sectional study on the Prevalence, Behavioural and Environmental Risk Factors of Malaria Transmission in Two Senatorial Districts of Cross River State, Nigeria

There is a dearth of information on the behavioural and environmental risk factors enhancing malaria transmission in the Cross River State. This study, therefore, investigated the prevalence of malaria and the behavioural and environmental risk factors enhancing malaria parasite transmission in four Local Government Areas in Cross River State, Nigeria. The study employed a cross-sectional design involving 400 participants aged 5-60 years and was conducted between August and November 2021. Thick and thin blood films prepared were examined using microscopy at ×10 magnification. A standard questionnaire was also used to collect data on socio-demographic and environmental factors. The overall prevalence of malaria infection recorded in the study is 18.2% (73/400). All malaria infections were observed to be caused by Plasmodium falciparum. The prevalence of malaria infection was higher in the age group 11-20 years (22.2%) (P&lt;0.001). According to gender, males (23.3%) were more infected with malaria than females (12.9%) (P=0.007). An overall mean (±S.D) parasite density and parasites count of 250.00±18.80 and 15.60±1.20 parasite/μLof blood, respectively, was recorded in the study. In Calabar South Local Government Area (LGA), there was a negative correlation between the use of bed nets and malaria infection (r= -0.226) (P=0.024). Mud houses, use of bed nets, and the availability of refuse dump around households were significantly (P&lt;0.001) associated with the presence of mosquitoes. A negative correlation was observed in the relationship between the presence of mosquitoes and the use of insecticide in Calabar South LGA (r= -0.390) (P&lt;0.001). There was a negative correlation between the use of bed nets and the presence of mosquitos in Calabar Municipal (r= -0.286) and Obudu (r= -0.286) LGAs (P=0.004). In conclusion, this study suggests that malaria management efforts should take an integrated strategy that includes good environmental sanitation.

Assessment of knowledge of malaria and its control practices in mining and sugarcane growing regions of Western Kenya highlands.

Despite upscaled control efforts, deaths and hospitalization due to malaria remained high in counties of western Kenya highlands. This study assessed the knowledge of malaria in two rural communities, the control strategies they use, and their capacity to integrate the available control programs. A cross-sectional survey was carried out in two rural villages in November - December 2018. Focus group discussions and a questionnaire survey were carried out in 736 households. Frequencies and proportions were used for descriptive analysis while the Chi-square test was used to determine factors that were associated with knowledge of malaria at p ≤ 0.05. Ninety-seven percent of the respondents had knowledge of malaria and this was associated with the level of education attained (χ2 = 30.108; p > 0.0001). Bed net ownership was at 86% and 92% correctly identified its use. Draining stagnant water (53.9%) was the most cited environmental management practice. There was awareness of the risk factors of malaria transmission in the study sites. The local communities must be mobilized and empowered through EIC for the control practises to bear fruit against malaria transmission. However, more sensitization needs to be done to optimize the use of malaria control practices.

Risk factors for malaria in high incidence areas of Viet Nam: a case\u2013control study

BackgroundA key step to advancing the goal of malaria elimination in Viet Nam by 2030 is focusing limited resources for treatment and prevention to groups most at risk for malaria transmission.MethodsTo better understand risk factors for malaria transmission in central Viet Nam, a survey of 1000 malaria positive cases and 1000 malaria negative controls was conducted. Cases and controls were matched for age and gender and self-presented at commune health stations (CHS) in Binh Phuoc, Dak Nong and Dak Lak Provinces. Diagnoses were confirmed with microscopy, rapid diagnostic test and PCR. Participants were interviewed about 50 potential risk factors for malaria, which included information about occupation, forest visitation, travel, healthcare-seeking behaviour and prior use of anti-malaria interventions. Participants were enrolled by trained government health workers and the samples were analysed in Vietnamese government laboratories. Data were analysed by univariable, block-wise and multivariable logistic regression.ResultsAmong cases, 61.8% had Plasmodium falciparum, 35.2% Plasmodium vivax and 3% mixed species infections. Median (IQR) age was 27 (21–36) years and 91.2% were male. Twenty-five risk factors were associated with being a case and eleven with being a control. Multivariable analysis found that malaria cases correlated with forest workers, recent forest visitation, longer duration of illness, having a recorded fever, number of malaria infections in the past year, having had prior malaria treatment and having previously visited a clinic.ConclusionsThis study demonstrates the benefits of increased statistical power from matched controls in malaria surveillance studies, which allows identification of additional independent risk factors. It also illustrates an example of research partnership between academia and government to collect high quality data relevant to planning malaria elimination activities. Modifiable risk factors and implications of the findings for malaria elimination strategy are presented.

