Leptospirosis: an emerging health problem in Thailand.

Leptospirosis is an emerging health problem in Thailand, with dramatic increases in reported incidence since 1996. The annual number of reported leptospirosis cases increased from 398 cases in 1996 to 14,285 cases in 2000. In 2001, 2002, and 2003, the number of reported cases decreased, but still remained high at 10,217, 6,864, and 4,958 cases, respectively. The epidemiological characteristics of leptospirosis in Thailand include a peak incidence in September and October in association with the rainy season. A vast majority of the cases (90%) were reported in the Northeast region. The case fatality rate was as high as 4.4%, having a predominant association with male farmers aged 15 to 45 years. Outpatient cases were approximately 9 times more common than admitted cases, with an apparent recent shift in the pattern of infecting serovars among reservoir animals and humans.

Environmental and travel factors related to leptospirosis in Thailand.

To identify potential environmental and travel factors related to leptospirosis, we conducted an unmatched case controlled study and household assessment of cases and controls in Nakhon Ratchasima province (north-eastern, Thailand) from August to December, 1998. Fifty-six cases and 145 controls were included in the study. Cases were hospitalized patients who had been diagnosed with leptospirosis and tested positive for anti-leptospiral IgM antibody using the Panbio ELISA (Panbio Inc, Brisbane, Australia). Controls were the neighbors of cases who had tested negative. Standardized questionnaires and household assessments were used to collect information on demographics, number of animals kept, evidence of rats in the home, presence of rat food inside the home, road characteristics, awareness of leptospirosis disease, environment, and travel history. Multivariant, unconditional logistic regression demonstrated that travel on potholed roads was independently associated with leptospirosis infection (OR 5.0; 95%CI 1.2-20.2) and traveling by car was a protective factor (OR 0.2; 95%CI 0.06-0.9).

Food poisoning outbreak from contaminated fish-balls.

On February 9th, 1998, a food poisoning outbreak occurred at a boarding school for underprivileged students. An unmatched case-control study was done. An environmental survey, laboratory study of rectal swab culture, fish-balls, water and the cooking utensils were also performed. There were 132 suspect cases, of which the attack rate in teachers was 9.8 per cent (4/41), 16.7 per cent (1/6) in the food handlers and 15.7 per cent (127/810) in the students. The median incubation period was 18 hours. Analysis of food consumption revealed those who ate lunch noodles had the highest risk (OR 3.8, 95% CI 0.6-5.9). In details of food components, those who ate fish-balls in curry had the only significant risk (OR 3.5, 95% CI 1.2-0.8) of becoming ill when compared to those who did not. Fish-balls in noodles and curry had a dose response relationship. Bacterial culture from 25 grams of fish-balls was positive for Vibrio parahaemolyticus. The fish-balls in noodles and curry were identified as the implicated food. The modes of contamination were uncooked food, cooking utensils and the food handlers. The manufacturer, which had no license to operate and had poor standards of sanitation, was closed by the Food and Drug Administration.

An outbreak of Influenza A virus in a hilltribe village of Mae Hong Son Province Thailand, 1997.

An outbreak of Influenza A virus occurred in a hilltribe village between July 18th and August 8th, 1997. The overall infection rate was 92.5 per cent. The household infection rate was higher in the crowded part of the village. The symptoms analyzed after all, were fever (100%), cough (99%), headache, myalgia (78.1%) and rhinorrhea (50.5%). The patients were self - recovery within 5-7 days. Isolation and Haemagglutination inhibition test (HI) were undertaken to identify the causative agent. The results were positive for influenza A/Wuhan/359/95(H3N2) - like strain. The outbreak did not spread to the town, possibly because of the differences in environmental condition. Predisposing factors of the village that may have influenced the outbreak were crowded living quarters, cold (8 - 10 degrees C) and moist weather, poor personal hygiene and improper sanitation.

Serological study of hantavirus in the rodent population of Nakhon Pathom and Nakhon Ratchasima Provinces Thailand.

A serological survey has been carried out to detect evidence of hantavirus infection in rodents from two provinces of Thailand. This study aimed to examine virus antibody in 354 rodents trapped among 6 different villages of Nakhon Pathom Province (February-March, 1998) and in 326 rodents trapped among 14 villages of Nakhon Ratchasima Province (August-October, 1998). Seroprevalence among rodents from Nakhon Pathom Province (2.3%), was mostly find in Rattus norvegicus (3.8%) and Bandicota indica (2.6%). In Nakhon Ratchasima Province seroprevalence (4.0%) was mostly in Bandicota indica (19.1%) and Rattus exulans (3.5%).