Association between tuberculosis in men and social network structure in Kampala, Uganda

Background

Globally, tuberculosis disease (TB) is more common among males than females. Recent research proposes that differences in social mixing by sex could alter infection patterns in TB. We examine evidence for two mechanisms by which social-mixing could increase men’s contact rates with TB cases. First, men could be positioned in social networks such that they contact more people or social groups. Second, preferential mixing by sex could prime men to have more exposure to TB cases.

Methods

We compared the networks of male and female TB cases and healthy matched controls living in Kampala, Uganda. Specifically, we estimated their positions in social networks (network distance to TB cases, degree, betweenness, and closeness) and assortativity patterns (mixing with adult men, women, and children inside and outside the household).

Results

The observed network consisted of 11,840 individuals. There were few differences in estimates of node position by sex. We found distinct mixing patterns by sex and TB disease status including that TB cases have proportionally more adult male contacts and fewer contacts with children.

Conclusions

This analysis used a network approach to study how social mixing patterns are associated with TB disease. Understanding these mechanisms may have implications for designing targeted intervention strategies in high-burden populations.

Large-cage assessment of a transgenic sex-ratio distortion strain on populations of an African malaria vector

Background

Novel transgenic mosquito control methods require progressively more realistic evaluation. The goal of this study was to determine the effect of a transgene that causes a male-bias sex ratio on Anopheles gambiae target populations in large insectary cages.

Methods

Life history characteristics of Anopheles gambiae wild type and Ag(PMB)1 (aka ^gfp124L-2) transgenic mosquitoes, whose progeny are 95% male, were measured in order to parameterize predictive population models. Ag(PMB)1 males were then introduced at two ratios into large insectary cages containing target wild type populations with stable age distributions and densities. The predicted proportion of females and those observed in the large cages were compared. A related model was then used to predict effects of male releases on wild mosquitoes in a west African village.

Results

The frequency of transgenic mosquitoes in target populations reached an average of 0.44 ± 0.02 and 0.56 ± 0.02 after 6 weeks in the 1:1 and in the 3:1 release ratio treatments (transgenic male:wild male) respectively. Transgenic males caused sex-ratio distortion of 73% and 80% males in the 1:1 and 3:1 treatments, respectively. The number of eggs laid in the transgenic treatments declined as the experiment progressed, with a steeper decline in the 3:1 than in the 1:1 releases. The results of the experiment are partially consistent with predictions of the model; effect size and variability did not conform to the model in two out of three trials, effect size was over-estimated by the model and variability was greater than anticipated, possibly because of sampling effects in restocking. The model estimating the effects of hypothetical releases on the mosquito population of a West African village demonstrated that releases could significantly reduce the number of females in the wild population. The interval of releases is not expected to have a strong effect.

Conclusions

The biological data produced to parameterize the model, the model itself, and the results of the experiments are components of a system to evaluate and predict the performance of transgenic mosquitoes. Together these suggest that the Ag(PMB)1 strain has the potential to be useful for reversible population suppression while this novel field develops.

Genetic variants of MAOB affect serotonin level and specific behavioral attributes to increase autism spectrum disorder (ASD) susceptibility in males

Serotonergic system participates in various developmental processes and modulation of behaviour. Autism Spectrum Disorder (ASD) is characterized by a range of behavioral symptoms scaling from mild to severe. Abnormal 5-HT synthesis and signalling, platelet hyperserotonemia and amelioration of repetitive behaviours by SSRI are some of the key findings, which reinforced the hypothesis that serotonergic genes might act as ASD susceptible genes. Therefore, genes encoding monoamine oxidases A/B (MAOA/MAOB) received special attention as these genes are located on the X-chromosome and the gene products are responsible for 5-HT degradation. In the present study, we conducted population-based association analysis of eight markers of MAOB with ASD in a study cohort of 203 cases and 236 controls form India and examined its effect on platelet 5-HT content and behaviour. Gender-specific changes were observed for the contrasting LD between pair of markers among cases and controls. Case-control analysis demonstrated over-distribution of major C allele of rs2283728 and rs2283727 in male and female ASD cases respectively. Haplotypic distribution and interaction among markers showed more robust effect in male cases. Interestingly, male ASD cases displayed higher platelet 5-HT content in comparison to the respective controls. Quantitative trait analysis revealed significant correlation of genetic variants and haplotypes of MAOB markers, rs1799836 and rs6324 with increased platelet 5-HT level and CARS scores for specific behavioral symptoms respectively in males. This study suggests that MAOB increases ASD risk in males, possibly through its sex-specific regulatory effect on 5-HT metabolism and behavior.