Salmonellosis in Horses: Contagious Diarrhea and Biosecurity Basics
- See your vet immediately if your horse has sudden diarrhea, fever, depression, or signs of dehydration.
- Salmonellosis is a contagious bacterial disease that can spread through manure, contaminated water, feed, equipment, and people’s hands or clothing.
- Some horses become very sick with endotoxemia, colic, or laminitis, while others may shed Salmonella with milder signs.
- Diagnosis often requires repeated fecal culture or PCR testing because shedding can be intermittent.
- Supportive care, isolation, manure control, and strict cleaning and disinfection are central parts of treatment and outbreak control.
- Because Salmonella can infect people, careful hand hygiene and barn biosecurity matter for both horse and human health.
What Is Salmonellosis in Horses?
Salmonellosis is an intestinal infection caused by Salmonella enterica. In horses, it is one of the most common infectious causes of diarrhea and can range from mild illness to life-threatening enterocolitis. Some horses develop fever, severe watery diarrhea, dehydration, and toxemia. Others may carry and shed the bacteria with fewer obvious signs.
This disease matters because it is both contagious and zoonotic, meaning it can spread to other horses and to people. Horses may contaminate stalls, trailers, buckets, grooming tools, and shared walkways through manure. In barns and hospitals, stress, transport, surgery, feed changes, other gastrointestinal disease, and recent antimicrobial use can increase risk.
For pet parents, the biggest takeaways are speed and containment. A horse with acute diarrhea should be treated as potentially infectious until your vet says otherwise. Early supportive care can improve comfort and reduce complications, while early isolation helps protect the rest of the barn.
Symptoms of Salmonellosis in Horses
- Sudden watery or foul-smelling diarrhea
- Fever
- Depression or marked lethargy
- Reduced appetite or going off feed
- Colic signs, including pawing, flank watching, or discomfort
- Dehydration, tacky gums, or prolonged skin tent
- Increased heart rate
- Weakness or reluctance to move
- Signs of endotoxemia, such as injected gums or worsening shock
- Foot soreness or shifting weight that may suggest laminitis
Not every horse with Salmonella looks the same. Some have dramatic diarrhea and fever, while others start with dullness, poor appetite, or mild colic before diarrhea becomes obvious. Shedding can also occur before a diagnosis is confirmed.
See your vet immediately if your horse has diarrhea plus fever, weakness, dehydration, repeated colic signs, or any concern for laminitis. A horse with acute diarrhea should be separated from other horses right away, and anyone handling that horse should use dedicated boots, gloves, and equipment until your vet guides next steps.
What Causes Salmonellosis in Horses?
Salmonellosis happens when a horse is exposed to Salmonella enterica through contaminated manure, water, feed, surfaces, or direct contact with an infected or shedding animal. The bacteria are common in the environment, which makes prevention challenging. Some healthy-looking horses may shed Salmonella without obvious illness, especially during times of stress.
Common risk factors include recent transport, hospitalization, abdominal surgery, feed or routine changes, concurrent gastrointestinal disease, and treatment with broad-spectrum antimicrobials. These stressors can disrupt the normal gut environment and make it easier for Salmonella to multiply and cause disease.
Outbreaks are especially concerning in equine hospitals, boarding barns, training facilities, and other shared spaces. Once manure contaminates a stall, trailer, aisle, or water source, the bacteria can move quickly unless strict cleaning, disinfection, and isolation practices are used.
How Is Salmonellosis in Horses Diagnosed?
Your vet will start with the horse’s history, physical exam, hydration status, and the pattern of illness in the barn. Because many causes of equine diarrhea look similar, diagnosis usually involves ruling in or ruling out several possibilities, such as Potomac horse fever, clostridial disease, coronavirus, sand enteropathy, colitis after antimicrobial use, or other inflammatory bowel problems.