Risk Factors Analysis of Malaria Transmission at Cross-Boundaries Area in Menoreh Hills, Java, Indonesia.

Background:Risk factors of Malaria transmission at cross-boundaries area is important to be identified. This study aimed to identify the risk factors of Malaria transmission at cross-boundaries area in Menoreh Hills, Java, Indonesia.Methods:The design of the study was an observational study with a case-control design. Data on malaria cases and controls were obtained from the Primary Health Care in Menoreh. All malaria positive patients with clinical and laboratory examinations recorded in health services during 1 Jan 2015–31 Dec 2015. Overall, 138 cases and 138 controls were included. Several variables were collected such as altitude, night out behavior, the use of mosquito nets, nighttime bed, travel history, mosquito bite prevention activities, cattle ownership, distance to mosquito breeding site, etc. Data were obtained by structured questionnaires and observation. Data were analyzed by univariate, bivariate and multivariateResults:The altitude of house >500 m above sea level proved to be influential as a risk factor for Malaria (OR 3.62, 95% CI 1.61–8.16, P=0.002). Several variables were identified as a risk factor of Malaria such as the wall of the house from bamboo/wood, no insecticide and distance of house <100 m from mosquito breeding site.Conclusion:An awareness for the local health sector particularly to provide a recommendation for house construction to protect a community from Malaria transmission.

Identification of Anopheles sp. at Cibenda Urban Village Parigi Sub-District Pangandaran District

Malaria is an endemic parasitic disease that attacks countries with dense populations, which can reappear according to changes in natural phenomena, for example following environmental changes related to the growth of Anopheles sp. Anopheles sp. mosquitoes act as malaria vectors in the Southeast Asia region. Identification of Anopheles sp. species. is an important step to recognize the characteristics of various types of Anopheles sp. mosquito. Cibenda Village is located in the lowlands and borders the coast to be the mouth of the river and the waters of the Indonesian Ocean which allows the Anopheles sp. breeding. This study aims to determine the presence of Anopheles sp. in Cibenda Urban Village Parigi Sub District Pangandaran District as a risk factor for malaria transmission. This research is a descriptive research. The data obtained is presented in the form of tables and narratives. The examination method used is a microscopic methode. The conclusions of this study are founded of Anopheles sundaicus, Anopheles barbirostris, Anopheles subpictus, Anopheles vagus in in Cibenda Urban Village Parigi Sub District Pangandaran District which have potential as risk factors for malaria transmission.

Environmental and socioeconomic analysis of malaria transmission in the Brazilian Amazon, 2010–2015

ABSTRACTOBJECTIVE To analyze the environmental and socioeconomic risk factors of malaria transmission at municipality level, from 2010 to 2015, in the Brazilian Amazon.METHODS The municipalities were stratified into high, moderate, and low transmission based on the annual parasite incidence. A multinomial logistic regression that compared low with medium transmission and low with high transmission was performed. For each category, three models were analyzed: one only with socioeconomic risk factors (Gini index, illiteracy, number of mines and indigenous areas); a second with the environmental factors (forest coverage and length of the wet season); and a third with all covariates (full model).RESULTS The full model showed the best performance. The most important risks factors for high transmission were Gini index, length of the wet season and illiteracy, OR 2.06 (95%CI 1.19–3.56), 1.73 (95%CI 1.19–2.51) and 1.10 (95%CI 1.03–1.17), respectively. The medium transmission showed a weaker influence of the risk factors, being illiteracy, forest coverage and indigenous areas statistically significant but with marginal influence.CONCLUSIONS As a disease of poverty, the reduction in wealth inequalities and, therefore, health inequalities, could reduce the transmission considerably. Besides, environmental risk factors as length of the wet season should be considered in the planning, prevention and control. Municipality-level and fine-scale analysis should be done together to improve the knowledge of the local dynamics of transmission.

