Surveillance of Salmonella in Canada (1993 - 1996)

Abstract

In Canada, during 1993-1996 there were 29,670 laboratory reported cases of Salmonella infections. The frequency of the five most common Salmonella serotypes from human sources were as follows: S. Typhimurium 18.9%, S. Enteritidis 15.5%, S. Hadar 83%t S. Heidelberg 7.9% and S. Thompson 3.2%. Although the rank and frequency of these serotypes varied from year to year, these five common serotypes comprised 53.8% of the total Salmonella serotypes isolated in Canada during 1993-1996. S. Heidelberg ranked first at 20:1% (2,343/11,657) among nonhuman sources, followed by S. Hadar at 12.5% (1,458/11,657). In addition to these, during this period two new Salmonella serotypes identified by LCDC were designated by the Institut Pasteur: S. Surrey isolated from a patient involving travel to India and S. Taiping isolated from dried fish maw from Hong Kong. Recently, there has been an increase of salmonellosis in humans, which has been associated with exotic pets. From 1993 to 1995, an estimated 3% to 5% of all human cases were associated with exposure to exotic pets, including iguanas, pet turtles, sugar gliders and hedgehogs. During this period, 188 outbreaks belonging to various Salmonella serotypes were investigated. The major outbreaks belonged to the following serotypes: S. Enteritidis, S. Newport, S. Stanley, and S. Typhimurium. A study of outbreaks and animal-host associations of the various serotypes by phagetyping indicated that contaminated poultry, eggs, alfalfa sprouts and bovine products appeared to be the common sources of human infections in Canada. During this period, there has been an increased number of cases of S. Typhimurium phagetype (PT) 104, commonly known as definite type (DT) 104 (3 in 1993 to 144 in 1996) and they were found to be singularly or multiresistant to the following antibiotics: ampicillin, chloramphenicol, streptomycin, sulphonamide and tetracycline (R-type ACSSuT). One episode of 10 cases of S. Typhimurium DT104, R-type ACSSuT oc-curred in 1995 was acquired from contaminated meat Monitoring ofS. Typhimurium DT104 during 1995 and 1996 revealed that R-type ACSSuT increased from 38.3% in 1995 to 65% in 1996. Surveillance and hazard identification using phenotypic markers provide valuable epidemiological information on the incidence, trends and risk factors related to outbreaks and clinical cases associated with Salmonella infections.