Spatial analysis and efficiency of systematic designs in intercropping experiments.

Thesis (M.Sc.) - University of Natal, Pietermaritzburg, 2002In studies involving intercropping plant populations, the main interest is to locate the position of the maximum response or to study the response pattern. Such studies normally require many plant population levels. Thus, designs such as spacing systematic designs that minimise experimental land area are desired. Randomised block designs may not perform well as they allow few population levels which may not span the maximum or enable exploration of other features of the response surface. However, lack of complete randomisation in systematic designs may imply spatial variability (largescale and small-scale variations i.e. trend and spatial dependence) in observations. There is no correct statistical method laid out for data analysis from such designs. Given that spacing systematic designs are not well explored in literature, the main thrusts of this study are two fold; namely, to explore the use of spatial modelling techniques in analysing and modelling data from systematic designs, and to evaluate the efficiency of systematic designs used in intercropping experiments. Three classes of models for trend and error modelling are explored/introduced. These include spatial linear mixed models, semi-parametric mixed models and beta-hat models incorporating spatial variability. The reliability and precision of these methods are demonstrated. Relative efficiency of systematic designs to completely randomised design are evaluated. The analysis of data from systematic designs is shown be easily implemented. Measures of efficiency that include <pp directed measures (A and E criteria), D1 and DB efficiencies for regression parameters, and power are used. Systematic designs are shown to be efficient; on average 72% for A and E- efficiencies and 93% for D1 and DB efficiencies. Overall, these results suggest that systematic designs are suitable and reliable for intercropping plant population studies

Assessing risk of HIV and hepatitis C among people who inject drugs in East Africa: findings from a rapid assessment

Rapid assessment cross-sectional surveys and qualitative interviews were conducted among people who inject drugs (PWID) in Burundi and Uganda, as well as key informants working with drug users, to assess risk associated with HIV and hepatitis C (HCV). A total of 127 PWID were recruited in Burundi and 125 in Uganda of which the majority were male and aged between 24 and 26 years. Blood samples were collected in Burundi to test for antibodies to HIV, HCV and B Surface Antigen (HBsAg). Heroin was mainly injected in Uganda and Burundi with a small minority injecting crack/cocaine. Half of participants in Burundi, and 86% in Uganda had been HIV tested. The minority had been tested for HCV in any site (5-7%). HIV prevalence from the serological testing in Burundi indicated that 10% tested positive for antibodies to HIV, 6% to HCV and 9% to HBsAg. Qualitative data suggested that structural factors including costs of needle/syringes as well policies prohibiting pharmacies selling injecting equipment to PWID were related to reuse and sharing of needles/syringes among PWID, despite awareness HIV transmission risk. Police arrest was common in Burundi and Uganda and the use of bribes by police compounded existing high levels of poverty. Findings accentuate the need for policy shifts to enable easier access to clean injecting equipment, increased availability of HIV and HCV testing and increased access to affordable drug treatment and introduction of opioid substitution therapy. Specific attention is needed to the potential for sexual transmission of HIV among this population

Utilization of sexual and reproductive health services among young people in refugee settings in Uganda

There is a considerable high level of unmet need for reproductive health services among refugees. Yet, there is limited research about the provision and utilization of sexual and reproductive health (SRH) services among young people in refugee settings. Drawing on a sample of 575 young refugees (15–24 years) from a cross-sectional survey, this study aims to fill this gap by identifying the factors associated with SRH utilization among young people living in refugee settings in Northern Uganda. The utilization of SRH services at the health facilities was significantly different between female and male young people after adjusting for all other variables (aOR = 2.46, 95% CI, 1.58, 3.84). Young people who were not living in a marital union (aOR = 0.38, 95% CI, 0.20, 0.71), or held inequitable gender norms about services (aOR = 0.28, 95% CI, 0.12, 0.66) had about a third of the odds of utilizing SRH services. Young women with comprehensive knowledge about contraception, modern contraceptives, and HIV and STI prevention, had more than twice the odds of utilizing SRH services (aOR = 2.23, 95% CI, 2.67, 6.90). There is need to integrate social norm measurements and social norm change strategies in strategies for promoting utilization of SRH services among refugees in low-income countries especially in Ugand

