Malarial Transmission Research Articles

What is the burden of submicroscopic malaria in pregnancy in central India?

Background:Conventional microscopy underestimates the burden of malarial infection when compared with molecular diagnosis using polymerase chain reaction (PCR)-based methods. Lower density parasitemias serve as a reservoir for infection. We evaluated the prevalence of submicroscopic infections in an area of unstable malarial transmission in India and determined whether these infections negatively impacted maternal or fetal outcomes.Methods:This cross-sectional study (2007–2008) was undertaken in two districts of Chhattisgarh, recruiting women from both antenatal clinics (ANCs) and delivery units (DUs). For ANC/DU subjects, peripheral/placental blood, respectively, was obtained for conventional microscopy and collected onto filter paper for PCR analysis.Results:There were 3425 pregnant women, including 2477 ANC subjects and 948 DU subjects who had both microscopic and PCR samples available. Polymerase chain reaction detected significantly more Plasmodium infections than traditional light microscopy both from peripheral (3·4 vs 1·2%; OR 2·9, 95% confidence intervals (CIs) 1·9–4·5) and placental (4·2 vs 1·7%; OR 2·5, 95% CIs 1·4–4·8) blood samples. Submicroscopic infections were not associated with anemia or severe maternal anemia among ANC or DU participants and were not associated with low birth weight (LBW) among DU participants. In contrast, microscopically detected infections were associated with severe anemia and LBW.Conclusions:In this area of unstable malarial transmission from India, submicroscopic infections did not identify a set of pregnant women at increased risk for anemia or LBW. Until PCR techniques become much less expensive and available as a point of care test for the field setting, its use will be limited for malarial detection.

Prevalence of mosquito-borne Plasmodium infection in patients attending fever clinic in a tertiary-care teaching hospital, western India

Background: Malaria is a serious vector-borne parasitic infection worldwide in distribution, and it is still one of the important causes of morbidity and mortality in India. In a developing country such as India, it has dramatic socioeconomic consequences. Objective: To study the prevalence of fever cases being diagnosed as malaria and to determine the trend of malaria. Materials and Methods: The blood samples of about 2,047 patients who presented with fever between the time period of May 2014 and April 2015 were examined by peripheral blood smear (PBS) for malaria. Result: In this study, the blood samples of 2,047 fever cases suspected for malaria were sent for diagnosis to a microbiology laboratory in a tertiary-care teaching hospital. Among those, 48 (2.34%) of them showed positivity for malaria. According to the types of Plasmodium spp., Plasmodium vivax and Plasmodium falciparum accounted for 95.83% and 4.17% of malaria cases, respectively. The prevalence of malarial infection exhibited seasonal trend with many cases from the month of May to November with a peak in September. Malaria was reported in all age groups and both sexes, but commonly affected age group were between 21 and 30 years of age, and male patients were affected more than two times than the female patients. Conclusion: This study about the survey on malaria reflected seasonal malarial transmission, and P. vivax was the most common type of malaria parasite. The lower socioeconomic and the younger aged groups were the mostly affected, causing serious health problems.

The epidemiology of imported malaria in Taiwan between 2002-2013: the importance of sensitive surveillance and implications for pre-travel medical advice.

The purpose of this study was to assess the epidemiology of imported malaria in Taiwan between 2002 and 2013. We analyzed the national data recorded by the Taiwan Centers for Disease Control (Taiwan CDC). Malaria cases were diagnosed by blood films, polymerase chain reaction, or rapid diagnostic tests. The risk of re-establishment of malarial transmission in Taiwan was assessed. A total of 229 malaria cases were included in our analysis. All of the cases were imported. One hundred and ninety-two cases (84%) were diagnosed within 13 days of the start of symptoms/signs; 43% of these cases were acquired in Africa and 44% were acquired in Asia. Plasmodium falciparum was responsible for the majority (56%) of these cases. Travel to an endemic area was associated with the acquisition of malaria. The malaria importation rate was 2.36 per 1,000,000 travelers (range 1.20–5.74). The reproductive number under control (Rc) was 0. No endemic transmission of malaria in Taiwan was identified. This study suggests that a vigilant surveillance system, vector-control efforts, case management, and an educational approach focused on travelers and immigrants who visit malaria endemic countries are needed to prevent outbreaks and sustain the elimination of malaria in Taiwan.

