What are Salmonellosis?
Salmonellosis in horses is caused by oral ingestion of contaminated fecal material into which the bacteria have been shed. This isn’t as gross as it sounds for horses; they not necessarily literally eating each other’s feces...the oral ingestion occurs when an infected horse defecates in the pasture and another animal comes along and eats vegetation which has been contaminated by the infected fecal material. Other non-edible things like boots, buckets, tack, shared grooming tools and unwashed hands can also spread the bacteria from infected horses to uninfected ones.
Salmonellosis in horses is defined as a gastrointestinal infection caused by the bacteria called salmonella which causes severe diarrhea and sometimes systemic disease. It has been found not only in horses but also in humans, most mammals, birds, and even reptiles.
Symptoms of Salmonellosis in Horses
For adult horses, here are the symptoms you will likely see to some degree:
- Severe very watery diarrhea - can be projectile
- General colic symptoms including getting up and down in an attempt to find a more comfortable position
- Foul smell to the diarrhea
- Sometimes diarrhea will be bloody
- Lack of appetite - cessation of eating
- Foals can become septicemic (bacteria moving through body in bloodstream) and become dull, depressed and carry a high fever
- Some septicemic foals may present with lameness and swollen joints
- Horse will be uncomfortable and will display signs like tail twitching, straining and rectal prolapse
Salmonellosis in horses should be considered an emergency and horses suspected of having it or displaying the symptoms should be treated immediately as death can result with a fair amount of rapidity if it is not treated emergently. Frequently, horses may have the diarrhea and fever symptoms for several days or weeks before it is detected by the owner or handler. Because horses can lose a large amount of fluids pretty rapidly, dehydration can occur fairly quickly, especially in the case of the more severe infections, and dehydration can quickly lead to the death of the equine.
Causes of Salmonellosis in Horses
There are over 100 strains of salmonella known and some do not cause infections. In fact, the digestive system of the horse normally has one or more strains of salmonella that live in it under normal circumstances. It is the presence of the normal flora of the intestines and the horse’s immune system that keep the infection possibilities under control. Here are some of the causes for the infection to become active:
- Rodents carry the bacteria into the farm area, introducing new bacteria
- The normal salmonella bacteria present in the horse’s intestines become activated when the horse is stressed due to things like transport or surgery and the food changes, watering changes and movement through stock yards that normally occurs can take their toll
- Mares can pass the bacteria to their foals in the birthing process, even though they may have been tested negative before being allowed to foal
- The bacteria can be picked up when the horse is hospitalized for surgeries or other reasons due to the normal shedding of the bacteria from carriers
Diagnosis of Salmonellosis in Horses
Your vet will evaluate your equine and do a physical examination. He will likely need to get a fecal specimen and send it to the laboratory for analysis. You will likely need to collect a specific quantity of feces and it may need to be collected several days successively and sent to the lab. There will need to be special testing done by the lab to accurately identify the salmonella bacteria.
You will be given special instructions for collection and shipping by the laboratory staff who will be processing the specimens. Salmonella is a zoonotic disease, meaning that it can be transmitted between animals and humans and there is huge potential for both animals and humans to become very sick. In view of this, you will also be given specific instructions for precautions to be used to prevent the spread of the bacteria.
Treatment of Salmonellosis in Horses
The primary concern of your veterinary professional will be to re-hydrate your horse. Dehydration is a major concern because the diarrhea will cause your horse to lose large quantities of fluid very quickly and this rapid, large fluid loss can result in death. Restoration of fluid and electrolyte balance is vital. The treatment may range from none to emergency transportation and admission to a hospital for your equine where IV fluids and electrolytes can be given and the levels of hydration monitored. Antibiotics may be administered to help beef up the immune system to help fight the infection. Anti inflammatory drugs (nonsteroidal) might be given to help reduce shock, plasma may be given to provide needed protein, replace fluid and help reduce shock. Large amounts of fluid delivered via intravenous flow will be required and it could take 12 to 24 hours or longer to restore hydration for severe cases.
Once the equine has stabilized, then water may be given orally through a stomach tube and eventually he will be allowed to drink normally. Fresh, clean water is a must when re-hydrating your horse. These measures will allow the return to normal fecal consistency without the use of antidiarrheal medications. In the case of a foal with septicemia, expect that a course of IV antibiotics will be given.
Recovery of Salmonellosis in Horses
These may seem like extreme measures but salmonellosis in horses is an emergent, potentially life threatening infection. It ranks just as highly when found in humans. The bacterial infection will likely run its course in 5 to 7 days, though the return to normal fecal consistency will take longer, perhaps several weeks. It is important to allow plenty of quiet rest for your horse to allow his body and his immune system to heal from the bacterial infection. During this healing period, expect that you will be required to provide some supportive care; this may include administration of fluids and electrolytes and various types of medication, some of which will be given to keep the animal as comfortable as possible while he heals.