Cholera vaccines

The currently licensed parenteral cholera vaccine has not been a useful public health tool in the control of cholera. Building on the knowledge that primary infection offers significant protection against reinfection and that mucosal immunity mediates this protection, several oral cholera vaccines have been developed. These vaccine candidates or future candidates derived using the techniques of molecular biology will no doubt contribute to the control of cholera.

An oral B subunit: whole cell vaccine against cholera

During the last decade there has been a rapid progress in the development of new, much improved vaccines against cholera. These vaccines, which are given orally to stimulate the gut mucosal immune system, are based on either a combination of purified cholera toxin B (binding) subunit and killed cholera vibrios of Inaba and Ogawa serotypes and El Tor and classical biotypes (B subunit-whole cell vaccine, B-WC) or on a live attenuated mutant strain of Vibrio cholerae producing the B subunit (CVD 103-HgR). The safety of the oral B-WC cholera vaccine and the immunogenicity and protective efficacy of this vaccine against both cholera and diarrhoea caused by enterotoxigenic Escherichia coli have been extensively documented, e.g. in a large randomized, placebo-controlled field trial in 90,000 persons living in a cholera endemic area. The potential for inexpensive large-scale manufacturing of the B-WC vaccine has recently been much facilitated by the introduction of recombinant DNA technology for production of the B subunit component. This now gives promise that this vaccine could become a useful, cost-effective tool in future strategies to control cholera both in endemic situations and in relation to acute epidemic outbreaks.

The clinical and immunologic response of Chilean infants to Haemophilus influenzae type b polysaccharide-tetanus protein conjugate vaccine coadministered in the same syringe with diphtheria-tetanus toxoids-pertussis vaccine at two, four and six months of age

The safety and immunogenicity of a vaccine against Haemophilus influenzae type b consisting of purified polyribosylribitolphosphate conjugated to tetanus toxoid (PRP-T) was evaluated in 278 Chilean infants who were randomly assigned to one of three treatment groups: Group A, PRP-T mixed with diphtheria-tetanus toxoids-pertussis (DTP) vaccine in a single syringe and given as a single inoculation in one arm and placebo in the other arm; Group B, PRP-T given in one arm and DTP in the other arm; Group C, DTP given in one arm and placebo in the other. Infants were immunized at 2, 4 and 6 months of age and examined daily for 4 days after each immunization; serum PRP antibodies were measured at baseline and 2 months after each dose. The only adverse systemic reaction attributable to PRP-T beyond that caused by DTP alone was a 7 to 20% increase in febrile responses in the first 24 hours after the first and second doses of vaccine; the fevers were largely low grade and not accompanied by increased irritability, diminished activity or loss of appetite, compared with the group who received DTP without PRP-T. After the first dose 72% of infants who received PRP-T combined with DTP and 67% who received it in a separate arm attained antibody concentrations greater than or equal to 0.15 micrograms/ml. After two doses of PRP-T, 93 and 95%, respectively, had concentrations greater than or equal to 0.15 microgram/ml and after three doses 100% of infants who received PRP-T had such titers.(ABSTRACT TRUNCATED AT 250 WORDS)

Rotavirus-associated diarrhea in rural Bangladesh: two-year study of incidence and serotype distribution

Stools were evaluated from 5,811 patient visits for treatment of diarrhea in Matlab, Bangladesh, between June 1987 and May 1989. The stools were analyzed to determine the distribution of serotypes of group A rotaviruses (RV). A total of 898 stool samples (15.5%) contained RV, as determined by using an enzyme-linked immunosorbent assay. RV isolates from 855 of these samples were serotyped by using serotype-specific synthetic oligonucleotide probes. A total of 558 (65.3%) could be assigned to specific serotypes: 166 (19.4%), 228 (26.7%), 39 (4.6%), and 125 (14.6%) belonged to serotypes 1 through 4, respectively; 12 (1.4%) hybridized with more than one serotype; and 285 (33.3%) failed to hybridize. RV diarrhea was evident throughout the year, with peaks in the dry winter months and in September 1988, coinciding with a major flood. RV was isolated from 46.6% of patients between 7 and 12 months old. Among children under 24 months of age with RV diarrhea, 1.2% (10 of 828) died. The corresponding percentage for children with diarrhea from all causes is 0.9% (29 of 3,301).

