Risk Of Plasmodium Falciparum Infection Research Articles

Influence of landscape heterogeneity on entomological and parasitological indices of malaria in Kisumu, Western Kenya

BackgroundIdentification and characterization of larval habitats, documentation of Anopheles spp. composition and abundance, and Plasmodium spp. infection burden are critical components of integrated vector management. The present study aimed to investigate the effect of landscape heterogeneity on entomological and parasitological indices of malaria in western Kenya.MethodsA cross-sectional entomological and parasitological survey was conducted along an altitudinal transect in three eco-epidemiological zones: lakeshore along the lakeside, hillside, and highland plateau during the wet and dry seasons in 2020 in Kisumu County, Kenya. Larval habitats for Anopheles mosquitoes were identified and characterized. Adult mosquitoes were sampled using pyrethrum spray catches (PSC). Finger prick blood samples were taken from residents and examined for malaria parasites by real-time PCR (RT-PCR).ResultsIncreased risk of Plasmodium falciparum infection was associated with residency in the lakeshore zone, school-age children, rainy season, and no ITNs (χ2 = 41.201, df = 9, P < 0.0001). Similarly, lakeshore zone and the rainy season significantly increased Anopheles spp. abundance. However, house structures such as wall type and whether the eave spaces were closed or open, as well as the use of ITNs, did not affect Anopheles spp. densities in the homes (χ2 = 38.695, df = 7, P < 0.0001). Anopheles funestus (41.8%) and An. arabiensis (29.1%) were the most abundant vectors in all zones. Sporozoite prevalence was 5.6% and 3.2% in the two species respectively. The lakeshore zone had the highest sporozoite prevalence (4.4%, 7/160) and inoculation rates (135.2 infective bites/person/year). High larval densities were significantly associated with lakeshore zone and hillside zones, animal hoof prints and tire truck larval habitats, wetland and pasture land, and the wet season. The larval habitat types differed significantly across the landscape zones and seasonality (χ2 = 1453.044, df = 298, P < 0.0001).ConclusionThe empirical evidence on the impact of landscape heterogeneity and seasonality on vector densities, parasite transmission, and Plasmodium infections in humans emphasizes the importance of tailoring specific adaptive environmental management interventions to specific landscape attributes to have a significant impact on transmission reduction.Graphical abstract

Prevalence of Plasmodium falciparum Infection among HIV Patients Attending Selected Hospitals in Niger State, Nigeria

Malaria and Acquired Immune Deficiency Syndrome (AIDS) are among the world’s greatest health problems and are concentrated in the tropical and sub-tropical regions of the world. Together, they are the cause of death of millions of people each year, hence they become a burden and a threat for development in India, Southern Asia, South America and Africa including Nigeria. The prevalence of malaria among HIV patients attending selected hospitals in Niger State, Nigeria was determined. A total of 300 HIV patients within the age range of 2-69years were enrolled, of which 217 were females and 83 were males. Four (4) mL of venous blood was drawn from each participant. The blood samples were examined for the presence of Plasmodium falciparum using thin and thick films while the CD4count was determined using flow cytometer (Partec Cyflow). Plasmodium falciparum was detected in 43 out of 300 participants with a prevalence of 14.3%.The prevalence was observed to be higher in males (18.07%) than in females (12.90%) and in the age group 1-10years (28.57%). Statistically, there was no association between Plasmodium falciparum infection with sex (p = 0.223) or age (p =0.253). The CD4 counts of all the participants ranges between 28-2000 cells/μL with a mean of 1111.40 + 739.589. Patients with Plasmodium falciparum infection had lower CD4 counts than those that were negative. Conclusively, HIV individuals with severe immunosuppression (CD4 counts &lt;200 cells/µL) are at higher risk of Plasmodium falciparum infection. Hence, HIV individuals should take all necessary measures to prevent the infection to avoid the negative impact.

