Understanding key vectors and vector-borne diseases associated with freshwater ecosystem across Africa: Implications for public health

The emerging and re-emerging vector-borne diseases transmitted by key freshwater organisms have remained a global concern. As one of the leading biodiversity hotspots, the African ecoregion is suggested to harbour the highest number of freshwater organisms globally. Among the commonly found organisms in the African ecoregion are mosquitoes and snails, with a majority of their life cycle in freshwater, and these freshwater organisms can transmit diseases or serve as carriers of devastating diseases of public health concerns. However, synthetic studies to link the evident abundant presence and wide distribution of these vectors across the freshwater ecosystems in Africa with the increasing emerging and re-emerging vector-borne diseases in Africa are still limite

Helicobacter pylori patient isolates from South Africa and Nigeria differ in virulence factor pathogenicity profile and associated gastric disease outcome

Helicobacter pylori is a gram-negative, spiral-shaped bacterial pathogen and the causative agent for gastritis, peptic ulcer disease and classified as a WHO class I carcinogen. While the prevalence of H. pylori infections in Africa is among the highest in the world, the incidence of gastric cancer is comparably low. Little is known about other symptoms related to the H. pylori infection in Africa and the association with certain phenotypes of bacterial virulence. We established a network of study sites in Nigeria (NG) and South Africa (ZA) to gain an overview on the epidemiological situation. In total 220 isolates from 114 patients were analyzed and 118 different patient isolates examined for the presence of the virulence factors cagA, vacA, dupA, their phylogenetic origin and their resistance against the commonly used antibiotics amoxicillin, clarithromycin, metronidazole and tetracycline. We report that H. pylori isolates from Nigeria and South Africa differ significantly in their phylogenetic profiles and in their expression of virulence factors. VacA mosaicism is intensive, resulting in m1-m2 vacA chimeras and frequent s1m1 and s1m2 vacA subtypes in hpAfrica2 strains. Gastric lesions were diagnosed more frequent in Nigerian versus South African patients and H. pylori isolates that are resistant against one or multiple antibiotics occur frequently in both countries

Elevated rates of horizontal gene transfer in the industrialized human microbiome

Industrialization has impacted the human gut ecosystem, resulting in altered microbiome composition and diversity. Whether bacterial genomes may also adapt to the industrialization of their host populations remains largely unexplored. Here, we investigate the extent to which the rates and targets of horizontal gene transfer (HGT) vary across thousands of bacterial strains from 15 human populations spanning a range of industrialization. We show that HGTs have accumulated in the microbiome over recent host generations and that HGT occurs at high frequency within individuals. Comparison across human populations reveals that industrialized lifestyles are associated with higher HGT rates and that the functions of HGTs are related to the level of host industrialization. Our results suggest that gut bacteria continuously acquire new functionality based on host lifestyle and that high rates of HGT may be a recent development in human history linked to industrialization.Peer reviewe

Helicobacter pylori strains from a Nigerian cohort show divergent antibiotic resistance rates and a uniform pathogenicity profile

Antibiotic resistance in Helicobacter pylori is a factor preventing its successful eradication. Particularly in developing countries, resistance against commonly used antibiotics is widespread. Here, we present an epidemiological study from Nigeria with 111 isolates. We analyzed the associated disease outcome, and performed a detailed characterization of these isolated strains with respect to their antibiotic susceptibility and their virulence characteristics. Furthermore, statistical analysis was performed on microbiological data as well as patient information and the results of the gastroenterological examination. We found that the variability concerning the production of virulence factors between strains was minimal, with 96.4% of isolates being CagA-positive and 92.8% producing detectable VacA levels. In addition, high frequency of bacterial resistance was observed for metronidazole (99.1%), followed by amoxicillin (33.3%), clarithromycin (14.4%) and tetracycline (4.5%). In conclusion, this study indicated that the infection rate of H. pylori infection within the cohort in the present study was surprisingly low (36.6%). Furthermore, an average gastric pathology was observed by histological grading and bacterial isolates showed a uniform pathogenicity profile while indicating divergent antibiotic resistance rates

Non-alcoholic fatty liver disease and the metabolic syndrome in an urban hospital serving an African community

