Seasonality and within-subject clustering of rotavirus infections in an eight-site birth cohort study.

Improving understanding of the pathogen-specific seasonality of enteric infections is critical to informing policy on the timing of preventive measures and to forecast trends in the burden of diarrhoeal disease. Data obtained from active surveillance of cohorts can capture the underlying infection status as transmission occurs in the community. The purpose of this study was to characterise rotavirus seasonality in eight different locations while adjusting for age, calendar time and within-subject clustering of episodes by applying an adapted Serfling model approach to data from a multi-site cohort study. In the Bangladesh and Peru sites, within-subject clustering was high, with more than half of infants who experienced one rotavirus infection going on to experience a second and more than 20% experiencing a third. In the five sites that are in countries that had not introduced the rotavirus vaccine, the model predicted a primary peak in prevalence during the dry season and, in three of these, a secondary peak during the rainy season. The patterns predicted by this approach are broadly congruent with several emerging hypotheses about rotavirus transmission and are consistent for both symptomatic and asymptomatic rotavirus episodes. These findings have practical implications for programme design, but caution should be exercised in deriving inferences about the underlying pathways driving these trends, particularly when extending the approach to other pathogens.

Hybrid & El Tor variant biotypes of Vibrio cholerae O1 in Thailand.

BACKGROUND & OBJECTIVES: El Tor Vibrio cholerae O1 carrying ctxB C trait, so-called El Tor variant that causes more severe symptoms than the prototype El Tor strain, first detected in Bangladesh was later shown to have emerged in India in 1992. Subsequently, similar V. cholerae strains were isolated in other countries in Asia and Africa. Thus, it was of interest to investigate the characteristics of V. cholerae O1 strains isolated chronologically (from 1986 to 2009) in Thailand. METHODS: A total of 330 V. cholerae O1 Thailand strains from hospitalized patients with cholera isolated during 1986 to 2009 were subjected to conventional biotyping i.e., susceptibility to polymyxin B, chicken erythrocyte agglutination (CCA) and Voges-Proskauer (VP) test. The presence of ctxA, ctxB, zot, ace, toxR, tcpA C , tcpA E, hlyA C and hlyA E were examined by PCR. Mismatch amplification mutation assay (MAMA) - and conventional- PCRs were used for differentiating ctxB and rstR alleles. RESULTS: All 330 strains carried the El Tor virulence gene signature. Among these, 266 strains were typical El Tor (resistant to 50 units of polymyxin B and positive for CCA and VP test) while 64 had mixed classical and El Tor phenotypes (hybrid biotype). Combined MAMA-PCR and the conventional biotyping methods revealed that 36 strains of 1986-1992 were either typical El Tor, hybrid, El Tor variant or unclassified biotype. The hybrid strains were present during 1986-2004. El Tor variant strains were found in 1992, the same year when the typical El Tor strains disappeared. All 294 strains of 1993-2009 carried ctxBC ; 237 were El Tor variant and 57 were hybrid. INTERPRETATION & CONCLUSIONS: In Thailand, hybrid V. cholerae O1 (mixed biotypes), was found since 1986. Circulating strains, however, are predominantly El Tor variant (El Tor biotype with ctxB C).

Emerging fluoroquinolone and macrolide resistance of Campylobacter jejuni and Campylobacter coli isolates and their serotypes in Thai children from 1991 to 2000.

This study investigated fluoroquinolone, macrolide resistances and serotype distributions among Campylobacter jejuni and Campylobacter coli isolated from children in Bangkok and rural settings during 1991-2000. Phenotypic identification, serotyping, and susceptibility testing were performed by standard microbiological procedures. The predominant serotypes of C. jejuni were Lior 36, 2 and 4 and of C. coli were Lior 8, 29 and 55. Resistance to nalidixic acid increased significantly during 1991-2000 and the frequency of isolates resistant to both nalidixic acid and ciprofloxacin in Bangkok was significantly greater than in rural settings. In 1996-2000, a significant trend was observed in C. jejuni isolates resistant to ciprofloxacin from Bangkok but not for macrolide resistance from both settings. In summary, fluoroquinolone resistance among C. jejuni and C. coli isolates became widespread in both Bangkok and rural settings in Thailand in the 1990s while widespread resistance to macrolides was undetected.