Risk of Plasmodium falciparum infection in south-west Burkina Faso: potential impact of expanding eligibility for seasonal malaria chemoprevention

Burkina Faso has one of the highest malaria burdens in sub-Saharan Africa despite the mass deployment of insecticide-treated nets (ITNs) and use of seasonal malaria chemoprevention (SMC) in children aged up to 5 years. Identification of risk factors for Plasmodium falciparum infection in rural Burkina Faso could help to identify and target malaria control measures. A cross-sectional survey of 1,199 children and adults was conducted during the peak malaria transmission season in the Cascades Region of south-west Burkina Faso in 2017. Logistic regression was used to identify risk factors for microscopically confirmed P. falciparum infection. A malaria transmission dynamic model was used to determine the impact on malaria cases averted of administering SMC to children aged 5–15 year old. P. falciparum prevalence was 32.8% in the study population. Children aged 5 to < 10 years old were at 3.74 times the odds (95% CI = 2.68–5.22, P < 0.001) and children aged 10 to 15 years old at 3.14 times the odds (95% CI = 1.20–8.21, P = 0.02) of P. falciparum infection compared to children aged less than 5 years old. Administration of SMC to children aged up to 10 years is predicted to avert an additional 57 malaria cases per 1000 population per year (9.4% reduction) and administration to children aged up to 15 years would avert an additional 89 malaria cases per 1000 population per year (14.6% reduction) in the Cascades Region, assuming current coverage of pyrethroid-piperonyl butoxide ITNs. Malaria infections were high in all age strata, although highest in children aged 5 to 15 years, despite roll out of core malaria control interventions. Given the burden of infection in school-age children, extension of the eligibility criteria for SMC could help reduce the burden of malaria in Burkina Faso and other countries in the region.

Forest malaria in Cambodia: the occupational and spatial clustering of Plasmodium vivax and Plasmodium falciparum infection risk in a cross-sectional survey in Mondulkiri province, Cambodia

BackgroundAfter a marked reduction in malaria burden in Cambodia over the last decades, case numbers increased again in 2017–2018. In light of the national goal of malaria elimination by 2025, remaining pockets of high risk need to be well defined and strategies well-tailored to identify and target the persisting burden cost-effectively. This study presents species-specific prevalence estimates and risk stratification for a remote area in Cambodia.MethodsA cross-sectional survey was conducted in 17 villages in the high-incidence province Mondulkiri in the dry season (December 2017 to April 2018). 4200 randomly selected participants (2–80 years old) were tested for Plasmodium infection by PCR. Risk of infection was associated with questionnaire-derived covariates and spatially stratified based on household GPS coordinates.ResultsThe prevalence of PCR-detectable Plasmodium infection was 8.3% (349/4200) and was more than twice as high for Plasmodium vivax (6.4%, 268) than for Plasmodium falciparum (3.0%, 125, p < 0.001). 97.8% (262/268) of P. vivax and 92.8% (116/125, p < 0.05) of P. falciparum infections were neither accompanied by symptoms at the time of the interview nor detected by microscopy or RDT. Recent travels to forest sites (aOR 2.17, p < 0.01) and forest work (aOR 2.88, p < 0.001) were particularly strong risk factors and risk profiles for both species were similar. Large village-level differences in prevalence of Plasmodium infection were observed, ranging from 0.6% outside the forest to 40.4% inside. Residing in villages at the forest fringe or inside the forest compared to outside was associated with risk of infection (aOR 2.14 and 12.47, p < 0.001). Villages inside the forest formed spatial hotspots of infection despite adjustment for the other risk factors.ConclusionsPersisting pockets of high malaria risk were detected in forested areas and in sub-populations engaging in forest-related activities. High levels of asymptomatic infections suggest the need of better case detection plans and the predominance of P. vivax the implementation of radical cure. In villages inside the forest, within-village exposure was indicated in addition to risk due to forest activities. Village-level stratification of targeted interventions based on forest proximity could render the elimination efforts more cost-effective and successful.

