Cost of illness for cholera in a high risk urban area in Bangladesh: an analysis from household perspective

Background

Cholera poses a substantial health burden to developing countries such as Bangladesh. In this study, the objective is to estimate the economic burden of cholera treatments incurred by households. The study was carried out in the context of a large vaccine trial in an urban area of Bangladesh.

Methods

The study used a combination of prospective and retrospective incidence-based cost analyses of cholera illness per episode per household. A total of 394 confirmed cholera hospitalized cases were identified and treated in the study area during June–October 2011. Households with cholera patients were interviewed within 15 days after discharge from hospitals or clinics. To estimate the total cost of cholera illness a structured questionnaire was used, which included questions on direct medical costs, non-medical costs, and the indirect costs of patients and caregivers.

Results

The average total household cost of treatment for an episode of cholera was US$30.40. Total direct and indirect costs constituted 24.6% (US$7.40) and 75.4% (US$23.00) of the average total cost, respectively. The cost for children under 5 years of age (US$21.50) was higher than that of children aged 5–14 years (US$17.50). The direct cost of treatment was similar for male and female patients, but the indirect cost was higher for males.

Conclusion

Our study suggests that by preventing one cholera episode (3 days on an average), we can avert a total cost of 2,278.50 BDT (US$30.40) per household. Among medical components, medicines are the largest cost driver. No clear socioeconomic gradient emerged from our study, but limited demographic patterns were observed in the cost of illness. By preventing cholera cases, large production losses can be reduced.

Knowledge of, attitudes toward, and preventive practices relating to cholera and oral cholera vaccine among urban high-risk groups: findings of a cross-sectional study in Dhaka, Bangladesh

BACKGROUND

In endemic countries such as Bangladesh, consequences of cholera place an enormous financial and social burden on patients and their families. Cholera vaccines not only provide health benefits to susceptible populations but also have effects on the earning capabilities and financial stability of the family. Community-based research and evaluations are necessary to understand perceptions about and practices of the community relating to cholera and oral cholera vaccines. This may help identify the ways in which such vaccines may be successfully introduced, and other preventive measures can be implemented. The present study assessed the knowledge of, attitudes toward, and preventive practices relating to cholera and oral cholera vaccine among an urban population residing in a high cholera-prone setting in Dhaka, Bangladesh.

METHODS

This cross-sectional study was conducted in an area of high cholera prevalence in 15 randomly-selected clusters in Mirpur, Dhaka city. A study team collected data through a survey and in-depth interviews during December 2010-February 2011.

RESULTS

Of 2,830 families included in the final analysis, 23% could recognize cholera as acute watery diarrhea and 16% had ever heard of oral cholera vaccine. About 54% of the respondents had poor knowledge about cholera-related issues while 97% had a positive attitude toward cholera and oral cholera vaccine. One-third showed poor practice relating to the prevention of cholera.The findings showed a significant (p < 0.05) association between the respondents' knowledge and sex, education, occupation, monthly overall household expenditure, attitudes and practice. In the adjusted model, male sex, having a lower monthly overall household expenditure, and having a less positive attitude toward cholera were the significant predictors to having poor knowledge.

CONCLUSIONS

The findings suggest the strengthening of health education activities to improve knowledge on cholera, its prevention and treatment and information on cholera vaccination among high-risk populations. The data also underscore the potential of mass cholera vaccination to prevent and control cholera.

Frequency of reexposure to Vibrio cholerae O1 evaluated by subsequent vibriocidal titer rise after an episode of severe cholera in a highly endemic area in Bangladesh

Vibriocidal antibody is a marker of recent exposure to Vibrio cholerae O1 infection. We examined vibriocidal titers for 1 year after an episode of severe cholera in patients in Dhaka, Bangladesh; 16 of 53 (30%) patients had a fourfold or greater increase in vibriocidal titer between 6 and 12 months after an episode of severe cholera, suggesting reexposure to the organism. Among patients with rises in titers during follow-up, the patients initially infected with serotype Ogawa had earlier rises in titer than the patients initially infected with serotype Inaba. These data and others suggest that an episode of severe cholera protects against symptomatic disease for several years, but reexposure to the organism occurs frequently in an endemic area, with immunological boosts beginning as early as 6 months after severe disease. Repeated exposures to V. cholerae in endemic areas may be a necessary component for long-lasting protection against severe disease.