Bacterial enteric pathogens in children with acute dysentery in Thailand: increasing importance of quinolone-resistant Campylobacter.

Current data on pathogen prevalence and drug resistance patterns are important for treatment and vaccine-development strategies. An etiologic study of acute bacterial dysentery was conducted in children up to 12 years of age in 2 major hospitals in and around Bangkok. Stool samples or rectal swabs and clinical data were collected. Standard microbiological methods were used to detect Salmonella, Shigella, Campylobacter, Vibrio, Aeromonas and Plesiomonas. Pathogenic E. coli (ETEC, EIEC, STEC) was identified by digoxigenin-labeled probes. A total of 623 cases were enrolled: median age 11.0 months (range 1 month-12 years). At least one bacterial pathogen was isolated in 55% of cases. Campylobacter was the most common pathogen found (28%), whereas Salmonella, Shigella and ETEC were isolated from 18%, 9% and 6% respectively. EIEC, Vibrio and Plesiomonas were isolated from <1% and no STEC was detected. C. jejuni serotypes 36, 4 and 11 were the most common. The mean age of cases with Campylobacter was significantly lower than with Shigella (17.9 vs 52.8 months, p<0.001). Clinical presentations of Campylobacter and Shigella infections were compared: fever (28% vs 37%), abdominal colic (62% vs 80%, p<0.05), vomiting (38% vs 70%, p<0.001) and bloody stools (52% vs 48%). The Campylobacter isolates (80% C. jejuni, 20% C. coli) were 90% resistant to ciprofloxacin but sensitive to macrolides. All the Shigella isolates (70% S. sonnei) were sensitive to quinolones. Our study illustrates the increasing importance of quinolone-resistant Campylobacter and the decline of Shigella in the etiology of dysentery in Thailand. The clinical presentation of campylobacteriosis is similar to that of shigellosis, except that the patients may be younger and there may be less association with colic and vomiting; having fecal leukocytes will be >10/HPF. The use of macrolide antibiotics rather than quinolones would be reasonable in children <24 months of age; fluoroquinolones will be ineffective in at least half of culture-positive cases.

Prospective study of the incidence of diarrhoea and prevalence of bacterial pathogens in a cohort of Vietnamese children along the Red River.

We prospectively studied diarrhoea incidence among 1655 children < 5 years of age in northern Vietnam for 1 year using primarily passive surveillance. Standard culture methods were used to detect bacterial pathogens. Overall 2160 cases occurred (13 cases/child per year). Peak rates of diarrhoea occurred in children < 12 months old. Rates ranged from 3.3 cases/child per year in children < 1 year old, to 0.7 cases/child per year in 4-year-olds. Campylobacter, shigella and enterotoxigenic Escherichia coli were most commonly isolated. Rates detected by active surveillance were about twice those detected passively. S. flexneri was the most common shigella serogroup (65 %). S. flexneri serotypes 6, 4, 1 and Y were most common, but 40% were untypable using commercial antisera. The data illustrate important regional differences in pathogen prevalence and shigella serotype distribution. Shigella vaccine development strategies, commonly targeting S. flexneri 2a, S. sonnei and S. dysenteriae 1, will have little impact on diarrhoea rates in Vietnam.

A high proportion of Vibrio cholerae strains isolated from children with diarrhoea in Bangkok, Thailand are multiple antibiotic resistant and belong to heterogenous non-O1, non-O139 O-serotypes.