Association of Inhibitory Killer Cell Immunoglobulin-like Receptor Ligands With Higher Plasmodium falciparum Parasite Prevalence.

Killer cell immunoglobulin-like receptors (KIRs) and their HLA ligands influence the outcome of many infectious diseases. We analyzed the relationship of compound KIR-HLA genotypes with risk of Plasmodium falciparum infection in a longitudinal cohort of 890 Ugandan individuals. We found that presence of HLA-C2 and HLA-Bw4, ligands for inhibitory KIR2DL1 and KIR3DL1, respectively, increased the likelihood of P. falciparum parasitemia in an additive manner. Individuals homozygous for HLA-C2, which mediates strong inhibition via KIR2DL1, had the highest odds of parasitemia, HLA-C1/C2 heterozygotes had intermediate odds, and individuals homozygous for HLA-C1, which mediates weaker inhibition through KIR2DL2/3, had the lowest odds of parasitemia. In addition, higher surface expression of HLA-C, the ligand for inhibitory KIR2DL1/2/3, was associated with a higher likelihood of parasitemia. Together these data indicate that stronger KIR-mediated inhibition confers a higher risk of P. falciparum parasitemia and suggest that KIR-expressing effector cells play a role in mediating antiparasite immunity.

Effect of immune regulatory pathways after immunization with GMZ2 malaria vaccine candidate in healthy lifelong malaria-exposed adults

BackgroundDespite appreciable immunogenicity in malaria-naive populations, many candidate malaria vaccines are considerably less immunogenic in malaria-exposed populations. This could reflect induction of immune regulatory mechanisms involving Human Leukocyte Antigen G (HLA-G), regulatory T (Treg), and regulatory B (Breg) cells. Here, we addressed the question whether there is correlation between these immune regulatory pathways and both plasmablast frequencies and vaccine-specific IgG concentrations. MethodsFifty Gabonese adults with lifelong exposure to Plasmodium spp were randomized to receive three doses of either 30 µg or 100 µg GMZ2-CAF01, or 100 µg GMZ2-alum, or control vaccine (rabies vaccine) at 4-week intervals. Only plasma and peripheral blood mononuclear cells isolated from blood samples collected before (D0) and 28 days after the third vaccination (D84) of 35 participants were used to measure sHLA-G levels and anti-GMZ2 IgG concentrations, and to quantify Treg, Breg and plasmablast cells. Vaccine efficacy was assessed using controlled human malaria infection (CHMI) by direct venous inoculation of Plasmodium falciparum sporozoites (PfSPZ Challenge). ResultsThe sHLA-G concentration increased from D0 to D84 in all GMZ2 vaccinated participants and in the control group, whereas Treg frequencies increased only in those receiving 30 µg or 100 µg GMZ2-CAF01. The sHLA-G level on D84 was associated with a decrease of the anti-GMZ2 IgG concentration, whereas Treg frequencies on D0 or on D84, and Breg frequency on D84 were associated with lower plasmablast frequencies. Importantly, having a D84:D0 ratio of sHLA-G above the median was associated with an increased risk of P. falciparum infection after sporozoites injection. ConclusionRegulatory immune responses are induced following immunization. Stronger sHLA-G and Treg immune responses may suppress vaccine induced immune responses, and the magnitude of the sHLA-G response increased the risk of Plasmodium falciparum infection after CHMI. These findings could have implications for the design and testing of malaria vaccine candidates in semi-immune individuals.

Evidence of positively selected G6PD A- allele reduces risk of Plasmodium falciparum infection in African population on Bioko Island.

