Detection of clusters of Salmonella in animals in Ontario from 1991 to 2001.

The temporal patterns of Salmonella serovars isolated from animals in Ontario by 2 major laboratories between 1991 and 2001 were identified. Overall, the number of isolates remained relatively stable and the more frequent isolates were dominant, as in earlier surveys. However, the temporal patterns of specific isolates and the serovars isolated differed depending on the laboratory, species of animal, and reason for obtaining the culture (monitoring versus diagnostic sample). A number of temporal clusters were identified, but their dates of occurrence differed by laboratory. Whereas the laboratories serve an essential role for diagnosis and monitoring, the summary information should be interpreted cautiously. The importance of additional information, such as demographic source, specimen type, and appropriate denominator, when interpreting the data is discussed.