The dreaded salmonella bacteria is believed to be the cause of the death of 130 horses this week at the Bureau of Land Management's (BLM) National Wild Horse and Burro Center at Palomino Valley near Reno, Nevada, according to newspapers in the area.
This brings to mind the memory of the death of four Mustangs--reported at length by the New York Times--at a BLM adoption sale at the New Jersey Horse Park in 1993. Five Mustangs died at a similar sale held in Ithaca, New York that year. Salmonella was believed to have been the cause of those deaths. Speculation was that transport stress was the trigger for the illness.
Salmonella is highly contagious and difficult to control. Infected horses "shed" it when they become stressed or ill. Stress and illness also make horses more susceptible. It sometimes breaks out at veterinary hospitals and a massive sanitizing is needed to eradicate it. Most healthy horses tolerate some level of salmonella. Sick horses with salmonella may possibly infect humans working around them.
An interesting study in the 1970s showed that a surprisingly high percentage of horse meat at US slaughter houses was contaminated with salmonella, perhaps due to stress levels in the horses and subsequent exposure to salmonella during transport or auction or holding pens. However, human workers at the slaughterhouses who handled horses or the meat had a low infection rate.
Over 1600 horses are usually warehoused at Palomino Valley; the facility will be closed for 30 days, when it will be re-tested for contamination. The horses who died are believed to have been a recently added group off the range who were in poor condition and would have been susceptible to infection and stress.
In January 2006, horses at the University of Nevada Equestrian Center in Reno tested positive for salmonella.
Photo links to Bureau of Land Management site.