HIV Incidence and Risk Factors for Acquisition in HIV Discordant Couples in Masaka, Uganda: An HIV Vaccine Preparedness Study

To determine the incidence of and risk factors for HIV acquisition in a cohort of HIV-uninfected partners from HIV discordant couples in Masaka, Uganda, and to establish its suitability for HIV vaccine trials.HIV-uninfected adults living in HIV discordant couple relationships were enrolled and followed for 2 years. Interviews, medical investigations, HIV counseling and testing, syphilis and urine pregnancy (women) tests were performed at quarterly visits. Sexual risk behaviour data were collected every 6 months.495 participants were enrolled, of whom 34 seroconverted during 786.6 person-years of observation (PYO). The overall HIV incidence rate [95% confidence interval (CI)] was 4.3 [3.1-6]; and 4.3 [2.8-6.4] and 4.4 [2.5-8] per 100 PYO in men and women respectively. Independent baseline predictors for HIV acquisition were young age [18-24 (aRR = 4.1, 95% CI 1.6-10.8) and 25-34 (aRR = 2.7, 95% CI 1.2-5.8) years]; alcohol use (aRR = 2.6, 95% CI 1.1-6); and reported genital discharge (aRR = 3.4, 95% CI 1.6-7.2) in the past year. Condom use frequency in the year preceding enrolment was predictive of a reduced risk of HIV acquisition [sometimes (aRR = 0.4, 95% CI 0.2-0.8); always (aRR = 0.1, 95% CI 0.02-0.9)]. In the follow-up risk analysis, young age [18-24 (aRR = 6.2, 95% CI 2.2-17.3) and 25-34 (aRR = 2.3, 95% CI 1.1-5.0) years], reported genital discharge (aRR = 2.5, 95% CI 1.1-5.5), serological syphilis (aRR 3.2, 95% CI 1.3-7.7) and the partner being ART naïve (aRR = 4.8, 95% CI 1.4-16.0) were independently associated with HIV acquisition. There were no seroconversions among participants who reported consistent condom use during the study.The study has identified important risk factors for HIV acquisition among HIV discordant couples. HIV-uninfected partners in discordant couples may be a suitable population for HIV vaccine efficacy trials. However, recent confirmation that ART reduces heterosexual HIV transmission may make it unfeasible to conduct HIV prevention trials in this population

Long-term consistent use of a vaginal microbicide gel among HIV-1 sero-discordant couples in a phase III clinical trial (MDP 301) in rural south-west Uganda.

BACKGROUND: A safe and effective vaginal microbicide could substantially reduce HIV acquisition for women. Consistent gel use is, however, of great importance to ensure continued protection against HIV infection, even with a safe and effective microbicide. We assessed the long-term correlates of consistent gel use in the MDP 301 clinical trial among HIV-negative women in sero-discordant couples in south-west Uganda. METHODS: HIV-negative women living with an HIV-infected partner were enrolled between 2005 and 2008, in a three-arm phase III microbicide trial and randomized to 2% PRO2000, 0.5% PRO2000 or placebo gel arms. Follow-up visits continued up to September 2009. The 2% arm was stopped early due to futility and the 229 women enrolled in this arm were excluded from this analysis. Data were analyzed on 544 women on the 0.5% and placebo arms who completed at least 52 weeks of follow-up, sero-converted or became pregnant before 52 weeks. Consistent gel use was defined as satisfying all of the following three conditions: (i) reported gel use at the last sex act for at least 92% of the 26 scheduled visits or at least 92% of the visits attended if fewer than 26; (ii) at least one used applicator returned for each visit for which gel use was reported at the last sex act; (iii) attended at least 13 visits (unless the woman sero-converted or became pregnant during follow-up). Logistic regression models were fitted to investigate factors associated with consistent gel use. RESULTS: Of the 544 women, 473 (86.9%) were followed for at least 52 weeks, 29 (5.3%) sero-converted and 42 (7.7%) became pregnant before their week 52 visit. Consistent gel use was reported by 67.8%. Women aged 25 to 34 years and those aged 35 years or older were both more than twice as likely to have reported consistently using gel compared to women aged 17 to 24 years. Living in a household with three or more rooms used for sleeping compared to one room was associated with a twofold increase in consistent gel use. CONCLUSION: In rural Uganda younger women and women in houses with less space are likely to require additional support to achieve consistent microbicide gel use. TRIAL REGISTRATION: Protocol Number ISRCTN64716212