Results of a surveillance on cholera conducted with patients seen at the Children Hospital in Bangkok, Thailand from August 1993 to July 1995 are presented. Annually, isolation rates for Vibrio cholerae varied between 1.7 and 4.4% of patients with diarrhoea. V. cholerae O1 serotype Ogawa accounted for between 31 and 47% of patients cultured positive for V. cholerae, whereas the O139 serotype dominated in early 1994 after which it disappeared. Non-O1, non-0139 strains were isolated at similar rates as serotype O1 in 1993 and 1994, but accounted for 69% of V. cholerae culture positive specimens in 1995. However, the annual proportion of the isolation of non-O1, non-O139 strains showed little variation and remained low between 1.0 and 1.3%. Serotyping of 69 epidemiological unrelated non-O1, non-O139 strains produced 37 different O-serotypes. BglI ribotyping of serotypes containing more than two strains demonstrated a high degree of heterogeneity within and between serotypes, except seven serotype O37 strains which showed an identical ribotype suggesting clonality. None of the 69 strains hybridized with a cholera toxin probe and only two strains hybridized with a heat-stable enterotoxin probe. Susceptibility testing to 12 antibiotics showed that 40 of 69 (58%) non-O1, non-O139 strains were resistant to colistin, streptomycin and sulphisoxazole and 28 of 69 (41%) were multiple antibiotic resistant (MAR; > or = 4 antibiotics). Although 26 of 69 (38%) strains contained one or more plasmids, the plasmids were of low molecular weights and did not seem to encode antibiotic resistance. The results of the present study showed that a high proportion of heterogenous MAR V. cholerae non-O1, non-O139 strains were isolated from children at the hospital. With reference to the emergence of V. cholerae O139 in 1992, we suggest that non-O1, non-O139 strains should be monitored carefully to detect new serotypes with a possible epidemic potential, but also to determine the development and mechanism of antibiotic resistance.

Prospective study of the incidence of diarrheal disease and Helicobacter pylori infection among children in an orphanage in Thailand.

To evaluate the hypothesis that gastric infection with Helicobacter pylori increases risk for diarrheal disease in children, we conducted a yearlong prospective study among 160 orphanage children < 5 years of age in Nonthaburi, Thailand. Serum samples collected at six-month intervals were examined by ELISA for antibodies to H. pylori, and children were followed daily for the development of diarrhea. Seven percent of children were seropositive on enrollment, 59% were seronegative, and 34% were indeterminate. Among the seronegative children, seroconversion occurred at a rate of 7% per six months. Forty-six percent of children developed 214 total episodes of diarrhea. By age group, children < 18 months, 18-24 months and > 24 months of age experienced 2.6, 1.1, and 0.2 mean diarrhea episodes per six months. The incidence of diarrhea was not significantly different between children by H. pylori serostatus. We conclude that H. pylori infection was not associated with an increased risk of diarrheal disease.

Epidemiologic study of Vibrio cholerae O1 and O139 in Thailand: at the advancing edge of the eighth pandemic.

Vibrio cholerae O139 Bengal emerged on the Indian subcontinent in late 1992 and was first recognized in Thailand in 1993. To characterize the epidemiology of this disease, a hospital-based case-control study was conducted in Samutsakorn, a port city 30 km southwest of Bangkok. Between November 15, 1993, and June 3, 1994, 366 patients were confirmed to have cholera by culture, including 165 (45%) with O139 Bengal, 191 (52%) with O1 Ogawa, and 10 (3%) with both serogroups. During the same time period the previous year, 319 culture-confirmed cholera cases occurred, all serogroup O1. Questionnaires were obtained from 105 patients with O139 Bengal and 103 with O1 infections; for each case patient, two asymptomatic age- and sex-matched control persons were selected. Of the patients with O139 Bengal infections, 93% were adults (> or = 15 years) compared with 92% of patients with O1 infections. Risk factors for cholera identified by case-control comparisons were similar for the two serogroups and included consumption of untreated water, uncooked seafood, and food served at group gatherings. V. cholerae O139 Bengal has emerged in Thailand as a cause of endemic cholera, with epidemiologic features and incidence similar to those of the preexisting O1 strain.

PIP: Vibrio cholera 0139 Bengal emerged on the Indian subcontinent in late 1992 and was first recognized in Thailand in 1993. To characterize the epidemiology of this disease, a hospital-based case-control study was conducted in Samutsakorn, a port city 30 km southwest of Bangkok. Between November 15, 1993, and June 3, 1994, cultures confirmed that 366 patients had cholera, including 165 (45%) with O139 Bengal, 191 (52%) with O1 Ogawa, and 10 (3%) with both serogroups. During the same time period in the previous year, 319 culture-confirmed cholera cases occurred, all serogroup O1. Questionnaires were completed for 217 (59%) of the 366 patients. 105 patients were infected with 0139 Bengal, 103 with V. cholera O1, and 9 with both serogroups. For each case patient, two asymptomatic age- and sex-matched control persons were selected. Of the 105 case patients with 0139 Bengal infections, 98 (93%) were adults (age 15 or older) compared with 95 (92%) of 103 patients with 01 infections. Patient infected with 0139 Bengal were more often male than patients with O1 (58% vs. 42%, p = .018). Cholera cases and matched controls were similar with regard to matching criteria of age and sex. Risk factors for cholera identified by case-control comparisons were similar for the two serogroups and included consumption of untreated water, uncooked seafood, and food served at group gatherings. Raw seafood exhibited a strong trend toward an association with O1 infections, and this variable was a significant risk factor among all cholera cases (matched odds ratio = 2.54). V. cholera 0139 Bengal rapidly displaced existing strains of V. cholera O1 and accounted for over 95% of V. cholera isolates in India and Bangladesh during the first year of its appearance. It has emerged in Thailand as a cause of endemic cholera with epidemiologic features and incidence similar to those of the preexisting O1 strain.

