Vitamin A supplementation and childhood malaria in northern Ghana

Vitamin A supplementation for preventing morbidity and mortality in children from six months to five years of age

BACKGROUND

Vitamin A deficiency (VAD) is a major public health problem in low- and middle-income countries, affecting 190 million children under five years of age and leading to many adverse health consequences, including death. Based on prior evidence and a previous version of this review, the World Health Organization has continued to recommend vitamin A supplementation (VAS) for children aged 6 to 59 months. The last version of this review was published in 2017, and this is an updated version of that review.

OBJECTIVES

To assess the effects of vitamin A supplementation (VAS) for preventing morbidity and mortality in children aged six months to five years.

SEARCH METHODS

We searched CENTRAL, MEDLINE, Embase, six other databases, and two trials registers up to March 2021. We also checked reference lists and contacted relevant organisations and researchers to identify additional studies.

SELECTION CRITERIA

Randomised controlled trials (RCTs) and cluster-RCTs evaluating the effect of synthetic VAS in children aged six months to five years living in the community. We excluded studies involving children in hospital and children with disease or infection. We also excluded studies evaluating the effects of food fortification, consumption of vitamin A rich foods, or beta-carotene supplementation.

DATA COLLECTION AND ANALYSIS

For this update, two review authors independently assessed studies for inclusion resolving discrepancies by discussion. We performed meta-analyses for outcomes, including all-cause and cause-specific mortality, disease, vision, and side effects. We used the GRADE approach to assess the quality of the evidence.

MAIN RESULTS

The updated search identified no new RCTs. We identified 47 studies, involving approximately 1,223,856 children. Studies were set in 19 countries: 30 (63%) in Asia, 16 of these in India; 8 (17%) in Africa; 7 (15%) in Latin America, and 2 (4%) in Australia. About one-third of the studies were in urban/periurban settings, and half were in rural settings; the remaining studies did not clearly report settings. Most studies included equal numbers of girls and boys and lasted about one year. The mean age of the children was about 33 months. The included studies were at variable overall risk of bias; however, evidence for the primary outcome was at low risk of bias. A meta-analysis for all-cause mortality included 19 trials (1,202,382 children). At longest follow-up, there was a 12% observed reduction in the risk of all-cause mortality for VAS compared with control using a fixed-effect model (risk ratio (RR) 0.88, 95% confidence interval (CI) 0.83 to 0.93; high-certainty evidence). Nine trials reported mortality due to diarrhoea and showed a 12% overall reduction for VAS (RR 0.88, 95% CI 0.79 to 0.98; 1,098,538 children; high-certainty evidence). There was no evidence of a difference for VAS on mortality due to measles (RR 0.88, 95% CI 0.69 to 1.11; 6 studies, 1,088,261 children; low-certainty evidence), respiratory disease (RR 0.98, 95% CI 0.86 to 1.12; 9 studies, 1,098,538 children; low-certainty evidence), and meningitis. VAS reduced the incidence of diarrhoea (RR 0.85, 95% CI 0.82 to 0.87; 15 studies, 77,946 children; low-certainty evidence), measles (RR 0.50, 95% CI 0.37 to 0.67; 6 studies, 19,566 children; moderate-certainty evidence), Bitot's spots (RR 0.42, 95% CI 0.33 to 0.53; 5 studies, 1,063,278 children; moderate-certainty evidence), night blindness (RR 0.32, 95% CI 0.21 to 0.50; 2 studies, 22,972 children; moderate-certainty evidence), and VAD (RR 0.71, 95% CI 0.65 to 0.78; 4 studies, 2262 children, moderate-certainty evidence). However, there was no evidence of a difference on incidence of respiratory disease (RR 0.99, 95% CI 0.92 to 1.06; 11 studies, 27,540 children; low-certainty evidence) or hospitalisations due to diarrhoea or pneumonia. There was an increased risk of vomiting within the first 48 hours of VAS (RR 1.97, 95% CI 1.44 to 2.69; 4 studies, 10,541 children; moderate-certainty evidence).

AUTHORS' CONCLUSIONS

This update identified no new eligible studies and the conclusions remain the same. VAS is associated with a clinically meaningful reduction in morbidity and mortality in children. Further placebo-controlled trials of VAS in children between six months and five years of age would not change the conclusions of this review, although studies that compare different doses and delivery mechanisms are needed. In populations with documented VAD, it would be unethical to conduct placebo-controlled trials.

Vitamin A Supplementation for Prevention and Treatment of Malaria during Pregnancy and Childhood: A Systematic Review and Meta-analysis

Animal studies have shown that vitamin A plays a role in immunity and protection against infectious diseases. Its role reducing incidence of diarrhea and measles, and childhood mortality is known, but its role in relation to malaria is unclear. Thus, a comprehensive, systematic literature search was conducted on PubMed and Cochrane Library to identify randomized controlled trials (RCTs) on the role of vitamin A during pregnancy and childhood for prevention and treatment of malaria. A total of 107 titles/abstracts were identified, of which 15 articles (11 studies) were selected for final inclusion. Based on the meta-analysis, vitamin A supplementation during pregnancy had no benefit for placental infection (relative risk = 1.09; 95% confidence interval (CI), 0.95–1.25; fixed effects, I² = 0; 2 RCTs). Similarly, there was no effect on peripheral parasitemia or episodes of new clinical malaria. Preventive vitamin A supplementation in children younger than 5 years did not reduce the incidence of peripheral parasitemia or malaria mortality (latter rate ratio = 0.49; 95% CI, 0.07–3.26; random effects, I² = 72%, 2 RCTs). Vitamin A as an adjunct treatment for cerebral or severe malaria in children did not have benefit on survival, fever resolution time, parasite clearance time, or incidence of neurological or other complications. Vitamin A has no benefit for malarial infection either as prevention or treatment in pregnancy or childhood based on RCT evidence.

Vitamin A Deficiency Disorders in Children and Women

Vitamin A deficiency is an endemic nutrition problem throughout much of the developing world, especially affecting the health and survival of infants, young children, and pregnant and lactating women. These age and life-stage groups represent periods when both nutrition stress is high and diet likely to be chronically deficient in vitamin A. Approximately 127 million preschool-aged children and 7 million pregnant women are vitamin A deficient. Health consequences of vitamin A deficiency include mild to severe systemic effects on innate and acquired mechanisms of host resistance to infection and growth, increased burden of infectious morbidity, mild to severe (blinding) stages of xerophthalmia, and increased risk of mortality. These consequences are defined as vitamin A deficiency disorders (VADD). Globally, 4.4 million preschool children have xerophthalmia and 6 million mothers suffer night blindness during pregnancy. Both conditions are associated with increased risk of morbidity and mortality. While reductions of child mortality of 19–54% following vitamin A treatment have been widely reported, more recent work suggests that dosing newborns with vitamin A may, in some settings, lower infant mortality. Among women, one large trial has so far reported a ≥ 40% reduction in mortality related to pregnancy with weekly, low-dose vitamin A supplementation. Epidemiologic data on vitamin A deficiency disorders can be useful in planning, designing, and targeting interventions.

Vitamin A supplementation for preventing morbidity and mortality in children from six months to five years of age

BACKGROUND

Vitamin A deficiency (VAD) is a major public health problem in low- and middle-income countries, affecting 190 million children under five years of age and leading to many adverse health consequences, including death. Based on prior evidence and a previous version of this review, the World Health Organization has continued to recommend vitamin A supplementation for children aged 6 to 59 months. There are new data available from recently published randomised trials since the previous publication of this review in 2010, and this update incorporates this information and reviews the evidence.

OBJECTIVES

To assess the effects of vitamin A supplementation (VAS) for preventing morbidity and mortality in children aged six months to five years.

