Epidemiologic Notes and Reports Brucellosis -- Texas

On April 7, 1983, a case of possible brucellosis was reported to the city of Houston, Texas, Health Department's Bureau of Epidemiology. Three weeks later, 12 suspected cases had been reported, and by July 19, 29 cases were identified. Six of the cases were reported by physicians and nurses, and the remainder were discovered during epidemiologic investigation in the community.

The patients ranged in age from 2 to 81 years. All were Mexican emigrants living in northeast Houston. Twenty-eight of the 29 patients reported eating goat cheese ("queso blanco") before the onset of symptoms. Twenty-three patients reported purchasing cheese from neighborhood weekend vendors selling the product from their motor vehicles.

None of the patients interviewed had any leftover cheese, but one was able to purchase additional cheese for analysis from a vendor in his neighborhood. The cheese was reportedly produced in Linares, Mexico, and laboratory analysis determined that it was unpasteurized; all attempts to isolate Brucella sp. from the cheese were unsuccessful. On May 6, a news release was circulated to the media, and the public was made aware of the potential dangers of purchasing cheese from unlicensed food vendors. Since that time, neighborhood contacts reportedly have not seen the street vendors.

As of this report, 19 of the 29 patients have had blood cultures positive for B. melitensis, and one had B. melitensis isolated from blood and bone marrow. Three additional cases were confirmed by a fourfold rise or fall in agglutinating titer. Seven patients with presumptive diagnoses displayed clinical symptoms compatible with brucellosis in addition to agglutinating titers of

1:160. Reported by P Perkins, MPH, A Rogers, M Key, MD, V Pappas, R Wende, DrPH, City of Houston Health Dept, J Epstein, MD, Houston, M Thapar, MD, Ripley Clinic, Houston, F Jensen, MD, Harris County Health Dept, TL Gustafson, MD, Acting State Epidemiologist, Texas State Dept of Health; E Young, MD, Veterans Administration Hospital, Houston; Div of Bacterial Diseases, Center for Infectious Diseases, CDC.

Editorial Note

Editorial Note: In the 14-year period 1965-1978, 3,316 cases of brucellosis were reported to CDC by state health departments. Unpasteurized (raw) dairy products accounted for 268 (8%) of these cases; 127 (47%) of the 268 cases were associated with raw dairy products from Mexico, predominantly fresh cheese made from unpasteurized goat milk, as in the present outbreak. Similar outbreaks have been reported previously from Colorado (1) and Texas (2).

An additional 50 (19%) of the 268 raw dairy product-associated cases were traced to ingestion of products from countries in the Mediterranean basin, Far East, Middle East, and South America. Most were sporadic events involving individual American travelers or foreign visitors to the United States who consumed dairy products acquired abroad; however, outbreaks of multiple cases have occurred among members of tour groups to countries bordering the Mediterranean Sea (3). Because these individuals frequently have no vocational or avocational exposure to Brucella spp., other more common causes of fever are generally ruled out before a diagnosis of brucellosis is entertained, thereby delaying appropriate therapy. Countries reporting more than 1,000 human cases of brucellosis per year in their indigenous populations include Argentina, Greece, Iran, Italy, Mexico, Peru, and Spain (4). The remaining 91 (34%) raw dairy product-associated human brucellosis cases were linked to unpasteurized milk or cheese produced in the United States.

Unpasteurized dairy products have been associated with Group C streptococcal infections in New Mexico (5). Raw milk cheese contaminated with staphylococcal enterotoxin is reported to be widespread (6,7). In addition, salmonellae, which are readily killed by pasteurization, have been shown repeatedly to survive the cheese-making process (6). Other organisms that have caused cheese-associated diseases or have been shown to survive the cheese-making process include Escherichia coli, Mycobacterium tuberculosis, and Campylobacter jejuni.

References

1. Eckman MR. Brucellosis linked to Mexican cheese. JAMA 1975;232:636-7.

2. Young EJ, Suvannoparrat U. Brucellosis outbreak attributed to ingestion of unpasteurized goat cheese. Arch Intern Med 1975;135:240-3.

3. Arnow PM. Brucellosis in a tour group. JAMA (in press).

4. Kaufmann AF, Martone WJ. Brucellosis. In: JM Last, ed. Maxcy-Rosenau public health and preventive medicine. 11th ed. New York: Appleton-Century-Crofts. 1980:419-22.

5. CDC. Group C streptococcal infections associated with eating homemade cheese--New Mexico. MMWR 1983;32:510,515-6.

6. Keogh BP. Reviews of the progress of dairy science. Section B. The survival of pathogens in cheese and milk powder. J Dairy Res 1971;38:91-111.

7. Bryan FL. Epidemiology of milk-borne diseases. J Food Protection 1983;46:637-49.

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