Evidence for recent diarrhoeal morbidity as a risk factor for persistent diarrhoea: a case-control study

The association between persistent diarrhoea and 'recent morbidity' defined as that occurring within the two-month period immediately preceding the onset of persistent diarrhoea was investigated in a population-based case-control study in rural North India. In two separate matched case-control analyses children with persistent diarrhoea (cases) were compared to population controls (five controls matched to each case) and acute diarrhoeal controls (three controls matched to each case). After correcting for possible confounding variables, comparing children with persistent diarrhoea and matched population controls, presence of a recent diarrhoeal illness was significantly associated with persistent diarrhoea with an odds ratio (OR) 2.6 (95%) confidence interval (CI): 1.1-7.1; p less than 0.05); during infancy this OR was 5.2 (95% CI: 1.0-31.9; p less than 0.01). Comparing children with persistent diarrhoea to matched acute diarrhoeal controls, presence of recent diarrhoeal illness was associated with an OR of 5.1 (95% CI: 1.3-20.3) in favour of the episode becoming persistent; in infants this OR was 10.4 (95% CI: 1.1-132.4; p less than 0.001).

Differential diagnosis of acute viral hepatitis using rapid, fully automated immunoassays

We report the development of three rapid, fully automated immunoassays allowing the differential diagnosis of acute viral hepatitis. These assays detect HBsAg, IgM antibody to hepatitis B core antigen (IgM anti-HBc) and IgM antibody to hepatitis A virus (IgM anti-HAV) using the IMx instrument system. All IMx assays were run in less than 45 minutes and all steps were fully automated including specimen dilution steps. Specimens from blood donors, diagnostic and hospital patients, and individuals with a variety of infectious and immune diseases were tested for IgM anti-HAV (n = 1473) or for IgM anti-HBc (n = 1606) or for HBsAg (n = 9700) by the IMx and commercially available EIA and RIA. Each IMx assay showed 99.8% agreement with current EIA. Reproducibility in all hepatitis IMx assays was significantly better than that observed with manual or semiautomated assays; within-run and between-run % CV ranged from 2.2 to 4.8 and 3.5 to 10.3 respectively. In 29 acute hepatitis B patients studied, HBsAg and IgM anti-HBc were detected in the first available patient bleed collected from 0 to 4 week from the onset of symptoms. IgM anti-HBc persisted at reactive levels in the IMx assay for 1 to 24 weeks (mean 12.1 +/- 5.3 weeks) after the patient presented with symptoms. In individuals exposed to hepatitis A, IgM anti-HAV was detectable by IMx by 40 days post exposure (average 33.5 days) and IgM had declined to unreactive levels in IMx for all patients by from 3 to 6 months post exposure. These data demonstrate the use of these rapid IMx assays for differentiation of acute hepatitis A and B.

A population-based retrospective assessment of the disease burden resulting from invasive Haemophilus influenzae in infants and young children in Santiago, Chile

Clinical discharge and laboratory records were reviewed in the seven government hospitals that provide care for 93% of the pediatric population of Santiago, Chile, to detect cases of meningitis and other invasive (bacteremia-associated) infections caused by Haemophilus influenzae. infections that occurred in children less than five years of age from January, 1985, through December, 1987, were recorded and matched with census data to calculate incidence rates. The incidence of meningitis and non-meningitis syndromes peaked in the 6- to 11-month age group and tapered sharply after 12 months of age. The city-wide incidence (ca. 21.6 cases/10(5) children less than 5 years of age) is one-third to one-half that reported for the general pediatric population in the United States. However, there is much evidence for under-reporting in Santiago. In Area Norte, served by Roberto del Rio Children's Hospital where H. influenzae has been a subject of research by pediatricians for years, the incidence of invasive H. influenzae infections (42.5/105) is approximately two-fold higher than the rest of Santiago. The cumulative proportions of episodes of H. influenzae disease occurring in successively older age groups closely parallel the pattern seen in the general United States pediatric population. Although only ca. 20% of all episodes occur during the first 6 months of life, nearly 80% of episodes are seen by 18 months of age. Based on the observed incidence rates, the apparent underreporting and the high city-wide case fatality of Hib meningitis (16%), invasive H. influenzae infections represent an important public health problem in Santiago, Chile.

Periampullary neoplasms in von Recklinghausen's disease

A case of neurofibromatosis is reported in a patient who was initially seen with obstructive jaundice caused by a carcinoid tumor originating from the ampulla of Vater. An extensive review of the literature suggests that patients with von Recklinghausen's disease are at significant risk for periampullary neoplasms of neural-crest and non-neural-crest origin. The tendency of those tumors to arise from the ampulla of Vater has diagnostic and therapeutic implications.