SEARCH METHODS

In March 2016 we searched CENTRAL, Ovid MEDLINE, Embase, six other databases, and two trials registers. We also checked reference lists and contacted relevant organisations and researchers to identify additional studies.

SELECTION CRITERIA

Randomised controlled trials (RCTs) and cluster-RCTs evaluating the effect of synthetic VAS in children aged six months to five years living in the community. We excluded studies involving children in hospital and children with disease or infection. We also excluded studies evaluating the effects of food fortification, consumption of vitamin A rich foods, or beta-carotene supplementation.

DATA COLLECTION AND ANALYSIS

For this update, two reviewers independently assessed studies for inclusion and abstracted data, resolving discrepancies by discussion. We performed meta-analyses for outcomes, including all-cause and cause-specific mortality, disease, vision, and side effects. We used the GRADE approach to assess the quality of the evidence.

MAIN RESULTS

We identified 47 studies (4 of which are new to this review), involving approximately 1,223,856 children. Studies took place in 19 countries: 30 (63%) in Asia, 16 of these in India; 8 (17%) in Africa; 7 (15%) in Latin America, and 2 (4%) in Australia. About one-third of the studies were in urban/periurban settings, and half were in rural settings; the remaining studies did not clearly report settings. Most of the studies included equal numbers of girls and boys and lasted about a year. The included studies were at variable overall risk of bias; however, evidence for the primary outcome was at low risk of bias. A meta-analysis for all-cause mortality included 19 trials (1,202,382 children). At longest follow-up, there was a 12% observed reduction in the risk of all-cause mortality for vitamin A compared with control using a fixed-effect model (risk ratio (RR) 0.88, 95% confidence interval (CI) 0.83 to 0.93; high-quality evidence). This result was sensitive to choice of model, and a random-effects meta-analysis showed a different summary estimate (24% reduction: RR 0.76, 95% CI 0.66 to 0.88); however, the confidence intervals overlapped with that of the fixed-effect model. Nine trials reported mortality due to diarrhoea and showed a 12% overall reduction for VAS (RR 0.88, 95% CI 0.79 to 0.98; 1,098,538 participants; high-quality evidence). There was no significant effect for VAS on mortality due to measles, respiratory disease, and meningitis. VAS reduced incidence of diarrhoea (RR 0.85, 95% CI 0.82 to 0.87; 15 studies; 77,946 participants; low-quality evidence) and measles (RR 0.50, 95% CI 0.37 to 0.67; 6 studies; 19,566 participants; moderate-quality evidence). However, there was no significant effect on incidence of respiratory disease or hospitalisations due to diarrhoea or pneumonia. There was an increased risk of vomiting within the first 48 hours of VAS (RR 1.97, 95% CI 1.44 to 2.69; 4 studies; 10,541 participants; moderate-quality evidence).

AUTHORS' CONCLUSIONS

Vitamin A supplementation is associated with a clinically meaningful reduction in morbidity and mortality in children. Therefore, we suggest maintaining the policy of universal supplementation for children under five years of age in populations at risk of VAD. Further placebo-controlled trials of VAS in children between six months and five years of age would not change the conclusions of this review, although studies that compare different doses and delivery mechanisms are needed. In populations with documented vitamin A deficiency, it would be unethical to conduct placebo-controlled trials.

Vitamin A supplements, routine immunization, and the subsequent risk of Plasmodium infection among children under 5 years in sub-Saharan Africa

Recent studies, partly based on murine models, suggest childhood immunization and vitamin A supplements may confer protection against malaria infection, although strong evidence to support these theories in humans has so far been lacking. We analyzed national survey data from children aged 6–59 months in four sub-Saharan African countries over an 18-month time period, to determine the risk of Plasmodium spp. parasitemia (n=8390) and Plasmodium falciparum HRP-2 (PfHRP-2)-related antigenemia (n=6121) following vitamin A supplementation and standard vaccination. Bacille Calmette Guerin-vaccinated children were more likely to be PfHRP-2 positive (relative risk [RR]=4.06, 95% confidence interval [CI]=2.00–8.28). No association was identified with parasitemia. Measles and polio vaccination were not associated with malaria. Children receiving vitamin A were less likely to present with parasitemia (RR=0.46, 95% CI=0.39–0.54) and antigenemia (RR=0.23, 95% CI=0.17–0.29). Future studies focusing on climate seasonality, placental malaria and HIV are needed to characterize better the association between vitamin A and malaria infection in different settings.

DOI:http://dx.doi.org/10.7554/eLife.03925.001

More than half of the world's population is at risk of malaria, with an estimated 198 million clinical cases each year. A vaccine that fully prevents it has not yet been discovered. Most cases of malaria occur among children living in sub-Saharan Africa, a region where many receive routine vaccinations designed to prevent other diseases; for example, 75% of children in sub-Saharan Africa receive measles vaccines. Many also receive vitamin A supplements, which have been linked not only to the protection of a child's vision, but also to a lower risk of death and an improved ability to fight off infections.

Some researchers have suggested that vitamin A supplements and routine childhood vaccinations for other diseases may also provide some protection against malaria. For example, some studies performed in mice have shown that a commonly used tuberculosis vaccine may eliminate Plasmodium parasites that cause malaria infections. However, this effect depended on several factors, including how the vaccine was administered and whether the vaccination was given before or after the mouse developed malaria.

It is less clear whether vaccines or vitamin A have antimalarial effects in humans. To address this, Hollm-Delgado et al. analyzed national survey data collected from thousands of children aged between 6 months and 5 years old who lived in four different countries in sub-Saharan Africa. The surveys contained information about the vaccines and supplements the children received, and whether their blood showed signs of infection with malaria-causing Plasmodium parasites.

Hollm-Delgado et al. found that routine vaccinations did not affect the likelihood of malaria parasites being detected in the child's blood. However, children vaccinated against tuberculosis were more likely to have a specific type of protein released when malaria infects the blood. Hollm-Delgado et al. suspect that the tests may actually have inadvertently detected other parasitic infections in the children, such as Schistosoma, producing false-positive results for malaria.

In contrast, Hollm-Delgado et al. found that children who received vitamin A supplements were less likely to become infected with malaria. The benefits of the supplements appeared to be affected by several conditions, including the time of year when the children received their supplements or when they were tested for malaria, and whether their mother had malaria when pregnant. Clinical trials are now needed to confirm these results and investigate how effectively vitamin A prevents malaria.

DOI:http://dx.doi.org/10.7554/eLife.03925.002

Supplementation with multivitamins and vitamin A and incidence of malaria among HIV-infected Tanzanian women

Introduction:

HIV and malaria infections occur in the same individuals, particularly in sub-Saharan Africa. We examined whether daily multivitamin supplementation (vitamins B complex, C, and E) or vitamin A supplementation altered malaria incidence in HIV-infected women of reproductive age.

Methods:

HIV-infected pregnant Tanzanian women recruited into the study were randomly assigned to daily multivitamins (B complex, C, and E), vitamin A alone, both multivitamins and vitamin A, or placebo. Women received malaria prophylaxis during pregnancy and were followed monthly during the prenatal and postpartum periods. Malaria was defined in 2 ways: presumptive diagnosis based on a physician's or nurse's clinical judgment, which in many cases led to laboratory investigations, and periodic examination of blood smears for malaria parasites.

Results:

Multivitamin supplementation compared with no multivitamins significantly lowered women's risk of presumptively diagnosed clinical malaria (relative risk: 0.78, 95% confidence interval: 0.67 to 0.92), although multivitamins increased their risk of any malaria parasitemia (relative risk: 1.24, 95% confidence interval: 1.02 to 1.50). Vitamin A supplementation did not change malaria incidence during the study.

