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Salmonella Serotype Montevideo Infections Associated with Chicks -- Idaho, Washington, and Oregon, Spring 1995 and 1996

During 1995 and 1996, public health laboratories in Idaho, Washington, and Oregon identified clusters of infections with Salmonella serotype Montevideo. Epidemiologic investigations, including enhanced surveillance, of these clusters indicated association with exposure to chicks. This report summarizes the findings of these investigations, which suggest that handling chicks is a health risk, especially for children; consequently, thorough handwashing is recommended after handling of chicks.

Idaho and Washington

During April 1-May 31, 1995, the public health laboratories of the Idaho Department of Health and Welfare (IDHW) and the Washington Department of Health (WDH) identified three and nine S. Montevideo isolates, respectively, compared with annual averages of less than 1 and 20 during 1984-1994. In April and May 1996, a total of 11 S. Montevideo isolates were reported in Washington. For this investigation, a case was defined as culture-confirmed S. Montevideo infection in an Idaho or Washington resident with onset of illness during April 1-May 31 in 1995 or 1996; illness in all 23 persons met the case definition. Of the 23 case-patients, 12 (52%) were aged less than or equal to 2 years; of these, five (42%) were aged less than or equal to 6 months. An isolate obtained from a child aged 14 months was cultured from blood, indicating invasive disease. Three (13%) case-patients were hospitalized.

To identify exposures associated with illness, IDHW and WDH conducted a case-control study in 1995 and 1996. Twenty-two of the 23 persons with illness meeting the case definition were included in the study. Two controls (i.e., persons reporting no diarrheal illness during the referent period) were matched to each case-patient by age and neighborhood. Of 22 case-patients, 17 (77%) had exposure to chicks during the week before illness onset, compared with four (9%) of 44 controls (matched odds ratio=29.3; 95% confidence interval {CI}=4.6-1243.2).

The chicks associated with the 17 case-patients who reported such exposure were purchased in at least four different counties in 1995 and at least six different counties in 1996. No common hatchery, place of purchase, or feed sources were identified. Fecal samples were obtained from two chicks associated with two geographically separated case-patients; S. Montevideo was isolated from each.

Isolates from the seven Washington patients who had chick exposure in 1995 and from the seven Washington patients who had chick exposure in 1996 and two chicks were subtyped by pulsed-field gel electrophoresis (PFGE). The patterns differed in 1995 and 1996. However, for the 1995 isolates, the patterns from five isolates were indistinguishable, and for the 1996 isolates, the patterns from five of the human isolates and the two chick isolates were indistinguishable.

Oregon

During March-June 1996, the Oregon State Public Health Laboratory identified 16 cases of S. Montevideo, compared with an annual average of nine cases during 1984-1995. For this investigation, a case was defined as culture-confirmed S. Montevideo infection in an Oregon resident with illness onset during April 1-June 30. Illness in all 16 persons met the case definition. The median age of case-patients was 32 years (range: 5 months-81 years); three (19%) were aged less than or equal to 2 years; of these, two (67%) were aged less than or equal to 6 months. Two (13%) case-patients were hospitalized.

To identify exposures associated with illness, the State Health Division, Oregon Department of Human Resources, began a case-control study by reviewing salmonellosis case-report forms. Eleven of the 16 case-patients were included in the study. Controls were selected from among culture-confirmed cases of Salmonella infection other than S. Montevideo identified during the same period from counties reporting S. Montevideo cases. Nineteen controls were selected with a median age of 22 years (range: 9 months-80 years). Seven (64%) of 11 persons with S. Montevideo infection compared with one (5%) of 19 persons with other Salmonella infections had handled live poultry (chicks, hens, or roosters) during the 5 days before illness onset (odds ratio=31.5; 95% CI=2.5-1494.5). Fecal samples were obtained from five poultry, including two chicks, associated with two case-patients; S. Montevideo was isolated from the two chicks obtained from one of the case-patients. No common hatchery, place of purchase, or feed sources were identified among poultry associated with different case-patients.

S. Montevideo isolates were available from five of the seven patients who reported handling live poultry. Among these five isolates, two PFGE patterns were identified. The pattern for four of these isolates and the two chick isolates were indistinguishable; this pattern also was indistinguishable from the pattern identified in the five human and two chick isolates in Washington in 1996. The two culture-positive chicks in Oregon had been purchased from the same hatchery as one of the culture-positive chicks in Washington.