Diversity and population structure of Plasmodium falciparum in Thailand based on the spatial and temporal haplotype patterns of the C-terminal 19-kDa domain of merozoite surface protein-1

BackgroundThe 19-kDa C-terminal region of the merozoite surface protein-1 of the human malaria parasite Plasmodium falciparum (PfMSP-119) constitutes the major component on the surface of merozoites and is considered as one of the leading candidates for asexual blood stage vaccines. Because the protein exhibits a level of sequence variation that may compromise the effectiveness of a vaccine, the global sequence diversity of PfMSP-119 has been subjected to extensive research, especially in malaria endemic areas. In Thailand, PfMSP-119 sequences have been derived from a single parasite population in Tak province, located along the Thailand-Myanmar border, since 1995. However, the extent of sequence variation and the spatiotemporal patterns of the MSP-119 haplotypes along the Thai borders with Laos and Cambodia are unknown.MethodsSixty-three isolates of P. falciparum from five geographically isolated populations along the Thai borders with Myanmar, Laos and Cambodia in three transmission seasons between 2002 and 2008 were collected and culture-adapted. The msp-1 gene block 17 was sequenced and analysed for the allelic diversity, frequency and distribution patterns of PfMSP-119 haplotypes in individual populations. The PfMSP-119 haplotype patterns were then compared between parasite populations to infer the population structure and genetic differentiation of the malaria parasite.ResultsFive conserved polymorphic positions, which accounted for five distinct haplotypes, of PfMSP-119 were identified. Differences in the prevalence of PfMSP-119 haplotypes were detected in different geographical regions, with the highest levels of genetic diversity being found in the Kanchanaburi and Ranong provinces along the Thailand-Myanmar border and Trat province located at the Thailand-Cambodia border. Despite this variability, the distribution patterns of individual PfMSP-119 haplotypes seemed to be very similar across the country and over the three malarial transmission seasons, suggesting that gene flow may operate between parasite populations circulating in Thailand and the three neighboring countries.ConclusionThe major MSP-119 haplotypes of P. falciparum populations in all endemic populations during three transmission seasons in Thailand were identified, providing basic information on the common haplotypes of MSP-119 that is of use for malaria vaccine development and inferring the population structure of P. falciparum populations in Thailand.

PIN1 - Dynamic Modeling of Vector-Borne Diseases (VBD): The Example of Malaria

VBD, such as Chagas disease, dengue, or malaria, are transmitted from to humans by insects or other organisms and can be difficult to control. VBD transmission involves a combination of interactions among multiple factors including animal hosts, vectors, and humans. Dynamic modeling methodologies used to describe infectious disease transmission processes are amenable to a situation when infection and interaction of ≥1 species, as is the case of VBD. This work demonstrates the use of such methodology for the example of malaria. A dynamic, compartmental model was developed to simulate malarial disease transmission among the human and mosquito populations. The model consists of a mosquito population divided into susceptible, exposed but not infectious, and infectious and a human population including susceptible, exposed but not infectious, infectious but immune and infectious susceptible individuals. Parameters include human and mosquito birth rates and life expectancies, probabilities of disease transmission between humans and mosquitoes, and number of mosquito blood meals per day. The effect of anti-malarial treatment was modeled to assess epidemiologic outcomes under various scenarios. The model was solved analytically to determine the expected number of cases per person per year under each scenario. When transmission intensity is low, treatment of infected individuals with a therapy providing a subsequent 15-day period of immunity reduces the incidence of disease from 0.481 with no treatment to 0.475 cases per person per year (pppy). In moderate and very high transmission settings the incidence of disease is reduced from 2.385 to 2.171 cases pppy and 9.899 to 7.007 cases pppy, respectively. This model demonstrates the utility of dynamic modeling methodology to examine the spread of VBD. Several model parameters may be varied to assess the epidemiologic impact of a number of treatments and vector control mechanisms. These models may be expanded for cost-effectiveness analysis.

Can Iron Supplementation be Reconciled with Benefits and Risks in Areas Hyperendemic for Malaria?

