Cholera Associated with Imported Frozen Coconut Milk -- Maryland, 1991

During August 1991, three cases of cholera in Maryland were associated with the consumption of frozen coconut milk imported from Asia. Following an investigation, the product was recalled, and no other cases have been reported.

On August 19, a woman residing in Maryland had onset of severe watery diarrhea and vomiting and, on August 22, was hospitalized with dehydration. Vibrio cholerae O1, serotype Ogawa, biotype El Tor, and Plesiomonas shigelloides were isolated from the stool specimen obtained from the patient; the V. cholerae O1 isolate was confirmed at the Maryland State Department of Health and Mental Hygiene (MDHMH) and CDC and was toxigenic.

The patient had neither traveled outside the United States nor eaten raw shellfish during the preceding month. She and five other persons had attended a private party on August 17. Two of the other persons also had onset of an acute diarrheal illness after the party; incubation periods were 6 hours and 14 hours. Vibriocidal antibody titers were elevated, indicating recent infection with V. cholerae O1. One asymptomatic person also had an elevated vibriocidal antibody titer. Thus, four persons attending the party had laboratory evidence of recent infection, and three of the four had symptoms of cholera. None of the four reported recent foreign travel or cholera vaccination.

Food served at the party included steamed crabs and a homemade Thai-style rice pudding served with a topping made from frozen coconut milk. All six persons ate crabs and rice pudding with coconut milk. However, crabs left over from this party were served at a second party held later on August 17 at the same site; the coconut milk topping was not served. One of 20 persons at the second party had onset of mild diarrhea; specimens obtained from this person and 14 others were negative for vibriocidal antibodies when tested 12-26 days after the party.

The Food and Drug Administration's (FDA) Baltimore District Laboratory cultured unopened packages of the same brand of frozen coconut milk (but a different shipment) as that served at the party. Toxigenic V. cholerae O1, serotype Ogawa, biotype El Tor, was isolated from one of six bags tested. In addition, V. cholerae non-O1, V. fluvialis, V. alginolyticus, Aeromonas species, and group B, E1, and E2 Salmonella were isolated from this product, with coliform counts measuring up to 11,000 most probable number per gram.

No secondary cases of cholera were identified among contacts of the affected persons. In addition, surveillance through emergency rooms failed to identify additional cases in the area. The MDHMH placed Moore swabs in four central sewage collection points in the Baltimore metropolitan and Montgomery County areas as a surveillance measure for the presence of V. cholerae O1 infection in the general population; swabs collected from September 11 through October 3 did not yield V. cholerae O1.

The implicated product in this outbreak was Asian Best brand of frozen coconut milk, produced in Thailand and exported by a Bangkok trading company to a Maryland distributor. Nineteen shipments, totaling 36,160 8-ounce bags, had been imported since January 1, 1991. On September 20, the distributor issued a voluntary product recall, and FDA halted all further importation of this product. The Thai Ministry of Public Health reported that the manufacturer of this brand was not licensed by the Thai FDA and shipped the product only to the United States. Reported by: C Lacey, Montgomery County Health Dept; R Talbot, Howard County Health Dept; J Taylor, MPH, D Dwyer, MD, B Jolbitado, C Morrison, E Butler-Senkel, S Strauss, MD, D Murphy-Baxam, MS, J Libonati, PhD, E Israel, MD, State Epidemiologist, Maryland State Dept of Health and Mental Hygiene. N Ridley, MS, Massachusetts Dept of Public Health. M Smith, MD, State Epidemiologist, New Hampshire State Dept of Health and Human Svcs. J Zingeser, DVM, Vermont Dept of Health. G Miller Jr, MD, State Epidemiologist, Virginia Dept of Health. K Ungchusak, MD, Thai Ministry of Public Health. Baltimore District; Div of Emergency and Epidemiological Operations, Food and Drug Administration. Enteric Diseases Br, Div of Bacterial and Mycotic Diseases, National Center for Infectious Diseases, CDC.

Editorial Note

Editorial Note: Of the 24 cases of cholera reported in the United States during 1991, 16 were exposed during travel to South America (1-3); all 16 patients were infected with V. cholerae O1, serotype Inaba, the strain epidemic in Latin America. Three were exposed during travel to Asia; two of the three were infected with serotype Ogawa, the serotype identified in the patient from Maryland.

The source of infection of the coconut milk implicated in the Maryland cholera outbreak remains under investigation. This product, marketed primarily for home use (distribution to restaurants was limited), is usually consumed well-cooked in ethnic curries and desserts. In this outbreak, the heating of the coconut milk was apparently insufficient to kill cholera organisms, and prolonged holding time at room temperature was sufficient to allow the organisms to multiply to infectious levels (4). The risk for cholera infection to the general public by this product is minimal given its limited distribution and usual preparation procedure. However, this outbreak illustrates the potential for global dissemination of cholera in a frozen food product. Canned coconut milk is safe because heat treatment during the standard canning process is sufficient to kill vibrios.

References

1. CDC. Importation of cholera from Peru. MMWR 1991;40:258-9.

2. CDC. Cholera--New Jersey and Florida. MMWR 1991;40:287-9.

3. CDC. Cholera--New York, 1991. MMWR 1991;40:516-8.

4. Kolvin JL, Roberts D. Studies on the growth of Vibrio cholerae biotype El Tor and biotype classical in foods. J Hyg Epidemiol Microbiol Immunol 1982;89:243-52.

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