BackgroundGlucose‐6‐phosphate dehydrogenase (G6PD) is an essential enzyme that protects red blood cells from oxidative damage. Although G6PD‐deficient alleles appear to confer a protective effect of malaria, the link with clinical protection against Plasmodium infection is conflicting.MethodsA case–control study was conducted on Bioko Island, Equatorial Guinea and further genotyping analysis used to detect natural selection of the G6PD A‐ allele.ResultsOur results showed G6PD A‐ allele could significantly reduce the risk of Plasmodium falciparum infection in male individuals (adjusted odds ratio [AOR], 0.43; 95% confidence interval [CI], 0.20–0.93; p < .05) and homozygous female individuals (AOR, 0.11; 95% CI, 0.01–0.84; p < .05). Additionally, the parasite densities were significantly different in the individuals with different G6PD A‐ alleles and individual levels of G6PD enzyme activity. The pattern of linkage disequilibrium and results of the long‐range haplotype test revealed a strong selective signature in the region encompassing the G6PD A‐ allele over the past 6,250 years. The network of inferred haplotypes suggested a single origin of the G6PD A‐ allele in Africans.ConclusionOur findings demonstrate that glucose‐6‐phosphate dehydrogenase (G6PD) A‐ allele could reduce the risk of P. falciparum infection in the African population and indicate that malaria has a recent positive selection on G6PD A‐ allele.

Impact of asymptomatic Plasmodium falciparum on haematological parameters of pregnant women at first antenatal visit in South-western Nigeria

Background: Pregnant women in malaria-endemic areas are at high risk of Plasmodium falciparum infection and its complications. This study investigated the impact of asymptomatic P. falciparum on haematological parameters of pregnant women at first antenatal visit in south-western Nigeria.Methods: Hospital-based cross-sectional evaluation of 130 asymptomatic pregnant women was conducted. Plasmodium infection was diagnosed using Giemsa-stained blood smear microscopy and rapid diagnostic test, while haemoglobin levels (Hb), Packed Cell Volume (PCV), white blood cells (WBC) count, red blood cell (RBC), mean corpuscular volume (MCV), mean corpuscular haemoglobin (MCH) and mean corpuscular haemoglobin concentration (MCHC) were determined using semi-automated haematology analyser.Results: Multigravid pregnant women presented more during their second trimester. Overall malaria prevalence in the sampled population was 14.6%. Prevalence of malaria parasitaemia was highest (68.4%) in the second trimester. P. falciparum infected pregnant women had significantly lower mean values of packed cell volume (PCV), haematocrit (Hb), and total white blood cell (WBC) compared to non-infected individuals (t = -4.07, p= 0.001; t = 3.30, p = &lt;0.001; t = -2.77, p &lt;0.001).Conclusion: There is asymptomatic P. falciparum infection in the study area and this may form a reservoir for transmission. Pregnant women infected with malaria parasites exhibited important changes in haematocrit level, haemoglobin concentration, and total white blood cells. Use of anti-malaria therapy and insecticide-treated bed net would result in greater haematological benefits.

Stool microbiota composition is associated with the prospective risk of Plasmodium falciparum infection.

BackgroundIn humans it is unknown if the composition of the gut microbiota alters the risk of Plasmodium falciparum infection or the risk of developing febrile malaria once P. falciparum infection is established. Here we collected stool samples from a cohort composed of 195 Malian children and adults just prior to an intense P. falciparum transmission season. We assayed these samples using massively parallel sequencing of the 16S ribosomal RNA gene to identify the composition of the gut bacterial communities in these individuals. During the ensuing 6-month P. falciparum transmission season we examined the relationship between the stool microbiota composition of individuals in this cohort and their prospective risk of both P. falciparum infection and febrile malaria.ResultsConsistent with prior studies, stool microbial diversity in the present cohort increased with age, although the overall microbiota profile was distinct from cohorts in other regions of Africa, Asia and North America. Age-adjusted Cox regression analysis revealed a significant association between microbiota composition and the prospective risk of P. falciparum infection; however, no relationship was observed between microbiota composition and the risk of developing febrile malaria once P. falciparum infection was established.ConclusionsThese findings underscore the diversity of gut microbiota across geographic regions, and suggest that strategic modulation of gut microbiota composition could decrease the risk of P. falciparum infection in malaria-endemic areas, potentially as an adjunct to partially effective malaria vaccines.Electronic supplementary materialThe online version of this article (doi:10.1186/s12864-015-1819-3) contains supplementary material, which is available to authorized users.