Malaria is associated with about a million fatalities annually, largely among young children in zones of intense malarial transmission. The last thing needed would be measures that might increase the severity of clinical malaria. Thus, the finding in a field trial on Pemba Island, Tanzania, that routine oral iron supplementation produced adverse effects in iron-sufficient subjects had a ripple effect throughout the international public health community; it has effectively paralyzed efforts to redress iron-deficiency anemia in malaria-endemic regions. From a Hippocratic perspective, we consider the de facto moratorium on oral supplementation in such circumstance as a prudent interim measure. Public health programs to combat iron-deficiency anemia cannot be denied indefinitely to malaria-endemic populations, but the universal campaigns of iron provision cannot simply resume in the manner of the past. Contemporary biological and epidemiological understanding of the coevolution of humans and their pathogens should be able to provide guidance within the context of the essential and harmful aspects of iron. From these evolutionary standpoints, we identify a series of unresolved dilemmas. Toward a way forward, we highlight the pros and cons, as well as possible directions toward short-term strengthening, within three domains: tailored oral iron compounds, iron administration targeted only to iron-deficient individuals through screening, and prudent use of antimalarial prophylaxis. Although the tension between the essentiality of iron for humans and its role in pathogen virulence looms through every consideration, this recognition is a starting point toward the weighing of appropriate options balancing benefits and safety.

Malaria Control in Andhra Pradesh: Case Study of a Tribal Primary Health Centre

Although India had some successes in controlling malaria from the time of Independence, it still faces a substantial socio-economic burden from this disease. This study presents a case study of a highly endemic Primary Health Centre (PHC) with an Annual Parasite Incidence (API) of 30.9 in tribal regions of Andhra Pradesh. It reviews the various operations involved in malaria control from vector control methods like bed nets, insecticide spraying, anti-larval operations and surveillance methods of collecting blood smears of fever cases and related operations. Based on the data available with the health functionaries and household level surveys, it makes operational suggestions to improve the efficacy of control measures. It finds that the current focus is heavily skewed towards surveillance with inadequate attention towards vector control methods. Ensuring the adoption of vector control methods by the community will yield rich dividends in curtailing the malarial transmission process.

Spatial and Temporal Distribution of Plasmodium vivax Malaria in Korea Estimated with a Hierarchical Generalized Linear Model

ObjectivesThe spatial and temporal correlations were estimated to determine Plasmodium vivax malarial transmission pattern in Korea from 2001–2011 with the hierarchical generalized linear model. MethodsMalaria cases reported to the Korea Centers for Disease Control and Prevention from 2001 to 2011 were analyzed with descriptive statistics and the incidence was estimated according to age, sex, and year by the hierarchical generalized linear model. Spatial and temporal correlation was estimated and the best model was selected from nine models. Results were presented as diseases map according to age and sex. ResultsThe incidence according to age was highest in the 20–25-year-old group (244.52 infections/100,000). Mean ages of infected males and females were 31.0 years and 45.3 years with incidences 7.8 infections/100,000 and 7.1 infections/100,000 after estimation. The mean month for infection was mid-July with incidence 10.4 infections/100,000. The best-fit model showed that there was a spatial and temporal correlation in the malarial transmission. Incidence was very low or negligible in areas distant from the demilitarized zone between Republic of Korea and Democratic People's Republic of Korea (North Korea) if the 20–29-year-old male group was omitted in the diseases map. ConclusionMalarial transmission in a region in Korea was influenced by the incidence in adjacent regions in recent years. Since malaria in Korea mainly originates from mosquitoes from North Korea, there will be continuous decrease if there is no further outbreak in North Korea.

Habitat suitability of Anopheles vector species and association with human malaria in the Atlantic Forest in south-eastern Brazil

Every year, autochthonous cases of Plasmodium vivax malaria occur in low-endemicity areas of Vale do Ribeira in the south-eastern part of the Atlantic Forest, state of São Paulo, where Anopheles cruzii and Anopheles bellator are considered the primary vectors. However, other species in the subgenus Nyssorhynchus of Anopheles (e.g., Anopheles marajoara) are abundant and may participate in the dynamics of malarial transmission in that region. The objectives of the present study were to assess the spatial distribution of An. cruzii, An. bellator and An. marajoara and to associate the presence of these species with malaria cases in the municipalities of the Vale do Ribeira. Potential habitat suitability modelling was applied to determine both the spatial distribution of An. cruzii, An. bellator and An. marajoara and to establish the density of each species. Poisson regression was utilized to associate malaria cases with estimated vector densities. As a result, An. cruzii was correlated with the forested slopes of the Serra do Mar, An. bellator with the coastal plain and An. marajoara with the deforested areas. Moreover, both An. marajoara and An. cruzii were positively associated with malaria cases. Considering that An. marajoara was demonstrated to be a primary vector of human Plasmodium in the rural areas of the state of Amapá, more attention should be given to the species in the deforested areas of the Atlantic Forest, where it might be a secondary vector.

Human malaria in the highlands of Yemen.