Immune responses to cholera in children

Cholera is a severe acute dehydrating diarrheal disease caused by Vibrio cholerae O1 or O139 infection, and is associated with significant mortality and morbidity globally. Although young children bear a high burden of the disease, currently available oral vaccines give a lower efficacy and shorter duration of protection in this group than in adults. According to the studies of natural infection, young children achieve comparable systemic anti-V. cholerae antigen-specific antibody, gut-homing antibody-secreting cell and memory B-cell responses as adults. Studies on innate and cell-mediated immune responses are lacking in children, and may offer important insights into differences in vaccine efficacy. The impact of host factors such as malnutrition, genetics and coinfection with other pathogens also remains to be fully defined.

Individuals with Le(a+b-) blood group have increased susceptibility to symptomatic vibrio cholerae O1 infection

BACKGROUND

Human genetic factors such as blood group antigens may affect the severity of infectious diseases. Presence of specific ABO and Lewis blood group antigens has been shown previously to be associated with the risk of different enteric infections. The aim of this study was to determine the relationship of the Lewis blood group antigens with susceptibility to cholera, as well as severity of disease and immune responses to infection.

METHODOLOGY

We determined Lewis and ABO blood groups of a cohort of patients infected by Vibrio cholerae O1, their household contacts, and healthy controls, and analyzed the risk of symptomatic infection, severity of disease if infected and immune response following infection.

PRINCIPAL FINDINGS

We found that more individuals with cholera expressed the Le(a+b-) phenotype than the asymptomatic household contacts (OR 1.91, 95% CI 1.03-3.56) or healthy controls (OR 1.90, 95% CI 1.13-3.21), as has been seen previously for the risk of symptomatic ETEC infection. Le(a-b+) individuals were less susceptible to cholera and if infected, required less intravenous fluid replacement in hospital, suggesting that this blood group may be associated with protection against V. cholerae O1. Individuals with Le(a-b-) blood group phenotype who had symptomatic cholera had a longer duration of diarrhea and required higher volumes of intravenous fluid replacement. In addition, individuals with Le(a-b-) phenotype also had lessened plasma IgA responses to V. cholerae O1 lipopolysaccharide on day 7 after infection compared to individuals in the other two Lewis blood group phenotypes.

CONCLUSION

Individuals with Lewis blood type Le(a+b-) are more susceptible and Le(a-b+) are less susceptible to V. cholerae O1 associated symptomatic disease. Presence of this histo-blood group antigen may be included in evaluating the risk for cholera in a population, as well as in vaccine efficacy studies, as is currently being done for the ABO blood group antigens.

Safety and immunogenicity study of a killed bivalent (O1 and O139) whole-cell oral cholera vaccine Shanchol, in Bangladeshi adults and children as young as 1 year of age

BACKGROUND

Safety and immunogenicity study of an oral, killed, bivalent whole-cell, cholera vaccine, Shanchol was carried out in Bangladeshi participants. This study was conducted prior to initiating a feasibility study in Bangladesh.

STUDY PARTICIPANTS

The double-blind, randomized placebo controlled study was carried out in adults (18-45 years), toddlers (2-5 years) and younger children (12-23 months). Two doses of the vaccine/placebo were given 14 days apart.

RESULTS

Shanchol did not elicit major adverse events in any age group. Vibriocidal antibody responses in adults were 60% against Vibrio cholerae O1 Inaba, 72% against V. cholerae O1 Ogawa and 21% against V. cholerae O139. In toddlers, responses were 84%, 75% and 64% and in younger children it was 74%, 78% and 54% against Inaba, Ogawa and O139 serotypes. The responses in all ages were higher in vaccinees compared to pre-immune titers or to responses in placebo recipients (P<0.001). Plasma IgA antibody response to O1 Inaba LPS was seen in 61%, 73% and 45% of adults, toddlers and younger children, respectively.