Malaria prevention practices and associated environmental risk factors in a rural community in Wakiso district, Uganda.

BackgroundBesides use of insecticide-treated mosquito nets (ITNs) and indoor residual spraying (IRS), other complimentary measures including suitable housing structures, and environmental management that reduce breeding of malaria vectors, can be implemented at households to prevent the disease. However, most studies on malaria prevention have focused mainly on ITNs and IRS. The aim of this study was therefore to assess malaria prevention practices beyond ITNs and IRS, and associated environmental risk factors including housing structure in rural Wakiso district, Uganda.MethodsA clustered cross-sectional survey was conducted among 727 households in Wakiso district. Data were collected using an interviewer-administered questionnaire and observational checklist. The questionnaire assessed participants’ household practices on malaria prevention, whereas the checklist recorded environmental risk factors for malaria transmission, and structural condition of houses. Poisson regression modeling was used to identify factors associated with use of mosquito nets by households.ResultsOf the 727 households, 471 (64.8%) owned at least one mosquito net. Use of mosquito nets by households was higher with increasing education level of participants—primary (aPR = 1.27 [95% CI: 1.00–1.60]), secondary (ordinary level) (aPR = 1.47 [95% CI: 1.16–1.85]) and advanced level / tertiary (aPR = 1.55 [95% CI: 1.19–2.01]), and higher household income (aPR = 1.09 [95% CI: 1.00–1.20]). Additionally, participants who were not employed were less likely to have mosquito nets used in their households (aPR = 0.83 [95% CI: 0.70–0.98]). Houses that had undergone IRS in the previous 12 months were 42 (5.8%), while 220 (43.2%) households closed their windows before 6.00 pm. Environmental risk factors found at households included presence of vessels that could potentially hold water for mosquito breeding 414 (56.9%), and stagnant water in compounds 144 (19.8%). Several structural deficiencies on houses that could promote entry of mosquitoes were found such as lack of screening in ventilators 645 (94.7%), and external doors not fitting perfectly into walls hence potential for mosquito entry 305 (42.0%).ConclusionThere is need to increase coverage and utilisation of ITNs and IRS for malaria prevention in Wakiso district, Uganda. In addition, other malaria prevention strategies such as environmental management, and improving structural condition of houses are required to strengthen existing malaria prevention approaches.

Faktor Risiko Perilaku dan Lingkungan dalam Penularan Malaria di Pulau Sebatik, Kabupaten Nunukan, Kalimantan Timur

Malaria transmission is influenced by several factors, including parasites, human, mosquito and environment. In 2009, slide positive rate (SPR) in Puskesmas Aji Kuning, Sungai Nyamuk and Setabu in Sebatik Island were identified as amount 63,61%, 28,04% and 30,12% respectively, while the target malaria pre-elimination SPR &lt; 5%. The aim of this study was to determine the behavioral and environmental risk factors of malaria transmission. This is a cross sectional study and the number of sample were 101 respondents. The results showed that there was significant association between the habit of using mosquito nets, the habit of using mosquito coils, repellent and others, the respondent's house near breeding mosquitoes habitats and the respondent’s house near the cocoa/coffee plantation with the occurrence of malaria cases. Relative risk (RR) value were 2,0, 2,3, 2,9 and 1,7, respectively. Behavioral risk factors of malaria transmission were the habit of using a mosquito nets and habit of using mosquito coils, repellent and others. Environmental risk of malaria transmission were the house near mosquito breeding habitats, and the house near the cocoa and coffee plantation.