Reported by: D Blythe, MD, M Goldoft, MD, J Lewis, P Stehr-Green, DrPH, State Epidemiologist, Washington Dept of Health. R Chehey, J Greenblatt, MD, State Epidemiologist, Idaho Dept of Health and Welfare. PR Cieslak, MD, KR Stefonek, MPH, FC Hoesly, MD, D Fleming, MD, State Epidemiologist, State Health Div, Oregon Dept of Human Resources. Foodborne and Diarrheal Diseases Br, Div of Bacterial and Mycotic Diseases, National Center for Infectious Diseases; and Div of Applied Public Health Training (proposed), Epidemiology Program Office, CDC.

Editorial Note

Editorial Note: Salmonella infections occur in an estimated 2-4 million persons each year in the United States; of these, approximately 40,000 are culture-confirmed and reported to CDC by state health departments (1). Most human Salmonella infections are foodborne, but when contact with pets has been implicated, reptiles have been a common source (2,3). Molecular subtyping techniques (e.g., PFGE) are valuable tools in epidemiologic investigations because they can link geographically dispersed cases and small clusters of cases to a common source.

The proportion of all salmonellosis cases associated with exposure to chicks and ducklings is unknown; however, previous reports document transmission of Salmonella from these small fowl to humans (4-7). Many of these outbreaks have occurred during the spring, particularly around Easter. Children may be at greater risk for salmonellosis from these pet or farmyard fowl because of more frequent receipt of fowl as gifts, less frequent handwashing after handling, and more frequent hand-to-mouth contact. In addition, infants with salmonellosis may be at greater risk for developing invasive disease (8).

Previous reports of chick- and duckling-associated salmonellosis have resulted in statewide legislation restricting the sale of these baby fowl as pets, such as in Maryland in 1967 (9). However, these regulations are difficult to enforce and the effectiveness of such legislation is unknown. Interstate transport and sale of pet baby turtles were banned in 1975 by the Food and Drug Administration to prevent turtle-associated salmonellosis (10). The likelihood of transmission of Salmonella from pet or farmyard chicks and ducklings can be reduced by avoiding contact with feces from these animals and carefully washing hands with soap and water after handling either chicks, ducklings, or anything that has had contact with these fowl. In addition, persons who, if infected with Salmonella, may be at increased risk for illness (e.g., infants, immunocompromised persons, or the elderly) should consider limiting their exposure to these fowl. Chicks and ducklings may not be appropriate pets for children. During investigations of Salmonella infections, especially during the spring and Easter seasons, health-care workers and public health personnel should consider contact with chicks and ducklings as a potential risk factor for salmonellosis.

References

  1. Tauxe RV. Salmonellosis. In: Kelley WN, ed. Textbook of internal medicine. 3rd ed. Philadelphia, Pennsylvania: Lippincott-Raven, 1997:1639-42.

  2. Fonseca RJ, Dubey LM. Salmonella Montevideo sepsis from a pet snake {Letter}. Pediatr Infect Dis J 1994;13:550.

  3. CDC. Reptile-associated salmonellosis -- selected states, 1994-1995. MMWR 1995;44:347-50.

  4. CDC. Salmonella hadar associated with pet ducklings -- Connecticut, Maryland, and Pennsylvania, 1991. MMWR 1992;41:185-7.

  5. Anderson AS, Bauer H, Nelson CB. Salmonellosis due to Salmonella typhimurium with Easter chicks as likely source. JAMA 1955;158:1153-5.

  6. Coohon DB. Infant diarrhea presumably acquired from Easter chicks shedding Salmonella chester. In: National Communicable Disease Center. Salmonella surveillance, May 1963. Atlanta, Georgia: US Department of Health, Education, and Welfare, Public Health Service, 1963:22-3; report no. 14.

  7. Dougherty WJ. Salmonellosis acquired from an Easter pet duckling. In: National Communicable Disease Center. Salmonella surveillance, June 1963. Atlanta, Georgia: US Department of Health, Education, and Welfare, Public Health Service, 1963:4; report no. 15.

  8. Miller SI, Hohmann EL, Pegues DA. Salmonella (including Salmonella typhi). In: Mandell GL, Bennett JE, Dolin R, eds. Principles and practice of infectious diseases. 4th ed. New York: Churchill Livingstone, 1995:2013-33.

  9. Crawford KL. Legislation concerning the sale of live baby fowl as pets. In: National Communicable Disease Center. Salmonella surveillance, April 1967. Atlanta, Georgia: US Department of Health, Education, and Welfare, Public Health Service, 1967:7;report no. 61.

  10. Cohen ML, Potter M, Pollard R, Feldman RA. Turtle-associated salmonellosis in the United States: effect of public health action, 1970 to 1976. JAMA 1980;243:1247-9.




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