How equitable is bed net ownership and utilisation in Tanzania? A practical application of the principles of horizontal and vertical equity

BACKGROUND: Studies show that the burden of malaria remains huge particularly in low-income settings. Although effective malaria control measures such as insecticide-treated nets (ITNs) have been promoted, relatively little is known about their equity dimension. Understanding variations in their use in low-income settings is important for scaling up malaria control programmes particularly ITNs. The objective of this paper is to measure the extent and causes of inequalities in the ownership and utilisation of bed nets across socioeconomic groups (SEGs) and age groups in Tanga District, north-eastern Tanzania. METHODS: A questionnaire was administered to heads of 1,603 households from rural and urban areas. Households were categorized into SEGs using both an asset-based wealth index and education level of the household head. Concentration indices and regression-based measures of inequality were computed to analyse both vertical and horizontal inequalities in ownership and utilisation of bed nets. Focus Group Discussions (FGDs) were used to explore community perspectives on the causes of inequalities. RESULTS: Use of ITNs remained appallingly low compared to the RBM target of 80% coverage. Inequalities in ownership of ITNs and all nets combined were significantly pro-rich and were much more pronounced in rural areas. FGDs revealed that lack of money was the key factor for not using ITNs followed by negative perceptions about the effect of insecticides on the health of users. Household SES, living within the urban areas and being under-five were positively associated with bed net ownership and/or utilisation. CONCLUSION: The results highlight the need for mass distribution of ITN; a community-wide programme to treat all untreated nets and to promote the use of Long-Lasting Insecticidal nets (LLINs) or longer-lasting treatment of nets. The rural population and under-fives should be targeted through highly subsidized schemes and mass distribution of free nets. Public campaigns are also needed to encourage people to use treated nets and mitigate negative perceptions about insecticides

Vivax malaria in Mauritania includes infection of a Duffy-negative individual

<p>Abstract</p> <p>Background</p> <p>Duffy blood group polymorphisms are important in areas where <it>Plasmodium vivax </it>is present because this surface antigen is thought to act as a key receptor for this parasite. In the present study, Duffy blood group genotyping was performed in febrile uninfected and <it>P. vivax</it>-infected patients living in the city of Nouakchott, Mauritania.</p> <p>Methods</p> <p><it>Plasmodium vivax </it>was identified by real-time PCR. The Duffy blood group genotypes were determined by standard PCR followed by sequencing of the promoter region and exon 2 of the Duffy gene in 277 febrile individuals. Fisher's exact test was performed in order to assess the significance of variables.</p> <p>Results</p> <p>In the Moorish population, a high frequency of the <it>FYB^ES/FYB^ES</it>genotype was observed in uninfected individuals (27.8%), whereas no <it>P. vivax</it>-infected patient had this genotype. This was followed by a high level of <it>FYA/FYB</it>, <it>FYB/FYB</it>, <it>FYB/FYB^ES</it>and <it>FYA/FYB^ES</it>genotype frequencies, both in the <it>P. vivax</it>-infected and uninfected patients. In other ethnic groups (Poular, Soninke, Wolof), only the <it>FYB^ES/FYB^ES</it>genotype was found in uninfected patients, whereas the <it>FYA/FYB^ES</it>genotype was observed in two <it>P. vivax</it>-infected patients. In addition, one patient belonging to the Wolof ethnic group presented the <it>FYB^ES/FYB^ES</it>genotype and was infected by <it>P. vivax</it>.</p> <p>Conclusions</p> <p>This study presents the Duffy blood group polymorphisms in Nouakchott City and demonstrates that in Mauritania, <it>P. vivax </it>is able to infect Duffy-negative patients. Further studies are necessary to identify the process that enables this Duffy-independent <it>P. vivax </it>invasion of human red blood cells.</p

Forcing Versus Feedback: Epidemic Malaria and Monsoon Rains in Northwest India

Malaria epidemics in regions with seasonal windows of transmission can vary greatly in size from year to year. A central question has been whether these interannual cycles are driven by climate, are instead generated by the intrinsic dynamics of the disease, or result from the resonance of these two mechanisms. This corresponds to the more general inverse problem of identifying the respective roles of external forcings vs. internal feedbacks from time series for nonlinear and noisy systems. We propose here a quantitative approach to formally compare rival hypotheses on climate vs. disease dynamics, or external forcings vs. internal feedbacks, that combines dynamical models with recently developed, computational inference methods. The interannual patterns of epidemic malaria are investigated here for desert regions of northwest India, with extensive epidemiological records for Plasmodium falciparum malaria for the past two decades. We formulate a dynamical model of malaria transmission that explicitly incorporates rainfall, and we rely on recent advances on parameter estimation for nonlinear and stochastic dynamical systems based on sequential Monte Carlo methods. Results show a significant effect of rainfall in the inter-annual variability of epidemic malaria that involves a threshold in the disease response. The model exhibits high prediction skill for yearly cases in the malaria transmission season following the monsoonal rains. Consideration of a more complex model with clinical immunity demonstrates the robustness of the findings and suggests a role of infected individuals that lack clinical symptoms as a reservoir for transmission. Our results indicate that the nonlinear dynamics of the disease itself play a role at the seasonal, but not the interannual, time scales. They illustrate the feasibility of forecasting malaria epidemics in desert and semi-arid regions of India based on climate variability. This approach should be applicable to malaria in other locations, to other infectious diseases, and to other nonlinear systems under forcing

