M.A.B. van der Sande

Atopy, intestinal helminth infection and total serum IgE in rural and urban adult Gambian communities

Background The rarity of atopy in traditional societies has been attributed to high parasite‐driven blocking IgE concentrations. Information is lacking on the relationship between atopy, IgE and intestinal helminth infection in African populations.

Long-Term Protection against Carriage of Hepatitis B Virus after Infant Vaccination

BACKGROUND Carriage of hepatitis B virus (HBV) is a major risk factor for liver cirrhosis and hepatocellular carcinoma. Infant vaccination has been effective in preventing horizontal transmission during early childhood. It is unknown whether protection is maintained into early adulthood. METHODS In 1984, early childhood vaccination was introduced in 2 rural Gambian villages. In 2003, serological assessment of 81.5% of 1,350 eligible participants 1-24 years old was done, to determine vaccine efficacy against infection and carriage. RESULTS Overall vaccine efficacy against infection and carriage was 83.4% (95% confidence interval [CI], 79.8%-86.6%) and 96.5% (85% CI, 93.9%-98.9%), respectively. Vaccine efficacy against infection was similar when restricted to primary responders (85.3%), but a significant effect of peak antibody concentration was found. Both vaccine efficacy and levels of hepatitis B surface antibody (anti-HBs) decreased with age, resulting in a vaccine efficacy against infection and carriage among 20-24-year-old participants of 70.9% (95% CI, 60.4%-80.5%) and 91.1% (95% CI, 75.8%-100%), respectively. Fifteen years after vaccination, fewer than half of the vaccinees had detectable anti-HBs. The prevalence of carriage in the unvaccinated population was similar to the prevalence 20 years earlier. CONCLUSIONS HBV vaccination early during life can provide long-lasting protection against carriage, despite decreasing antibody levels. The role played by subclinical boosting and the necessity of a booster need to be evaluated.

Blood pressure patterns and cardiovascular risk factors in rural and urban Gambian communities

Hypertension is emerging as an important public health problem in sub-Saharan Africa. We studied blood pressure (BP) patterns, hypertension and other cardiovascular risk factors in a rural and an urban area of The Gambia. A total of 5389 adults (⩾15 years) were selected by cluster sampling in the capital Banjul and a rural area around Farafenni. A questionnaire was completed, BP, pulse rate, height and weight were recorded. Glucose was measured 2 h after a 75 g glucose load among participants ⩾35 years (n = 2301); total cholesterol, triglycerides, creatinine and uric acid were measured among a stratified subsample (n = 1075). A total of 7.1% of the study participants had a BP ⩾160/95 mm Hg; 18.4% of them had a BP ⩾140/90 mm Hg. BP was significantly higher in the urban area. BP increased with age in both sexes in both areas. Increasing age was the major independent risk factor for hypertension. Related cardiovascular risk factors (obesity, diabetes and hyperlipidaemia) were significantly more prevalent in the urban area and among hypertensives; 17% of measured hypertensives were aware of this, 73% of people who reported to have been diagnosed as hypertensive before had discontinued treatment; 56% of those who reported being on treatment were normotensive. We conclude that hypertension is no longer rare in either urban or rural Gambians. In the urban site hypertension and related cardiovascular risk factors were more prevalent. Compliance with treatment was low. Interventions aimed at modifying risk factors at the population level, and at improving control of diagnosed hypertension are essential to prevent future increases of cardiovascular morbidity and mortality. In view of limited resources and feasibility of intervention in rural Gambia, these could initially be directed towards urbanised populations.

Internet-based monitoring of influenza-like illness in the general population: Experience of five influenza seasons in the Netherlands

Like in most other countries, influenza surveillance in The Netherlands is based upon influenza-like illness (ILI) consultations reported by sentinel general practitioners (GP). In addition, an internet-based monitoring of ILI in the general population started in 2003/2004 (Great Influenza Survey (GIS)). We compared GIS results over 5 influenza seasons with results from the GP system. Weekly ILI incidence from GIS correlated well with ILI incidence from the GP system the same week and even better 1 week later. This suggests that GIS is useful for early detection of trends in influenza activity. However, two important vulnerable groups, children and the elderly, are clearly underrepresented in the GIS. Furthermore, virological confirmation is lacking in the GIS. So, GIS can be a useful addition to the GP system, especially when representativeness can be improved and when participation remains at the current high level.