Conclusions:

Multivitamin supplements have been previously shown to reduce HIV disease progression among HIV-infected women, and consistent with that, these supplements protected against development of symptomatic malaria. The clinical significance of increased risk of malaria parasitemia among supplemented women deserves further research, however. Preventive measures for malaria are warranted as part of an integrated approach to the care of HIV-infected individuals exposed to malaria.

Relative undernourishment and food insecurity associations with Plasmodium falciparum among Batwa pygmies in Uganda: evidence from a cross-sectional survey

Although malnutrition and malaria co-occur among individuals and populations globally, effects of nutritional status on risk for parasitemia and clinical illness remain poorly understood. We investigated associations between Plasmodium falciparum infection, nutrition, and food security in a cross-sectional survey of 365 Batwa pygmies in Kanungu District, Uganda in January of 2013. We identified 4.1% parasite prevalence among individuals over 5 years old. Severe food insecurity was associated with increased risk for positive rapid immunochromatographic test outcome (adjusted relative risk [ARR] = 13.09; 95% confidence interval [95% CI] = 2.23–76.79). High age/sex-adjusted mid-upper arm circumference was associated with decreased risk for positive test among individuals who were not severely food-insecure (ARR = 0.37; 95% CI = 0.19–0.69). Within Batwa pygmy communities, where malnutrition and food insecurity are common, individuals who are particularly undernourished or severely food-insecure may have elevated risk for P. falciparum parasitemia. This finding may motivate integrated control of malaria and malnutrition in low-transmission settings.

Impact of vitamin A with zinc supplementation on malaria morbidity in Ghana

BACKGROUND

Malaria is a leading cause of morbidity and mortality among young children and is estimated to cause at least 1 million deaths each year especially among pregnant women and young children under the age of five years. Vitamin A supplementation is known to reduce morbidity and mortality in young children. Zinc is required for growth and immunity and we sought to replicate the study by Zeba et al. which showed 30% lower cases of clinical malaria in children on a combination of zinc and a large dose of vitamin A compared with children on vitamin A alone based on the hypothesis that combined vitamin A and zinc reduced symptomatic malaria compared to vitamin A alone.

OBJECTIVES

The primary objective was to determine the effect of vitamin A alone vs. vitamin A and zinc supplements on the incidence of clinical malaria and other anthropometric indices. It also sought to assess the effects on the incidence of anaemia, diarrhoea and pneumonia.

METHODS

The study was community-based and 200 children between the ages of 6-24 months were randomised to receive either vitamin A (100,000 IU for infants less than 12 months & 200,000 IU for children greater than 12 months and 10 mg daily zinc in the intervention group or vitamin A and zinc placebo for 6 months in the control group.

RESULTS

The number of children who were diagnosed with uncomplicated malaria in the intervention group was 27% significantly lower compared with the children in the control group (p = 0.03). There were, however, no effects on severe malaria, pneumonia, anaemia and diarrhea.

CONCLUSIONS

Our study confirms a significant role of vitamin A and zinc in reducing malaria morbidity.

Non-specific effects of diphtheria-tetanus-pertussis and measles vaccinations? An analysis of surveillance data from Navrongo, Ghana

OBJECTIVES

Studies from low-income countries have suggested that routine vaccinations may have non-specific effects on child mortality; measles vaccine (MV) is associated with lower mortality and diphtheria-tetanus-pertussis (DTP) with relatively higher mortality. We used data from Navrongo, Ghana, to examine the impact of vaccinations on child mortality.

METHODS

Vaccination status was assessed at the initiation of a trial of vitamin A supplementation and after 12 and 24 months of follow-up. Within the placebo group, we compared the mortality over the first 4 months and the full 2 years of follow-up for different vaccination status groups with different likelihoods of additional vaccinations during follow-up. The frequency of additional vaccinations was assessed among children whose vaccination card was seen at 12 and 24 months of follow-up.

RESULTS

Among children with a vaccination card, more than 75% received missing DTP or MV during the first 12 months of follow-up, whereas only 25% received these vaccines among children with no vaccination card at enrollment. Children without a card at enrollment had a significant threefold higher mortality over the 2-year follow-up period than those fully vaccinated. The small group of children with DTP3-4 but no MV at enrollment had lower mortality than children without a card and had the same mortality as fully vaccinated children. In contrast, children with 1-2 DTP doses but no MV had a higher mortality during the first 4 months than children without a card [MRR = 1.65 (0.95, 2.87)]; compared with the fully vaccinated children, they had significantly higher mortality after 4 months [MRR = 2.38 (1.07, 5.30)] and after 2 years [MRR = 2.41 (1.41, 4.15)]. Children with 0-2 DTP doses at enrollment had higher mortality after 4 months (MRR = 1.67 (0.82, 3.43) and after 2 years [MRR = 1.85 (1.16, 2.95)] than children who had all three doses of DTP at enrollment.

CONCLUSIONS

As hypothesised, DTP vaccination was associated with higher child mortality than measles vaccination. To optimise vaccination policies, routine vaccinations need to be evaluated in randomised trials measuring the impact on survival.

Seeking consent to genetic and genomic research in a rural Ghanaian setting: a qualitative study of the MalariaGEN experience

Background

Seeking consent for genetic and genomic research can be challenging, particularly in populations with low literacy levels, and in emergency situations. All of these factors were relevant to the MalariaGEN study of genetic factors influencing immune responses to malaria in northern rural Ghana. This study sought to identify issues arising in practice during the enrolment of paediatric cases with severe malaria and matched healthy controls into the MalariaGEN study.

Methods

The study used a rapid assessment incorporating multiple qualitative methods including in depth interviews, focus group discussions and observations of consent processes. Differences between verbal information provided during community engagement processes, and consent processes during the enrolment of cases and controls were identified, as well as the factors influencing the tailoring of such information.

Results

MalariaGEN participants and field staff seeking consent were generally satisfied with their understanding of the project and were familiar with aspects of the study relating to malaria. Some genetic aspects of the study were also well understood. Participants and staff seeking consent were less aware of the methodologies employed during genomic research and their implications, such as the breadth of data generated and the potential for future secondary research.

Moreover, trust in and previous experience with the Navrongo Health Research Centre which was conducting the research influenced beliefs about the benefits of participating in the MalariaGEN study and subsequent decision-making about research participation.

Conclusions

It is important to recognise that some aspects of complex genomic research may be of less interest to and less well understood by research participants and that such gaps in understanding may not be entirely addressed by best practice in the design and conduct of consent processes. In such circumstances consideration needs to be given to additional protections for participants that may need to be implemented in such research, and how best to provide such protections.

Capacity building for research ethics committees with limited familiarity with genetic and genomic research, and appropriate engagement with communities to elicit opinions of the ethical issues arising and acceptability of downstream uses of genome wide association data are likely to be important.

Aligning community engagement with traditional authority structures in global health research: a case study from northern Ghana

Despite the recognition of its importance, guidance on community engagement practices for researchers remains underdeveloped, and there is little empirical evidence of what makes community engagement effective in biomedical research. We chose to study the Navrongo Health Research Centre in northern Ghana because of its well-established community engagement practices and because of the opportunity it afforded to examine community engagement in a traditional African setting. Our findings suggest that specific preexisting features of the community have greatly facilitated community engagement and that using traditional community engagement mechanisms limits the social disruption associated with research conducted by outsiders. Finally, even in seemingly ideal, small, and homogeneous communities, cultural issues exist, such as gender inequities, that may not be effectively addressed by traditional practices alone.

