An outbreak of salmonellosis among children attending a reptile exhibit at a zoo

Objective: In January 1996, an outbreak of diarrhea caused by Salmonella Enteritidis occurred in children attending a Komodo dragon exhibit at a metropolitan zoo. We sought to determine the extent of the outbreak and mode of transmission. Study design: A case-control study was conducted. Controls were randomly selected from zoo membership lists and matched to patients by age group and date of exhibit visit. Results: Of 65 patients identified, 39 had confirmed and 26 had suspected cases. The median age was 7 years (range, 3 months to 48 years) 55% were male, and 56% had bloody diarrhea. Twenty-six patients and 49 controls were enrolled in the case-control study. No patients and two (4%) controls reported touching a dragon; however, 83% of patients but only 52% of controls touched the wooden barrier that surrounded the dragon pen (odds ratio = 4.0, 95% CI 1.2 to 13.9). Washing hands at the zoo after visiting the dragons was highly protective (OR = 0.14, 95% CI 0.03 to 0.7). Cultures from the patients, one dragon, and the exhibit barriers yielded Salmonella Enteritidis, phage type 8. On the basis of an attack rate of 4.3% among exhibit attendees under 13 years old on whom data were collected, we estimate that 315 additional cases of salmonellosis occurred among visitors in this age group. Conclusion: This large outbreak demonstrates the importance of environmental contamination in the transmission of Salmonella from reptiles, and the protective value of hand washing. Recommendations regarding reptile exhibits and reptilian pets should emphasize this indirect route.