Campylobacter jejuni Infection Associated with Unpasteurized Milk and Cheese --- Kansas, 2007
On October 26, 2007, a family health clinic nurse informed the Kansas Department of Health and Environment (KDHE) that Campylobacter jejuni had been isolated from two ill persons from different families who were members of a closed community in a rural Kansas county. By October 29, 17 additional members of the community had reported gastrointestinal illness and visited the clinic within a week. All 19 persons reported consuming fresh cheese* on October 20 that was made the same day at a community fair from unpasteurized milk obtained from a local dairy. This report summarizes the findings of an investigation by KDHE and the local health department to determine the source and extent of the outbreak. Eating fresh cheese at the fair was the only exposure associated with illness (relative risk [RR] = 13.9). Of 101 persons who ate the cheese, 67 (66%) became ill. C. jejuni isolates from two ill persons had indistinguishable pulsed-field gel electrophoresis (PFGE) patterns, and the isolate from a third ill person was nearly identical to the other two. Although all samples of cheese tested negative for Campylobacter, results of the epidemiologic investigation found an association between illness and consumption of fresh cheese made from unpasteurized milk. To minimize the risk for illness associated with milkborne pathogens, unpasteurized milk and milk products should not be consumed.
The outbreak occurred in an insular religious community (population approximately 150) consisting nearly exclusively of agricultural workers who practice small-scale and traditional farming techniques. On October 20, 2007, members held a community fair celebrating their pioneer heritage. During the fair, unpasteurized cheese was made at an activity station by adding rennet extract to unpasteurized milk donated by a local dairy, producing soft cheese in 5--6 hours. Butter also was made, but from pasteurized milk. Adults and children were encouraged to participate in these activities. Hand-washing stations were available at the food preparation stations. The cheese was served at a banquet that evening. Foods made at other activity stations, including buffalo stew and chili, and potluck meals brought from community member homes also were served at the banquet.
As part of the investigation, a self-administered questionnaire was distributed at a community meeting on November 4, 2007, to collect information regarding demographics, illness status and characteristics, food history, and other possible exposures. A case was defined as diarrhea (three or more loose stools in a 24-hour period) in a member of the community, with onset during October 20--30, 2007. Of the 150 community members, 130 (87%) completed the questionnaire, and 68 (52%) persons met the case definition. Among ill persons, 66 (97%) reported watery diarrhea, 18 (27%) reported bloody diarrhea, and 16 (24%) reported vomiting and diarrhea. None of the respondents had diarrhea immediately before the fair; illness onset occurred during October 21--29 (Figure). Two patients were hospitalized for dehydration. One was released the next day; the other, a pregnant woman, remained in the hospital for 5 days. No deaths were reported. Median age of ill persons was 25 years (range: 1--75 years); 41 (60%) were aged <15 years, and 37 (54%) were female.
In a cohort analysis, consuming the fresh cheese was significantly associated with illness (RR = 13.9). Factors not significantly associated with illness included making cheese (RR = 1.3), making (RR = 1.2) or consuming butter made from pasteurized milk (RR = 1.4), and drinking well water (RR = 2.1) (Table). Of the 101 persons who reported consuming fresh cheese made from unpasteurized milk, 67 (66%) met the case definition. One apparent case of secondary transmission occurred in a person who did not consume the fresh cheese, but became ill on October 29, 6 days after her child became ill.
Stool specimens were collected from three persons who met the case definition and sent to the KDHE laboratory. C. jejuni was isolated from all three specimens. Isolates from two of the samples had indistinguishable PFGE patterns (PulseNet pattern number DBRS16.1150) and the third isolate differed by only two bands (PulseNet pattern number DBRS16.0024).
On November 3, KDHE collected six slabs of leftover cheese from the freezer of the community church for laboratory testing and advised community leaders to discard all other cheese remaining from the community fair. On November 6, the Kansas Department of Agriculture inspected the dairy floor, roof, and ceiling; milk tank; equipment; and animal housing for cleanliness and rodent control but did not find any regulatory violations. Milk samples also were examined for bacterial content, antibiotic residue, and presence of added water. Samples of fresh cheese remaining from the event and milk from the dairy were sent for laboratory analysis. C. jejuni was not isolated from the samples of leftover fresh cheese or unpasteurized milk.