Background. Liver disease continues to be a major cause of morbidity and mortality in sub-Saharan Africa, including Nigeria, due to the high endemicity of viral hepatitis B. However non-alcoholic fatty liver disease may be an important contributory factor. The impact of fatty liver disease in our region has not been evaluated.AIM. To determine the prevalence of non-alcoholic fatty liver disease (NAFLD) among a population of diabetic (DM) subjects attending the endocrine clinic of LASUTH compared with non-diabetic subjects; ascertain other contributing factors and compare the occurrence of the metabolic syndrome in subjects with and without NAFLD.Methodology. Consecutive patients who satisfy the study criteria were enrolled. An investigator-administered questionnaire was used to determine symptoms of liver disease, followed by physical examination to obtain anthropometric indices as well as signs of liver disease. Abdominal scan was performed to determine radiologic evidence of fatty liver and fasting blood samples were collected from for the measurement of fasting lipid profile, glucose, liver biochemistry and serology for hepatitis B and C markers.Results. One hundred and fifty subjects, mean age 56years (standard deviation = 9, range 20-80 yr) and gender ratio (F: M) of 83:67(55%:45%), were recruited. 106 were diabetics and 44 non-diabetics. The overall prevalence of NAFLD amongst all study subjects was 8.7%. The prevalence rate of NAFLD was higher in the DM cases than in the Control subjects but this difference was not statistically significant (9.5 vs. 4.5%, p = 0.2). Only one of the subjects with fatty liver disease had elevated transaminase levels (steatohepatitis) and also had type 2 DM. Central obesity as measured by waist circumference (WC) and SGPT levels were significantly higher in people with fatty liver. The mean body mass index (BMI) of diabetic and non-diabetic patients was similar (31 vs. 30 kg/m2). The prevalence of the metabolic syndrome was higher in the subjects with NAFLD than in those without fatty liver disease but this difference was not statistically significant (p = 0.8).Conclusion. Non-alcoholic fatty liver disease is present in Africa but is less than what one would expect based on American and European studies

A clinicopathological study of dyspeptic subjects in Lagos, Nigeria

The clinicopathological and endoscopic features of dyspepsia have not been well studied in Nigeria due to the high cost of gastroscopes and lack of the relevant expertise. This study was designed to highlight these features and possible risk factors. This prospective study was conducted on adult dyspeptic patients who fulfilled the study criteria from November 2007 to December 2008 at a University hospital in Lagos, Nigeria. Demographic and clinical presentation including possible risk factors were obtained through a questionnaire administered by an interviewer followed by an upper gastrointestinal endoscopy and gastric biopsy. Of the 123 subjects who took part in the study, 100 gave their consent to an upper gastrointestinal endoscopy and biopsy. The male:female ratio was 1:1, mean age was 44.98 (SD 15.4) years and the modal age group was 38-47years. The prevalence of dyspepsia was 29% and epigastric pain was the most common presentation. Endoscopic findings were superficial mucosal lesion (21%), peptic ulcer (16%), features of gastroesophageal reflux disease (10%), and gastric cancer (2%), as well normal findings (44%). Non-steroidal antiinflammatory drug (NSAID) use as a risk factor had a significant association with positive endoscopic findings; relative risk for development of positive endoscopic findings was 1.5% (P =0.03). Histology showed rates of chronic gastritis to be 91% and normal values 9%. The most common type of gastritis was the non-specific form (59.3%), followed by <em>H. Pylori</em>-associated gastritis (36.3%). The topography of gastritis was mainly pangastritis (68.1%) and antral predominant in 23.1%. The prevalence of<em> H. pylori</em> by histology was 41%. The presence of <em>H</em>. <em>pylori</em> was not associated with severity, location or duration of symptoms. H. pylori was, however, found to be a significant contributor to the development of positive endoscopic findings (P=0.01; OR 2.92 95% CI 1.50-3.17). Alarm symptoms were found to be important markers of malignancy. Dyspeptic illness is common,with peak incidence in the 4th decade of life and no gender predilection. Epigastric pain has the most discriminatory value with alarm symptoms in cases of gastric cancer. Risk factors such as NSAID use and <em>H. pylori</em> infection had a very significant impact on endoscopic findings while presence of <em>H. pylori</em>, smoking and alcohol consumption were associated with increased risk of developing chronic gastritis

High-density SNP genotyping to define β-globin locus haplotypes

Five major β-globin locus haplotypes have been established in individuals with sickle cell disease (SCD) from the Benin, Bantu, Senegal, Cameroon, and Arab-Indian populations. Historically, β-haplotypes were established using restriction fragment length polymorphism (RFLP) analysis across the β-locus, which consists of five functional β-like globin genes located on chromosome 11. Previous attempts to correlate these haplotypes as robust predictors of clinical phenotypes observed in SCD have not been successful. We speculate that the coverage and distribution of the RFLP sites located proximal to or within the globin genes are not sufficiently dense to accurately reflect the complexity of this region. To test our hypothesis, we performed RFLP analysis and high-density single nucleotide polymorphism (SNP) genotyping across the β-locus using DNA samples from healthy African Americans with either normal hemoglobin A (HbAA) or individuals with homozygous SS (HbSS) disease. Using the genotyping data from 88 SNPs and Haploview analysis, we generated a greater number of haplotypes than that observed with RFLP analysis alone. Furthermore, a unique pattern of long-range linkage disequilibrium between the locus control region and the β-like globin genes was observed in the HbSS group. Interestingly, we observed multiple SNPs within the HindIII restriction site located in the Gγ-globin intervening sequence II which produced the same RFLP pattern. These findings illustrated the inability of RFLP analysis to decipher the complexity of sequence variations that impacts genomic structure in this region. Our data suggest that high-density SNP mapping may be required to accurately define β-haplotypes that correlate with the different clinical phenotypes observed in SCD. © 2008 Elsevier Inc. All rights reserved