Rural Gabon Research Articles

Enhanced Pro-Inflammatory Cytokine Responses following Toll-Like-Receptor Ligation in Schistosoma haematobium-Infected Schoolchildren from Rural Gabon

Background Schistosoma infection is thought to lead to down-regulation of the host's immune response. This has been shown for adaptive immune responses, but the effect on innate immunity, that initiates and shapes the adaptive response, has not been extensively studied. In a first study to characterize these responses, we investigated the effect of Schistosoma haematobium infection on cytokine responses of Gabonese schoolchildren to a number of Toll-like receptor (TLR) ligands.MethodologyPeripheral blood mononuclear cells (PBMCs) were collected from S. haematobium-infected and uninfected schoolchildren from the rural area of Zilé in Gabon. PBMCs were incubated for 24 h and 72 h with various TLR ligands, as well as schistosomal egg antigen (SEA) and adult worm antigen (AWA). Pro-inflammatory TNF-α and anti-inflammatory/regulatory IL-10 cytokine concentrations were determined in culture supernatants.Principal FindingsInfected children produced higher adaptive IL-10 responses than uninfected children against schistosomal antigens (72 h incubation). On the other hand, infected children had higher TNF-α responses than uninfected children and significantly higher TNF-α to IL-10 ratios in response to FSL-1 and Pam3, ligands of TLR2/6 and TLR2/1 respectively. A similar trend was observed for the TLR4 ligand LPS while Poly(I:C) (Mda5/TLR3 ligand) did not induce substantial cytokine responses (24 h incubation).ConclusionsThis pilot study shows that Schistosoma-infected children develop a more pro-inflammatory TLR2-mediated response in the face of a more anti-inflammatory adaptive immune response. This suggests that S. haematobium infection does not suppress the host's innate immune system in the context of single TLR ligation.

Prevalence of Plasmodium falciparum infection in asymptomatic rural Gabonese populations

BackgroundMalaria may be perennial or epidemic in sub-Saharan Africa, and its transmission may be stable or unstable, depending on the region. The prevalence of asymptomatic Plasmodium falciparum carriage is poorly documented in Gabon. A large survey of P. falciparum infection was conducted in asymptomatic individuals living in rural Gabon.MethodsTwo hundred and twenty-two villages were randomly selected in the nine administrative regions. With the participants' informed consent, blood samples were collected for thick and thin blood film examination after 20% Giemsa staining. Prevalence rates were calculated per village, per region and per ecosystem, and nationwide. Demographic risk factors were identified with STATA software version 9.0. Significance was assumed at p < 0.05.Results and discussionThe prevalence of P. falciparum in adults was 6.2% (269/4342) nationwide, with a maximum of 37.2% in one village; a linear decrease was observed with increasing age (p = 0.045). Only 5% of the 399 children from forest areas tested positive. The prevalence was significantly higher in forest areas (7%) than in savannah (4%) and lakeland (2.5%). Within the forest region, the prevalence was significantly higher in forest grassland (10.9%) than in the mountain forest (3.5%), interior forest (6.8%) and north-eastern forest (4.5%).ConclusionPlasmodium falciparum carriage remains high among adults in rural Gabon. Control measures must be adapted to the region and ecosystem. Routine treatment of asymptomatic individuals should be considered.

Searching for Success: Boys, Family Aspirations, and Opportunities in Gabon, ca. 1900-1940

Boys growing up in rural Gabon between 1900 and 1940 negotiated with many challenges: the rise of migrant labor, famines and hardships brought on by World War I, the growth of Christianity and African-based spiritual traditions, and the undermining of clans, which had been the main form of social and political organization in the nineteenth century. Parents, extended family members, missionaries, and European businesses recruited boys to serve their varied interests. Boys in turn developed new self-understandings by leaving their homes as students, workers, and clients of older men. This article examines the life histories of four boys to trace the successes and challenges that individual boys encountered in this turbulent era. Interestingly, older biological relatives of boys generally succeeded in maintaining their authority over children living far from home, although the education and wages that boys received forced older men to offer boys more benefits.

High prevalence of hepatitis C virus infection and predominance of genotype 4 in rural gabon

Hepatitis C (HCV) molecular epidemiology is documented poorly in central African countries. In response to this, a population-based study of 319 consenting adults resident in a remote village of Gabon was undertaken (mean age: 38 years; age range: 13-85+; sex ratio: 0.74). Screening for anti-HCV antibodies was performed using ELISA and recombinant immunoblot assay. Seropositive samples were assessed further with viral load and genotyping techniques. Sixty-six (20.7%) individuals were HCV seropositive. Viral loads ranged from 600 to 24.9 million IU/ml (median: 372,500). Seroprevalence and viral loads increased significantly with age (P < 10(-5) and P < 0.003, respectively). HCV sequences of the 5'UTR genome region were obtained from 60 (90.9%) samples and NS5B region sequences were obtained from 22 (36.6%) samples. All strains belonged to subtypes of genotype 4: 4e (72.7%), 4c (13.6%), 4p (4.5%), 4r (4.5%) and one unclassified genotype 4 strain. Evolutionary analysis of the subtype 4e sequences indicates a period of raised transmission during the early twentieth century.