Emergence of nalidixic acid resistant Shigella dysenteriae type 1 in Thailand: an outbreak associated with consumption of a coconut milk dessert.

BACKGROUND: Although Shigella dysenteriae type 1 has been responsible for large outbreaks of severe dysentery in many parts of Asia, relatively few cases of this disease have been reported from Thailand and have generally not involved nalidixic acid resistant strains. METHODS: Beginning March 1991, all patients with diarrhoea seen at the hospital outpatient department (OPD) in Suan Phung, Thailand (a western district near the Burmese border) were cultured for enteric pathogens. Shigella dysenteriae 1 was first recognized in July 1992, and an OPD-based case-control study was conducted to pinpoint the source of the outbreak in the community. For each case of culture confirmed S. dysenteriae 1, one control person without diarrhoea, matched by age and date of visit, was randomly selected from the OPD registry. RESULTS: Of 197 patients treated for diarrhoea at the hospital OPD in July and August 1992, 79 (40%) had bloody diarrhoea, compared with 86/561 (15%) patients seen during 16 months of previous surveillance (P < 0.0001). Shigella dysenteriae 1 was isolated from 33/197 (17%) patients. Compared to matched controls, patients with S. dysenteriae 1 were more likely to attend one of the local elementary schools (odds ratio = 6.74, P = 0.025), or live in the community surrounding this school (odds ratio for non-school age people = 18.0, P = 0.008). A cross-sectional study conducted at the school indicated that 50 (10%) of 485 students had dysentery in July. A coconut milk dessert prepared at the school was identified as the vehicle of transmission (relative risk = 24.9, P < 0.0001). CONCLUSIONS: Nalidixic acid resistant S. dysenteriae 1 emerged in a community in Thailand, and was traced to a point source outbreak at a local school.

PIP: Shigella dysenteriae type 1 has been responsible for large outbreaks of severe dysentery in many parts of Asia, but relatively few cases of the disease have been reported from Thailand and have generally not involved nalidixic acid resistant strains. Nalidixic acid resistant Shigella dysenteriae type 1, however, emerged in a community in Thailand and was traced to a point source outbreak at a local school. Beginning March 1991, as part of prospective surveillance for diarrheal disease in Suan Phung, all patients with diarrhea seen at the hospital outpatient department (OPD) in Suan Phung, Thailand, were cultured for enteric pathogens. 79 of the 197 patients treated for diarrhea at the hospital OPD in July and August 1992 had bloody diarrhea compared with 86/561 patients seen during 16 months of previous surveillance. Shigella dysenteriae type 1 was isolated from 33 of these 197 patients. Compared to matched controls, patients with Shigella dysenteriae type 1 were more likely to attend one of the local elementary schools or live in the community surrounding that school. A cross-sectional study conducted at the school found that 50 of 485 students had dysentery in July. A coconut milk dessert prepared at the school was identified as the vehicle of transmission.

Vibrio cholerae O139 in Thailand in 1994.

Vibrio cholerae O139 first appeared in India and Bangladesh in 1992. Surveillance for O139 was started at three hospitals in Thailand in 1993. By 1994 all three hospitals surveyed in Thailand had experienced an increase in Vibrio cholerae O139 infections.

Molecular characterization of Vibrio cholerae O139 isolates from Asia.