CONCLUSIONS

The safety and immunogenicity data for Shanchol is promising and warrants future use in large scale trial in cholera endemic areas, high risk Bangladeshi population and in other countries in the region.

Antigen-specific memory B-cell responses in Bangladeshi adults after one- or two-dose oral killed cholera vaccination and comparison with responses in patients with naturally acquired cholera

The mediators of protective immunity against cholera are currently unknown, but memory B-cell responses may play a central role in facilitating long-term and anamnestic responses against Vibrio cholerae, the cause of cholera. We compared memory B-cell responses in adults with natural cholera in Bangladesh (n = 70) to responses in Bangladeshi adults after one-dose (n = 30) or two-dose (n = 30) administration of an oral killed cholera vaccine, WC-rBS (Dukoral; Crucell), assessing the responses at the acute stage of disease or prevaccination and then on days 3, 30, 90, 180, 270, and 360. Individuals with natural cholera developed prominent vibriocidal and plasma anti-cholera toxin B subunit (CtxB) and lipopolysaccharide (LPS) IgG and IgA responses, but these responses returned to baseline by 1 year of follow-up. Vaccinees developed plasma anti-CtxB and anti-LPS IgG and IgA responses that were generally comparable to those in individuals recovering from natural disease, but vibriocidal responses were lower in vaccinees than in infected patients. Individuals recovering from natural disease developed memory B-cell IgG and IgA anti-CtxB and anti-LPS responses by day 30, and these responses were detectable through at least days 180 to 360. In contrast, we detected no IgA or IgG memory B-cell responses to LPS in vaccinees; anti-CtxB IgA responses were only detectable on day 30, and anti-CtxB IgG responses were detectable until days 90 to 180, compared to days 270 to 360 in patients. These findings may explain in part the relatively short-term protection afforded by oral cholera vaccination compared to natural disease.

Development, validation and application of ELISAs for pharmacokinetic and HACA assessment of a chimeric anti-CD40 monoclonal antibody in human serum

As part of a Phase I chimeric anti-CD40 monoclonal antibody clinical trial, two enzyme-linked immunosorbent assays (ELISAs) were developed for secondary endpoints: 1) for the pharmacokinetic (PK) monitoring of serum antibody levels and 2) for immunogenic screening of human anti-chimeric antibody (HACA) responses. The ELISA is a well established immunoassay, with clear guidelines for validation when used as a quantitative assay. However, these parameters may not always be relevant for a semi-quantitative assay used to assess whether a sample is positive or negative for a novel marker such as an antibody developed against a therapeutic antibody. We report here the development of a quantitative PK ELISA and a semi-quantitative HACA ELISA, and the different approaches of validation to prove each assay are 'fit for purpose.' The parameters of linearity (R²>0.99), accuracy (±30%), lowest level of detection (4 μg/ml), intra-assay (coefficient of variation (CV) <20%) and inter-assay (CV<20%) variability were assessed for the quantitative PK assay. For the semi-quantitative HACA assay, parameters of linearity (R²>0.99), lowest level of detection, intra (CV<10%) and inter-assay (CV<30%) variability were assessed using a surrogate positive control. The validation outcome showed that each assay was robust, reliable and accurate to meet the requirements of the intended analytical application, that being to 1) quantitatively determine the concentration of antibody in the serum and 2) determine whether a sample is positive or negative for human anti-chimeric antibodies. Each assay has been successfully translated for use in a clinical trial with adequate quality controls and acceptance criteria set for monitoring consistency and performance.