New cholera vaccines

Development of improved cholera vaccines has progressed rapidly in recent years. An oral killed vaccine, designed to evoke antibacterial as well as antitoxic intestinal immunity, has proved to be completely safe and to protect against cholera for at least 3 years. This vaccine also confers substantial though more short-lasting immunity against diarrhoea caused by enterotoxigenic Escherichia coli. Significant progress has also been made towards developing a live attenuated cholera vaccine using recombinant DNA techniques. The advent of effective oral cholera vaccines gives hope for improved control of cholera in the Third World.

General pharmacology of nizatidine in animals

Nizatidine (N-[2-[[[2-[(dimethylamino)methyl-4-thiazolyl]- methyl]thio]ethyl]-N'-methyl-2-nitro-1,1-ethenediamine, LY139037, Axid) is a novel, potent, and selective H2-antagonist. The potential secondary pharmacologic effects of this agent on the cardiovascular, respiratory, gastrointestinal, renal, hepatic, autonomic, and central nervous systems as well as effects on circulating blood glucose and the acute inflammatory response were examined. Nizatidine was generally inactive in the tests conducted in mice, rats, guinea pigs, rabbits, and dogs. Nizatidine and the reference H2-antagonist, cimetidine, both produced effects upon the cardiovascular and respiratory systems by intravenous administration in anesthetized dogs at doses in excess of the intended clinical exposure. In summary, these studies confirm the selective pharmacologic activity of nizatidine and indicate a low potential for secondary pharmacologic side effects to be encountered clinically.

User fees for health care in developing countries: a case study of Bangladesh

In designing country health care programs to achieve the goals of the Alma Alta declaration of 'Health for All', developing countries have been confronted with the problem of increased health care needs and decreased available resources. Health economists have proferred several possible solutions to this fiscal shortfall, including cost-recovery measures through the imposition of user fees for curative services at government health facilities. Health care providers have been noticeably absent from discussions of the many possible implications of these fees; consequently, resultant programs and policies may be economically sound but may fail to place a sufficient emphasis on features designed to maintain and improve the health of the population. In the present paper we examine the possible impact of user fees on the health of individuals residing in Bangladesh, one potential candidate country for user fees. We note evidence that the existing government health care system appears already to be providing care to two of the most medically vulnerable groups in Bangladesh, the poor and women, and provide evidence that such fees may seriously interfere with maintaining this patient profile. We discuss the significant public health role that curative care provides for the individuals, their families and the wider community. We suggest that additional questions should be asked by health care providers, anthropologists and economists prior to institution of user fees in the government system and that such measures should first be introduced in an experimental format with a rigorous and comprehensive impact evaluation.

Descriptive epidemiology of persistent diarrhoea among young children in rural northern India

In order to determine the descriptive epidemiology of persistent diarrhoea in rural northern India, a cohort of 963 children aged 0-71 months was followed prospectively for 12 months through weekly household visits. The incidence of persistent diarrhoea was 6.3 per 100 child-years among those aged 0-71 months, and was highest (31 per 100 child-years) among those aged 0-11 months. There were no significant sex-related differences in the incidence of the disease, and the overall seasonal distribution of acute and persistent diarrhoea was similar. The persistence of diarrhoeal symptoms was significantly correlated with a higher initial mean stool frequency (P less than 0.01) and passage of gross blood with stools (P less than 0.001). Persistent diarrhoea was an important problem among children during the first 2 years of life. Established enteric pathogens were isolated during the initial illness in 46.4% of persistent and 55.4% of acute episodes. Pathogens isolated during persistent episodes included enterotoxigenic Escherichia coli (ETEC 9.3%), Salmonella spp. (4.7%), as well as campylobacter (4.7%), Shigella spp. (2.3%), Entamoeba histolytica (2.3%), and rotavirus (2.3%). Similar proportions of these pathogens were isolated also during episodes of acute diarrhoea. Multiple pathogens were isolated in 7% of the persistent and 5% of the acute episodes. E. coli that manifested aggregative adherence (EAEC-A) was more common (34.9% versus 12.3%) in persistent than acute episodes (P less than 0.01), and initial faecal excretion of EAEC-A was significantly associated with the persistence of a diarrhoeal episode.

