BCG vaccination is associated with reduced malaria prevalence in children under the age of 5 years in sub-Saharan Africa

IntroductionMalaria continues to be a major cause of morbidity and mortality in sub-Saharan Africa (SSA) without effective interventions. Bacillus Calmette-Guérin (BCG) vaccine possesses protective non-specific effects, which extend beyond protection against tuberculosis. This study explores whether BCG is associated with protection against malaria in children under the age of 5 years in SSA.MethodsWe used data from the Demographic Health Survey programme, including 34 206 children from 13 SSA countries. BCG status was taken from vaccination cards when present; if not, mother’s recall was used. Presence of malaria was defined as a positive rapid diagnostic test. Maternally reported presence or absence of fever in the previous 2 weeks defined symptomatic status. Multilevel logistic regression was used to account for the two-stage cluster sampling method.ResultsOf the 34 206 children, 12 325 (36.0%) children were malaria positive and 29 766 (87.0%) were BCG vaccinated. After correction for relevant child, maternal and household factors, BCG vaccination was associated with a lower malaria prevalence (adjusted OR (aOR)=0.94, 95% CI 0.90 to 0.98), especially among children of whom BCG information was retrieved from a vaccination card (aORcard=0.88, 95% CI 0.82 to 0.94). Restricting the analysis to children from regions with suboptimal BCG coverage increased the association (aORcard=0.81, 95% CI 0.73 to 0.89). We observed an increasingly beneficial association with each month of age of the child (aORcard=0.996, 95% CI 0.993 to 0.999). BCG associations were similar for asymptomatic (aORcard=0.86, 95% CI 0.81 to 0.92) and symptomatic (aORcard=0.89, 95% CI 0.78 to 1.01) malaria.ConclusionsBCG vaccination is associated with protection against malaria. This protection is highest in regions with suboptimal BCG coverage. These results indicate a possible role for timely BCG vaccination in the protection of malaria and its elimination by reducing the transmission reservoir. If confirmed in further research, our findings have substantial implications for global efforts to reduce malaria burden.

Host-specific differences in the contribution of an ESBL IncI1 plasmid to intestinal colonization by Escherichia coli O104:H4

ObjectivesTo assess stability and contribution of a large ESBL-encoding IncI1 plasmid to intestinal colonization by Escherichia coli O104:H4 in two different mammalian hosts.MethodsSpecific-pathogen-free 3–4-day-old New Zealand White rabbits and conventionally reared 6-week-old weaned lambs were orally infected with WT E. coli O104:H4 or the ESBL-plasmid-cured derivative, and the recovery of bacteria in intestinal homogenates and faeces monitored over time.ResultsCarriage of the ESBL plasmid had differing impacts on E. coli O104:H4 colonization of the two experimental hosts. The plasmid-cured strain was recovered at significantly higher levels than WT during late-stage colonization of rabbits, but at lower levels than WT in sheep. Regardless of the animal host, the ESBL plasmid was stably maintained in virtually all in vivo passaged bacteria that were examined.ConclusionsThese findings suggest that carriage of ESBL plasmids has distinct effects on the host bacterium depending upon the animal species it encounters and demonstrates that, as for E. coli O157:H7, ruminants could represent a potential transmission reservoir.

Networks of genetic similarity reveal non-neutral processes shape strain structure inPlasmodium falciparum

Pathogens compete for hosts through patterns of cross-protection conferred by immune responses to antigens. InPlasmodium falciparummalaria, thevarmultigene family encoding for the major blood-stage antigenPfEMP1 has evolved enormous genetic diversity through ectopic recombination and mutation. With 50-60vargenes per genome, it is unclear whether immune selection can act as a dominant force in structuringvarrepertoires of local populations. The combinatorial complexity of thevarsystem remains beyond the reach of existing strain theory, and previous evidence for non-random structure cannot demonstrate immune selection without comparison to neutral models. We develop two neutral models that encompass malaria epidemiology but exclude competitive interactions between parasites. These models, combined with networks of genetic similarity, reveal non-neutral strain structure in both simulated systems and an extensively sampled population in Ghana. The unique population structure we identify underlies the large transmission reservoir characteristic of highly endemic regions in Africa.