The popularity of exotic pets such as reptiles has increased steadily since the 1980's. Among exotic pets, the most popular imported into the United States is iguana iguana, or, the Green Iguana; its numbers increasing from 41,183 in 1982 to 569,774 in 1994. In 1994, an estimated 3% of American households owned at least one reptile. Unfortunately, a lot of inaccurate information regarding care of exotic pets circulates, and many new exotic pet owners are unlearned in the care of their new pets. One important health concern is the risk of exposure to salmonella organisms to green iguana and other reptile owners. Although iguana lovers may be aware of a risk of salmonella exposure when handling their pets, they may not know how prevalent the organisms are in their pets. How much risk is involved in owning a pet iguana? What should be done to avoid contracting illness from iguanas? The article "Prevalence of fecal shedding of salmonella organisms among captive green iguanas and potential public health implications" (1998) conducted by Dr.
Bruce R. Burnham, et al., at the National Veterinary Services Laboratory in Ames, IA, attempts to shed some light on the issue and provide answers to iguana pet owners.
Although previous studies have been conducted to test the prevalence of salmonella shedding in the feces of reptiles, never before has a study been conducted that would test multiple fecal samples over an extended period of time. This is important because previous studies found that only 40 to 90% of reptiles were shedding salmonella at any one time, and multiple fecal samples over a longer period of time may reveal a higher prevalence of salmonella shedding in iguanas. It was hypothesized that some iguanas studied may not be shedding salmonella constantly, but would be shedding at some point in their lives. If the researchers hypothesis were correct, and more iguanas than previously expected did shed salmonella organisms in their feces, it would be important to let iguana pet owners know the results so that they may take the proper precautions to protect themselves from accidentally exposing themselves to salmonella organisms. Therefore, the purpose of the study reported here was to determine the prevalence of salmonella organisms in fecal samples from a group of iguanas over an extended period of time.
Twelve 30- to 40-cm-long green iguanas were purchased from pet stores in the Colorado Springs and Denver areas during 1997. By the length of the iguanas, it could be estimated that the "participants" were approximately one year of age at the time of the study, although growth rate and age can vary tremendously depending on nutritional intake during the first year of an iguana's life. Each iguana was housed in a separate 26x48x23-cm solid plastic cage, and cages were stored approximately 10 cm apart in a 2x3-m walk-in environmental chamber that maintained temperature between 28 and 30 C and relative humidity at 40%. For the purposes of the study, the cage dimensions were probably sufficient, although to prevent stress to the iguana, it should be housed in a cage that is 1.5 times its length on every side, and about 3 times its length in height. One possible complication to the study could have been if additional stress to the iguanas caused them to harbor a higher salmonella count than average. Iguanas were fed a mixture of fresh broccoli, spinach, and a commercial reptile diet. This is where another possible complication to the study occurs. Iguanas need to be fed a diet with a calcium to phosphorus ratio of 2:1 so that they may be able to use the calcium for bone formation. Broccoli and spinach are both foods that are considered to be too high in phosphorus for an iguana to utilize the calcium they contain. Food and water were changed daily and cages were cleaned weekly during the study. This was important because an unclean cage or food bowl could become contaminated with salmonella, providing a breeding ground for the organisms to grow and thus complicating the results of the study. At the end of each week for ten consecutive weeks, feces were collected from the floor of each iguana's cage and forwarded to the National Veterinary Service Laboratories for serotyping and serogrouping, which means that each sample was analyzed for salmonella and each different salmonella organism species was identified and separated.
The results of the study were that all twelve iguanas were found to be shedding salmonella organisms at least once during the study, and salmonella organisms were isolated from 88 of 106 fecal samples. This means that although every fecal sample from an iguana may not contain salmonella organisms, the majority (about 89%) do. By means of contrast, previous studies only found 40 to 90% of tested reptiles to be shedding salmonella. The hypothesis that iguanas shed salmonella more frequently seems to have been supported in this study, however conducting another study using bigger, less-stressful cages and food of higher nutritional value may be needed to conclusively generalize the results of this study to the broader population of all green iguanas that are pets. The bottom line of this study is this: between 1986 and 1995, the number of human patients reported to the Centers for Disease Control and Prevention who were confirmed, on the basis of results of bacterial culture, to be infected with salmonella increased almost sevenfold, from 96 to 671. Iguanas have been implicated as the source of many of these infections. Iguana pet owners need to be aware of the risk of salmonella exposure from handling their pets. Iguana owners should never, never kiss their beloved pets or forget to wash their hands thoroughly soon after every time they handle their pets.