Malaria determining risk factors at the household level in two rural villages of mainland Equatorial Guinea

BackgroundAfter the introduction of an artemisinin-based combination therapy, the reduction of prevalence of malaria infections has shown a remarkable progress during the last decade. However due to the lack of a consistent malaria control programme and socioeconomic inequalities, Plasmodium infection is still one of the major cause of disease in Equatorial Guinea, namely in the rural communities. This study explored the associated risk factors of malaria transmission at the microeconomic level (households) in two rural villages of mainland Equatorial Guinea.MethodsThis survey involved 232 individuals living in 69 households located in two rural villages, Ngonamanga and Miyobo, of coastal and interior of Equatorial Guinea, respectively. Malaria prevalence was measured by PCR and parasitaemia level by optical microscopy; household socioeconomic status (SES) was measured based on house characteristics using a 2-step cluster analysis. Logistic regression analysis was performed to investigate the relationship of a diverse set of independent variables on being diagnosed with malaria and on showing high levels of parasitaemia.ResultsThe prevalence of Plasmodium spp. infection was 69%, with 80% of households having at least one parasitaemic member. The majority of houses have eaves (80%), walls of clay/wood (90%) and zinc roof (99%) and only 10% of them have basic sanitation facilities. The studied areas showed reduced rates of indoor residual spraying coverage (9%), and long-lasting insecticide-treated net ownership (35%), with none of these preventive tools showing any significant effects on malaria risk in these areas. Neither the risk of malaria infection (PCR positive result) or the development of high parasitaemia did show association with SES.ConclusionsThis study has contributed to reinforce the importance of living conditions associated to a high risk of malaria infection and vulnerability to develop high parasitaemia. This study also contributes to future malaria control interventions to be implemented in mainland Equatorial Guinea or in other countries with similar environmental conditions.

A qualitative study of community perception and acceptance of biological larviciding for malaria mosquito control in rural Burkina Faso

BackgroundVector and malaria parasite’s rising resistance against pyrethroid-impregnated bed nets and antimalarial drugs highlight the need for additional control measures. Larviciding against malaria vectors is experiencing a renaissance with the availability of environmentally friendly and target species-specific larvicides. In this study, we analyse the perception and acceptability of spraying surface water collections with the biological larvicide Bacillus thuringiensis israelensis in a single health district in Burkina Faso.MethodsA total of 12 focus group discussions and 12 key informant interviews were performed in 10 rural villages provided with coverage of various larvicide treatments (all breeding sites treated, the most productive breeding sites treated, and untreated control).ResultsRespondents’ knowledge about the major risk factors for malaria transmission was generally good. Most interviewees stated they performed personal protective measures against vector mosquitoes including the use of bed nets and sometimes mosquito coils and traditional repellents. The acceptance of larviciding in and around the villages was high and the majority of respondents reported a relief in mosquito nuisance and malarial episodes. There was high interest in the project and demand for future continuation.ConclusionThis study showed that larviciding interventions received positive resonance from the population. People showed a willingness to be involved and financially support the program. The positive environment with high acceptance for larviciding programs would facilitate routine implementation. An essential factor for the future success of such programs would be inclusion in regional or national malaria control guidelines.

Faktor Risiko Perilaku dan Lingkungan dalam Penularan Malaria di Pulau Sebatik, Kabupaten Nunukan, Kalimantan Timur

Malaria transmission is influenced by several factors, including parasites, human, mosquito and environment. In 2009, slide positive rate (SPR) in Puskesmas Aji Kuning, Sungai Nyamuk and Setabu in Sebatik Island were identified as amount 63,61%, 28,04% and 30,12% respectively, while the target malaria pre-elimination SPR < 5%. The aim of this study was to determine the behavioral and environmental risk factors of malaria transmission. This is a cross sectional study and the number of sample were 101 respondents. The results showed that there was significant association between the habit of using mosquito nets, the habit of using mosquito coils, repellent and others, the respondent's house near breeding mosquitoes habitats and the respondent’s house near the cocoa/coffee plantation with the occurrence of malaria cases. Relative risk (RR) value were 2,0, 2,3, 2,9 and 1,7, respectively. Behavioral risk factors of malaria transmission were the habit of using a mosquito nets and habit of using mosquito coils, repellent and others. Environmental risk of malaria transmission were the house near mosquito breeding habitats, and the house near the cocoa and coffee plantation.

