Micronutrients and anaemia

Micronutrient deficiencies and anaemia remain as major health concerns for children in Bangladesh. Among the micronutrient interventions, supplementation with vitamin A to children aged less than five years has been the most successful, especially after distribution of vitamin A was combined with National Immunization Days. Although salt sold in Bangladesh is intended to contain iodine, much of the salt does not contain iodine, and iodine deficiency continues to be common. Anaemia similarly is common among all population groups and has shown no sign of improvement even when iron-supplementation programmes have been attempted. It appears that many other causes contribute to anaemia in addition to iron deficiency. Zinc deficiency is a key micronutrient deficiency and is covered in a separate paper because of its importance among new child-health interventions.

Susceptibility to Vibrio cholerae infection in a cohort of household contacts of patients with cholera in Bangladesh

Background

Despite recent progress in understanding the molecular basis of Vibrio cholerae pathogenesis, there is relatively little knowledge of the factors that determine the variability in human susceptibility to V. cholerae infection.

Methods and Findings

We performed an observational study of a cohort of household contacts of cholera patients in Bangladesh, and compared the baseline characteristics of household members who went on to develop culture-positive V. cholerae infection with individuals who did not develop infection. Although the vibriocidal antibody is the only previously described immunologic marker associated with protection from V. cholerae infection, we found that levels of serum IgA specific to three V. cholerae antigens—the B subunit of cholera toxin, lipopolysaccharide, and TcpA, the major component of the toxin–co-regulated pilus—also predicted protection in household contacts of patients infected with V. cholerae O1, the current predominant cause of cholera. Circulating IgA antibodies to TcpA were also associated with protection from V. cholerae O139 infection. In contrast, there was no association between serum IgG antibodies specific to these three antigens and protection from infection with either serogroup. We also found evidence that host genetic characteristics and serum retinol levels modify susceptibility to V. cholerae infection.

Conclusions

Our observation that levels of serum IgA (but not serum IgG) directed at certain V. cholerae antigens are associated with protection from infection underscores the need to better understand anti–V. cholerae immunity at the mucosal surface. Furthermore, our data suggest that susceptibility to V. cholerae infection is determined by a combination of immunologic, nutritional, and genetic characteristics; additional factors that influence susceptibility to cholera remain unidentified.

Vibrio cholerae is the bacterium that causes cholera, a severe form of diarrhea that leads to rapid and potentially fatal dehydration when the infection is not treated promptly. Cholera remains an important cause of diarrhea globally, and V. cholerae continues to cause major epidemics in the most vulnerable populations. Although there have been recent discoveries about how the bacterium adapts to the human intestine and causes diarrhea, there is little understanding of why some people are protected from infection with V. cholerae. This article describes several factors that are associated with the risk of developing V. cholerae infection among people living in the same household with a patient with severe cholera who are at high risk of contracting the infection. One of the findings is that IgA antibodies, a type of antibody associated with immunity at mucosal surfaces such as the intestine, that target several components of the bacteria are associated with immunity to V. cholerae infection. This article also describes genetic and nutritional factors that additionally influence susceptibility to V. cholerae infection.

Supplementation of fish-oil and soy-oil during pregnancy and psychomotor development of infants

Supplementation of docosahexaenoic acid (DHA) in infancy improves neuro-developmental outcomes, but there is limited information about the impact of supplementing pregnant mothers with DHA on the development of their infants. In a follow-up of a randomized, double-blind controlled trial with 400 pregnant mothers, the effects of supplementation of fish-oil or soy-oil (4 g/day) during the last trimester of pregnancy on psychomotor development and behaviour of infants at 10 months of age (n=249) were assessed. The quality of psychosocial stimulation at home (HOME) and nutritional status of the subjects were also measured. There were no significant differences in the fish-oil group and soy-oil group in any of the developmental (mean +/-SD mental development index: 102.5 +/- 8.0 vs. 101.5 +/- 7.8, psychomotor development index: 101.7 +/- 10.0 vs. 100.5 +/- 10.1) or behavioural outcomes. It may, therefore, be concluded that supplementation of fish-oil during the last trimester of pregnancy does not have any added benefit over supplementation of soy-oil on the development or behaviour of infants in this population.

Young children non-immunized against measles: characteristics and programmatic implications

AIM

To examine the presenting characteristics, including nutritional status, of young children without measles immunization and to suggest appropriate public health measures to improve immunization status.

METHODS

In this retrospective case-control analysis, we studied 4075 children aged 12-23 mo of either sex, who attended ICDDR,B's Dhaka hospital during 1994-2003. Cases included children who reported to this facility without receiving measles vaccine, and the control children were those who received the vaccine.

