Risk factors for acquisition of meningococcal carriage in the African meningitis belt.

OBJECTIVE: To investigate potential risk factors for acquisition in seven countries of the meningitis belt. METHODS: Households were followed up every 2 weeks for 2 months, then monthly for a further 4 months. Pharyngeal swabs were collected from all available household members at each visit and questionnaires completed. Risks of acquisition over the whole study period and for each visit were analysed by a series of logistic regressions. RESULTS: Over the course of the study, acquisition was higher in: (i) 5-to 14-year olds, as compared with those 30 years or older (OR 3.6, 95% CI 1.4-9.9); (ii) smokers (OR 3.6, 95% CI 0.98-13); and (iii) those exposed to wood smoke at home (OR 2.6 95% CI 1.3-5.6). The risk of acquisition from one visit to the next was higher in those reporting a sore throat during the dry season (OR 3.7, 95% CI 2.0-6.7) and lower in those reporting antibiotic use (OR 0.17, 95% CI 0.03-0.56). CONCLUSIONS: Acquisition of meningococcal carriage peaked in school age children. Recent symptoms of sore throat during the dry season, but not during the rainy season, were associated with a higher risk of acquisition. Upper respiratory tract infections may be an important driver of epidemics in the meningitis belt.

OBJECTIF: Investiguer les facteurs de risque potentiels d'acquisition dans sept pays de la ceinture de la méningite. MÉTHODES: Des ménages ont été suivis toutes les deux semaines pendant deux mois, puis tous les mois pendant quatre mois. Des prélèvements pharyngés sur écouvillons ont été collectés auprès de tous les membres disponibles du ménage à chaque visite et des questionnaires ont été remplis. Les risques d'acquisition sur l'ensemble de la période d'étude et pour chaque visite ont été analysés par une série de régressions logistiques. RÉSULTATS: Au cours de l'étude, l'acquisition a été plus élevée chez: (i) les 5-14 ans, par rapport à ceux âgés de 30 ans ou plus (OR = 3,6; IC95%: 1,4-9,9); (ii) les fumeurs (OR = 3,6; IC95%: 0,98-13); et (iii) les personnes exposées à la fumée de bois à la maison (OR = 2,6; IC95%: 1,3-5,6). Le risque d'acquisition d'une visite à l'autre était plus élevé chez les personnes signalant un mal de gorge pendant la saison sèche (OR = 3,7; IC95%: 2,0-6,7) et plus faible chez celles signalant une utilisation d'antibiotique (OR = 0,17; IC95%: 0,03-0,56). CONCLUSIONS: L'acquisition du portage du méningocoque a culminé chez les enfants d'âge scolaire. Les symptômes récents de maux de gorge pendant la saison sèche, mais pas pendant la saison des pluies, étaient associés à un risque d'acquisition plus élevé. Les infections des voies respiratoires supérieures pourraient être un facteur important d'épidémies dans la ceinture de la méningite.

Seasonal dynamics of human retinol status in mobile pastoralists in Chad.

Vitamin A deficiency is a prevalent public health problem in Africa and South-East Asia, although national population based surveys are lacking in many countries. This study investigated seasonal variation of human retinol concentrations in Chadian mobile pastoralists to identify critical time periods for interventions addressing vitamin A deficiency. The repeated cross-sectional study design used convenience sampling during three seasons to include 327 Fulani, Gorane and Arab adult mobile pastoralists in nine camps in the Lake Chad area. Human blood and pooled cattle milk retinol concentrations were rapidly assessed by portable flourometer (iCheck™). Linear regression models with random effects for correlation within camps were applied with human retinol concentration as outcome. Logistic regression models, with camp as random effect, were evaluated for the outcome human retinol deficiency. Human seasonal means were 2.14µmol/L (95% CI 1.82-2.46) in rainy, 0.99µmol/L (95% CI 0.91-1.07) in cold and 1.86µmol/L (95% CI 1.63-2.09) in dry season. Retinol concentration and deficiency varied according to season and ethnic group. Average values were highest in Gorane during rainy and in Fulani in the cold and dry seasons. Arabs had lowest average values in all seasons. Retinol deficiency (<0.70µmol/L) was found in 15% of study participants in the dry, 25% in the rainy and 32% in the cold season. Retinol concentrations varied according to age, sex, milk consumption level and pooled cattle milk retinol concentration. Effect sizes varied and not all were statistically significantly different. Pooled cattle milk retinol concentrations varied seasonally and were positively associated to human retinol concentrations. This study establishes seasonal variation in human blood and pooled cattle milk retinol concentrations in Chad, demonstrating a linkage from animals to humans through milk. Rapid analysis using portable technology is feasible in remote populations under harsh climatic conditions.