Malaria parasitaemia among infants and its association with breastfeeding peer counselling and vitamin A supplementation: a secondary analysis of a cluster randomized trial

Background

Malaria is the second highest contributor to the disease burden in Africa and there is a need to identify low cost prevention strategies. The objectives of this study were to estimate the prevalence of malaria parasitaemia among infants and to measure the association between peer counselling for exclusive breastfeeding (EBF), vitamin A supplementation, anthropometric status (weight and length) and malaria parasitaemia.

Methods

A cluster randomized intervention trial was conducted between 2006 and 2008 where 12 of 24 clusters, each comprising one or two villages, in Eastern Uganda were allocated to receive peer counselling for EBF. Women in their third trimester of pregnancy (based on the last normal menstrual period) were recruited in all 24 clusters and followed up until their children's first birthday. Blood was drawn from 483 infants between 3 and 12 months of age, to test for malaria parasitaemia.

Results

The prevalence of malaria parasitaemia was 11% in the intervention areas and 10% in the control areas. The intervention did not seem to decrease the prevalence of malaria (PR 1.7; 95% CI: 0.9, 3.3). After controlling for potential confounders, infants not supplemented with Vitamin A had a higher prevalence for malaria compared to those who had been supplemented (PR 6.1; 95% CI: 2.1, 17.6). Among children supplemented with vitamin A, every unit increase in length-for-age Z (LAZ) scores was associated with a reduced prevalence in malaria (PR 0.5; 95% CI:0.4, 0.6). There was no association between LAZ scores and malaria among children that had not been supplemented.

Conclusion

Peer counselling for exclusive breastfeeding did not decrease the prevalence of malaria parasitaemia. Children that had not received Vitamin A supplementation had a higher prevalence of malaria compared to children that had been supplemented.

Trial registration

Clinicaltrials.gov: NCT00397150.

Vitamin A supplementation for preventing morbidity and mortality in children from 6 months to 5 years of age

BACKGROUND

Vitamin A deficiency (VAD) is a major public health problem in low and middle income countries affecting 190 million children under 5. VAD can lead to many adverse health consequences, including death.

OBJECTIVES

To evaluate the effect of vitamin A supplementation (VAS) for preventing morbidity and mortality in children aged 6 months to 5 years.

SEARCH STRATEGY

We searched the Cochrane Central Register of Controlled Trials (CENTRAL 2010 Issue 2),  MEDLINE (1950 to April Week 2 2010), EMBASE (1980 to 2010 Week 16), Global Health (1973 to March 2010), Latin American and Caribbean Health Sciences (LILACS), metaRegister of Controlled Trials and African Index Medicus (27 April 2010).

SELECTION CRITERIA

Randomised controlled trials (RCTs) and cluster RCTs evaluating the effect of synthetic VAS in children aged 6 months to 5 years living in the community. We excluded studies concerned with children in hospital and children with disease or infection. We excluded studies evaluating the effects of food fortification, consumption of vitamin A rich foods or beta-carotene supplementation.

DATA COLLECTION AND ANALYSIS

Two review authors independently assessed studies for inclusion. Data were double abstracted and discrepancies were resolved by discussion. Meta-analyses were performed for outcomes including all-cause and cause-specific mortality, disease, vision, and side-effects.

MAIN RESULTS

43 trials involving 215,633 children were included. A meta-analysis for all-cause mortality included 17 trials comprising 194,795 children with 3536 deaths in both groups. At follow-up, there was a 24% observed reduction in the risk of all-cause mortality for Vitamin A compared with Control (Relative risk (RR) = 0.76 [95% confidence interval (CI) 0.69, 0.83]). Seven trials reported diarrhoea mortality and a 28% overall reduction for VAS (RR = 0.72 [0.57, 0.91]). There was no significant effect of VAS on cause specific mortality of measles, respiratory disease and meningitis. VAS reduced incidence of diarrhoea (RR = 0.85 [0.82, 0.87]) and measles morbidity (RR = 0.50 [0.37, 0.67]); however, there was no significant effect on incidence of respiratory disease or hospitalisations due to diarrhoea or pneumonia. There was an increased risk of vomiting within the first 48 hours of VAS (RR = 2.75 [1.81, 4.19]).

AUTHORS' CONCLUSIONS

VAS is effective in reducing all-cause mortality by about 24% compared to no treatment. In our opinion, given the evidence that VAS causes considerable reduction in child mortality, further placebo-controlled trials of VAS in children between 6 months and 5 years of age are not required. There is a need for further studies comparing different doses and delivery mechanisms (for example, fortification).

Does vitamin A supplementation interact with routine vaccinations? An analysis of the Ghana Vitamin A Supplementation Trial

BACKGROUND

The World Health Organization recommends vitamin A supplementation (VAS) at vaccination contacts after 6 mo of age to reduce mortality. However, it is unknown whether the effect of VAS is independent of vaccinations. One of the original VAS trials from Ghana had collected vaccination information.

OBJECTIVE

We reanalyzed the data to explore the hypothesis that VAS reduces mortality in children who had bacille Calmette-Guérin or measles vaccine as their most recent vaccine but increased mortality when diphtheria-tetanus-pertussis vaccine (DTP) was the most recent vaccine. On the basis of previous studies, we expected the effects to be strongest in girls.

DESIGN

At enrollment, children aged 6-90 mo were randomly assigned to receive VAS or placebo every 4 mo for 2 y. Vaccination status was assessed at enrollment and after 1 and 2 y by reviewing the children's health cards. Lack of a health card was presumed to mean that the child had not been vaccinated.

RESULTS

VAS had a beneficial effect only in children with no record of vaccination at enrollment (n = 5066); the mortality rate ratio (MRR) was 0.64 (95% CI: 0.47, 0.88) compared with 0.95 (95% CI: 0.72, 1.26) in children with one or more vaccinations (n = 6656). Among vaccinated children, the effect of VAS differed between boys (MRR: 0.74; 95% CI: 0.51, 1.08) and girls (MRR: 1.18; 95% CI: 0.84, 1.67) (P = 0.046 for interaction). VAS had a negative effect in measles-vaccinated girls who were missing one or more doses of DTP at enrollment, a group who often received DTP during follow-up (MRR: 2.60; 95% CI: 1.41, 4.80).

CONCLUSIONS

The effect of VAS differed by vaccination status. This is potentially problematic because VAS is provided at vaccination contacts.

Malaria and vitamin A deficiency in African children: a vicious circle?

Vitamin A deficiency and malaria are both highly prevalent health problems in Africa. Vitamin A deficiency affects over 30 million children, most of whom are in the age-group (under five years) most affected by malaria. Vitamin A deficiency increases all-cause mortality in this part of the population, and malaria is an important cause of death in children at this age. A low serum retinol concentration (a marker of vitamin A deficiency) is commonly found in children suffering from malaria, but it is not certain whether this represents pre-existing vitamin A deficiency, a contribution of malaria to vitamin A deficiency, or merely an acute effect of malaria on retinol metabolism or binding. In this paper, available evidence in support of a causal relationship in each direction between vitamin A deficiency and malaria is reviewed. If such a relationship exists, and especially if this is bidirectional, interventions against either disease may convey an amplified benefit for health.

Effect of iron or multiple micronutrient supplements on the prevalence of anaemia among anaemic young children of a malaria-endemic area: a randomized double-blind trial

OBJECTIVE

To assess the effect of supplementation with iron or multiple micronutrients (MM) on the prevalence of anaemia in a malaria-endemic area.

