Seroepidemiology of cholera in Gulf coastal Texas.

Single serum samples from 559 volunteers from a Texas Gulf Coast area were examined for vibriocidal antibody to Vibrio cholerae O1 (biotype El Tor, serotype Inaba) by a microtiter method. Elevated levels of vibriocidal antibody were present in 14% of the subjects. Also, 6.8% of the subjects had elevated levels of antibody to the enterotoxin of V. cholerae O1 by the immunoglobulin G enzyme-linked immunosorbent assay. Recent infection, defined on the basis of elevations in both vibriocidal and antitoxin antibodies, had occurred in 1.3% of the subjects. When subjects who reported Brucella infection, travel to a cholera-endemic area, and/or cholera vaccination within a year of the study were removed from the analysis, a prevalence of recent infection of 0.89% was obtained. Significantly higher titers of vibriocidal antibody were found in those with exposure to seawater (fishermen, shrimpers, merchant marines, and dock workers) than in those without such exposure (P less than 0.005). Furthermore, titers of antitoxin antibody were significantly higher in those who consumed shellfish than in nonconsumers. Finally, titers of vibriocidal antibody were significantly higher in Vietnamese subjects than in non-Vietnamese subjects. The results of this study indicate that an endemic focus of infection with V. cholerae occurs in this area.

Acute infectious diarrhea among children in day care: epidemiology and control.

The incidence of diarrhea among children in day care centers is highest for those under three years of age. Limited studies indicate that diarrhea occurs more frequently among children enrolled at these centers than among age-matched children cared for at home or in family day care. Most reported outbreaks have been caused by rotavirus, Giardia, Shigella, or combinations of these organisms. Children in day care centers commonly excrete enteropathogens in the absence of symptoms; the significance of this phenomenon in transmission is unknown. An association between higher rates of diarrhea and selected characteristics of centers--the most important of which is the presence of non-toilet-trained children--has been shown. The contamination of hands, communal toys, and other classroom objects as well as a lack of infection control measures play a role in the transmission of enteropathogens in outbreaks of diarrhea in day care centers. Spread of infection from non-toilet-trained children in centers to their families is common. Potential ways of dealing with this situation include education; development, implementation, and enforcement of regulations; and use of infection control measures. However, the effectiveness of specific control measures has not been systematically evaluated.

Norwalk virus gastroenteritis. An outbreak associated with a cafeteria at a college.

An explosive outbreak of gastrointestinal illness occurred among students and employees at a small college in Florida in November 1980. Common symptoms were diarrhea, nausea, weakness, abdominal cramps, chills, vomiting, and low-grade fever. Cases of illness were identified in 40% of 628 students and 15% of 162 employees who responded to a survey. Among students, there was a sevenfold excess risk associated with eating one or more meals at the campus cafeteria November 3-5 (p much less than 0.001). Tossed salad from one meal was strongly associated with illness (p less than 0.0001). Fecal contamination of the salad was documented, although the source of contamination was not identified. Person-to-person spread could not be demonstrated. Seroconversion to Norwalk antigen occurred in significantly more cases (5/6) than noncases (1/6) (p = 0.04).

The relationship of staff to the incidence of diarrhea in day-care centers.

Sixty randomly selected day-care centers in Houston, Texas, were surveyed for cases of diarrhea by weekly telephone calls during the period October 1980 to May 1981. Visits to each day-care center were made upon enrollment and again to collect self-administered questionnaires which had been mailed to the staff of each center. During the eight-month survey, 986 cases of diarrhea were reported, with an average day-care center incidence of 1.15 cases per 100 person-weeks of observation. A significant positive correlation (p less than 0.05 to p less than 0.01) was found between the incidence of diarrhea in a day-care center and each of the following variables reported by the day-care center staff: the average frequency of diapering, the average frequency of working with children less than two years of age, the average frequency of meal preparation, the average frequency of serving food to the children, and the percentage of staff who both diaper and either serve food or prepare meals daily. Day-care centers which accepted children less than two years of age had a 3.55-fold higher incidence of diarrhea compared with centers which did not accept children less than two years of age. Day-care centers in which one or more staff members prepared meals, served food, and diapered children on a daily basis had a 3.28-fold higher incidence of diarrhea compared with centers in which staff did not combine on a daily basis the duties of diapering children with either meal preparation or food service. The results suggest that staff members may play a role in the transmission of diarrhea in day-care centers through diapering, meal preparation, working with children less than two years of age, or a daily combination of diapering and either meal preparation or food service.