In 1992, a serologically novel clone of Vibrio cholerae, designated O139, caused large epidemics of diarrhea in India and Bangladesh. To determine the extent of the spread of V. cholerae O139 worldwide, 484 V. cholerae non-O1 strains isolated from different patients with diarrhea in Thailand, Indonesia, the Philippines, and Peru in 1993 were tested for agglutination in O139 antisera. One hundred fifty-one of these 484 isolates were examined for genes encoding cholera toxin, zonula occlulans toxin, the repetitive sequence 1, and the toxin coregulated pilin A (the V. cholerae virulence gene complex). Thirty-three percent (122 of 364) of V. cholerae non-O1 strains isolated from different patients with diarrhea in Thailand agglutinated in O139 antisera. Ninety-eight percent (120 of 122) of V. cholerae O139 contained the V. cholerae virulence gene complex. None of the 104 V. cholerae non-O1 strains isolated from patients with diarrhea in Indonesia or the 14 strains from patients with diarrhea in the Philippines were serotype O139. Four different ribotypes were found in V. cholerae O139 isolated in Asia. Twenty-three (47%) of 49 Thai O139 strains examined were of different ribotypes than isolates from India and Bangladesh; V. cholerae strains that were not O1 or O139 that were isolated from flies and water in Thailand 11 years previously in 1981 contained the same V. cholerae virulence gene complex found in V. cholerae O1 and O139. This suggests that other unidentified virulence determinants are involved in V. cholerae O139 pathogenesis.

Detection of Shigella and enteroinvasive Escherichia coli by PCR in the stools of patients with dysentery in Thailand.

The rate of detection of Shigella and enteroinvasive Escherichia coli (EIEC) using a PCR technique was compared with the rate detected by standard microbiological methods (bacteriology plus hybridization of E. coli colonies with a 17 kb EIEC probe) among patients with dysentery before and after antibiotic therapy. The PCR amplified DNA sequences encoding IpaH, a multiple copy sequence located on the chromosome and the invasion plasmid. Shigella or EIEC were detected using the IpaH PCR system among 72 (61%) of 119 patients with dysentery on the first day they were seen at hospital, compared to 50 (42%) using standard microbiological methods (p = 0.006). After three days of antibiotic therapy, IpaH sequences were detected in stools from 38 percent of patients, compared to 10 percent using standard microbiology (p < 0.001). After seven days of therapy, the rates were 26 percent vs. 8 percent respectively (p < 0.001). The IpaH PCR system appeared to be specific for Shigella or EIEC based on low rates of positive reactions among non-diarrhoea controls, and a strong correlation between persistently positive reactions and antibiotic resistance of bacterial isolates. IpaH sequences were detected in 10 (8%) of 119 drinking water samples from homes of patients with disease; none of these specimens were positive for Shigella or EIEC by standard microbiology. In conclusion, PCR amplification of IpaH sequences and detection of target DNA with a non-radioactive probe increased the rates of identification of Shigella and EIEC by 45% in initial clinical specimens and by nearly 300% in specimens obtained from patients receiving antibiotic therapy.

Bacterial Enteric Pathogens in Uncooked Foods in Thai Markets.

In developing countries, the morbidity and mortality rates of gastrointestinal tract infections from food borne bacteria have been difficult to establish. Most studies have only been able to gather data prospectively from isolated geographic sources, rather than from large point-source epidemics. This study investigates the types of bacterial enteric pathogens found in food that was collected in a community in Western Thailand, where sporadic cases of hemolytic uremia syndrome and cholera have been reported. Samples of six different uncooked foods were collected from markets in two villages and in the hills in an area near Bangkok and were tested at a district hospital laboratory within 2 hours of collection. From the 820 food samples collected, enteric pathogens were isolated from approximately 12%. These included nontyphoidal salmonella; Vibrio parahemolyticus; attaching and effacing Escherichia coli of nonenteropathogenic E. coli serogroups; Campylobacter jejuni; enterotoxigenic E. coli; Shigella; and V. cholerae. Travelers in developing countries should be made aware by diarrheal disease programs that food obtained in markets may contain bacterial enteric pathogens and, therefore, the hygienic preparation of such foods is important in the prevention of gastrointestinal disease.

Etiology of diarrhea in a rural community in western Thailand: importance of enteric viruses and enterovirulent Escherichia coli.

