Statistical Tests for Pairwise Comparisons of Signal-to-Noise Ratios: The Smaller the Better Case

We propose statistical tests for pairwise comparisons of signal-to-noise ratios when the response variable is “the smaller the better” case. A Monte Carlo study and an illustrative example on real data are provided

Assessing the effects of air temperature and rainfall on malaria incidence: an epidemiological study across Rwanda and Uganda

We investigate the short-term effects of air temperature, rainfall, and socioeconomic indicators on malaria incidence across Rwanda and Uganda from 2002 to 2011. Delayed and nonlinear effects of temperature and rainfall data are estimated using generalised additive mixed models with a distributed lag nonlinear specification. A time series cross-validation algorithm is implemented to select the best subset of socioeconomic predictors and to define the degree of smoothing of the weather variables. Our findings show that trends in malaria incidence agree well with variations in both temperature and rainfall in both countries, although factors other than climate seem to play an important role too. The estimated short-term effects of air temperature and precipitation are nonlinear, in agreement with previous research and the ecology of the disease. These effects are robust to the effects of temporal correlation. The effects of socioeconomic data are difficult to ascertain and require further evaluation with longer time series. Climate-informed models had lower error estimates compared to models with no climatic information in 77 and 60% of the districts in Rwanda and Uganda, respectively. Our results highlight the importance of using climatic information in the analysis of malaria surveillance data, and show potential for the development of climateinformed malaria early warning systems

Constraints of small-scale irrigated fodder production and nutrition assessment for livestock feed, a case study in Ethiopia

Livestock is an integral part of the agricultural system in sub-Saharan Africa, serving as a food source, income, fertilizer, and power for farming and transportation. However, the productivity of the livestock system has been hampered due to a lack of sufficient quantity and quality feed. This study evaluates the gaps and constraints of fodder and nutritional potential for livestock feed using small-scale irrigation (SSI). The study comprised of 30 randomly selected farmers from two different ecological zones in Ethiopia. Half of the farmers cultivated Napier grass (Pennisetum purpureum) in the Robit watershed in northern Ethiopia, and the other half cultivated mixed vetch (Lathyrus cicera) and oats (Avena sativa) in Lemo watershed in southern Ethiopia. The Soil and Water Assessment Tool (SWAT) and Agricultural Policy Environmental eXtender (APEX) were applied in an integrated manner to assess the impacts of SSI at the watershed and field-scale levels, respectively. The watershed-scale analysis showed that there is a substantial amount of surface runoff and shallow groundwater recharge that could be used for dry season fodder production using irrigation. Field data calibrated APEX model indicated that Napier yield could be maximized with 550 mm of water in Robit watershed. While in the Lemo watershed, maximum vetch and oats yield may be achieved with 250 mm of water. The major constraints for Napier and oats production in the study sites were soil fertility, especially nitrogen and phosphorus, and vetch production was limited by high temperature. Fodder samples were collected at the time of harvest to evaluate feed quality. The nutritional analysis indicated that Napier grass has a higher dry matter and ash (mineral) content compared to oats and vetch. However, vetch has higher crude protein content (18%) compared to Napier (10%) and oats (6%). Overall the study indicated that cultivating vetch provided superior performance in terms of providing quality feed and environmental services

HIV-free survival among nine- to 24-month-old children born to HIV-positive mothers in the Rwandan national PMTCT programme: a community-based household survey

<p>Abstract</p> <p>Background</p> <p>Operational effectiveness of large-scale national programmes for the prevention of mother to child transmission (PMTCT) of HIV in sub-Saharan Africa remains limited. We report on HIV-free survival among nine- to 24-month-old children born to HIV-positive mothers in the national PMTCT programme in Rwanda.</p> <p>Methods</p> <p>We conducted a national representative household survey between February and May 2009. Participants were mothers who had attended antenatal care at least once during their most recent pregnancy, and whose children were aged nine to 24 months. A two-stage stratified (geographic location of PMTCT site, maternal HIV status during pregnancy) cluster sampling was used to select mother-infant pairs to be interviewed during household visits. Alive children born from HIV-positive mothers (HIV-exposed children) were tested for HIV according to routine HIV testing protocol. We calculated HIV-free survival at nine to 24 months. We subsequently determined factors associated with mother to child transmission of HIV, child death and HIV-free survival using logistic regression.</p> <p>Results</p> <p>Out of 1448 HIV-exposed children surveyed, 44 (3.0%) were reported dead by nine months of age. Of the 1340 children alive, 53 (4.0%) tested HIV positive. HIV-free survival was estimated at 91.9% (95% confidence interval: 90.4-93.3%) at nine to 24 months. Adjusting for maternal, child and health system factors, being a member of an association of people living with HIV (adjusted odds ratio: 0.7, 95% CI: 0.1-0.995) improved by 30% HIV-free survival among children, whereas the maternal use of a highly active antiretroviral therapy (HAART) regimen for PMTCT (aOR: 0.6, 95% CI: 0.3-1.07) had a borderline effect.</p> <p>Conclusions</p> <p>HIV-free survival among HIV-exposed children aged nine to 24 months is estimated at 91.9% in Rwanda. The national PMTCT programme could achieve greater impact on child survival by ensuring access to HAART for all HIV-positive pregnant women in need, improving the quality of the programme in rural areas, and strengthening linkages with community-based support systems, including associations of people living with HIV.</p