Longitudinal study of occurrence of diarrheal disease in day care centers.

Sixty day care centers (DCC) randomly selected from 736 licensed child care facilities in Harris County (Houston), Texas were surveyed for the incidence of diarrhea by periodic visits and weekly telephone calls over two years. A total of 2,708 episodes of diarrhea were reported in 3,800 children under 6 years of age, and 84 cases occurred in center staff. Overall incidence was 0.44 episodes/person/year among children and 0.14 among staff. Attack rates among the 60 DCC ranged from none to 3.64 cases/year in each child. The incidence for children under 36 months of age was 17 times higher than for the older group. Characteristics of DCC associated with higher rates of disease among children were the presence of young, non-bowel trained children, staff who both diapered infants and prepared food on a regular basis, DCC for profit management, and DCC whose only guidelines were provided by the State. The socioeconomic burden associated with DCC disease, its transmission, and control is considerable and needs to be further addressed.

Occurrence of Giardia lamblia in children in day care centers.

We prospectively evaluated excretion of Giardia lamblia in children in day care centers in Houston by conducting two prevalence studies of 600 children enrolled in 30 DCC, day care centers, and an 18-month longitudinal study in 82 children in one center. In the two prevalence surveys, Giardia cysts were identified in 72 (21%) and 67 (26%) children, respectively, who provided stool specimens. Trophozoites were found in 15 (4%) and 8 (3%), respectively. There was no correlation between the frequency of recent diarrheal episodes and the finding of Giardia. Stool specimens containing cysts were significantly (P less than 0.0001) more frequent in the 13- to 30-month-old children than in children younger than 12 months. Children attending day care centers for more than 3 months were more likely to be excreting Giardia than those attending for less than 3 months. In the longitudinal study, cysts were detected in stool specimens from 27 (33%) of the 82 children at least once during the survey. Twelve children had Giardia cysts in weekly stool specimens for a mean of 6.2 +/- 1.2 months and trophozoites for 3.3 +/- 1.2 months. The number of enteric symptoms observed in children and the classification of nutritional status based on monthly height and weekly weight measurements did not differ significantly when infected and noninfected children were compared. Asymptomatic Giardia excretion in children younger than 36 months is common and appears to be well tolerated.

Survival and detection of rotaviruses on environmental surfaces in day care centers.

Previously, we demonstrated that children in day care centers commonly experience diarrhea due to rotavirus, giardia, and bacterial pathogens. Multiple agents frequently coexist, and the environment is heavily contaminated with enteric bacteria during outbreaks. A study of environmental surface contamination with rotavirus was performed during three non-outbreak periods. Of 25 samples collected from environmental surfaces and teachers hands at a day care center, 4 (16%) were positive for rotavirus antigen when a fluorescence assay was used. We also examined the survival of two animal viruses, rotavirus SA-11 and poliovirus type 1, and bacteriophage 12 on similar environmental surfaces in a laboratory. Poliovirus type 1 and bacteriophage f2 were more resistant to drying than rotavirus SA-11 and could be recovered after a 90-min exposure on a dry surface. Rotavirus SA-11 could be detected for 30 min. All three viruses survived longer when they were suspended in fecal material than when they were suspended in distilled water. These data suggest that several agents, including rotavirus, can remain viable on contaminated surfaces long enough to be transmitted to susceptible children. This finding helps explain why rotavirus shows a mode of spread like that of parasitic and bacterial agents within day care center settings.

An analysis of the relationship of host factors to clinical falciparum malaria by multiple regression techniques.

Clinical records of 58 infections with the Vietnam Smith strain of Plasmodium falciparum in human volunteers were studied in order to 1) characterize the clinical course of infections; 2) investigate the effects of race, weight, age, method of induction, and previous malaria experience on the course of infection using methods of multiple regression; and 3) establish whether differences in drug-treatment groups may have influenced the current study results. We found that blacks tolerated infection better than whites, that heterologous as well as homologous strain immunity persists after infection and that these results could not be attributed to differences in treatment. The clinical course of infections with the Vietnam Smith strain of P. falciparum is described.