METHODS

A community-based randomized double-blind trial was conducted in rural Burkina Faso, including children aged 6-23 months with haemoglobin (Hb) concentrations of 70-109 g/l who were randomized into an iron group (Fe, n = 96), an iron and zinc group (IZ, n = 100) or an MM group (MM, n = 100), 5 days/week for 6 months. All children were provided with insecticide-treated bednets; those who had a Plasmodium falciparum (PF) positive-smear at baseline and/or at each monthly checking received antimalarial therapy.

RESULTS

The mean (SD) endpoint Hb concentration was higher in the MM group [113.2 (13.6) g/l] than in the IZ group [106.3 (15.6) g/l] and the Fe group [107.1 (12.9) g/l] (P = 0.001). Children in the MM group were more likely to recover from anaemia than those in the Fe group [prevalence rate ratios, PRR (95% confidence interval, CI) = 1.62 (1.22-2.15), P < 0.001]. The IZ group did not differ from the Fe group [PRR (95% CI) = 0.94 (0.65-1.35), P = 0.72]. None of the interactions on the effect of supplementation of baseline age (0.13), or baseline height-for-age z-score (P = 0.33), or incident PF parasitemia (P = 0.99), was significant.

CONCLUSION

In this malaria-endemic area, in combination with malaria management, the MM supplement was more efficacious than the Fe supplement and the IZ supplement for reducing anaemia. Further investigation into limiting factors and amounts of micronutrients that would be more efficacious for reducing anaemia is recommended.

The role of retinol in the etiology and outcome of suppurative otitis media

Vitamin A deficiency is still a serious public health problem affecting an estimated 127 million preschool children. The resulting immunological dysfunctions lead to increased risks of respiratory tract infections, diarrhoeal diseases and blindness, among others. The aim of this study is to determine the significance of the role of serum retinol in the etiology of acute suppurative otitis media (ASOM) and its chronicity (CSOM). In a prospective follow-up of patients with ASOM for 6-9 months, serum retinol determination was done using the high performance liquid chromatography. Participants comprised 358 ASOM and 52 control subjects. Six-month follow-up was achieved in 264 subjects (74%); of these, there was persistence of otorrhoea (CSOM) in 116, while 148 had resolved ASOM. Of the 264 subjects, 146 were males and 118 were females, between the ages of 6 months and 9 years and a mean of 7 years (SD = 2.32), whereas the control subjects comprised 29 males and 22 females, between the ages of 6 months and 11 years and a mean of 7.8 years (SD = 3.6). The range of serum retinol in the ASOM subjects was 1.63-2.64 microg/L, mean of 1.53 microg/L, median value of 2.61 microg/L and (SD = 0.16). Among control subjects, the range was 2.5-2.8 microg/L, mean of 2.58 microg/L and median value of 2.61 microg/L (SD = 0.14) (Table 1). The range of serum retinol in the resolved ASOM subjects was 1.61-2.63 microg/L, mean of 2.07 microg/L and median value of 2.09 microg/L (SD = 0.16) while the CSOM subjects ranged between 0.8-2.86 microg/L, mean of 1.58 microg/L and median value of 1.28 microg/L, (SD = 0.48) (Table 2). Univariate analysis using unpaired t test to compare the mean serum retinol revealed significant difference between ASOM and control (P = 0.0000) and between resolved ASOM and CSOM (P = 0.0000). In conclusion, hyporetinolaemia was a significant etiological factor in the etiology ASOM and CSOM, suggesting retinol supplementation as one strategy in control of SOM.

The effect of community nurses and health volunteers on child mortality: the Navrongo Community Health and Family Planning Project

BACKGROUND

Despite effective treatments and preventive measures for the major causes of child illness and death in less wealthy nations, child mortality remains high in resource-poor settings due in part to ineffective health service delivery models.

METHODS

The Navrongo Community Health and Family Planning Project is a longitudinal community trial of alternative organizational strategies for health service delivery in a rural, impoverished area of Ghana. In one area, nurses are placed in communities with doorstep visitation and service responsibilities. A second area includes training of a local health volunteer and community involvement in health delivery. A third area combines both strategies. Under-five mortality rates were calculated and Poisson regression was used to adjust for potential confounding characteristics.

RESULTS

In areas with village-based community nurse services, under-five child mortality fell by 14% during five years of program implementation compared with before the intervention, with reductions in infant (5%), early child (18%), and late child (39%) mortality. The volunteer intervention was associated with a 14% increase in mortality, primarily driven by a 135% increase in early child mortality. Areas with both nurses and volunteers saw an 8% increase, with small increases in all age groups. Mortality in a comparison area with standard Ministry of Health services fell by 4% during the same time period.

CONCLUSIONS

These results suggest that convenient, accessible professional nursing care can reduce child mortality in impoverished African settings. However, they do not demonstrate a beneficial effect of community volunteers and suggest a possible negative impact on children's survival.

Major reduction of malaria morbidity with combined vitamin A and zinc supplementation in young children in Burkina Faso: a randomized double blind trial

Background

Vitamin A and zinc are crucial for normal immune function, and may play a synergistic role for reducing the risk of infection including malaria caused by Plasmodium falciparum.

Methods

A randomized, double-blind, placebo-controlled trial of a single dose of 200 000 IU of vitamin A with daily zinc supplementation was done in children of Sourkoudougou village, Burkina Faso. Children aged from 6 to 72 months were randomized to receive a single dose of 200 000 IU of vitamin A plus 10 mg elemental zinc, six days a week (n = 74) or placebo (n = 74) for a period of six months. Cross-sectional surveys were conducted at the beginning and the end of the study, and children were evaluated daily for fever. Microscopic examination of blood smear was done in the case of fever (temperature ≥37.5°C) for malaria parasite detection.

Results

At the end of the study we observed a significant decrease in the prevalence malaria in the supplemented group (34%) compared to the placebo group (3.5%) (p < 0.001). Malaria episodes were lower in the supplemented group (p = 0.029), with a 30.2% reduction of malaria cases (p = 0.025). Time to first malaria episode was longer in the supplemented group (p = 0.015). The supplemented group also had 22% fewer fever episodes than the placebo group (p = 0.030).

Conclusion

These results suggest that combined vitamin A plus zinc supplementation reduces the risk of fever and clinical malaria episodes among children, and thus may play a key role in malaria control strategies for children in Africa.

The effect of weekly iron and vitamin A supplementation on hemoglobin levels and iron status in adolescent schoolgirls in western Kenya

BACKGROUND/OBJECTIVES

Iron deficiency anemia is a major public health problem in developing countries and may affect school performance and physical work capacity in nonpregnant adolescents, and may increase the risk of anemia during subsequent teenage pregnancies. We assessed the effect of weekly iron (120 mg elemental iron) and vitamin A (25 000 IU) supplementation on hemoglobin, iron status and malaria and nonmalaria morbidity in adolescent schoolgirls.

SUBJECTS/METHODS

A total of 279 schoolgirls aged 12-18 years from public primary schools in Kisumu, western Kenya. Double-blind randomized placebo-controlled trial using a factorial design.

RESULTS

Five months of iron supplementation was associated with a 0.52 g dl(-1) (0.21, 0.82) greater increase in hemoglobin relative to iron placebo. The effect was only observed in girls with iron deficiency on enrollment (1.34 g dl(-1) (0.79, 1.88)), but not in iron-replete girls (-0.20 g dl(-1) (-0.59, 0.18)). Similar differences in treatment effect were seen between menstruating and nonmenstruating girls. The effect of iron was independent of vitamin A. The baseline prevalence of vitamin A deficiency was low (6.7%) and no sustained increase in hemoglobin was seen with weekly vitamin A (-0.07 g dl(-1) (-0.38, 0.25)). Incidence of malaria parasitemia was higher in the iron than iron-placebo groups (Rate ratio 1.33 (0.94, 1.88)).