The etiology of gastroenteritis was determined in children and adults with diarrhea seen at a district hospital and three government health clinics in Suan Phung, western Thailand, in 1991. Enteric viruses (rotavirus and astrovirus) were identified in 40%, shigellae in 18%, attaching and effacing Escherichia coli in 13%, Campylobacter jejuni in 9%, and enterotoxigenic E. coli in 7% of children < 5 years old with diarrhea seen at the hospital. Enteric viruses were detected in 15% (24/156) of patients with diarrhea > or = 5 years old and were the only enteric pathogens identified in 12 patients ages 7-79 years (2 astrovirus, 10 rotavirus infections). Attaching and effacing E. coli, rotavirus, and astrovirus were potential causes of diarrhea in children and adults in this population.

Diagnosis of Helicobacter pylori infection in a developing country: comparison of two ELISAs and a seroprevalence study.

Serology to detect antibodies to Helicobacter pylori is not frequently used as a diagnostic tool in developing countries. When compared to a commercial ELISA, an ELISA constructed and validated in Thailand had a higher sensitivity (98% vs. 85%), specificity (76% vs. 66%), and negative predictive value (97% vs. 76%) for the detection of H. pylori infection among 104 patients with dyspepsia evaluated by endoscopy. The positive predictive value was 88% for both tests. Serum antibody levels fell significantly 5-8 months after eradication of infection in 8 Thai patients (P = .009). By 8 years of age, > 50% of Thai persons living in urban and rural locations were seropositive. The low negative predictive value of the commercial ELISA limits the usefulness of this assay as a diagnostic tool in Thailand and suggests a need to reevaluate H. pylori serologic tests when used in populations living in developing countries.

Ciprofloxacin and loperamide in the treatment of bacillary dysentery.

OBJECTIVE: To compare the safety and efficacy of loperamide plus ciprofloxacin with those of ciprofloxacin alone in the treatment of bacillary dysentery. DESIGN: Double-blind, placebo-controlled, randomized clinical trial. SETTING: Hospital in Thailand. PARTICIPANTS: Eighty-eight adults with dysentery seeking medical care between November 1990 and February 1992. Patients who had received prior antibiotics or antimotility drugs were excluded. INTERVENTION: All 88 patients with dysentery were treated with ciprofloxacin, 500 mg twice daily for 3 days. Forty-two of these patients were randomly assigned to receive loperamide, a 4-mg initial dose followed by 2 mg after every loose stool (as many as eight caplets [16 mg] daily), and 46 were randomly assigned to receive placebo. MEASUREMENTS: Stools were collected daily until resolution of diarrhea and again after 10 days. The time to passage of the last unformed stool, number of unformed stools, and symptoms were recorded after treatment. RESULTS: Shigella or enteroinvasive Escherichia coli (53%), Vibrio parahaemolyticus (16%), and Salmonella (7%) were the most common bacterial enteric pathogens identified in 88 patients with dysentery. In patients infected with Shigella or enteroinvasive E. coli, the median duration of diarrhea was 19 hours (25th to 75th percentiles, 6 to 42 hours) for those receiving loperamide plus ciprofloxacin compared with 42 hours (21 to 46 hours) for those receiving ciprofloxacin alone (P = 0.028). The median number of diarrheal stools for those receiving ciprofloxacin and loperamide was 2.0 (1 to 5 stools) compared with 6.5 (2 to 9 stools) for those receiving ciprofloxacin alone (P = 0.016). None of the participants had a temperature greater than 38 degrees C after 24 hours of treatment. None of the patients was infected with the same bacterial enteric pathogen more than 1 day after receiving treatment. CONCLUSIONS: Loperamide decreases the number of unformed stools and shortens the duration of diarrhea in dysentery caused by Shigella in adults treated with ciprofloxacin.

Diarrheal disease in Cambodian children at a camp in Thailand.

The etiology of acute diarrhea (less than or equal to 3 days duration) and persistent diarrhea (greater than or equal to 14 days duration) was determined in Cambodian children under age 5 years in a refugee camp on the Thai-Cambodian border between May and October 1989; potential risk factors associated with persistent diarrhea were examined in an age-matched case-control study. Specimens collected from children and environmental sources were examined by standard microbiologic methods; Escherichia coli isolates were examined for hybridization with specific DNA probes and in tissue culture adherence assays. The same bacterial, viral, or parasitic agents were identified in 79 children with persistent diarrhea and in 408 children with acute diarrhea. Only one of nine children with persistent diarrhea excreted the same organism, Cryptosporidium, for that extended period. The most important risk factors identified for developing persistent diarrhea were living with other young children (odds ratio (OR) = 2.0, 95% confidence interval (Cl) 1.2-3.4) and being undernourished (OR = 2.6, 95% Cl 1.2-5.7). Persistent diarrhea in children in this camp was associated with several different agents rather than persistent infections with a single organism.