Comparison of clinical features and immunological parameters of patients with dehydrating diarrhoea infected with Inaba or Ogawa serotypes of Vibrio cholerae O1

Vibrio cholerae O1, Ogawa and Inaba serotypes, both cause severe cholera. We compared clinical and immunological features in patients in Bangladesh infected with these 2 serotypes. Blood was collected from hospitalized Ogawa (N=146) or Inaba (N=191) patients at the acute stage (day 2) and 5 and 19 days later. Ogawa patients were younger than Inaba, presented with shorter duration of diarrhoea, and had more frequent abdominal pain, vomiting and need for intravenous fluids (p<0.05). Inaba patients more frequently had dark-field positive stools (p<0.01). Inaba strains were more susceptible to tetracycline and erythromycin than Ogawa strains (p<0.001). Ogawa infection produced higher plasma vibriocidal as well as IgG responses to cholera toxin B subunit, toxin-coregulated pilus subunit and lipopolysaccharide (LPS); higher IgA responses to LPS in 'antibody in lymphocyte supernatant' (ALS) specimens were also seen. These results suggest that a cholera vaccine based on the Ogawa serotype needs to be further investigated.

Clinical outcomes in household contacts of patients with cholera in Bangladesh

BACKGROUND

Multiple Vibrio cholerae infections in the same household are common. The objective of this study was to examine the incidence of V. cholerae infection and associated clinical symptoms in household contacts of patients with cholera and to identify risk factors for development of severe dehydration in this cohort.

METHODS

Household contacts of hospitalized patients with cholera were observed with frequent clinical assessments and collection of serum and rectal swab samples for culture for a period of 21 days after presentation of the index case.

RESULTS

One-half (460 of 944) of all contacts reported diarrhea during the study period, and symptoms most frequently began 2 days after presentation of the index case. Antibiotics were used by 199 (43%) of 460 contacts with diarrhea. Results of rectal swab cultures for V. cholerae were positive for 202 (21%) of 944 contacts, and 148 (73%) infected contacts experienced diarrhea. Significant dehydration developed in 26 contacts; predictors of dehydration included vomiting, each additional day of diarrhea, and blood group O status.

CONCLUSIONS

In urban Bangladesh, the burden of diarrheal illness among household contacts of patients with cholera is higher than was previously estimated, and prophylactic intervention is feasible, because the majority of symptomatic cases of V. cholerae infection in contacts begin soon after presentation of the index case. Re-evaluation of targeted chemoprophylaxis for household contacts of patients with cholera may be warranted.

Development of immunoglobulin M memory to both a T-cell-independent and a T-cell-dependent antigen following infection with Vibrio cholerae O1 in Bangladesh

Vibrio cholerae O1 can cause severe watery diarrhea that can be life-threatening without treatment. Infection results in long-lasting protection against subsequent disease. Development of memory B cells of the immunoglobulin G (IgG) and IgA isotypes to V. cholerae O1 antigens, including serotype-specific lipopolysaccharide (LPS) and the B subunit of cholera toxin (CTB), after cholera infection has been demonstrated. Memory B cells of the IgM isotype may play a role in long-term protection, particularly against T-cell-independent antigens, but IgM memory has not been studied in V. cholerae O1 infection. Therefore, we assayed acute- and convalescent-phase blood samples from cholera patients for the presence of memory B cells that produce cholera antigen-specific IgM antibody upon polyclonal stimulation in in vitro culture. We also examined the development of serological and antibody-secreting cell responses following infection. Subjects developed significant IgM memory responses by day 30 after infection, both to the T-cell-independent antigen LPS and to the T-cell-dependent antigen CTB. No significant corresponding elevations in plasma IgM antibodies or circulating IgM antibody-secreting cells to CTB were detected. In 17 subjects followed to day 90 after infection, significant persistence of elevated IgM memory responses was not observed. The IgM memory response to CTB was negatively correlated with the IgG plasma antibody response to CTB, and there was a trend toward negative correlation between the IgM memory and IgA plasma antibody responses to LPS. We did not observe an association between the IgM memory response to LPS and the vibriocidal titer.