Which determinants should be targeted to increase influenza vaccination uptake among health care workers in nursing homes

Although health care workers (HCWs) have been recommended to be immunized against influenza, vaccine uptake remains low. So far, research on determinants of influenza vaccination among HCWs has been limited by design, population or theoretical framework. Therefore we conducted a questionnaire study in Dutch nursing homes to assess which demographical, behavioural and organisational determinants were associated with influenza vaccine uptake among HCWs. We were able to accurately predict vaccine uptake based on a 13-item prediction model including two demographical, nine behavioural and two organisational determinants developed with data from 1,125 respondents (response rate 60%). To further increase influenza vaccine uptake, implementation programs should target these determinants.

Plasmodium falciparum infection of the placenta affects newborn immune responses

The effects of exposure to placental malaria infection on newborn immunological responses, in particular Th1/Th2 cytokines and antigen‐presenting cell (APC) function, were compared between cord blood mononuclear cells (CBMC) from parasitized and non‐parasitized placentas of Gambian women. Cells were analysed in vitro for their ability to respond to mitogens [phorbol myristate acetate (PMA)/ionomycin, phytohaemagglutinin (PHA)], a malaria‐unrelated test antigen [purified protein derivative of Mycobacterium tuberculin[purified protein derivative (PPD)] and Plasmodium falciparum schizont extracts. Mitogens induced strong proliferation and secretion of high concentrations of both IL‐13 and sCD30 in CBMC from both groups. Conversely, significantly lower amounts of IFN‐γ were induced in the parasitized group in response to low doses of PHA. Protein antigens induced very low amounts of all tested cytokines, in particular IFN‐γ. However, a significantly higher release of sCD30 was observed in response to schizont extracts in the parasitized group. Addition of LPS to activate APC to low doses of PHA or schizont extracts increased the IFN‐γ production in both groups but levels remained lower in CBMC from the parasitized group. This result correlates with the lower production of IL‐12 found following lipopolysaccharide (LPS) stimulation in this group. Taken together, these data show that placental infection with P. falciparum affects Th1 differentiation and sCD30 priming of neonatal lymphocytes and that the probable mode of action is via APC.

Asthma, smoking and chronic cough in rural and urban adult communities in The Gambia

Background Asthma is reported to be rare in traditional rural communities, but is thought to be increasing as lifestyles become more urbanized or ‘western’.

Absence of association between delayed type hypersensitivity to tuberculin and atopy in children in The Gambia.

Background An inverse association between delayed type hypersensitivity to tuberculin and atopy has been observed in children, suggesting that exposure to mycobacteria may influence the immune response to allergens.

Effects of a multi-faceted program to increase influenza vaccine uptake among health care workers in nursing homes: A cluster randomised controlled trial

Despite the recommendation of the Dutch association of nursing home physicians (NVVA) to be immunized against influenza, vaccine uptake among HCWs in nursing homes remains unacceptably low. Therefore we conducted a cluster randomised controlled trial among 33 Dutch nursing homes to assess the effects of a systematically developed multi-faceted intervention program on influenza vaccine uptake among HCWs. The intervention program resulted in a significantly higher, though moderate, influenza vaccine uptake among HCWs in nursing homes. To take full advantage of this measure, either the program should be adjusted and implemented over a longer time period or mandatory influenza vaccination should be considered.

Plasmodium falciparum infection of the placenta impacts on the T helper type 1 (Th1)/Th2 balance of neonatal T cells through CD4+CD25+ forkhead box P3+ regulatory T cells and interleukin-10.

Placental malaria infection affects the T helper type 1 (Th1)/Th2 balance in neonatal children. We investigated a potential role of regulatory T cells in this balance by comparing T cell responses of cord blood mononuclear cells (CBMC) from parasitized and non‐parasitized placenta of Gambian women. CBMC were depleted of CD4+CD25+ forkhead box P3 (FoxP3)+ regulatory T cells and analysed in vitro for their ability to produce interferon (IFN)‐γ, sCD30 and interleukin (IL)‐10 in response to phytohaemagglutinin (PHA), live Plasmodium falciparum, schizont extracts and the recombinant P. falciparum blood stage antigen merozoite surface protein 1 (MSP119). As expected, lower IFN‐γ and higher sCD30 responses were observed for the cells from the parasitized group. In addition, higher IL‐10 levels were produced by CBMC from the parasitized group. Depletion of regulatory T cells decreased IL‐10 production, which resulted in a restoration of IFN‐γ expression in response to all stimuli. The Th2 marker sCD30 remained significantly higher in the parasitized group in response to malaria protein antigens while similar levels were recovered between both groups in response to live P. falciparum. Similar effects were observed by adding an antibody that blocks IL‐10 function. These results suggest that the impact of P. falciparum infection on Th1 differentiation of neonatal T cells can be ascribed to regulatory T cells through production of IL‐10.