Emergence of Salmonella Typhimurium definitive type 104 (DT104) as an important cause of salmonellosis in horses in Ontario

Salmonella Typhimurium definitive type 104 (DT 104) has emerged as a common cause of salmonellosis in humans and cattle, yet previous reports involvin g horses are sparse. This study reports the emergence of DT 104 as an impor tant pathogen in horses in Ontario. The first clinical case of DT104 infect ion at the Ontario Veterinary College was identified in 1997. Seventeen cas es of DT104-associated salmonellosis were identified between 1997 and 2000. In 2000, 12 of 13 cases of salmonellosis were due to DT104. Salmonellosis in horses due to DT104 is of concern, since the organism is multiresistant to antibiotics and poses increased zoonotic risk. Phage type distribution o f Salmonella isolates should be monitored to determine whether DT 104 will remain a prevalent equine pathogen.