MALARIA HUTAN DI PROVINSI KALIMANTAN TENGAH DAN KALIMANTAN SELATAN, INDONESIA TAHUN 2013

Forests malaria is one of the epidemiological prototypes related to ecological conditions. Major changes in the forest environment cause changes in the pattern of malaria transmission and the transmission of primate malarias to humans has made forest malaria more highlighted recently. During 2013, a cases finding of malaria and passive case detection have been conducted. Case finding of malaria was done by survey to residents around the forest and the people who work in the forestry sector. Passive case detection conducted in some health facilities in Central Kalimantan and South Kalimantan, in order to determine the extent of the transmission of primate malaria, Plasmodium knowlesi, to humans. The results presented in this paper is about the parasite rate of microscopic examination results in all locations and risk factors of malaria transmission. Results shown that the Slide Positivity Rate (SPR) at the village level ranged from 0% to 12%, and most infections occured at male and age of > 15 years. In Central Kalimantan, the results indicated no significant difference of SPR between the miners and non-miner (P <0,0001) with an OR of 7,25 (95% CI: 3,08 to 17,08). In South Kalimantan, there is a significant difference of SPR between loggers and non-loggers (P <0,0001) with an OR of 5,4 (95% CI: 3,1 to 9,5). In conclusion, forest is one of the suitable environment for malaria transmission in Central Kalimantan and South Kalimantan with the highest transmission is among adults and males. In Central Kalimantan, forest miner is five times more at risk of malaria than non-miners. Whereas in South Kalimantan, logger is seven times more at risk of malaria than non-logger. It is recommended that the local government should intensify malaria case finding surveillance in both occupation.

Systematized Literature Review on Spatial Analysis of Environmental Risk Factors of Malaria Transmission

Malaria is still the major parasitic disease in the world, with approximately 438,000 deaths in 2015. Environmental risk factors (ERF) have been widely studied, however, there are discrepancies in the results about their influence on malaria transmission. Recently, papers have been published about geospatial analysis of ERF of malaria to explain why malaria varies from place to place. Our primary objective was to identify the environmental variables most used in the geospatial analysis of malaria transmission. The secondary objective was to identify the geo-analytic methods and techniques, as well as geo-analytic statistics commonly related to ERF and malaria. We conducted a systematized review of articles published from January 2004 to March 2015, within Web of Science, Pubmed and LILACS databases. Initially 676 articles were found, after inclusion and exclusion criteria, 29 manuscripts were selected. Temperature, land use and land cover, surface moisture and vector breeding site were the most frequent included variables. As for geo-analytic methods, geostatistical models with Bayesian framework were the most applied. Kriging interpolations, Geographical Weighted Regression as well as Kulldorff’s spatial scan were the techniques more widely used. The main objective of many of these studies was to use these methods and techniques to create malaria risk maps. Spatial analysis performed with satellite images and georeferenced data are increasing in relevance due to the use of remote sensing and Geographic Information System. The combination of these new technologies identifies ERF more accurately, and the use of Bayesian geostatistical models allows a wide diffusion of malaria risk maps. It is known that temperature, humidity vegetation and vector breeding site play a critical role in malaria transmission; however, other environmental risk factors have also been identified. Risk maps have a tremendous potential to enhance the effectiveness of malaria-control programs.

Use of remote sensing to identify spatial risk factors for malaria in a region of declining transmission: a cross-sectional and longitudinal community survey

BackgroundThe burden of malaria has decreased dramatically within the past several years in parts of sub-Saharan Africa. Further malaria control will require targeted control strategies based on evidence of risk. The objective of this study was to identify environmental risk factors for malaria transmission using remote sensing technologies to guide malaria control interventions in a region of declining burden of malaria.MethodsSatellite images were used to construct a sampling frame for the random selection of households enrolled in prospective longitudinal and cross-sectional surveys of malaria parasitaemia in Southern Province, Zambia. A digital elevation model (DEM) was derived from the Shuttle Radar Topography Mission version 3 DEM and used for landscape characterization, including landforms, elevation, aspect, slope, topographic wetness, topographic position index and hydrological models of stream networks.ResultsA total of 768 individuals from 128 randomly selected households were enrolled over 21 months, from the end of the rainy season in April 2007 through December 2008. Of the 768 individuals tested, 117 (15.2%) were positive by malaria rapid diagnostic test (RDT). Individuals residing within 3.75 km of a third order stream were at increased risk of malaria. Households at elevations above the baseline elevation for the region were at decreasing risk of having RDT-positive residents. Households where new infections occurred were overlaid on a risk map of RDT positive households and incident infections were more likely to be located in high-risk areas derived from prevalence data. Based on the spatial risk map, targeting households in the top 80th percentile of malaria risk would require malaria control interventions directed to only 24% of the households.ConclusionsRemote sensing technologies can be used to target malaria control interventions in a region of declining malaria transmission in southern Zambia, enabling a more efficient use of resources for malaria elimination.