Bacterial enteropathogens of neonates admitted to an urban diarrhoeal hospital in Bangladesh

Data on the aetiology of diarrhoea in neonates are scarce, especially from developing countries including Bangladesh. A retrospective review of the electronic database of the Microbiology Laboratory of the International Centre for Diarrhoeal Disease Research, Bangladesh (ICDDR,B), was carried out to examine enteropathogens associated with diarrhoea in neonates. Stool specimens of the neonates on admission to the Dhaka Hospital of ICDDR,B were collected and sent to the laboratory for direct plating onto taurocholate tellurite gelatin agar, Salmonella-Shigella agar and MacConkey's agar. Stool specimens of 2511 neonates of either sex were examined. Bacterial pathogens were recovered from the stools of 699 (27.8%) of these neonates--a single bacterial pathogen from 670 neonates and more than one pathogen from 29 neonates. Vibrio cholerae, Shigella, Salmonella, Aeromonas spp. and Plesiomonas shigelloides were isolated from 294, 108, 52, 222 and 19, respectively, of the neonates. The year-wise isolation of these pathogens varied between 4.9-23.4%, 2.7-5.4%, 0-4.7%, 0-19.4% and 0-1.6%, respectively, of the neonates. The results of the study indicate that infection by V. cholerae, Shigella spp., Salmonella spp., Aeromonas and P. shigelloides is common in neonatal diarrhoea in Bangladesh.

Immunologic responses to Vibrio cholerae in patients co-infected with intestinal parasites in Bangladesh

Background

Infection with intestinal helminths is common and may contribute to the decreased efficacy of Vibrio cholerae vaccines in endemic compared to non-endemic areas. However, the immunomodulatory effects of concomitant intestinal parasitic infection in cholera patients have not been systematically evaluated.

Methods

We evaluated V. cholerae-specific immune responses in a cohort of patients with severe cholera. 361 patients completed 21 days of observation and 53 (15%) had evidence of a concomitant intestinal parasitic infection based on direct microscopy. Although there were no significant differences in the vibriocidal or lipopolysaccharide (LPS)-specific immune responses to V. cholerae, helminth-infected cholera patients had decreased fecal and serum IgA immune responses to the B subunit of cholera toxin (CTB) as well as a more modest decrease in serum IgG response to CTB. These findings remained significant for all classes of helminth infection and when controlling for potential confounding variables such as age and nutritional status. Although we hypothesized the differential effect on CTB and LPS immune responses was due to T-cell-dependent immunomodulatory effects of helminth infection, we did not find additional evidence to support a classic Th1 or Th2 polarization of the immune response to V. cholerae infection related to parasite infection.

Conclusions/Significance

The finding that helminth infection has a profound association with the mucosal humoral immune response to V. cholerae has implications for the development of protective immunity in cholera-endemic areas and provides an additional basis for deworming programs in cholera-endemic areas. Additional studies, including further characterization of the role of T cells in the immune response to human V. cholerae infection and the development of an animal model of co-infection, may provide additional insight into the mechanisms underlying these findings.

Vibrio cholerae causes cholera, a severe diarrhea that may lead to fatal dehydration if not treated. Cholera occurs mostly in impoverished areas where there is poor sanitation and intestinal parasites are also common. However, little is known about the relationship between intestinal parasites and cholera. To learn about how parasites affect the immune response to Vibrio cholerae, this article describes 361 patients with cholera, including 53 who had intestinal parasitic infection. We found that cholera patients with parasitic worms had decreased antibody response to cholera toxin. The decrease was greatest in IgA antibodies, which are secreted in the intestine. However, patients with worm infection did not have a difference in their immune response to lipopolysaccharide, a sugar-based molecule that is important for immunity. These different effects on the immune response to cholera toxin and lipopolysaccharide could be explained by the effect of parasitic infection on CD4+ T cells, a type of cell that influences the development of the antibody response to proteins such as cholera toxin but may not always influence the response to sugar-based molecules. The finding that worm infection is associated with decreased immune responses to cholera provides an additional reason for deworming in cholera-endemic areas.