IgG responses to the gSG6-P1 salivary peptide for evaluating human exposure to Anopheles bites in urban areas of Dakar region, Sénégal

<p>Abstract</p> <p>Background</p> <p>Urban malaria can be a serious public health problem in Africa. Human-landing catches of mosquitoes, a standard entomological method to assess human exposure to malaria vector bites, can lack sensitivity in areas where exposure is low. A simple and highly sensitive tool could be a complementary indicator for evaluating malaria exposure in such epidemiological contexts. The human antibody response to the specific <it>Anopheles </it>gSG6-P1 salivary peptide have been described as an adequate tool biomarker for a reliable assessment of human exposure level to <it>Anopheles </it>bites. The aim of this study was to use this biomarker to evaluate the human exposure to <it>Anopheles </it>mosquito bites in urban settings of Dakar (Senegal), one of the largest cities in West Africa, where <it>Anopheles </it>biting rates and malaria transmission are supposed to be low.</p> <p>Methods</p> <p>One cross-sectional study concerning 1,010 (505 households) children (n = 505) and adults (n = 505) living in 16 districts of downtown Dakar and its suburbs was performed from October to December 2008. The IgG responses to gSG6-P1 peptide have been assessed and compared to entomological data obtained in or near the same district.</p> <p>Results</p> <p>Considerable individual variations in anti-gSG6-P1 IgG levels were observed between and within districts. In spite of this individual heterogeneity, the median level of specific IgG and the percentage of immune responders differed significantly between districts. A positive and significant association was observed between the exposure levels to <it>Anopheles gambiae </it>bites, estimated by classical entomological methods, and the median IgG levels or the percentage of immune responders measuring the contact between human populations and <it>Anopheles </it>mosquitoes. Interestingly, immunological parameters seemed to better discriminate the exposure level to <it>Anopheles </it>bites between different exposure groups of districts.</p> <p>Conclusions</p> <p>Specific human IgG responses to gSG6-P1 peptide biomarker represent, at the population and individual levels, a credible new alternative tool to assess accurately the heterogeneity of exposure level to <it>Anopheles </it>bites and malaria risk in low urban transmission areas. The development of such biomarker tool would be particularly relevant for mapping and monitoring malaria risk and for measuring the efficiency of vector control strategies in these specific settings.</p

Using the SaTScan method to detect local malaria clusters for guiding malaria control programmes

Mpumalanga Province, South Africa is a low malaria transmission area that is subject to malaria epidemics. SaTScan methodology was used by the malaria control programme to detect local malaria clusters to assist disease control planning. The third season for case cluster identification overlapped with the first season of implementing an outbreak identification and response system in the area. SaTScan™ software using the Kulldorf method of retrospective space-time permutation and the Bernoulli purely spatial model was used to identify malaria clusters using definitively confirmed individual cases in seven towns over three malaria seasons. Following passive case reporting at health facilities during the 2002 to 2005 seasons, active case detection was carried out in the communities, this assisted with determining the probable source of infection. The distribution and statistical significance of the clusters were explored by means of Monte Carlo replication of data sets under the null hypothesis with replications greater than 999 to ensure adequate power for defining clusters. SaTScan detected five space-clusters and two space-time clusters during the study period. There was strong concordance between recognized local clustering of cases and outbreak declaration in specific towns. Both Albertsnek and Thambokulu reported malaria outbreaks in the same season as space-time clusters. This synergy may allow mutual validation of the two systems in confirming outbreaks demanding additional resources and cluster identification at local level to better target resources. Exploring the clustering of cases assisted with the planning of public health activities, including mobilizing health workers and resources. Where appropriate additional indoor residual spraying, focal larviciding and health promotion activities, were all also carried out

Prevalence and risk factors of malaria among children in southern highland Rwanda