Malaria transmission and vector behaviour in a forested malaria focus in central Vietnam and the implications for vector control

BackgroundIn Vietnam, malaria is becoming progressively restricted to specific foci where human and vector characteristics alter the known malaria epidemiology, urging for alternative or adapted control strategies. Long-lasting insecticidal hammocks (LLIH) were designed and introduced in Ninh Thuan province, south-central Vietnam, to control malaria in the specific context of forest malaria. An entomological study in this specific forested environment was conducted to assess the behavioural patterns of forest and village vectors and to assess the spatio-temporal risk factors of malaria transmission in the province.MethodsFive entomological surveys were conducted in three villages in Ma Noi commune and in five villages in Phuoc Binh commune in Ninh Thuan Province, south-central Vietnam. Collections were made inside the village, at the plot near the slash-and-burn fields in the forest and on the way to the forest. All collected mosquito species were subjected to enzyme-linked immunosorbent assay (ELISA) to detect Plasmodium in the head-thoracic portion of individual mosquitoes after morphological identification. Collection data were analysed by use of correspondence and multivariate analyses.ResultsThe mosquito density in the study area was low with on average 3.7 anopheline bites per man-night and 17.4 culicine bites per man-night. Plasmodium-infected mosquitoes were only found in the forest and on the way to the forest. Malaria transmission in the forested malaria foci was spread over the entire night, from dusk to dawn, but was most intense in the early evening as nine of the 13 Plasmodium positive bites occurred before 21H. The annual entomological inoculation rate of Plasmodium falciparum was 2.2 infective bites per person-year to which Anopheles dirus s.s. and Anopheles minimus s.s. contributed. The Plasmodium vivax annual entomological inoculation rate was 2.5 infective bites per person-year with Anopheles sawadwongporni, Anopheles dirus s.s. and Anopheles pampanai as vectors.ConclusionThe vector behaviour and spatio-temporal patterns of malaria transmission in Southeast Asia impose new challenges when changing objectives from control to elimination of malaria and make it necessary to focus not only on the known main vector species. Moreover, effective tools to prevent malaria transmission in the early evening and in the early morning, when the treated bed net cannot be used, need to be developed.

Temporal and spatial patterns of malaria reinfection in northeastern Venezuela.

We stratified the risk of malaria transmission (Plasmodium vivax) in 35 villages along a coastal range in northeastern Venezuela (51 km2) where the main vector is the mosquito Anopheles aquasalis. After 20 years without local malaria transmission, reinfection of the entire area occurred from May to December 1985 by local (continuous) and jump (discontinuous) dispersal. Epidemiologic, environmental, and vector variables were investigated with the aid of a Geographic Information System. Risk factors for malaria transmission were human population density, proximity to pre-adult mosquito habitats (< 500 m), and the number of pre-adult habitats nearby. Most inhabitants, immature mosquito habitats, and malaria cases were located at low elevations and on gentle slopes. High prevalence of malaria during the dry seasons was associated with the presence of permanent bodies of water containing An. aquasalis. Occurrence of a La Niña event in 1988 (wet and cool phase of the El Niño Southern Oscillation) triggered malaria transmission to unusually high levels, consolidating infection in the area, and rendering traditional control efforts useless. We recommend tracking malaria persistence per village and associated risk factors as methods to reduce the cost of malaria control programs.

Risk factors for malaria transmission in a hypoendemic malarious community in Bataan, the Philippines

Risk factors for malaria transmission in a hypoendemic malarious community in Bataan, the Philippines