Effect of low dose ethanol on the EEG of alcohol-preferring and -nonpreferring rats

Low dose ethanol has been shown to differentially affect the behavior of alcohol-preferring (P) and -nonpreferring (NP) rats. The present study was undertaken to determine if this differential effect is reflected in the EEG of these two rat lines. Frontocortical and hippocampal EEG were recorded from P and NP rats after intragastric infusions of ethanol (0.5 g/kg) and vehicle. Spectra were created from sequential 8-second epochs and power was calculated for frequency bands 0-4, 4-8, 8-16 and 16-50 Hz. Band power data was then grouped according to the rat's behavior and compared for P and NP rats. During nonREM sleep, ethanol produced a persistent increase in power in the NP rats, while power in the P rats was initially decreased, then returned to baseline. This differential effect was seen at both recording sites. The results suggest the P rats were midly aroused by low dose ethanol, while the NP rats were mildly sedated.

The insulin-like growth factor-II (IGF-II) receptor of rat brain: regional distribution visualized by autoradiography

The presence of insulin-like growth factor-II (IGF-II) in brain and cerebral spinal fluid prompted us to investigate the distribution of receptors for this peptide in rat brain slices. Human 125I-IGF-II (10 pM) was incubated for 16 h at 4 degrees C with thaw-mounted slices of rat brain from 11 different brain regions. Incubations in the absence or presence of excess unlabeled human IGF-II or insulin were performed and the labeled tissues were exposed to X-ray film for 4-7 days. Autoradiographs showed dense labeling in the granule layers of the olfactory bulbs, deep layers of the cerebral cortex, pineal gland, anterior pituitary, hippocampus (CA1-CA4, and dentate gyrus), and the granule cell layers of the cerebellum. Unlabeled IGF-II eliminated most of the binding in these brain regions while insulin produced only a minimal reduction in the amount of 125I-IGF-II bound. These results indicate that a neural receptor for IGF-II is uniquely distributed in rat brain tissue supporting the notion that this peptide might play an important role in neuronal functioning.

Comparability of results obtained by two-week home maintained diarrhoeal calendar with two-week diarrhoeal recall

Many community based studies of diarrhoea in the developing world employ face-to-face interviews to obtain diarrhoeal histories. An alternative recording device that preserved the accuracy but avoided the expense and time commitment of the interview would be extremely valuable. To evaluate the comparability of episodes of diarrhoea obtained from a home-maintained two-week calendar with those histories given in response to a two-week health recall interview in a largely uneducated population, we studied approximately 1500 families for six months in Dhaka, Bangladesh. The diarrhoea records obtained for children by the two methods were highly comparable (Kappa value 0.83). The comparability was not impaired either by lack of maternal education nor by increased numbers of children in the household. We conclude that the two-week home maintained diarrhoea calendar offers comparable results with the two-week recall and in certain situations could be a useful substitute.

Impact of multiple comparisons in randomized clinical trials

The randomized clinical trial is the preferred research design for evaluating competing diagnostic and therapeutic alternatives, but confidence in the conclusions from a randomized clinical trial depends on the authors' attention to acknowledged methodologic and statistical standards. This survey assessed the level of attention to the problem of multiple comparisons in the analyses of contemporary randomized clinical trials. Of the 67 trials surveyed, 66 (99 percent) performed multiple comparisons with a mean of 30 therapeutic comparisons per trial. When criteria for statistical impairment were applied, 50 trials (75 percent) had the statistical significance of at least one comparison impaired by the problem of multiple comparisons, and 15 (22 percent) had the statistical significance of all comparisons impaired by the problem of multiple comparisons. Although some statistical techniques are available, there still exists a great need for future work to clarify further the problem of multiple comparisons and determine how the impact of this problem can best be minimized in subsequent research.

Follow-up of children discharged from hospital after treatment for diarrhoea in urban Bangladesh

To determine the subsequent mortality of urban children in Bangladesh after an episode of diarrhoea we visited 74 children aged 2 to 5 years in their homes four months after they had received treatment for diarrhoea at the International Centre for Diarrhoeal Disease Research, Bangladesh (ICDDR,B). Parents and health workers were questioned about their perceptions of the nutritional status of the children at this time. Although 43% of the children were severely malnourished and 28% were moderately malnourished at the time of presentation to ICDDR,B only two deaths (3%) had occurred in the cohort during follow-up. No deaths were noted for the severely malnourished two year old group, which contrasts with the high post-discharge mortality (33%) in similarly malnourished two year old Bangladeshi children living in rural areas (p = 0.004) at the time of follow-up parents were significantly (p = 0.02) less likely than health workers to recognize malnutrition in the children. We suggest that there may be substantial rural-urban differences in the survival of children after receiving treatment for diarrhoea. Further, we note that parental under-recognition of malnutrition may impede the nutritional rehabilitation that is necessary to avert much of the morbidity and mortality that ensues after an episode of diarrhoea.