Content area
Full Text
Infection of horses with non-host-adapted Salmonella serovars is not uncommon. Carriage of Salmonella can occur in the absence of clinical signs and carrier horses are a common source of infection for other horses. 1 Carriers can develop clinical signs in the presence of predisposing factors such as stress, illness or immune depression.
Foals and young horses are more likely to develop disease than adult animals. Hospitalisation, gastrointestinal surgery, transportation and overcrowding are some of the factors that have been associated with the onset of clinical salmonellosis. 2
Nosocomial outbreaks of salmonellosis in equine hospitals are extensively reported in the literature and the closure of affected premises for intensive decontamination may be the only effective strategy to break the cycle of infection. 3-5
Infection with the sole host-adapted serovar of horses, Salmonella Abortusequi, the causative agent of equine paratyphoid, is associated with abortion in mares and neonatal septicaemia and polyarthritis. This serovar is commonly reported in parts of Asia and Africa, but is only sporadically reported in Europe, South America and the USA. 6
S Abortusequi has not been reported from horses in Great Britain since 1989. Serum agglutination tests (SAT) for S Abortusequi are required to demonstrate freedom from disease for horses to be exported to some countries.
Infection with any Salmonella serovar occurs through the faecal-oral route, by ingestion of feed or water contaminated by faeces or, in the case of S Abortusequi, fetal membranes and fluids of aborted fetuses. 2
Multidrug-resistant strains of Salmonella in horses are reported with increasing frequency, in particular in hospitalised horses, and might result from exposure to therapeutic antibiotic selection pressure. 7,8
Salmonella at a glance
Bacterial classification Family: Enterobacteriaceae; Genus: Salmonella. Gram-negative, facultative, rod-shaped
Transmission Faecal-oral route. Direct contact from infected animals including clinical and subclinical cases, contaminated personnel and equipment, ingestion of contaminated feedstuffs or water, ingestion of infected rodent, bird or livestock faeces. Can persist in the environment for months. Horses can be subclinical carriers and become clinical in response to external factors. Risk factors for development of disease include young animals, stress, transportation, surgery, feed change, antimicrobial treatment and antiparasitic treatment
Clinical signs Possible clinical presentations include subclinical shedding, mild pyrexia, toxic enterocolitis and sepsis. Possible gastrointestinal signs include ileus resulting in...