<title/> Between June 2008 and March 2009, a cross-sectional study of human malaria was carried out in four governorates of Yemen, two (Taiz and Hodiedah) representing the country's highlands and the others (Dhamar and Raymah) the country's coastal plains/foothills. The main aims were to determine the prevalences of Plasmodium infection among 455 febrile patients presenting for care at participating health facilities and to investigate the potential risk factors for such infection. Malarial infection was detected in 78 (17·1%) of the investigated patients and was more likely to be detected among the febrile patients from the highlands than among those presenting in the coastal plains/foothills (22·6% v.13·9%; χ(2)=10·102; P=0·018). Binary logistic-regression models identified low household income [odds ratio (OR)=13·52; 95% confidence interval (CI)=2·62-69·67; P=0·002], living in a household with access to a water pump (OR=4·18; CI=1·60-10·96; P=0·004) and living in a household near a stream (OR=4·43; CI=1·35-14·56; P=0·014) as significant risk factors for malarial infection in the highlands. Low household income was the only significant risk factor identified for such infection in the coastal plains and foothills (OR = 8·20; CI=1·80-37·45; P=0·007). It is unclear why febrile patients in the highlands of Yemen are much more likely to be found to have malarial infection than their counterparts from the coastal plains and foothills. Although it is possible that malarial transmission is relatively intense in the highlands, it seems more likely that, compared with those who live at lower altitudes, those who live in the highlands are less immune to malaria, and therefore more likely to develop febrile illness following malarial infection. Whatever the cause of the symptomatic malarial infection commonly found in the highlands of Yemen, it is a matter of serious concern that should be addressed in the national strategy to control malaria.

Unravelling the relationships betweenAnopheles darlingi(Diptera: Culicidae) densities, environmental factors and malaria incidence: understanding the variable patterns of malarial transmission in French Guiana (South America)

Anopheles darlingi, one of the main malaria vectors in the Neotropics, is widely distributed in French Guiana, where malaria remains a major public-health problem. Elucidation of the relationships between the population dynamics of An. darlingi and local environmental factors would appear to be an essential factor in the epidemiology of human malaria in French Guiana and the design of effective vector-control strategies. In a recent investigation, longitudinal entomological surveys were carried out for 2-4 years in one village in each of three distinct endemic areas of French Guiana. Anopheles darlingi was always the anopheline mosquito that was most frequently caught on human bait, although its relative abundance (as a proportion of all the anophelines collected) and human biting rate (in bites/person-year) differed with the study site. Seasonality in the abundance of human-landing An. darlingi (with peaks at the end of the rainy season) was observed in only two of the three study sites. Just three An. darlingi were found positive for Plasmodium (either P. falciparum or P. vivax) circumsporozoite protein, giving entomological inoculation rates of 0·0-8·7 infectious bites/person-year. Curiously, no infected An. darlingi were collected in the village with the highest incidence of human malaria. Relationships between malaria incidence, An. darlingi densities, rainfall and water levels in the nearest rivers were found to be variable and apparently dependent on land-cover specificities that reflected the diversity and availability of habitats suitable for the development and reproduction of An. darlingi.

The role of Pvs28 in sporozoite development in Anopheles sinensis and its longevity in BALB/c mice

To develop a vivax malaria vaccine for blocking malarial transmission, the ookinete surface protein Pvs28 was cloned from Korean malaria patients using polymerase chain reaction. The Pvs28 gene consists of 726bp and encodes 241 amino acids. It was subcloned into the expression vector pQE30 and expressed in Escherichia coli. The expressed recombinant protein, rPvs28, has a molecular weight of about 28kDa in SDS–PAGE analysis. A monoclonal antibody against rPvs28 was produced using BALB/c mice. It inhibited sporozoite development in Anopheles sinensis mosquitoes (n=81) which is one of the malaria vectors in Korea, with relatively high antibody titer against rPv28 persisting for more than 6 months. These results indicate that rPvs28 induces an immune response in mice that effectively blocks sporozoite development in mosquitoes. Therefore it could be a vaccine candidate for preventing vivax malaria in Korea.