Correction: A Seroepidemiological Study of Serogroup A Meningococcal Infection in the African Meningitis Belt.

[This corrects the article DOI: 10.1371/journal.pone.0147928.].

A Seroepidemiological Study of Serogroup A Meningococcal Infection in the African Meningitis Belt.

The pattern of epidemic meningococcal disease in the African meningitis belt may be influenced by the background level of population immunity but this has been measured infrequently. A standardised enzyme-linked immunosorbent assay (ELISA) for measuring meningococcal serogroup A IgG antibodies was established at five centres within the meningitis belt. Antibody concentrations were then measured in 3930 individuals stratified by age and residence from six countries. Seroprevalence by age was used in a catalytic model to determine the force of infection. Meningococcal serogroup A IgG antibody concentrations were high in each country but showed heterogeneity across the meningitis belt. The geometric mean concentration (GMC) was highest in Ghana (9.09 µg/mL [95% CI 8.29, 9.97]) and lowest in Ethiopia (1.43 µg/mL [95% CI 1.31, 1.57]) on the margins of the belt. The force of infection was lowest in Ethiopia (λ = 0.028). Variables associated with a concentration above the putative protective level of 2 µg/mL were age, urban residence and a history of recent vaccination with a meningococcal vaccine. Prior to vaccination with the serogroup A meningococcal conjugate vaccine, meningococcal serogroup A IgG antibody concentrations were high across the African meningitis belt and yet the region remained susceptible to epidemics.

Household crowding, social mixing patterns and respiratory symptoms in seven countries of the African meningitis belt.

OBJECTIVES: To describe the variation in household crowding and social mixing patterns in the African meningitis belt and to assess any association with self-reported recent respiratory symptoms. METHODS: In 2010, the African Meningococcal Carriage Consortium (MenAfriCar) conducted cross-sectional surveys in urban and rural areas of seven countries. The number of household members, rooms per household, attendance at social gatherings and meeting places were recorded. Associations with self-reported recent respiratory symptoms were analysed by univariate and multivariate regression models. RESULTS: The geometric mean people per room ranged from 1.9 to 2.8 between Ghana and Ethiopia respectively. Attendance at different types of social gatherings was variable by country, ranging from 0.5 to 1.5 per week. Those who attended 3 or more different types of social gatherings a week (frequent mixers) were more likely to be older, male (OR 1.27, p<0.001) and live in urban areas (OR 1.45, p<0.001). Frequent mixing and young age, but not increased household crowding, were associated with higher odds of self-reported respiratory symptoms (aOR 2.2, p<0.001 and OR 2.8, p<0.001 respectively). A limitation is that we did not measure school and workplace attendance. CONCLUSION: There are substantial variations in household crowding and social mixing patterns across the African meningitis belt. This study finds a clear association between age, increased social mixing and respiratory symptoms. It lays the foundation for designing and implementing more detailed studies of social contact patterns in this region.

Serum retinol of Chadian nomadic pastoralist women in relation to their livestocks' milk retinol and beta-carotene content.

Human serum retinol and livestock milk retinol levels were assessed as part of a study on the health status of Chadian nomadic pastoralists and their livestock in close partnership between Chadian public health and livestock institutions. Of the examined women (n = 99), 43% were moderately retinol-deficient (0.35 mol/L < x < 0.7 mol/L 95% CI; 33-54%), and 17% severely retinol-deficient (< 0.35 mol/L 95% CI; 10-26%). None of the interviewed women (n = 87) reported the consumption of fruit, and only two of fresh vegetables were reported consumed in the past 24 hours. Milk is the almost exclusive source of vitamin A for these populations. Goats (n = 6) had the highest average milk retinol level (329 +/- 84 micrograms/kg [mean +/- SEM]), followed by cattle (n = 25; 247 +/- 32 micrograms/kg), and camels (n = 12; 120 +/- 18 micrograms/kg). Milk retinol levels did not differ between the rainy and dry seasons. Human serum retinol depends significantly on livestock milk retinol levels (partial slope 0.23; 95% CI: 0.008-0.47). Our study supports the use of goat and cow milk as an important source of vitamin A in pastoral nomadic settings. However, the levels still require to be complemented further by promoting green leafy vegetables, fruits, and supplements.