Cases of Vibrio cholerae 01 infection has been documented in the Eastern Province of the Kingdom of Saudi Arabia for over a decade. Cases occur mainly in the summer months. In the period between 1417-1423 H, 226 cholera cases were reported in the Eastern Province alone, accounting for 71% of the total cases of cholera in the whole Kingdom. The factors reported associated with these cases are still ambiguous, causing headache to the authorities and public health professionals. The FETP decided to investigate the occurrence of these cases of Vibrio Cholerae 01 infection in the Eastern Province, in order to identify risk factors and to establish prevention and control measures.
Methodology
Preliminary case reports sent by the Regional Infectious Disease office to the Central Infectious Disease Department in The Ministry of Health within twenty-four hours. Locally acquired symptomatic cases were selected from these preliminary case reports and a prospective case-control study design was conducted. A case was defined as any resident of the Eastern Province, during 1424 H, with a history of watery diarrhea and a positive stool/rectal-swab culture for Vibrio cholerae 01, who had not traveled outside the Eastern Province for a week prior to his/her illness. Four controls were selected for each case, matched for age-group and residential neighborhood. The investigators interviewed both the cases and the controls within 3 days of notification. The association between different risk-exposures and occurrence of Vibrio cholerae 01 infection was evaluated using univariate analysis. Different source of drinking water and municipal piped water were also investigated. SPSS version 10 software was used for data analysis.
Results
A total of 32 Vibrio Cholerae 01 isolates were reported in the Eastern Province during the year 1424 H. Cases appeared between 19/2/1424H (21/4/2003G) and 14/9/1424H (8/11/2003). Thirty one isolates were Ogawa serotype and only one was Inaba serotype. Nineteen cases were identified as locally acquired symptomatic Vibrio Cholerae 01 infection (LSVC) with typical symptoms; all were Ogawa serotype. Most of the cases of LSVC with typical symptoms were Saudis (90%). All ages were affected; with a median age of 26 years. There were no secondary cases and no fatalities. Dammam city had the highest attack rate and the highest risk of LSVC. The investigative team was able to interview only 12 (63.2%) of the 19 cases that fit the case definition. All had watery diarrhea, followed by abdominal pain and vomiting (33.3%). Different sources of drinking water and municipal piped water were not significantly associated with risk of infection. Eating food or beverages from outside homes (i.e. restaurants or cafeteria) was associated with 2.57 increased risk of infection, but with a 95% CI including 1, hence chance cannot be ruled out. All the cases used water only to wash raw fruit and vegetables compared to 35 controls (72.9%); other controls used water with added soap or vinegar. There was a significant risk of acquiring infection when eating raw fruit and vegetables washed with water only (P-value=0.015).
Conclusion
The Eastern Province of the Kingdom of Saudi Arabia seems to be a hypo-endemic area of Vibrio cholerae 01 infection. The source of infection and the method of transmission are still unknown and could be multiple. The main reservoir of infection seems to be in Dammam city. It is suggested that the use of human excreta in agriculture as a fertilizer should be investigated. However, it remains uncertain whether these Vibrio cholerae 01 infections are cholera disease, as Vibrio cholerae 01 isolates in the Eastern Province are not tested for toxigenicity. Since cholera outbreaks can become massive epidemics, sensitive surveillance and prompt reporting assist in the rapid containment of epidemics and every Vibrio cholerae 01 or 0139 should be tested for toxin production. Any illness caused by strains of non-toxigenic Vibrio cholerae 01 or 0139 should be reported as self and not as cases of cholera.