Salmonellosis, commonly known as salmonella, affects a great many animals, including horses. Most varieties of the disease are zoonotic, meaning they can be transferred from animals to humans. This bacterial illness can affect both foals and mature horses and causes severe, sometimes life-threatening, diarrhea. While equine salmonellosis typically confines itself to the gastrointestinal tract in adult horses, in foals it can more easily migrate into the bloodstream resulting in sepsis, a very dangerous systemic infection.
Transmission of Equine Salmonellosis
Equine salmonellosis is spread is a variety of ways, making it a difficult disease to control. The disorder is spread through contact with the feces of infected animals, including other horses, birds, rodents or other wild animals. It is all too easy for pastures where horses graze, or troughs where they feed or drink, to become contaminated by the feces of infected rodents or birds, or by the manure of other horses. While most horses don't ingest one another's manure, mares and newborn foals do, and since newborn foals have compromised immunity, this represents a very real danger.
Animals that are not ill themselves are capable of "shedding" the illness and infecting others. Making the situation even more difficult, the bacteria that cause equine salmonellosis can survive in a wide range of temperatures on shared tools, water buckets and other objects. Most horses have some measure of resistance to the disease, but animals with another illness, or recovering from surgery, may more easily succumb.
Symptoms of Equine Salmonellosis
Symptoms of this disease may vary, depending on age and other factors.
Symptoms in Foals
Foals can pick up equine salmonellosis through their mother's milk, contaminated bedding or through eating manure. Because foals may become septic almost immediately, and can die within 24 to 48 hours, their symptoms must be given immediate attention. Their symptoms may include:
- Depression or lethargy
- High fever
- Loose stools
- Breathing difficulty
Symptoms in Adult Horses
Adult horses are more likely to have:
- Watery or bloody diarrhea
- Severe abdominal pain
In mature horses, equine salmonellosis may also cause infections in some other regions of the body. Asymptomatic horses that are shedding bacteria in their feces may develop an active infection if exposed to increased stress.
Diagnosis of Equine Salmonellosis
Although cultures are frequently performed to diagnose equine salmonellosis, their results may not be reliable. It is possible to receive both false positives and false negatives for the disease, both because shedding of the bacteria is intermittent and because the manure may test positive for a long time after the horse has completely recovered. Even when a positive result is believed to be correct, the course of antibiotic treatment may involve some guesswork and some risk of creating an antibiotic resistant strain of the disorder.
Treatment of Equine Salmonellosis
Apart from some use of antibiotics, most treatment of horses with salmonellosis is supportive in nature, involving intravenous hydration, replenishment of electrolytes, plasma infusions, and administration of anti-inflammatories. The latter is important because strong anti-inflammatories, like Banamine, help to prevent the development of laminitis. Prescription of antibiotics not only risks creating an antibiotic-resistant strain of bacteria, it also risks oversterilizing the horse's gastrointestinal tract, destroying helpful, as well as disease-producing, bacteria.
Controlling Equine Salmonellosis
It is important to manage horses well to prevent the development or spread of this disease. The following steps should be taken:
- Dispose of manure frequently
- Isolate any horses with diarrhea
- Use a new pair of disposable gloves to handle each horse
- Use professional rodent extermination services when necessary
- Block up areas where birds may nest near stalls
It is helpful to keep horses in separate groups for sleeping or pasturing so that the disease isn't inadvertently spread. If a group of horses has traveled and come into contact with horses from elsewhere, that group should be isolated from the horses that did not travel for several weeks. This kind of temporary segregation can limit the number of horses exposed to disease.