Indeterminate and discrepant rapid HIV test results in couples' HIV testing and counselling centres in Africa

<p>Abstract</p> <p>Background</p> <p>Many HIV voluntary testing and counselling centres in Africa use rapid antibody tests, in parallel or in sequence, to establish same-day HIV status. The interpretation of indeterminate or discrepant results between different rapid tests on one sample poses a challenge. We investigated the use of an algorithm using three serial rapid HIV tests in cohabiting couples to resolve unclear serostatuses.</p> <p>Methods</p> <p>Heterosexual couples visited the Rwanda Zambia HIV Research Group testing centres in Kigali, Rwanda, and Lusaka, Zambia, to assess HIV infection status. Individuals with unclear HIV rapid antibody test results (indeterminate) or discrepant results were asked to return for repeat testing to resolve HIV status. If either partner of a couple tested positive or indeterminate with the screening test, both partners were tested with a confirmatory test. Individuals with indeterminate or discrepant results were further tested with a tie-breaker and monthly retesting. HIV-RNA viral load was determined when HIV status was not resolved by follow-up rapid testing. Individuals were classified based on two of three initial tests as "Positive", "Negative" or "Other". Follow-up testing and/or HIV-RNA viral load testing determined them as "Infected", "Uninfected" or "Unresolved".</p> <p>Results</p> <p>Of 45,820 individuals tested as couples, 2.3% (4.1% of couples) had at least one discrepant or indeterminate rapid result. A total of 65% of those individuals had follow-up testing and of those individuals initially classified as "Negative" by three initial rapid tests, less than 1% were resolved as "Infected". In contrast, of those individuals with at least one discrepant or indeterminate result who were initially classified as "Positive", only 46% were resolved as "Infected", while the remainder was resolved as "Uninfected" (46%) or "Unresolved" (8%). A positive HIV serostatus of one of the partners was a strong predictor of infection in the other partner as 48% of individuals who resolved as "Infected" had an HIV-infected spouse.</p> <p>Conclusions</p> <p>In more than 45,000 individuals counselled and tested as couples, only 5% of individuals with indeterminate or discrepant rapid HIV test results were HIV infected. This represented only 0.1% of all individuals tested. Thus, algorithms using screening, confirmatory and tie-breaker rapid tests are reliable with two of three tests negative, but not when two of three tests are positive. False positive antibody tests may persist. HIV-positive partner serostatus should prompt repeat testing.</p

Under-two child mortality according to maternal HIV status in Rwanda: assessing outcomes within the National PMTCT Program

Introduction: We sought to compare risk of death among children aged under-2 years born to HIV positive mother (HIV-exposed) and to HIV negative mother (HIV non-exposed), and identify determinants of under-2 mortality among the two groups in Rwanda. Methods: In a stratified, two-stage cluster sampling design, we selected mother-child pairs using national Antenatal Care (ANC) registers. Household interview with each mother was conducted to capture socio-demographic data and information related to pregnancy, delivery and post-partum. Data were censored at the date of child death. Using Cox proportional hazard model, we compared the hazard of death among HIV-exposed children and HIV nonexposed children. Results: Of 1,455 HIV-exposed children, 29 (2.0%; 95% CI: 1.3%-2.7%) died by 6 months compared to 18 children of the 1,565 HIV non-exposed children (1.2%; 95% CI: 0.6%-1.7%). By 9 months, cumulative risks of death were 3.0% (95%; CI: 2.2%-3.9%) and 1.3% (96%; CI: 0.7%-1.8%) among HIV-exposed and HIV non-exposed children, respectively. By 2 years, the hazard of death among HIVexposed children was more than 3 times higher (aHR:3.5; 95% CI: 1.8-6.9) among HIV-exposed versus non-exposed children. Risk of death by 9-24 months of age was 50% lower among mothers who attended 4 or more antenatal care (ANC) visits (aHR: 0.5, 95% CI: 0.3-0.9), and 26% lower among families who had more assets (aHR: 0.7, 95% CI: 0.5-1.0). Conclusion: Infant mortality was independent of perinatal HIV exposure among children by 6 months of age. However, HIV-exposed children were 3.5 times more likely to die by 2 years. Fewer antenatal visits, lower household assets and maternal HIV seropositive status were associated with increased mortality by 9-24 months.Key words: HIV, PMTCT, maternal HIV infection, infant mortality, child mortality, under-five mortality, Rwand