CONCLUSIONS

Weekly iron supplementation results in substantial increases in hemoglobin concentration in adolescent schoolgirls in western Kenya, which may outweigh possible risks caused by malaria, but only in iron-deficient or menstruating girls and not in iron-replete and nonmenstruating girls.

Retinol supplementation in murine Plasmodium berghei malaria: Effects on tissue levels, parasitaemia and lipid peroxidation

Reduced plasma retinol concentrations occur in human malaria but the benefits of supplementation remain uncertain. We assessed the in vivo efficacy of retinol administration, and its effect on lipid peroxidation, in a Plasmodium berghei murine model. Animals received vehicle (n=17) or retinol (i) before P. berghei inoculation (four doses), (ii) at parasitaemia 10-15% (three to four doses) or (iii) before and after inoculation (six to seven doses; n=15 in each group), with euthanasia on day 8 post-inoculation or when the parasitaemia exceeded 50%. Multiple-dose pre-inoculation retinol reduced endpoint parasitaemia by 24% (P=0.001 versus controls). A reduction of 18% (P=0.042) was observed when retinol was given to parasitaemic animals. Retinol was ineffective when given both before and after infection (11% reduction; P=0.47). Although retinol supplementation did not change plasma retinol concentrations, liver retinol content increased and correlated inversely with endpoint parasitaemia (r=-0.45, P=0.001). Malaria infection augmented concentrations of the free radical lipid peroxidation end-product F(2)-isoprostanes in plasma, erythrocytes and liver by 1.8-, 2.8- and 4.9-fold, respectively, but retinol supplementation had no effect on these increases. Consistent with some human malaria studies, prophylactic retinol reduces P. berghei parasitaemia. This effect relates to augmentation of tissue retinol stores rather than to retinol-associated changes in oxidant status.

Interactions of malnutrition and immune impairment, with specific reference to immunity against parasites

1. Clinical malnutrition is a heterogenous group of disorders including macronutrient deficiencies leading to body cell mass depletion and micronutrient deficiencies, and these often coexist with infectious and inflammatory processes and environmental problems. 2. There is good evidence that specific micronutrients influence immunity, particularly zinc and vitamin A. Iron may have both beneficial and deleterious effects depending on circumstances. 3. There is surprisingly slender good evidence that immunity to parasites is dependent on macronutrient intake or body composition.

Vitamin A deficiency disorders in children and women

Vitamin A deficiency is an endemic nutrition problem throughout much of the developing world, especially affecting the health and survival of infants, young children, and pregnant and lactating women. These age and life-stage groups represent periods when both nutrition stress is high and diet likely to be chronically deficient in vitamin A. Approximately 127 million preschool-aged children and 7 million pregnant women are vitamin A deficient. Health consequences of vitamin A deficiency include mild to severe systemic effects on innate and acquired mechanisms of host resistance to infection and growth, increased burden of infectious morbidity, mild to severe (blinding) stages of xerophthalmia, and increased risk of mortality. These consequences are defined as vitamin A deficiency disorders (VADD). Globally, 4.4 million preschool children have xerophthalmia and 6 million mothers suffer night blindness during pregnancy. Both conditions are associated with increased risk of morbidity and mortality. While reductions of child mortality of 19-54% following vitamin A treatment have been widely reported, more recent work suggests that dosing newborns with vitamin A may, in some settings, lower infant mortality. Among women, one large trial has so far reported a > or = 40% reduction in mortality related to pregnancy with weekly, low-dose vitamin A supplementation. Epidemiologic data on vitamin A deficiency disorders can be useful in planning, designing, and targeting interventions.

Maternal vitamin A supplementation and immunity to malaria in pregnancy in Ghanaian primigravids

BACKGROUND

Vitamin A supplementation is believed to enhance immune responses to infection but few studies have assessed its effects on anti-malarial immunity, especially during pregnancy when women are at increased risk from both vitamin A deficiency and pregnancy-associated malaria. The pathological effects of malaria in pregnancy are believed to be due to the sequestration of parasites in the placenta mediated via binding of variant surface antigens (VSA) expressed on the surface of P. falciparum infected red blood cells to placental chondroitin sulphate A (CSA).

METHODS

We conducted a randomized double-blind controlled trial of vitamin A supplementation in 98 primigravid Ghanaian women to investigate the effects of vitamin A supplementation on levels of IgG antibodies binding to VSA of a clinical, P. falciparum placental isolate and to two isolates selected (or not) for adherence to CSA in vitro (anti-VSACSA IgG or anti-VSA IgG). Placental malarial infection was determined by placental blood smear and histology.

RESULTS

Vitamin A supplementation was non-significantly associated with a decreased risk of active or chronic-active placental malarial infection compared to past, resolved infection at delivery, as determined by histology (OR=0.42, P=0.13--adjusted for level of education). After adjustment for differences in baseline values, levels of anti-VSACSA IgG to a placental, CSA-adherent isolate (EJ-24) but not to two isolates selected for CSA-adhesion in vitro (FCR3CSA and BusuaCSA), were significantly lower in women receiving vitamin A supplementation than in women receiving placebo (P=0.002). There was no apparent effect of vitamin A supplementation to levels of Ab to non-CSA-adherent parasite isolates.

CONCLUSIONS

The data suggest that the reduction in the levels of anti-VSACSA antibodies to the known placental malaria isolate may reflect reduced intensity or duration of placental parasitaemia in women receiving vitamin A supplementation. These observations are of potential public health significance and deserve further investigation.

Retinoic acid amplifies the host immune response to LPS through increased T lymphocytes number and LPS binding protein expression

Vitamin A deficiency is associated with increased susceptibility to infection but the effects of Vitamin A supplementation on host response to pathogens are controversial. This study investigated the mechanisms by which all-trans retinoic acid (atRA) modulates the host immune response in an experimental model of Vitamin A supplementation before and after challenge with LPS in rats. We show here that a supplementation with five daily injections of 10mg/kg atRA increased the number of T lymphocytes in the peripheral blood. In addition, we show that atRA increased the expression of the LPS binding protein (LBP), a component of the LPS recognition system. The retinoic acid receptor (RAR)alpha agonist Ro 4060-55 but not the pan-retinoid X receptors (RXRs) agonist Ro 2573-86 mimicked the effects of atRA on LBP expression suggesting that atRA enhances LBP expression through a RARalpha-mediated pathway. In order to investigate the significance of increased LBP expression we challenged atRA-supplemented rats with the Gram-positive bacteria Listeria monocytogenes (LM) that activates the immune response independently from LBP. In sharp contrast to our previous observations that atRA supplementation enhances IFN-gamma expression and NOS2 pathway activation in LPS-challenged rats [Devaux, Y., Grosjean, S., Seguin, C., David, C., Dousset, B., Zannad, F., Meistelman, C., de Talancé, N., Mertes, P.M., Ungureanu-Longrois, D., 2000. Retinoic acid and host-pathogen interactions: effects on inducible nitric oxide synthase in vivo. Am. J. Physiol. 279, E1045-E1053], atRA did not increase the LM-induced IFN-gamma expression and NOS2 pathway activation. Overall, these data demonstrate that although atRA induces a "priming" of the immune system characterized by increased T lymphocytes number and LBP expression, the profile of the immune response depends on the inflammatory/infectious stimulus. These results could explain why Vitamin A supplementation could have beneficial/neutral or deleterious effects according to the identity of the infectious pathogen.