Malaria and immunity during pregnancy and postpartum: a tale of two species.

It is well established that pregnant women are at an increased risk of Plasmodium falciparum infection when compared to non-pregnant individuals and limited epidemiological data suggest Plasmodium vivax risk also increases with pregnancy. The risk of P. falciparum declines with successive pregnancies due to the acquisition of immunity to pregnancy-specific P. falciparum variants. However, despite similar declines in P. vivax risk with successive pregnancies, there is a paucity of evidence P. vivax-specific immunity. Cross-species immunity, as well as immunological and physiological changes that occur during pregnancy may influence the susceptibility to both P. vivax and P. falciparum. The period following delivery, the postpartum period, is relatively understudied and available epidemiological data suggests that it may also be a period of increased risk of infection to Plasmodium spp. Here we review the literature and directly compare and contrast the epidemiology, clinical pathogenesis and immunological features of P. vivax and P. falciparum in pregnancy, with a particular focus on studies performed in areas co-endemic for both species. Furthermore, we review the intriguing epidemiology literature of both P. falciparum and P. vivax postpartum and relate observations to the growing literature pertaining to malaria immunology in the postpartum period.

Editorial Commentary: Intermittent Preventive Treatment in Pregnancy With Sulfadoxine-Pyrimethamine: The Controversy Continues

Editorial Commentary: Intermittent Preventive Treatment in Pregnancy With Sulfadoxine-Pyrimethamine: The Controversy Continues

Four year immunogenicity of the RTS,S/AS02 A malaria vaccine in Mozambican children during a phase IIb trial

Previous studies with the malaria vaccine RTS,S/AS02 A in young children in a malaria endemic area of Mozambique have shown it to have a promising safety profile and to reduce the risk of Plasmodium falciparum infection and disease. In this study, we assessed the antibody responses to the P. falciparum and hepatitis B components of the RTS,S/AS02 A vaccine over a 45 months surveillance period in a large phase IIb trial which included 2022 children aged 1–4 years at recruitment. The RTS,S/AS02 A vaccine induced high anti-circumsporozoite antibody levels with at least 96% of children remaining seropositive during the entire follow-up period. IgG titers decayed over the first 6 months of follow-up to about 25% of the initial level, but still remained 30-fold higher until month 45 compared to controls. Children with higher levels of naturally acquired immunity at baseline, assessed by blood stage indirect fluorescent antibody test, had slightly higher anti-circumsporozoite levels, after adjusting for the effect of age. The RTS,S/AS02 A vaccine also induced high levels of anti-hepatitis B surface antigen antibodies (seroprotection >97%). RTS,S/AS02 A vaccine is immunogenic and induces long-lasting anti-circumsporozoite antibodies, persisting at least 42 months after immunization. These antibodies may play a role in protection against malaria.

Parity and Placental Infection Affect Antibody Responses againstPlasmodium falciparumduring Pregnancy