The relationship of oral rehydration solution to hypernatremia in infantile diarrhea.

PIP: A major criticism of the use of oral rehydration solution (ORS) in the treatment of diarrhea has been that the high sodium content of the solution might predispose the development of hypernatremia in infants not allowed access to additional free water and in whom glomerular filtration rate and urinary concentrating ability may be low. A study was undertaken in 1980 in Cairo, Egypt to assess the use of ORS. The study included 100 children under age 1, mean age 6.7 months, with dehydration secondary to diarrhea, and 17% were hypernatremic on admission, 27% hyponatremic and 56% isonatremic; the hypernatremic infants were found to be more dehydrated than the others. 24% of the hypernatremic infants had taken Rehydran whereas only 5% of the others had taken it and none had been given the medication in a proper fashion. Of the 17 with hypernatremia 16 completed the course of oral rehydration therapy and 63% had normal serum sodium values by 6 hours of therapy. It was found that the treatment of hypernatremic infants with ORS was successful while with the unsupervised use of Rehydran the risk of this condition was enhanced; errors made in the home included prolonged use of the solution and failure to use water. It is believed that because of widespread illiteracy sole reliance upon written instructions is potentially dangerous.^ieng

Biohydrogenation of cholesterol as an index of bacterial 7 alpha-dehydroxylase activity.

Fecal steroid compositions of 82 human subjects of various ages and diets and gastrointestinal status were examined by gas liquid chromatography. Progressive increases in bacterial activities on both bile acids and neutral sterols were observed with the advance of age in infants and children. The patterns in the 4-year-olds approached those observed in adults. Bacterial activities on fecal steroids were found to be decreased in adult subjects with acute shigellosis and in those challenged by castor oil. In contrast, no significant changes in fecal steroid profiles were observed in the subjects with traveller's diarrhea associated with toxigenic Escherichia coli. The effects of diarrhea on fecal steroids of infants under 1 1/2 years were less consistent than those of adults. However, a close relationship was observed between the degree of 7 alpha-dehydroxylation of cholic acid (expressed as the ratio of deoxycholic to the sum of deoxycholic and cholic acids) and the percentage of cholesterol in the feces (r = -0.921, p less than 0.001). The correlation between the production of lithocholic acid and the percentage cholesterol was also good (r = -0.739, p less than 0.001). Analysis of neutral steroids may be a good index of intraluminal bile acid metabolism.

Biohydrogenation of cholesterol as an index of bacterial 7α-dehydroxylase activity.

Fecal steroid compositions of 82 human subjects of various ages and diets and gastrointestinal status were examined by gas liquid chromatography. Progressive increases in bacterial activities on both bile acids and neutral sterols were observed with the advance of age in infants and children. The patterns in the 4-year-olds approached those observed in adults. Bacterial activites on fecal steroids were found to be decreased in adult subjects with acute shigellosis and in those challenged by castor oil. In contrast, no significant changes in fecal steroid profiles were observed in the subjects with traveller's diarrhea assoicated with toxigenicEscherichia coli. The effects of diarrhea on fecal steroids of infants under 1(1/2) years were less consistent than those of adults. However, a close relationship was observed between the degree of 7α-dehydroxylation of cholic acid (expressed as the ratio of deoxycholic to the sum of deoxycholic and cholic acids) and the percentage of cholesterol in the feces (r= 0.921, p<0.001). The correlation between the production of lithocholic acid and the percentage cholesterol was also good (r=-0.739, p<0.001). Analysis of neutral steroids may be a good index of intraluminal bile acid metabolism.

Volunteer studies of typhoid fever and vaccines.

A series of studies evaluated the efficacy of three categories of typhoid vaccines: killed organisms given parenterally and orally and living attenuated mutants given orally. Vaccinees and unvaccinated controls were challenged with a single strain of virulent Salmonella typhi. Control individuals with prior military service (i.e. mandatory parenteral immunization) were significantly protected compared to non-veterans. Clinical protection of vaccinees was greatest (87%) following oral immunization with a mutant strain lacking epimerase.