Iguana-Associated Salmonellosis -- Indiana, 1990

During 1990, the Indiana State Board of Health's Disease Control Laboratory reported isolates of a rare Salmonella serotype, S. marina, from two infants residing in different Indiana counties. This report summarizes epidemiologic and clinical information about these two cases. Case 1

During August 1990, a low-birthweight newborn (2500 g) was discharged after 1 week of hospitalization. Five days after discharge, on a continuing diet of breast milk and iron-enriched formula, the infant developed watery diarrhea (20 stools per day) but had no fever. A stool culture obtained from the infant yielded S. marina, and therapy with oral antibiotics was initiated. The diarrhea resolved within 10 days; stool cultures remained positive for S. marina for 7 months. No Salmonella illness was recognized among the neonates or hospital staff on the ward on which the infant had resided. All household contacts of the infant were asymptomatic and had negative stool cultures for Salmonella. In addition, a culture of the household well water was negative for fecal coliforms and Salmonella.

The only indoor pet was an iguana that remained in a glass aquarium in the home. During April 1991, a stool culture obtained from the iguana was negative; however, two of nine cultures taken from the aquarium's surface yielded S. marina. Although the infant had no direct contact with the iguana or its environment, the infant's mother fed the iguana and cleaned its cage; she reported handwashing after these activities. Case 2

During November 1990, a 3-month-old infant developed diarrhea and fever. Stool cultures obtained from the patient yielded S. marina. The infant was hospitalized for 6 days and treated with intravenous fluids and antibiotics; diarrhea persisted for 20 days. The infant was fed only powdered formula before onset of illness. Household contacts of the infant were asymptomatic, and stool cultures obtained from the contacts were negative for Salmonella; a culture of the household well water also was negative for Salmonella.

The only indoor pet was an iguana; during March 1991, the one stool culture obtained from it yielded S. marina. None of 10 cultures from surfaces in the cage yielded Salmonella. The iguana was confined to a wooden cage; the infant's father fed the iguana and cleaned the cage, and he reported handwashing after these activities. The mother and infant had no known contact with the iguana or its environment. Investigation Findings

The two case-households were 80 miles apart, and the households' members had no known contact with each other. The S. marina isolates from the infants in both cases and from the iguana associated with case 2 had intermediate resistance to streptomycin but were sensitive to other routine antibiotics. No plasmids were detected in these isolates. The isolate from the cage of the iguana associated with case 1 was not available for testing. Both iguanas were purchased during the summer of 1989 from different pet stores; however, both stores received iguanas from the same distributor, who was supplied by one importer. Reported by: B Barrett, K Khurana, MS, Disease Control Laboratory; JE Afanador, Acute Disease Div; ML Fleissner, DrPH, State Epidemiologist, Indiana State Board of Health. Div of Field Epidemiology, Epidemiology Program Office; Enteric Diseases Br, Div of Bacterial and Mycotic Diseases, National Center for Infectious Diseases, CDC.

Editorial Note

Editorial Note: S. marina is an uncommon cause of human illness; it was first isolated in 1964 from a marine iguana (1). From 1979 through 1989, CDC received reports of only 18 human isolates of this serotype (2) and 28 nonhuman isolates in the United States. Of the 28 nonhuman isolates, 19 were from reptiles, and eight of those were from iguanas (CDC, unpublished data, 1991). The two cases reported here highlight the potential for salmonellosis to occur among persons exposed to pet iguanas. Infants are highly susceptible to Salmonella from any source. As with pet turtles, direct contact between the reptile and the infant does not seem to be necessary for transmission to occur.

Iguanas are members of the lizard family and are native to tropical areas in the Western Hemisphere. Lizards carry a wide variety of Salmonella serotypes, and the percentage of lizards harboring Salmonella species may range from 36% to 77% (3-5). Lizards have transmitted salmonellosis to humans (3,6), including transmission of S. typhimurium from a pet iguana to an infant by contaminated bathtub water (7).

Because iguanas from different countries are often shipped together in a single lot, and iguanas are not tagged during the shipping process, trace-backs are not possible. The exporting country issues a certificate of health for each lot of iguanas shipped, and no quarantine or health inspections are required for entry into the United States (U.S. Fish and Wildlife Service, unpublished data, 1991). Colonization with Salmonella may occur in the country of origin or following contact with other iguanas during shipping. Those colonized with Salmonella may shed organisms intermittently, and Salmonella may be present in the environment of an iguana even in the absence of positive stool cultures (3). Persons in contact with iguanas should practice strict handwashing after handling these animals or their environments, particularly in households with infants or elderly persons who may be highly susceptible to infection (8).

References

1. McWhorter AC, Ball MM, Montague TS, McConnaughey J, Smith T. Two new Salmonella serotypes: S. gabon and S. marina. Int J Syst Bacteriol 1966;16:309-12.

2. CDC. Salmonella surveillance report 1989. Atlanta: US Department of Health and Human Services, Public Health Service, 1990.

3. Chiodini RJ, Sundberg JP. Salmonellosis in reptiles: a review. Am J Epidemiol 1981;113:494-9.

4. DeHamel FA, McInnes HM. Lizards as vectors of human salmonellosis. J Hyg 1971;69:247-53.

5. Cambre RC, Green DE, Smith EE, et al. Salmonellosis and arizonosis in the reptile collection at the National Zoological Park. J Am Vet Med Assoc 1980;9:800-3.

6. Richter M, Ashton E, Waters JR, Spencer J, Lior H. Salmonella isolations associated with reptiles--Alberta. Can Dis Wkly Rep 1991;17:141.

7. Stair GM, Tacal JV Jr, Lawrence W, et al. Association of Salmonella typhimurium infection with a household iguana. California Morbidity 1989;(no. 42).

8. Blaser MJ, Newman LS. A review of human salmonellosis: infective dose. Rev Infect Dis 1982;6:1096-106.

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