Women are at higher risk of Plasmodium falciparum infection when pregnant. The decreasing risk of malaria with subsequent pregnancies is attributed to parity-dependent acquisition of antibodies against placental parasites expressing variant surface antigens, VAR2CSA, that mediate placental sequestration through adhesion to chondroitin sulfate A (CSA). However, modulation of immunity during pregnancy may also contribute to increase the risk of malaria. We compared antibody responses among 30 Mozambican primigravidae and 60 multigravidae at delivery, 40 men, and 40 children. IgG levels were measured against the surface antigens of erythrocytes infected with P. falciparum isolated from 12 pregnant women (4 placental and 8 peripheral blood isolates) and 26 nonpregnant hosts. We also measured IgG levels against merozoite recombinant antigens and total IgG. Placental P. falciparum infection was associated with increased levels of total IgG as well as IgG levels against merozoite antigens and parasite isolates from pregnant and nonpregnant hosts. We therefore stratified comparisons of antibody levels by placental infection. Compared to multigravidae, uninfected primigravidae had lower total IgG as well as lower levels of IgGs against peripheral blood isolates from both pregnant and nonpregnant hosts. These differences were not explained by use of bed nets, season at delivery, neighborhood of residence, or age. Compared to men, infected primigravidae had higher levels of IgGs against isolates from pregnant women and CSA-binding lines but not against other isolates, supporting the concept of a pregnancy-specific development of immunity to these parasite variants. Results of this study show that parity and placental infection can modulate immune responses during pregnancy against malaria parasites.

As Trials Advance for a Malaria Vaccine, Policy Makers Urged to Plan for Its Use

AS THE FIRST PROMISING MALARIA vaccine makes its way through phase 3 clinical trials in subSaharan Africa, stakeholders’ greatest fears go beyond the possibility that the vaccine may fail to meet safety and efficacy goals. They worry that even if the vaccine is licensed, inadequate planning for its distribution could leave it to languish in warehouses. “After decades of research and tens of millions of dollars invested . . . it would be scandalous if this vaccine just sits on the shelf,” said Yvette Collymore, MA, of the nonprofit PATH Malaria Vaccine Initiative (MVI), during a recent Washington, DC, conference. MVI and the vaccine’s creator, GlaxoSmithKline (GSK) Biologicals, partnered in 2001 to develop the vaccine for infants and young children in sub-Saharan Africa. But the origins of the vaccine, known as RTS,S, date back to 1984 when GSK collaborated on preclinical studies with researchers at the Walter Reed Army Institute of Research in Silver Spring, Md. Human trials in adults in the United States and Belgium began in 1992. The first African trials were launched in 1995. Since then, several published studies have shown that the vaccine has a favorable safety and efficacy profile. A phase 2b trial with 340 infants in Tanzania showed that the vaccine reduced the risk of Plasmodium falciparum infection by 65% (Abdulla S et al. N Engl J Med. 2008;359[24]:2533-2544). RTS,Senteredphase3clinical trials in 2009. Eleven sites in 7 countries will enroll 16 000 infants and children, constituting the largest malaria vaccine trial to date. As of late September, about 12 500 children were enrolled: nearly 9000 in a cohortaged6to12weeksandmore than 3000 in a second cohort aged 5 to 17 months. Efficacy data from the older cohort of children are expected in late 2011 and shouldbe followedupayear laterbydata from the younger children, said MarieChantalUwamwezi,MSc, senior regulatoryaffairsscientistatGSK.The30-month follow-updataareexpectedat theendof 2014. The earliest the vaccine could be available for general use would be 2015. Collymore said that efforts began in 2006 to prepare policy makers in Africa forthestepsneededtobringamalariavaccine to the public. “Policy makers need data, and they need it well before this intervention is available; otherwise, this decision can take decades,” she said. Someof thecountries thatmay implement immunization once a malaria vaccine is available are using a decisionmaking tool based on the World Health Organization’s (WHO’s) guidelines for the introduction of any new vaccine. “It looks at the disease burden and the existing interventions, because [the vaccine] will be used alongside other interventions,” Collymore said. “It looks at the efficacy and safety of the vaccine and the sociocultural context of countries where it will be introduced: what communities think about malaria, what some of their beliefs are, and what they think about immunizations.” Tsiri Agbenyega, MD, principal investigator at a clinical trial site in Ghana, said that as phase 3 results become available, clinical data provided for the licensing process will describe not only safety and efficacy, but also the immunogenicity and reactogenicity of RTS,S when given with other vaccines through a WHO program. Safety and efficacy data from HIV-infected children who receive the vaccine also will be provided. Even with phase 3 trial results pending,GSKhasbeeninvolvedforthelastfew years in licensure discussions with African regulatory authorities as well as officials at the WHO and the European Medicines Agency (EMA), which evaluates medical products. “We have an innovative, streamlinedregulatorystrategy toensure licensureandexpediteaccess,” said Uwamwezi. If phase 3 trials are successful, GSK would ask the EMA to review the vaccine and certify it as safe and effective. The certification would pave the way for GSK to apply to African regulatory authorities for marketing authorization. “We can’t overemphasize the major societal, economic, and public health impact this vaccine would have on subSaharan Africa,” said Agbenyega.