PIP: Researchers conducted a age matched case control study from May-October 1989 of 5 year old Cambodian refugees with diarrhea examined at Greenhill hospital at Site B UN resettlement camp near Surin, Thailand on the Thai-Cambodian border to determine the etiology of the diarrhea and to identify potential risk factors. The age specific diarrheal disease rate stood at 63 episodes/1000 5 year old children and 123/1000 for 1 year old infants. Incidence was 9.5/1000 5 year old children and 17/1000 for 1 year old infants. Rotavirus was responsible for 24% of the 487 children with diarrhea. Campylobacter species and enterotoxigenic Escherichia coli caused the most frequent bacterial infections. The same enteric pathogens infected children with persistent diarrhea as well as those with acute diarrhea. Children with persistent diarrhea tended to not shed the same pathogen the entire time. 1 patient did excrete Cryptosporidium for an extended period, however. 37% of the children with persistent diarrhea received antibiotics after a positive culture, but they did not stop diarrhea. Besides 98% of the Shigella strains in children with acute diarrhea and all 4 strains in those with persistent diarrhea were resistant to sulfamethoxazole-trimethoprim. All Shigella strains were resistant to nalidixic acid. Further all aggregative adherent E. coli were resistant to colistin. Oral rehydration solution use and readily available medical care limited the number of deaths from diarrhea to 1. Living with other young children and malnutrition (3rd percentile weight/height standard) were the most significant risk factors for diarrhea (odds ration=2 and 2.6 respectively). In fact, with each percentile increment in weight for height, the risk for persistent diarrhea fell 1%. The hands of both mothers and children harbored enteric pathogens. Enteric pathogens were also isolated from water and animals, especially cats. Thus preventive measures should include hand washing, reduce overcrowding, and supplemental feeding.

Epidemiologic aspects of shigellosis and other causes of dysentery in Thailand.

Nearly 20% of children seen in the outpatient department of Children's Hospital in Bangkok, Thailand, for diarrheal disease had bloody diarrhea. Shigella species and enteroinvasive Escherichia coli--isolated from 13% and 2% of children with diarrhea, respectively--were the most frequent causes of bloody diarrhea. Campylobacter species and nontyphoidal Salmonella species were also isolated frequently but were much less often associated with bloody diarrhea. Shigella species were rarely isolated from patients who did not have diarrhea, while Campylobacter and Salmonella species were isolated frequently from well children. None of the species isolated always caused bloody diarrhea. Studies on infection with Campylobacter suggest that natural immunity may prevent bloody diarrhea and in fact may eventually prevent all disease due to this organism. Studies of endemic Shigella flexneri and epidemic Shigella dysenteriae 1 in Thailand have shown that immunity may also explain an age-related decrease in rates of S. flexneri infection but not in rates of S. dysenteriae 1 isolation.

Amebiasis at an evacuation site on the Thai-Cambodian border.

Symptomatic intestinal amebiasis was highly endemic among the Cambodians living at Green Hill, an evacuation site on the Thai-Cambodian border between June 1987 through May 1989. Monthly incidence rates of intestinal amebiasis were determined to be inversely proportional to cumulative monthly rainfall. The highest incidence of amebic dysentery was 63/1000 in children 12-23 months old. Behavioral risk factors were investigated by conducting a case-control study. A questionnaire was administered to 73 families, each having at least one member with confirmed intestinal amebiasis within the past 3 months, and to 95 randomly selected control families having no individual with diarrhea for at least 3 months. Individuals from families with greater than 4 members were at higher risk for acquiring intestinal amebiasis. No significant differences in behavioral risk factors were identified between case and control families. Eighty-six percent of 51 water samples drawn from wells where amebiasis patients obtained their drinking water had greater than 10 coliforms/100 ml. The main route of transmission of E. histolytica was not identified, but was most likely via the fecal-oral route.