Effects of vitamin a supplementation on immune responses and correlation with clinical outcomes

Vitamin A supplementation to preschool children is known to decrease the risks of mortality and morbidity from some forms of diarrhea, measles, human immunodeficiency virus (HIV) infection, and malaria. These effects are likely to be the result of the actions of vitamin A on immunity. Some of the immunomodulatory mechanisms of vitamin A have been described in clinical trials and can be correlated with clinical outcomes of supplementation. The effects on morbidity from measles are related to enhanced antibody production and lymphocyte proliferation. Benefits for severe diarrhea could be attributable to the functions of vitamin A in sustaining the integrity of mucosal epithelia in the gut, whereas positive effects among HIV-infected children could also be related to increased T-cell lymphopoiesis. There is no conclusive evidence for a direct effect of vitamin A supplementation on cytokine production or lymphocyte activation. Under certain circumstances, vitamin A supplementation to infants has the potential to improve the antibody response to some vaccines, including tetanus and diphtheria toxoids and measles. There is limited research on the effects of vitamin A supplementation to adults and the elderly on their immune function; currently available data provide no consistent evidence for beneficial effects. Additional studies with these age groups are needed.

Malaria parasitaemia in relation to HIV status and vitamin A supplementation among pre-school children

OBJECTIVES

To ascertain whether malaria parasitaemia in children is associated with HIV status. To examine the effect of vitamin A supplementation on malaria parasitaemia in children.

METHODS

We studied the cross-sectional associations between HIV status and malaria parasitaemia among 546 children 6-60 months of age who participated in a double-blind, randomized clinical trial of vitamin A supplementation. Prevalence ratios and 95% confidence intervals (CI) were estimated for the presence of malaria parasites at baseline by HIV status in uni- and multivariate models that adjusted for sociodemographic and environmental variables. Among children with malaria, correlates of high parasite loads were identified. Next, we examined the effect of vitamin A supplementation on the risk of malaria parasitaemia and high parasite density at 4-8 months of the first dose in a subset of children.

RESULTS

The prevalence of malaria parasitaemia was 11.4% among HIV-infected children, compared with 27.6% among uninfected. After adjusting for season, anaemia, use of bednets, maternal education and indicators of socioeconomic status, we found some evidence for lower prevalence of parasitaemia among HIV positive compared with HIV-negative children (prevalence ratio=0.56; 95% CI=0.29, 1.09; P=0.09). Other important correlates of malaria parasitaemia at baseline included low level of maternal education, poor quality of water supply, and the presence of animals at home. Vitamin A supplementation did not have a significant effect on malaria parasitaemia at 4-8 months of follow-up, overall or within levels of potential effect modifiers.

CONCLUSION

HIV infection appears to be negatively correlated with malaria parasitaemia in this group of children. Investing in women's education is likely to decrease the prevalence of malaria parasitaemia in children. Vitamin A supplementation does not seem to have an effect on malaria parasitaemia in this population; possible benefits against clinical episodes and severe malaria deserve further examination.

Vitamin A and infancy. Biochemical, functional, and clinical aspects

Vitamin A is a very intriguing natural compound. The molecule not only has a complex array of physiological functions, but also represents the precursor of promising and powerful new pharmacological agents. Although several aspects of human retinol metabolism, including absorption and tissue delivery, have been clarified, the type and amounts of vitamin A derivatives that are intracellularly produced remain quite elusive. In addition, their precise function and targets still need to be identified. Retinoic acids, undoubtedly, play a major role in explaining activities of retinol, but, recently, a large number of physiological functions have been attributed to different retinoids and to vitamin A itself. One of the primary roles this vitamin plays is in embryogenesis. Almost all steps in organogenesis are controlled by retinoic acids, thus suggesting that retinol is necessary for proper development of embryonic tissues. These considerations point to the dramatic importance of a sufficient intake of vitamin A and explain the consequences if intake of retinol is deficient. However, hypervitaminosis A also has a number of remarkable negative consequences, which, in same cases, could be fatal. Thus, the use of large doses of retinol in the treatment of some human diseases and the use of megavitamin therapy for certain chronic disorders as well as the growing tendency toward vitamin faddism should alert physicians to the possibility of vitamin overdose.

Enhancement of the inducible NO synthase activation by retinoic acid is mimicked by RARalpha agonist in vivo

We have previously shown that all-trans retinoic acid (atRA), the active metabolite of vitamin A, enhances the activation of the inducible nitric oxide synthase (NOS II) pathway, a component of innate immunity, in rats in vivo. We investigated the relative contribution of retinoic acid receptor-alpha (RARalpha) and retinoid X receptors (RXRs) to NOS II activation triggered by LPS. Five-day supplementation with 10 mg/kg of either atRA or the RARalpha selective agonist Ro-40-6055, but not with 10 mg/kg of the pan-RXR agonist Ro-25-7386, enhanced the LPS-induced NOS II mRNA, protein expression in liver, and plasma nitrite/nitrate concentration. Both atRA and the RARalpha agonist (but not the RXR agonist) increased the number of peripheral T helper lymphocytes and plasma interferon-gamma concentration. Synergism between retinoids and LPS on NOS II activation within an organ coincided with synergism on interferon regulatory factor-1 mRNA expression but not with the level of expression of the RARalpha protein. These results suggest that, in vivo, atRA activates NOS II through RARalpha and contributes to characterizing the complex effect of retinoids on the host inflammatory/immune response.

Micronutrient malnutrition and the pathogenesis of malarial anemia

Malaria is a leading cause of morbidity and mortality worldwide, and anemia is a common and sometimes serious complication of Plasmodium falciparum infection. Although micronutrient malnutrition is usually highly prevalent in malaria endemic areas, the contribution of micronutrient deficiencies to malarial anemia is often overlooked. Recent investigation suggests that micronutrients such as vitamin A, vitamin E, and zinc, may improve the morbidity of malaria through immune modulation and alteration of oxidative stress. Micronutrients are also involved in the pathogenesis of anemia and likely play a role in malarial anemia, but many clinical trials have not specifically addressed the impact of micronutrient supplementation on malarial anemia. Further work is needed to assess the effect of both clinic and community-based micronutrient interventions on malarial anemia in infants, children, and pregnant women.

Lack of influence of red palm oil on severity of malaria infection in pre-school Nigerian children

Vitamin A supplements are reported to reduce febrile episodes of malaria and parasite counts, especially in children aged 12-36 months. Red palm oil (RPO) is a good source of vitamin A, is rich in alpha- and beta-carotene and is as effective as high-dose retinyl palmitate supplements in improving vitamin A status. In western Nigeria, where malaria is endemic, RPO is widely used and consumption can be measured using plasma alpha-carotene as a proxy biomarker since there are few other prominent sources of this carotene in the diet. The influence of RPO consumption on malaria was investigated in 207 children (aged 0-60 months) who presented with fever in August-October 1999 at several hospital clinics around Ile-Ife. Medical and anthropometric data, body temperature, parasitaemia and plasma C-reactive protein (CRP), retinol, carotenoids and tocopherols were measured in the children. Mothers were interviewed on usage of cooking oil and mosquito nets in the home, education and occupation. Most families used RPO and median plasma concentrations of both alpha-carotene (0.518 mumol/L) and beta-carotene (0.698 mumol/L) in the children were high. Using body temperature, parasite density and plasma CRP as markers of disease severity, multiple linear regression analysis was carried out on those for whom complete data were available (n = 138), separated into 3 age-groups of < 12 months (n = 37), 12-36 months (n = 68) and > 36 months (n = 33). In the absence of plasma retinol, plasma alpha-carotene explained 13.9% of the variance in parasite density (P = 0.013) but only in children aged > 36 months. The relationship with disease severity was negative, i.e., there was some evidence that RPO usage protected against malaria, and other dietary indices generally indicated that better nutritional status was associated with a lower severity of malaria.