Wash-Resistance and Field Efficacy of Olyset™ Net, A Permethrin-Incorporated Long-Lasting Insecticidal Netting, AgainstAnopheles minimus-Transmitted Malaria in Assam, Northeastern India

The long-lasting insecticidal nets are ready-to-use, pretreated nets, which do not require retreatment for 4-5 years. Olyset nets that are made of high-density polyethylene monofilament yarn with 2% w/w permethrin incorporated (corresponding to 1 g/m(2)) are type-2 in which insecticide is incorporated into the polymers and are wash resistant. In these, insecticide migrates to the surface of the netting fiber to be bioavailable against mosquitoes and other insect pests. STUDY SITE AND OBJECTIVES: The present study was a village scale, field-based trial that was conducted in Plasmodium falciparum predominant area of Assam to assess feasibility, acceptability, and sustainability of this intervention against vector populations and disease transmission. We here report the research findings of Olyset net as an intervention against Anopheles minimus-transmitted malaria in foothill area of Assam for the first year of observations beginning July 2005 till June 2006. An. minimus, the mosquito vector species, was observed to be fully susceptible to permethrin. Follow-up investigations revealed that An. minimus mosquitoes had virtually disappeared in Olyset net villages, which was corroborated by data on human bait mosquito-landing catches. There was a consistent decline in the malarial incidence in Olyset net intervention villages, and the overall impact on the malarial transmission was significant compared to untreated net and no-net control villages for the corresponding study period. The bioavailability of insecticide on Olyset netting fiber was consistent (100% kill effect) up to 10 months of monitoring, and was observed to be wash resistant even after the 20th wash at fortnightly intervals. The Olyset nets were safe to use, wash resistant, and assessed to be operationally feasible, community-based intervention for sustainable management of disease vectors against malaria. Community compliance and acceptance was high, and users reported decreased nuisance due to biting mosquitoes.

Characteristics of Genetic Hitchhiking around Dihydrofolate Reductase Gene Associated with Pyrimethamine Resistance in Plasmodium falciparum Isolates from India

Sulfadoxine-pyrimethamine (SP) resistance in Plasmodium falciparum has been widespread across continents, causing the major hurdle of controlling malaria. Resistance is encoded mainly by point mutations in P. falciparum dihydrofolate reductase (pfdhfr) and dihydropteroate synthase (pfdhps) target genes. To study the origin and evolution of pyrimethamine resistance on the Indian subcontinent, microsatellite markers flanking the pfdhfr gene were mapped. Here we describe the characteristics of genetic hitchhiking around the pfdhfr gene among 190 P. falciparum isolates. These isolates were collected from five different geographical regions of India (Uttar Pradesh, Madhya Pradesh, Assam, Orissa, and Andaman and Nicobar Islands) where malarial transmission rates and levels of drug resistance vary across regions. Among the isolates, we observed a significant reduction in genetic variation in the +/-20-kb vicinity of the mutant pfdhfr alleles due to hitchhiking. This reduction in genetic diversity was more prominent around quadruple pfdhfr alleles (heterozygosity [H(e)] = 0.23) than around double (H(e) = 0.365) and single (H(e) = 0.465) mutant alleles. Asymmetry in the selective sweep flanking the pfdhfr alleles was observed with regional isolates, emphasizing the drug usage with the parasite population. All the pfdhfr alleles share a single microsatellite haplotype and seem to have originated from a single progenitor similar to that of Southeast Asian (Thailand) pfdhfr mutants. Results of the present study also indicate that the emergence of drug-resistant alleles is a recent phenomenon in India compared to Southeast Asian countries.

Where Ronald Ross (1857-1932) worked: the discovery of malarial transmission and the Plasmodium life cycle

Where Ronald Ross (1857-1932) worked: the discovery of malarial transmission and the Plasmodium life cycle

Cortisol, prolactin, cytokines and the susceptibility of pregnant Sudanese women toPlasmodium falciparummalaria

Understanding the hormonal and cytokine interactions that underlie susceptibility to the disease should be helpful in elucidating the pathogenesis of malaria during pregnancy. The current study was conducted in the Wad Medani hospital, in an area of central Sudan that is characterised by unstable malarial transmission. Its aims were to investigate the roles and interactions of cortisol, prolactin, interferon-gamma (IFN-gamma), interleukin-4 (IL-4) and interleukin-10 (IL-10) in pregnant women with Plasmodium falciparum malaria. The 82 pregnant subjects who were enrolled either had uncomplicated, P. falciparum malaria (the 47 cases) or were apparently uninfected and healthy women (the 37 controls) who were similar to the cases in terms of their mean age, weight, gravidity, gestational age and haemoglobin concentration. Compared with the controls, the cases were found to have significantly higher serum concentrations of total cortisol and IL-10 and significantly lower levels of prolactin and IFN-gamma (but similar concentrations of IL-4). The hormone and cytokine concentrations measured in the infected primigravidae were similar to those recorded in the infected multigravidae. Among the cases, there was a significant positive correlation between serum cortisol and IL-10 (r=0.188; P=0.025) and significant negative correlations between prolactin and both IL-4 (r=-0.175; P=0.038) and IL-10 (r=-0.186; P=0.027) but no significant correlation between prolactin and cortisol. During pregnancy, immune responses appear to be influenced by P. falciparum infections, irrespective of parity. Cortisol, prolactin and some cytokines appear to be key mediators in the host response to P. ?falciparum infection, although further research on this subject is clearly needed.