<p>Abstract</p> <p>Background</p> <p>Increased control has produced remarkable reductions of malaria in some parts of sub-Saharan Africa, including Rwanda. In the southern highlands, near the district capital of Butare (altitude, 1,768 m), a combined community-and facility-based survey on <it>Plasmodium </it>infection was conducted early in 2010.</p> <p>Methods</p> <p>A total of 749 children below five years of age were examined including 545 randomly selected from 24 villages, 103 attending the health centre in charge, and 101 at the referral district hospital. Clinical, parasitological, haematological, and socio-economic data were collected.</p> <p>Results</p> <p><it>Plasmodium falciparum </it>infection (mean multiplicity, 2.08) was identified by microscopy and PCR in 11.7% and 16.7%, respectively; 5.5% of the children had malaria. PCR-based <it>P. falciparum </it>prevalence ranged between 0 and 38.5% in the villages, and was 21.4% in the health centre, and 14.9% in the hospital. Independent predictors of infection included increasing age, low mid-upper arm circumference, absence of several household assets, reported recent intake of artemether-lumefantrine, and chloroquine in plasma, measured by ELISA. Self-reported bed net use (58%) reduced infection only in univariate analysis. In the communities, most infections were seemingly asymptomatic but anaemia was observed in 82% and 28% of children with and without parasitaemia, respectively, the effect increasing with parasite density, and significant also for submicroscopic infections.</p> <p>Conclusions</p> <p><it>Plasmodium falciparum </it>infection in the highlands surrounding Butare, Rwanda, is seen in one out of six children under five years of age. The abundance of seemingly asymptomatic infections in the community forms a reservoir for transmission in this epidemic-prone area. Risk factors suggestive of low socio-economic status and insufficient effectiveness of self-reported bed net use refer to areas of improvable intervention.</p

Malaria infection and disease in an area with pyrethroid-resistant vectors in southern Benin

<p>Abstract</p> <p>Background</p> <p>This study aimed to investigate baseline data on malaria before the evaluation of new vector control strategies in an area of pyrethroid-resistance of vectors. The burden of malaria was estimated in terms of infection (prevalence and parasite density) and of clinical episodes.</p> <p>Methods</p> <p>Between December 2007 and December 2008 in the health district of Ouidah - Kpomassè - Tori Bossito (southern Benin), a descriptive epidemiological survey of malaria was conducted. From 28 selected villages, seven were randomized from which a total of 440 children aged 0 to 5 years were randomly selected. Clinical and parasitological information was obtained by active case detection of malaria episodes carried out during eight periods of six consecutive days scheduled at six weekly intervals and by cross-sectional surveys of asymptomatic infection. Entomological information was also collected. The ownership, the use and the correct use of long-lasting insecticide-treated nets (LLINs) were checked over weekly-survey by unannounced visits at home in the late evening.</p> <p>Results</p> <p>Mean parasite density in asymptomatic children was 586 <it>P. falciparum </it>asexual forms per μL of blood (95%CI 504-680). Pyrogenic parasite cut-off was estimated 2,000 <it>P. falciparum </it>asexual blood forms per μL. The clinical incidence of malaria was 1.5 episodes per child per year (95%CI 1.2-1.9). Parasitological and clinical variables did not vary with season. <it>Anopheles gambiae </it><it>s.l</it>. was the principal vector closely followed by <it>Anopheles funestus</it>. Entomological inoculation rate was 5.3 (95%CI 1.1-25.9) infective bites per human per year. Frequency of the L1014F <it>kdr </it>(West) allele was around 50%. Annual prevalence rate of <it>Plasmodium falciparum </it>asymptomatic infection was 21.8% (95%CI 19.1-24.4) and increased according to age. Mean rates of ownership and use of LLINs were 92% and 70% respectively. The only correct use of LLINs (63%) conferred 26% individual protection against only infection (OR = 0.74 (95%IC 0.62-0.87), p = 0.005).</p> <p>Conclusion</p> <p>The health district of Ouidah-Kpomassè-Tori Bossito is a mesoendemic area with a moderate level of pyrethroid-resistance of vectors. The used LLINs rate was high and only the correct use of LLINs was found to reduce malaria infection without influencing malaria morbidity.</p

Antibody-Mediated Growth Inhibition of Plasmodium falciparum: Relationship to Age and Protection from Parasitemia in Kenyan Children and Adults

BACKGROUND: Antibodies that impair Plasmodium falciparum merozoite invasion and intraerythrocytic development are one of several mechanisms that mediate naturally acquired immunity to malaria. Attempts to correlate anti-malaria antibodies with risk of infection and morbidity have yielded inconsistent results. Growth inhibition assays (GIA) offer a convenient method to quantify functional antibody activity against blood stage malaria. METHODS: A treatment-time-to-infection study was conducted over 12-weeks in a malaria holoendemic area of Kenya. Plasma collected from healthy individuals (98 children and 99 adults) before artemether-lumefantrine treatment was tested by GIA in three separate laboratories. RESULTS: Median GIA levels varied with P. falciparum line (D10, 8.8%; 3D7, 34.9%; FVO, 51.4% inhibition). The magnitude of growth inhibition decreased with age in all P. falciparum lines tested with the highest median levels among children \u3c4 years compared to adults (e.g. 3D7, 45.4% vs. 30.0% respectively, p = 0.0003). Time-to-infection measured by weekly blood smears was significantly associated with level of GIA controlling for age. Upper quartile inhibition activity was associated with less risk of infection compared to individuals with lower levels (e.g. 3D7, hazard ratio = 1.535, 95% CI = 1.012-2.329; p = 0.0438). Various GIA methodologies had little effect on measured parasite growth inhibition. CONCLUSION: Plasma antibody-mediated growth inhibition of blood stage P. falciparum decreases with age in residents of a malaria holoendemic area. Growth inhibition assay may be a useful surrogate of protection against infection when outcome is controlled for age