Seasonal, nontoxigenic Vibrio cholerae O1 Ogawa infections in the Eastern Region of Saudi Arabia.
BACKGROUND
Surveillance for Vibrio cholerae in the Eastern Region of Saudi Arabia has been ongoing since 1985 to detect and prevent local proliferation of imported cholera. In 1996 and 1997 the authors performed additional microbiologic and epidemiologic assessment of V. cholerae surveillance to better characterize a recurrent summertime pattern of V. cholerae infections in the Eastern Region of Saudi Arabia.


METHODS
All health facilities routinely submitted stool or rectal swab specimens for isolation of V. cholerae from patients with gastroenteritis. In addition, specimens were taken from expatriate workers and household contacts of persons with confirmed V. cholerae infection. Forty-two isolates were evaluated for cholera enterotoxin by enzyme-linked immunosorbent assay, cholera toxin polymerase chain reaction, and Y1 adrenal cell assay; 12 isolates also were characterized by pulsed-field gel electrophoresis (PFGE). Interviews about potential exposures were done for all V. cholerae infections.


RESULTS
Vibrio cholerae O1 serotype Ogawa biotype El Tor was identified in 113 gastroenteritis patients (6.0 per 100,000 population per year), 28 asymptomatic expatriate workers, and 16 of 982 household contacts of index patients. All symptomatic infected persons had mild illness that was not typical of cholera, and all 42 isolates evaluated were nontoxigenic. All 12 isolates evaluated by PFGE had an indistinguishable pattern (pattern 81). Infections appeared in late May, decreased in mid-July through August, increased again in September, and disappeared from December through April. Infections had a uniform geographic distribution and affected all ages. No linkage was identified between affected households, or between community cases and food-handlers or domestic servants.


CONCLUSIONS
Surveillance in the Eastern Region of Saudi Arabia has identified a novel strain of nontoxigenic V. cholerae O1 Ogawa. This strain probably has a local environmental reservoir. Since cholera toxin is the primary virulence factor involved in the cause of cholera, assays for cholera toxin should be included in cholera surveillance.
Bubshait SA
Primary Health Care Administration, General Directorate of Health Affairs, Eastern Region, Saudi Arabia. salahbb@hotmail.com
Al-Turki
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Qadri
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Fontaine
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Cameron
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D000293:Adolescent; D000328:Adult; D017677:Age Distribution; D000368:Aged; D002648:Child; D002675:Child, Preschool; D002771:Cholera / Q000453:epidemiology*; D002772:Cholera Toxin / Q000235:genetics / Q000378:metabolism*; D005260:Female; D005759:Gastroenteritis / Q000382:microbiology; D006801:Humans; D007223:Infant; D008297:Male; D008875:Middle Aged; D016133:Polymerase Chain Reaction; D011159:Population Surveillance; D012529:Saudi Arabia / Q000453:epidemiology; D012621:Seasons; D017678:Sex Distribution; D014734:Vibrio cholerae
D002772:Cholera Toxin