Retinoic acid and lipopolysaccharide act synergistically to increase prostanoid concentrations in rats in vivo

Vitamin A and its active metabolite retinoic acid (RA) modulate host-pathogen interactions by interfering with the host immune and inflammatory response including prostaglandin (PG) biosynthesis. The effects of RA on phospholipase A(2) (PLA(2)) and cyclooxygenase (COX) isoforms in vitro are controversial, and few in vivo studies exist. We investigated the in vivo effects of RA on PG biosynthesis in the presence or absence of lipopolysaccharide (LPS) in rats. RA alone [10 mg/(kg. d) for 5 d] increased plasma and liver PG concentrations by increasing COX-1 protein expression (twofold that of control rats). RA acted synergistically with LPS to increase plasma (400-fold) and liver (15-fold) concentrations of prostaglandin E(2) (PGE(2)) and significantly, but to a lesser extent, other PG compared with RA rats, in the absence of major differences in PLA(2) expression or activity or COX-1 and COX-2 mRNA or protein expression. The RA + LPS-mediated increase in PGE(2) was significantly attenuated (97%) by aminoguanidine (AG), a relatively specific inhibitor of the inducible nitric oxide synthase (NOS2), consistent with the previously reported synergistic effect of RA and LPS on NOS2 expression and activity. In addition, RA and LPS induced the expression of the microsomal isoform of PGE synthase (mPGES). In conclusion, in vivo, RA and LPS increased PG and especially PGE(2) concentrations. The PGE(2) increase was associated with NOS2-mediated activation of COX and induction of mPGES. These results contribute to the characterization of the effects of vitamin A on the host inflammatory response.

A randomised, double-blind, placebo-controlled clinical trial of vitamin A in severe malaria in hospitalised Mozambican children

This paper reports a randomised, double-blind, placebo-controlled clinical trial of the effect of routine vitamin A supplementation given on admission to children with severe malaria with regard to survival, recovery during hospitalisation and outcome 6 weeks after discharge. Children aged between 6 and 72 months admitted to the paediatric wards of the Central Hospital of Maputo (CHM), Mozambique with a diagnosis of severe malaria were randomly assigned either to a control group (placebo) or an experimental group (vitamin A) and were followed up 6 weeks after discharge. There were 280 children in the experimental and 290 in the placebo group. Seven (2.5%) and 13 (4.5%) children died in the experimental and the placebo groups, respectively, a relative risk of death of 0.56 (95% CI 0.23-1.38, p = 0.201). During the 1st 5 hours of admission, the relative risk of death in the vitamin A-supplemented group was 2.54 (0.50-12.96); after 5 hours of admission it was 0.19 (95% CI 0.04-0.85; p = 0.015). In the supplemented group, 4/82 (4.9%) of the children developed neurological sequelae vs 2/78 (2.6%) in the placebo group (RR = 1.90; 95% CI 0.36-10.09; p = 0.682). Although the overall reduction in the risk of death observed for all children receiving vitamin A is not statistically significant, it might be clinically important. This finding cannot, however, be accepted as a firm conclusion and requires validation by future trials.

Retinoic acid and host-pathogen interactions: effects on inducible nitric oxide synthase in vivo

Vitamin A and its metabolite retinoic acid modulate the host response to pathogens through poorly characterized mechanisms. In vitro studies have suggested that retinoic acid decreases inducible NO synthase (NOS2, or iNOS) expression, a component of innate immunity, in several cell types stimulated with lipopolysaccharide (LPS) or cytokines. This study investigated the effect of retinoic acid on LPS-stimulated NOS2 expression in vivo. Wistar-Kyoto rats received all-trans retinoic acid (RA, 10 mg/kg) or vehicle intraperitoneally daily for 5 days followed by LPS (4 mg/kg) or saline intraperitoneally and were killed 6 h later. NOS2 activation was estimated by mRNA (RT-PCR) and protein (Western-blot) expression and plasma nitrate/nitrite accumulation. In sharp contrast to previous in vitro study reports, RA significantly enhanced NOS2 mRNA, protein expression, and plasma nitrate/nitrite concentration in LPS-injected rats but not in saline-injected rats. This was associated with increased expression of interleukin-2, interferon (IFN)-gamma and IFN regulatory factor-1 mRNAs in several organs and increased IFN-gamma plasma concentration. RA significantly increased mortality in LPS-injected rats. The NOS inhibitor aminoguanidine (50 mg/kg before LPS injection) significantly attenuated the RA-mediated increase in mortality. These results demonstrate for the first time that RA supplementation in vivo enhances activation of the LPS-triggered NOS2 pathway.

Nutritional modulation of malaria morbidity and mortality

This review critically examines the relationship between nutritional status and malaria. The data indicate that protein-energy malnutrition is associated with greater malaria morbidity and mortality in humans. In addition, controlled trials of either vitamin A or zinc supplementation show that these nutrients can substantially reduce clinical malaria attacks. Data for iron indicate that supplementation may minimally aggravate certain malariometric indices in some settings and also strongly improve hematologic status. Withholding of iron supplements from deficient population is, therefore, not currently indicated. Available evidence for other nutrients describe varied effects, with some deficiencies being exacerbative (e.g., thiamine), protective (e.g., vitamin E), or both exacerbative and protective in different settings (e.g., riboflavin, vitamin C). The roles of folate, other B vitamins, unsaturated fatty acids, amino acids, and selenium are also examined. Study of the interactions between nutrition and malaria may provide insight to protective mechanisms and result in nutrient-based interventions as low-cost and effective adjuncts to current methods of malaria prevention and treatment.

Effect of vitamin A supplementation on morbidity due to Plasmodium falciparum in young children in Papua New Guinea: a randomised trial

BACKGROUND

Many individuals at risk of malaria also have micronutrient deficiencies that may hamper protective immunity. Vitamin A is central to normal immune function, and supplementation has been shown to lower the morbidity of some infectious diseases. We investigated the effect of vitamin A supplementation on malaria morbidity.

METHODS

This randomised double-blind placebo-controlled trial of vitamin A supplementation took place in a P. falciparum endemic area of Papua New Guinea. Of 520 potentially eligible children aged 6-60 months, 480 were randomly assigned high-dose vitamin A (n=239) or placebo (n=241), every 3 months for 13 months. Malaria morbidity was assessed through weekly community-based case detection and surveillance of patients who self-reported to the health centre. Cross-sectional surveys were also done at the beginning, middle, and end of the study to assess malariometric indicators. Analyses were by intention to treat.

FINDINGS

The number of P. falciparum febrile episodes (temperature > or = 37.5 degrees C with a parasite count of at least 8000/microL) was 30% lower in the vitamin A group than in the placebo group (178 vs 249 episodes; relative risk 0.70 [95% CI 0.57-0.87], p=0.0013). At the end of the study P. falciparum geometric mean density was lower in the vitamin A than the placebo group (1300 [907-1863] vs 2039 [1408-2951]) as was the proportion with spleen enlargement (125/196 [64%] vs 148/207 [71%]); neither difference was significant (p=0.093 and p=0.075). Children aged 12-36 months benefited most, having 35% fewer febrile episodes (89 vs 141; relative risk 0.65 [14-50], p=0.0023), 26% fewer enlarged spleens (46/79 [58%] vs 67/90 [74%], p=0.0045), and a 68% lower parasite density (1160 [95% CI 665-2022] vs 3569 [2080-6124], p=0.0054). Vitamin A had no consistent effect on cross-sectional indices of proportion infected or with anaemia.

INTERPRETATION

Vitamin A supplementation may be an effective low-cost strategy to lower morbidity due to P. falciparum in young children. The findings suggest that clinical episodes, spleen enlargement, and parasite density are influenced by different immunological mechanisms from infection and anaemia.