Differences in Presentation of Severe Malaria in Urban and Rural Gabon

There are rare comparative studies of the clinical and laboratory features of severe and moderate malaria, including predictors of poor outcome, in rural and urban areas for regions of high malaria transmission. We therefore studied 2,235 children hospitalized for malaria in a rural (Lambaréné) and an urban (Libreville) area in Gabon between January 2001 and December 2002. From children screened, 33% and 48% were hospitalized for malaria in Libreville and Lambaréné, respectively (P < 0.001). Two malaria clinical groups were identified according to the World Health Organization 2000 classification of severe malaria. In both areas, severe malaria was characterized by a high proportion of severe anemia. The case fatality rate was 5-fold lower in Lambaréné than in Libreville (1% versus 5%; P < 0.0001). In both sites, cerebral malaria associated with respiratory distress was the most important predictor of fatal malaria (odds ratio = 10.7, 95% confidence interval = 4.8-23.8 P < 0.0001).

Identification of hepatitis B virus subgenotype A3 in rural Gabon

An hepatitis B virus (HBV) molecular survey was conducted in five remote villages in the equatorial forest in Gabon, Central Africa. Two hundred seventy out of 311 inhabitants (86.8%) were HBV-infected or had evidence of past HBV infection. Chronic hepatitis corresponding to hepatitis B surface antigen (HBsAg) positivity was suspected in 27 (8.6%) of the HBV-infected subjects. High HBV viral loads were detected mainly in children aged 4-7 years. The pre-S/S domains were sequenced in 13 cases and 12 strains belonged to HBV-A genotype. In one case we found evidence for recombination between genotypes A and E. Phylogenetic analysis revealed that Gabonese HBV strains were distinct from HBV-A subgenotypes (A1 and A2). These new HBV strains from Gabon clustered with previously reported HBV-A3 subgenotype strains from Cameroon and Democratic Republic of Congo. The analysis of the pre-S2 domain allowed us to determine two amino acid substitutions (N/152/S and N/174/T) specific to the Central African HBV-A3 subgenotype strains and one amino acid substitution (P/155/Q) unique to these new Gabonese HBV-A3 subgenotype isolates. Two full genome sequences of two new Gabonese HBV isolates are also presented and confirm the distinctive HBV-Gab-A3 cluster.

SHORT REPORT: PILOTING PAPERLESS DATA ENTRY FOR CLINICAL RESEARCH IN AFRICA

Direct data entry, using handheld computers, may simplify and streamline data management, especially in remote settings. We compared the accuracy of data entry using the current standard practice (a paper-based case report form with double data entry) with that using a personal digital assistant (PDA) in a clinical study in rural Gabon. The rate of discrepant entries was 1.7%. Categorical data (presented in "pull down" menus on the PDA) were more commonly discrepant than were continuous "typed in" data (2.4% versus 1.2%; P = 0.001). Both systems functioned smoothly and no data were lost. The clinicians involved in this study preferred the handheld computers, and their use will be considered in future studies in an African clinical research network.

Relationship between entomological inoculation rate, Plasmodium falciparum prevalence rate, and incidence of malaria attack in rural Gabon

To assess the relationships between variations of Plasmodium falciparum transmission and those of peripheral parasitaemia prevalence or malaria attack incidence rates in regions with limited fluctuations of transmission, we conducted a follow-up in two Gabonese populations. Entomological surveys were carried out from May 1995 to April 1996 in Dienga, and from May 1998 to April 1999 in Benguia. In Dienga, malaria transmission was seasonal, being not detected during two 3-month periods. Mean entomological inoculation rate (EIR) was 0.28 infective bite/person/night. In Benguia, malaria transmission was perennial with seasonal fluctuations, mean EIR being 0.76 infective bite/person/night. In Dienga, 301 schoolchildren were followed from October 1995 to March 1996. Clinical malaria attack was defined as fever associated with >5000 parasites/μl of blood. P. falciparum prevalence varied from 28 to 42%, and monthly malaria attack incidence from 30 to 169‰. In Benguia, the entire population (122 persons) was followed from November 1998 to April 1999. Prevalence varied from 22 to 50%, and monthly malaria attack incidence from 52 to 179‰. In each area, entomological variations were not related to parasite prevalence, but preceded malaria attack incidence with 1- or 2-month time lag, corresponding to the pre-patency period that differs in the two populations, possibly according to differences in immunity related to parasite transmission.