Testing often includes a CBC, chemistry panel, electrolyte testing, and blood protein measurements to assess dehydration, inflammation, and systemic effects. Fecal testing is central. Your vet may recommend repeated fecal cultures, PCR testing, or both, because Salmonella shedding can be intermittent and a single negative sample does not always exclude infection.
In some cases, your vet may also suggest abdominal ultrasound, blood lactate, or additional infectious disease testing based on season, geography, and severity. If multiple horses are affected, environmental sampling and outbreak tracking may become part of the plan. While waiting for results, horses with acute diarrhea are often managed as infectious suspects to reduce spread.
Treatment Options for Salmonellosis in Horses
Spectrum of Care means you have options. Here are treatment tiers at different price points.
Budget-Conscious Care
- Urgent farm call or clinic exam
- Initial bloodwork and one or more fecal Salmonella tests
- Oral or nasogastric fluids when appropriate and safe
- Anti-inflammatory and anti-endotoxemia support as directed by your vet
- Strict home isolation with dedicated buckets, tools, boots, and manure handling
- Close monitoring of temperature, manure output, hydration, appetite, and digital pulses
Recommended Standard Treatment
- Hospitalization or intensive on-farm care with isolation precautions
- IV fluids and electrolyte support
- Serial CBC/chemistry testing and repeated fecal culture or PCR
- Anti-inflammatory, anti-endotoxemia, and gastrointestinal supportive care chosen by your vet
- Laminitis prevention and foot monitoring, including cryotherapy when indicated
- Barrier nursing, manure control, and cleaning/disinfection protocols for the barn or hospital
Advanced / Critical Care
- Referral-hospital isolation and 24-hour critical care
- Aggressive IV fluid therapy, plasma or colloid support when indicated, and advanced electrolyte management
- Frequent bloodwork, lactate monitoring, and expanded infectious disease testing
- Continuous laminitis prevention strategies and advanced pain management directed by your vet
- Management of severe endotoxemia, shock, protein loss, or complications after surgery
- Outbreak-level biosecurity planning, environmental sampling, and staff protection protocols
Cost estimates as of 2026-03. Actual costs vary by location, clinic, and individual case.
Questions to Ask Your Vet About Salmonellosis in Horses
Bring these questions to your vet appointment to get the most out of your visit.
- How strongly do my horse’s signs fit salmonellosis versus other causes of acute diarrhea?
- What tests do you recommend today, and will my horse need repeated fecal culture or PCR samples?
- Does my horse need hospitalization, or is careful home isolation a reasonable option?
- What signs would mean my horse is becoming dehydrated, endotoxemic, or at risk for laminitis?
- What biosecurity steps should everyone in the barn follow right now?
- How long should my horse stay isolated, and what criteria should we use before returning to normal turnout or travel?
- Are there medications or recent stressors that may have increased my horse’s risk?
- What cost range should I expect for the first 24 to 72 hours based on my horse’s condition?
How to Prevent Salmonellosis in Horses
Prevention starts with manure control and traffic control. Horses with diarrhea should be isolated immediately, with dedicated thermometers, buckets, feed tubs, muck tools, and protective footwear. People should wash hands after handling the horse or manure, and clothing or boots used in the isolation area should not move freely through the rest of the barn.
Clean first, then disinfect. Organic debris like manure and bedding can inactivate many disinfectants, so surfaces need thorough cleaning before disinfection. Stalls, trailers, cross-ties, wheelbarrows, and waterers should be cleaned carefully, and manure from suspect horses should be handled in a way that limits spread through shared aisles or equipment.
Reducing stress also matters. Careful transport planning, consistent feeding routines, thoughtful antimicrobial use, and prompt management of other illnesses may lower risk. In hospitals and larger barns, written biosecurity protocols, staff training, and rapid identification of horses with fever or diarrhea are especially important.
There is no routine widely used vaccine strategy for preventing equine salmonellosis in the way pet parents may expect for some other infectious diseases. That makes practical biosecurity, early recognition, and fast veterinary involvement the most useful prevention tools.