Abandoning Presumptive Antimalarial Treatment for Febrile Children Aged Less Than Five Years—A Case of Running Before We Can Walk?

Background to the debate: Current guidelines recommend that all fever episodes in African children be treated presumptively with antimalarial drugs. But declining malarial transmission in parts of sub-Saharan Africa, declining proportions of fevers due to malaria, and the availability of rapid diagnostic tests mean it may be time for this policy to change. This debate examines whether enough evidence exists to support abandoning presumptive treatment and whether African health systems have the capacity to support a shift toward laboratory-confirmed rather than presumptive diagnosis and treatment of malaria in children under five.

Time To Move from Presumptive Malaria Treatment to Laboratory-Confirmed Diagnosis and Treatment in African Children with Fever

Background to the debate: Current guidelines recommend that all fever episodes in African children be treated presumptively with antimalarial drugs. But declining malarial transmission in parts of sub-Saharan Africa, declining proportions of fevers due to malaria, and the availability of rapid diagnostic tests mean it may be time for this policy to change. This debate examines whether enough evidence exists to support abandoning presumptive treatment and whether African health systems have the capacity to support a shift toward laboratory-confirmed rather than presumptive diagnosis and treatment of malaria in children under five.

Malaria in pregnancy in an area of stable and intense transmission: is it asymptomatic?

To report a study of the signs and symptoms of malarial infection during pregnancy in an area of stable and intense transmission. As part of a clinical trial, to assess the efficacy and safety of four antimalarial drug regimens in pregnant women, we collected clinical and laboratory data from 900 parasitaemic pregnant women and 223 non-parasitaemic pregnant women who attended an antenatal clinic at a district hospital in Ghana. Frequencies of signs and symptoms were calculated and their association with the level of parasitaemia was assessed using multivariate logistic regression. History of fever (7.8%vs. 44.4%; P < 0.0001), headache (12.5%vs. 43.9%; P < 0.0001), vomiting (0 vs. 11.5%; P = 0.01), malaise (1.6%vs. 31.6%; P < 0.0001) dizziness (0%vs. 23%; P < 0.0001) and fatigue (0%vs. 22.5%; P < 0.0001) was substantially higher in parasitaemic primigravidae than in aparasitaemic primigravid women. Similar differences in the distribution of the symptoms and signs were observed between parasitaemic and aparasitaemic multigravid women. The proportion of women with elevated concentrations of aspartate aminotransferase, alanine aminotransferase and total bilirubin and its fractions was also higher in parasitaemic than in non-parasitaemic women. In areas of stable malarial transmission, malaria in pregnancy is often symptomatic. Although the symptoms are mostly non-specific, careful recording of history may be useful to identify women who need a confirmatory test and an effective antimalarial treatment.

Using modelling to assess the risk of malarial infection during the dry season, on a local scale in an endemic area of rural Burkina Faso

Mathematical modelling has been used to assess the level of malarial transmission, during the dry season, in Nouna province, in north-western Burkina Faso. The data used were collected, at four sites (one semi-urban and three rural), from 867 children aged 6-60 months who were randomly selected. Almost all of the children (850) completed the follow-up, which involved the active detection of malaria (i.e. febrile, smear-positive malarial infection) throughout a single dry season (December 2003-May 2004). Light traps were used to sample the local populations of Anopheles vectors, in order to estimate the daily biting rate. The mathematical model was then used to simulate the incidence of malaria, which was compared with the observed incidence. At all four study sites, new cases of malaria were observed throughout the dry season, although the level of transmission was low. The monthly incidence of malaria estimated using the mathematical model was very close to the observed incidence. The fit was sensitive to daily mosquito survival and daily human parasite clearance. In Nouna province, effective interventions to prevent malaria should not be confined to the rainy season but must continue throughout the year. The focus should be on the clearance of parasitaemias, by the use of effective drugs, and on decreasing vector survival, by the use of vector-control methods.