Safety and Immunogenicity Study of Multiclade HIV-1 Adenoviral Vector Vaccine Alone or as Boost following a Multiclade HIV-1 DNA Vaccine in Africa

We conducted a double-blind, randomized, placebo-controlled Phase I study of a recombinant replication-defective adenovirus type 5 (rAd5) vector expressing HIV-1 Gag and Pol from subtype B and Env from subtypes A, B and C, given alone or as boost following a DNA plasmid vaccine expressing the same HIV-1 proteins plus Nef, in 114 healthy HIV-uninfected African adults.Volunteers were randomized to 4 groups receiving the rAd5 vaccine intramuscularly at dosage levels of 1×10(10) or 1×10(11) particle units (PU) either alone or as boost following 3 injections of the DNA vaccine given at 4 mg/dose intramuscularly by needle-free injection using Biojector® 2000. Safety and immunogenicity were evaluated for 12 months. Both vaccines were well-tolerated. Overall, 62% and 86% of vaccine recipients in the rAd5 alone and DNA prime - rAd5 boost groups, respectively, responded to the HIV-1 proteins by an interferon-gamma (IFN-γ) ELISPOT. The frequency of immune responses was independent of rAd5 dosage levels. The highest frequency of responses after rAd5 alone was detected at 6 weeks; after DNA prime - rAd5 boost, at 6 months (end of study). At baseline, neutralizing antibodies against Ad5 were present in 81% of volunteers; the distribution was similar across the 4 groups. Pre-existing immunity to Ad5 did not appear to have a significant impact on reactogenicity or immune response rates to HIV antigens by IFN-γ ELISPOT. Binding antibodies against Env were detected in up to 100% recipients of DNA prime - rAd5 boost. One volunteer acquired HIV infection after the study ended, two years after receipt of rAd5 alone.The HIV-1 rAd5 vaccine, either alone or as a boost following HIV-1 DNA vaccine, was well-tolerated and immunogenic in African adults. DNA priming increased the frequency and magnitude of cellular and humoral immune responses, but there was no effect of rAd5 dosage on immunogenicity endpoints.ClinicalTrials.gov NCT00124007

Addressing vulnerability, building resilience:community-based adaptation to vector-borne diseases in the context of global change

Abstract Background The threat of a rapidly changing planet – of coupled social, environmental and climatic change – pose new conceptual and practical challenges in responding to vector-borne diseases. These include non-linear and uncertain spatial-temporal change dynamics associated with climate, animals, land, water, food, settlement, conflict, ecology and human socio-cultural, economic and political-institutional systems. To date, research efforts have been dominated by disease modeling, which has provided limited practical advice to policymakers and practitioners in developing policies and programmes on the ground. Main body In this paper, we provide an alternative biosocial perspective grounded in social science insights, drawing upon concepts of vulnerability, resilience, participation and community-based adaptation. Our analysis was informed by a realist review (provided in the Additional file 2) focused on seven major climate-sensitive vector-borne diseases: malaria, schistosomiasis, dengue, leishmaniasis, sleeping sickness, chagas disease, and rift valley fever. Here, we situate our analysis of existing community-based interventions within the context of global change processes and the wider social science literature. We identify and discuss best practices and conceptual principles that should guide future community-based efforts to mitigate human vulnerability to vector-borne diseases. We argue that more focused attention and investments are needed in meaningful public participation, appropriate technologies, the strengthening of health systems, sustainable development, wider institutional changes and attention to the social determinants of health, including the drivers of co-infection. Conclusion In order to respond effectively to uncertain future scenarios for vector-borne disease in a changing world, more attention needs to be given to building resilient and equitable systems in the present