RESULTS

3181 of 4075 (78%) children, including 1227 (39%) girls and 1954 (61%) boys, received measles immunization. The proportion of vaccinated children increased from 74% in 1997 to 82% in 2001. Some non-specific effects of measles immunization were observed. Fifty-one per cent of the children without measles immunization were stunted, 76% were underweight, and 48% were wasted. The non-immunized children were twice as likely to be stunted, underweight, and wasted than the immunized children; they were more often dehydrated (some or severe dehydration) (28% vs 22%, p<0.001), required longer duration (>72 h) of hospitalization (15% vs 10%, p<0.001), did not receive vitamin A capsule in the previous 6 mo (56% vs 36%, p<0.001), and had more frequent abnormal lung auscultation indicative of acute lower respiratory tract infections (8% vs 5%, p<0.001). Female children, illiterate mother, lack of vitamin A supplementation, and history of measles were significantly associated with non-immunization against measles after controlling for co-variables. Results were similar when different nutritional indicators (underweight, stunting, or wasting) were added separately to logistic regression models.

CONCLUSION

Intervention strategies to enhance immunization coverage in infants should target illiterate mothers and their children, particularly the females and malnourished ones, provide them with measles immunization and vitamin A capsule, and encourage their periodic follow-up visits as part of a preventive nutritional programme.

Blood group, immunity, and risk of infection with Vibrio cholerae in an area of endemicity

Individuals with blood group O are more susceptible than other individuals to severe cholera, although the mechanism underlying this association is unknown. To assess the respective roles of both intrinsic host factors and adaptive immune responses that might influence susceptibility to infection with Vibrio cholerae, we prospectively followed a cohort of household contacts of patients with cholera in Bangladesh. In this study, we made the novel observation that persons with blood group O were less likely than those with other blood groups to become infected with V. cholerae O1 (odds ratio [OR], 0.67; 95% confidence interval [CI], 0.53 to 0.85; P = 0.008). Consistent with prior studies, however, household contacts with blood group O were more likely to develop severe illness if infected with V. cholerae O1 (OR, 2.3; 95% CI, 0.98 to 5.59; P = 0.05). While blood group O protected significantly against infection with V. cholerae O1, there was no evidence of protection against V. cholerae O139. A multivariate analysis demonstrated that the association between blood group O and protection from infection with V. cholerae O1 was independent of age, gender, and baseline anti-cholera toxin and vibriocidal antibody titers. Based on this epidemiologic evidence, we propose a hypothesis for understanding the association between blood group O and the risk of infection with V. cholerae O1 and O139 as well as the risk of developing severe symptoms once infected.

Enterotoxigenic Escherichia coli and Vibrio cholerae diarrhea, Bangladesh, 2004

Flooding in Dhaka in July 2004 caused epidemics of diarrhea. Enterotoxigenic Escherichia coli (ETEC) was almost as prevalent as Vibrio cholerae O1 in diarrheal stools. ETEC that produced heat-stable enterotoxin alone was most prevalent, and 78% of strains had colonization factors. Like V. cholerae O1, ETEC can cause epidemic diarrhea.

Use of antibodies in lymphocyte secretions for detection of subclinical tuberculosis infection in asymptomatic contacts

We have previously demonstrated that Mycobacterium bovis BCG-specific immunoglobulin G antibodies in lymphocyte secretions (ALS) can be employed as a marker for active tuberculosis (TB). We aimed to determine whether the ALS method allows detection of subclinical TB infection in asymptomatic individuals. A prospective study of family contacts (FCs) of patients with active TB and healthy controls was performed. Thirteen of 42 FCs had high ALS responses, including 6 FCs who subsequently developed active TB. No correlation was observed between the tuberculin skin test and the ALS responses in the FCs (r = 0.1, P = 0.23). Among patients with active TB, BCG-specific ALS responses steadily declined from the time of diagnosis through 6 months following antimycobacterial chemotherapy (P = 0.001). The ALS assay enabled detection of infection in exposed symptom-free contacts, who are at greater risk for developing active TB. The method may also allow discrimination between effective treatment of active infection and suboptimal response to therapy.

Presence of neutral fat in stool and its association with aetiology and presenting features of diarrhoea in children

Enteric infections, impaired digestion, loss of villous cells, and poor absorption of fat may lead to presence of neutral fat in stool, particularly in children with diarrhoea. We aimed to examine the association between presence of neutral fat in stool and aetiology of diarrhoea and nutritional status of the patients at different age groups. A total of 13,171 patients aged 5 days-106 years enrolled in the Diarrhoeal Disease Surveillance System of the Dhaka Hospital of ICDDR,B during 1996-2001 were studied. Presence of neutral fat in faecal specimens, aetiology of diarrhoea, and nutritional status in children below 5 years of age were determined and analysed. Of the total study individuals, 7,671 (58%) had neutral fat in their faecal specimens. Neutral fat was more frequently present in faeces of individuals infected with rotavirus in all age groups or in enterotoxigenic E. coli (ETEC) infection in children 0-23 months old while compared with those who did not have these infections (p=0.005, p=0.014, respectively). Neutral fat was less frequently (p<0.001) present in malnourished 0-23 months old children. Presence of neutral fat in the stool in diarrhoea due to rotavirus and in young childhood ETEC diarrhoea signifies compromised gastrointestinal function due to these infections. The mechanism of persistence of neutral fat in the stool of such patients, and its nutritional and clinical implications require further studies.