The sexual behavior of young people living with a disability: Findings from the KAP study in Northern Uganda

IntroductionYoung people living with disability form one of the most vulnerable population groups globally. There is limited information on the use of SRH services among young people living with a disability.MethodsThis analysis is based on household survey data among young people. Drawing on a sample of 861 young people living with a disability (15 -24 years), we investigate the sexual behaviour, and identify the risk factors associated with sexual behavior of young people living with a disability. Multilevel logistic regression was used.ResultsResults indicate that risky sexual behaviour was associated with alcohol consumption (aOR = 1.68; 95%CI: 0.97, 3.01), having limited knowledge of HIV and STI prevention methods (aOR = 6.03; 95%CI: 0.99, 30.00), and low life skills (aOR = 4.23; 95%CI: 1.59, 12.87). The odds of not using a condom at last sex were significantly higher among in-school young people than out of school young people (aOR = 0.34; 95%CI: 0.12, 0.99).DiscussionTargeted interventions aimed at reaching out to young people living with a disability should consider their sexual and reproductive health needs, barriers, and facilitators. Interventions can also promote self-efficacy and agency of young people living with a disability in making informed sexual and reproductive health choices

Estimated proportion of diabetes and Caesarean Section which could potentially be avoided if all obese mothers in this population were of normal BMI.

<p>Estimated proportion of diabetes and Caesarean Section which could potentially be avoided if all obese mothers in this population were of normal BMI.</p

Adjusted odds ratios (95% CI) for obstetric and child outcomes according to maternal obesity¹, presented for the whole population and separately by ethic group of the mother.

1<p>BMI 30 or more Kg/m²</p>2<p>Odds ratios adjusted for maternal age, parity, and deprivation.</p

Estimated proportion of Macrosomia and NICU/SCBU admission which could potentially be avoided if all obese mothers in this population were of normal BMI.

<p>Estimated proportion of Macrosomia and NICU/SCBU admission which could potentially be avoided if all obese mothers in this population were of normal BMI.</p

Prevalence and incidence of HIV in a rural community-based HIV vaccine preparedness cohort in Masaka, Uganda.

BackgroundLocal HIV epidemiology data are critical in determining the suitability of a population for HIV vaccine efficacy trials. The objective of this study was to estimate the prevalence and incidence of, and determine risk factors for HIV transmission in a rural community-based HIV vaccine preparedness cohort in Masaka, Uganda.MethodsBetween February and July 2004, we conducted a house-to-house HIV sero-prevalence survey among consenting individuals aged 18-60 years. Participants were interviewed, counseled and asked to provide blood for HIV testing. We then enrolled the HIV uninfected participants in a 2-year HIV sero-incidence study. Medical evaluations, HIV counseling and testing, and sample collection for laboratory analysis were done quarterly. Sexual risk behaviour data was collected every 6 months.ResultsThe HIV point prevalence was 11.2%, and was higher among women than men (12.9% vs. 8.6%, P = 0.007). Risk factors associated with prevalent HIV infection for men were age ConclusionsWe found a high prevalence but low incidence of HIV in this cohort. HIV vaccine efficacy trials in this population may not be feasible due to the large sample sizes that would be required. HIV vaccine preparatory efforts in this setting should include identification of higher risk populations