Unrestricted migration favours virulent pathogens in experimental metapopulations: evolutionary genetics of a rapacious life history

Understanding pathogen infectivity and virulence requires combining insights from epidemiology, ecology, evolution and genetics. Although theoretical work in these fields has identified population structure as important for pathogen life-history evolution, experimental tests are scarce. Here, we explore the impact of population structure on life-history evolution in phage T4, a viral pathogen of Escherichia coli. The host–pathogen system is propagated as a metapopulation in which migration between subpopulations is either spatially restricted or unrestricted. Restricted migration favours pathogens with low infectivity and low virulence. Unrestricted migration favours pathogens that enter and exit their hosts quickly, although they are less productive owing to rapid extirpation of the host population. The rise of such ‘rapacious’ phage produces a ‘tragedy of the commons’, in which better competitors lower productivity. We have now identified a genetic basis for a rapacious life history. Mutations at a single locus (rI) cause increased virulence and are sufficient to account for a negative relationship between phage competitive ability and productivity. A higher frequency of rI mutants under unrestricted migration signifies the evolution of rapaciousness in this treatment. Conversely, spatially restricted migration favours a more ‘prudent’ pathogen strategy, in which the tragedy of the commons is averted. As our results illustrate, profound epidemiological and ecological consequences of life-history evolution in a pathogen can have a simple genetic cause.     

Timely initiation of breastfeeding and its association with birth place in Ethiopia: a systematic review and meta-analysis

Background

Timely initiation of breastfeeding is defined as putting the newborn to the breast within 1 h of birth. In Ethiopia, different studies have been conducted to assess the prevalence of timely initiation of breastfeeding and associated factors. The findings of these studies were inconsistent and characterized by great variability. Therefore, the aim of this systematic review and meta-analysis was to estimate the pooled prevalence of timely initiation of breastfeeding and its association with birth place in Ethiopia using the available studies.

Methods

Databases, including PubMed, Google scholar, Science direct and Cochrane library were systematically searched. All original studies reporting the prevalence of timely initiation of breastfeeding in Ethiopia were considered. Two authors independently extracted all necessary data using a standardized data extraction format. STATA 11 statistical software was used to analyze the data. The Cochrane Q test statistics and I ² test were used to assess the heterogeneity between the studies. A random effect model was computed to estimate the pooled prevalence of timely initiation of breastfeeding. In addition, the associations between timely initiation of breastfeeding and place of birth were determined.

Results

Sixteen studies were finally included in the meta-analysis. The findings of this meta-analysis revealed that, the pooled prevalence of timely initiation of breastfeeding in Ethiopia was 61.4% (CI: 51.4, 71.5%). The study also indicated that rural mothers had lower rate of initiating breastfeeding within the first 1 h after delivery as compared to their urban counterparts. Additionally, mothers who gave birth at health institution were almost 2.11 times more likely to initiate breastfeeding within 1 h as compared to mothers who did not give birth at health institution.

Conclusion

In this study, timely initiation of breastfeeding in Ethiopia was significantly low compared to the current global recommendation on breastfeeding. Women from rural area were less likely to initiate breastfeeding within 1 h as compared with women from urban areas. Mothers who give birth at health institution were more likely to initiate breastfeeding timely.