Infectious Diseases of the Urinary System in Horses

Last Updated on March 29, 2022 by Allison Price

Many bacteria can cause infections of the urinary tract. Infections of the urinary system can occur by bacteria.

There are many factors that increase the likelihood of a urinary tract infection. Problems with urine flow, including not being able fully empty the bladder during urination, overly dilute urine, sugary urine (often a sign that the horse is diabetic), older age, weakened immune systems, and other diseases can increase the risk of urinary system infection. Horses that are healthy seem to be resistant to infections of the urinary tract.

Bladder Infection

Bacterial cystitis is an infection and inflammation of the bladder due to bacteria. Cystitis in horses is most likely caused by an obstruction of the urinary tract, paralysis of bladder (which could be due to nerve damage), or a combination of both. Cystitis may also be seen in mares who have chronic inflammation of their vagina.

Cystitis can be described as a loss of control over your urination and frequent urination. It can also cause urine scalding, urine dribbling, and straining to urinate. You may also find blood in your urine. Other signs, such as paralysis or tail, may occur if nerve damage is the cause.

Diseases of the Urinary System in Horses

To diagnose bacterial cystitis, a urine sample is required. The treatment includes the use of antibiotics that are effective against the bacteria that causes infection as well as the identification and treatment of any underlying causes.

Kidney Infection (Pyelonephritis).

Pyelonephritis refers to inflammation of the kidneys. This is often caused by a bacterial infection of the urinary tract. The bacteria climbed up into the bladder, then continued to the kidneys. Both bacterial cystitis and pyelonephritis have similar risk factors. Common causes include stones in the kidneys or ureters that prevent urine from flowing normally.

Pyelonephritis symptoms include side pain, particularly in the area surrounding the kidneys, fever, weight loss, and general feeling of not being well. You may also notice excessive thirst and excessive urination. This condition can be diagnosed by blood and urine tests. These tests may not be abnormal in long-term cases. Ultrasonography or x-rays may be required if this is the case. High doses of antibiotics are required for the treatment of pyelonephritis. Sometimes, intravenous fluids may be necessary or surgery to remove the affected renal.

Interstitial Nephritis

Interstitial Nephritis, another form of inflammation in the kidneys, is often caused by bacterial infection. Interstitial nephritis can be caused by infections that affect blood vessels. Infections can spread to the blood vessels and cause kidney damage. The infection may require antibiotics to be treated. If kidney failure has already occurred, fluids and supportive treatment may be required.


Most commonly, infection with Leptospira bacteria leads to eye infections (uveitis), and abortions in horses. It can also cause kidney damage in foals. The appropriate antibiotics can effectively treat infection.

Allison Price
Allison Price

I’m Allison, born and raised in San Diego California, the earliest memory I have with horses was at my grandfather’s farm. I used to sit at the stable as a kid and hang out with my Papa while he was training the horses. When I was invited to watch a horse riding competition, I got so fascinated with riding!