Reported by: DC Hunt, MPH, MC Bañez Ocfemia, MPH, D Neises, MPH, G Hansen, DVM, Kansas Dept of Health and Environment. ST Aghoghovbia, MSc, EIS Officer, CDC.
Unpasteurized milk products have been a documented source of infection with Campylobacter, Salmonella, Escherichia coli O157:H7, Listeria, Brucella, Mycobacterium bovis, and other pathogens (1). Milk can become contaminated with Campylobacter from cow feces or colonized cow teats (2,3). This investigation produced evidence that unpasteurized cheese was the source of the outbreak of diarrheal illness among persons who attended a community fair in Kansas. However, investigators could not establish definitively when in the manufacturing process the cheese was contaminated. The cheese could have been contaminated at any point in its manufacture, including at the fair when community members directly participated in making the cheese. Although the causative organism was not found in dairy samples taken after the event, contamination of the milk during transit to the fair cannot be ruled out.
Although unpasteurized milk could not be identified definitively as the source of the outbreak described in this report, it has been the source of numerous other Campylobacter outbreaks. In 2006, unpasteurized milk or unpasteurized milk products were the vehicle of infection identified in six outbreaks of Campylobacter spp. in the United States. In those outbreaks, 95 persons were infected, and seven of those persons were hospitalized (CDC, unpublished data, 2008). Kansas has had previous outbreaks of campylobacteriosis associated with unpasteurized milk. In April 2002, KDHE and a local health department investigated a campylobacteriosis outbreak among 86 preschoolers and adults who visited a local dairy. Of the 86 persons, 65 (76%) reported consuming raw milk when they visited the dairy; no illness was reported among those who did not consume raw milk. C. jejuni isolates from six children had indistinguishable PFGE patterns. Laboratory tests of samples from the dairy's bulk tank were inconclusive. During August--December 2007, in a separate incident, KDHE and two local health departments identified 25 persons who had diarrheal illness after consuming raw milk or products made with raw milk purchased from another local dairy. Seven (28%) patients had C. jejuni isolated from stool specimens; three of the isolates had indistinguishable PFGE patterns. Campylobacter was not isolated from any of the milk or cheese samples. Unpasteurized milk legally can be sold or donated at dairies in Kansas. Dairy farms in Kansas that sell unpasteurized milk on-site are not required to display notices regarding the potential hazards of consuming unpasteurized milk.
When Scotland banned the sale of unpasteurized milk in 1983, milkborne infection decreased markedly in that country. Before the ban, an average of 14 outbreaks annually affected an average of 1,090 persons per year; after the ban, an average of eight outbreaks annually affected an average of 46 persons per year in dairy farming communities. None of the outbreaks in the postban period occurred in the general community (4).
Required permits and point-of-sale signage warning of the potential dangers of unpasteurized milk and unpasteurized milk products have not demonstrably decreased outbreaks of gastrointestinal illness in other states (5--7). Stricter laws prohibiting the sale or donation of unpasteurized milk might better protect the public, especially members of certain groups that are at increased risk for infection-related complications (e.g., young and elderly persons and pregnant women) (8). To prevent milkborne infections, unpasteurized milk and unpasteurized milk products should not be consumed.
This report is based, in part, on contributions by ME Vajnar, Kansas Department of Health and Environment; L Johnson and C Brehman, Minnesota Dept of Agriculture Laboratories; the Kansas Dept of Agriculture; local health department staff members, and K Bisgard, Office of Workforce and Career Development, CDC.
* Fresh cheeses, such as cottage cheese and Neufchâtel, are made by curdling milk and draining the whey, with little additional processing, and also are referred to as soft or unripened cheeses.
The Kansas Dairy Law. Kansas Statute K.S.A. 65-789 Ch. 65 Art. 7(d). Available at http://www.ksda.gov/includes/statute_regulations/dairy/06dairylaw.pdf.
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Date last reviewed: 12/30/2008