Modelling malaria incidence with environmental dependency in a locality of Sudanese savannah area, Mali.

BackgroundThe risk of Plasmodium falciparum infection is variable over space and time and this variability is related to environmental variability. Environmental factors affect the biological cycle of both vector and parasite. Despite this strong relationship, environmental effects have rarely been included in malaria transmission models.Remote sensing data on environment were incorporated into a temporal model of the transmission, to forecast the evolution of malaria epidemiology, in a locality of Sudanese savannah area.MethodsA dynamic cohort was constituted in June 1996 and followed up until June 2001 in the locality of Bancoumana, Mali. The 15-day composite vegetation index (NDVI), issued from satellite imagery series (NOAA) from July 1981 to December 2006, was used as remote sensing data.The statistical relationship between NDVI and incidence of P. falciparum infection was assessed by ARIMA analysis. ROC analysis provided an NDVI value for the prediction of an increase in incidence of parasitaemia.Malaria transmission was modelled using an SIRS-type model, adapted to Bancoumana's data. Environmental factors influenced vector mortality and aggressiveness, as well as length of the gonotrophic cycle. NDVI observations from 1981 to 2001 were used for the simulation of the extrinsic variable of a hidden Markov chain model. Observations from 2002 to 2006 served as external validation.ResultsThe seasonal pattern of P. falciparum incidence was significantly explained by NDVI, with a delay of 15 days (p = 0.001). An NDVI threshold of 0.361 (p = 0.007) provided a Diagnostic Odd Ratio (DOR) of 2.64 (CI95% [1.26;5.52]).The deterministic transmission model, with stochastic environmental factor, predicted an endemo-epidemic pattern of malaria infection. The incidences of parasitaemia were adequately modelled, using the observed NDVI as well as the NDVI simulations. Transmission pattern have been modelled and observed values were adequately predicted. The error parameters have shown the smallest values for a monthly model of environmental changes.ConclusionRemote-sensed data were coupled with field study data in order to drive a malaria transmission model. Several studies have shown that the NDVI presents significant correlations with climate variables, such as precipitations particularly in Sudanese savannah environments. Non-linear model combining environmental variables, predisposition factors and transmission pattern can be used for community level risk evaluation.

Risk of Plasmodium falciparum infection during a malaria epidemic in highland Kenya, 1997

Malaria epidemics in highland areas of East Africa have occurred with increasing frequency since the late 1980s, but the actual risk of Plasmodium falciparum infection in children and adults during these epidemics has not been well characterized. During a malaria epidemic in a highland area of Kenya, risk of infection was assessed in 50 adults (≥18 years old) and 32 children (≤8 years old) after treatment and parasitologic clearance with sulfadoxine-pyrimethamine treatment. Over a 10-week period, 36 of the 82 study participants (43.9%) became infected. The risk of infection was similar in children and adults (hazard ratio for children = 1.21, 95% CI: 0.63–2.33). These findings contrast with the age-related protection from infection reported in areas of stable, intense transmission, and demonstrate that during malaria epidemics, both children and adults in highland areas of Kenya are at high risk of infection.