Shifting prevalence of major diarrheal pathogens in patients seeking hospital care during floods in 1998, 2004, and 2007 in Dhaka, Bangladesh

Bangladesh experienced severe flooding and diarrheal epidemics in 2007. We compared flood data from 2007 with 2004 and 1998 for diarrheal patients attending the ICDDR,B hospital in Dhaka. In 2007, Vibrio cholerae O1 (33%), rotavirus (12%), and enterotoxigenic Escherichia coli (ETEC) (12%) were most prevalent. More severe dehydration was seen in 2007 compared with 2004 and 1998 (P < 0.001). In 2007, V. cholerae O1 Inaba (52%) and Ogawa (48%) were seen, whereas in 2004 and 1998 it was primarily Inaba and the Ogawa types, respectively (P < 0.001). In 2007, 51% of ETEC produced the heat labile toxin (LT) (P < 0.001 compared with 2004), 22% expressed the heat stable (ST) (P < 0.001), and 27% were ST/LT positive (P = 0.231). The CS7 colonization factor (CF) was the most prevalent in 2007 (20% compared with 6% in 2004; P = 0.05). Our findings demonstrate alterations in clinical features and phenotypic changes of major bacterial pathogens in the recent Bangladesh flood.

A comparison of clinical and immunologic features in children and older patients hospitalized with severe cholera in Bangladesh

BACKGROUND

: Infection with Vibrio cholerae induces protection from subsequent severe disease, suggesting that an effective vaccine could be an important preventive strategy. Available vaccines provide less protection against cholera than natural infection, particularly in children.

METHODS

: We examined a cohort of 121 children (2 years-12 years of age) and 276 older patients (>12 years of age) hospitalized with cholera in Dhaka, Bangladesh over a 4-year period, to compare clinical features in older patients and children and immune responses to key antigens.

RESULTS

: Older patients had more severe disease. Children with cholera were more commonly retinol deficient, while zinc deficiency was equally prevalent in both groups. Children developed higher vibriocidal and serum immune responses to the B subunit of cholera toxin (CTB). In contrast, older patients mounted higher immune responses to 2 other key V. cholerae antigens, the lipopolysaccharide (LPS) and toxin coregulated pilus antigens (TcpA). We compared immune responses following infection with those occurring after receipt of a live, oral vaccine in both children and older patients in Bangladesh, during a similar time period. The response rates for vibriocidal and LPS antibodies were higher after infection than after vaccination. Both vaccinated older patients and children responded poorly to CTB and TcpA.

CONCLUSIONS

: Although children developed vigorous vibriocidal and CTB-specific responses following infection, they had lessened responses to LPS and TcpA compared with older patients, as well as lessened responses to vaccination. More studies need to be carried out to determine factors, including micronutrient interventions that can improve responses in children to both natural infection and vaccination.

Cholera toxin-specific memory B cell responses are induced in patients with dehydrating diarrhea caused by Vibrio cholerae O1

BACKGROUND

Infection with Vibrio cholerae induces durable immunity against subsequent disease, a process hypothesized to reflect anamnestic immune responses at the intestinal mucosa. The presence of antigen-specific memory B cells may therefore be a more direct measure of protection than serum antibody responses.

METHODS

We measured immunoglobulin (Ig) G memory B cells specific to cholera toxin B subunit (CTB) in 14 patients up to 90 days after V. cholerae O1 infection, by polyclonal stimulation of peripheral blood mononuclear cells followed by standard enzyme-linked immunospot assay.

RESULTS

All patients generated CTB-specific IgG memory B cell responses by day 30 (mean, 0.10% of total circulating IgG memory B cells; range, 0.037%-0.28%), which persisted to day 90 (mean, 0.07%; range, 0.003%-0.27%). In contrast, circulating CTB-specific IgG antibody-secreting cells and serum vibriocidal and anti-CTB antibody responses peaked on day 7 and declined to undetectable or significantly lower levels by day 90.

CONCLUSIONS

CTB-specific IgG memory B cell responses are detectable in the circulation at least 3 months after V. cholerae O1 infection and remain measurable even after serum antibody titers have declined to undetectable or considerably lower levels. This suggests that antigen-specific memory B cells may be an important long-term marker of the immune response to cholera.

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.