Pyelonephritis in Sheep: Kidney Infection Signs and Treatment

Pyelonephritis is a bacterial infection of the kidney and renal pelvis, the area where urine collects before moving to the ureter. In sheep, it is usually an ascending urinary tract infection, meaning bacteria first colonize the lower urinary tract and then travel upward into the kidney. In ruminants, Corynebacterium renale and Escherichia coli are among the better-known urinary pathogens, although other environmental and opportunistic bacteria can also be involved.

This condition is less common in sheep than in some other livestock species, but it can be serious when it occurs. Kidney infection can reduce appetite, hydration, growth, milk production, and overall thrift. If the infection is severe or prolonged, it may damage kidney tissue and affect long-term renal function.

Some sheep show obvious urinary signs, while others mainly look dull, lose condition, or develop a fever. Because the signs can overlap with urinary stones, cystitis, reproductive disease, or systemic infection, your vet is important for sorting out the cause and building a treatment plan that fits the animal and the flock.

Most cases start when bacteria gain access to the lower urinary tract and then ascend to the kidneys. In ruminants, urinary infections are associated with parturition or recent lambing in females, and with urolithiasis or urinary obstruction in males. Trauma to the urinary or reproductive tract can weaken normal defenses and make bacterial colonization easier.

Common bacteria in ruminant urinary infections include Corynebacterium renale and E. coli. Other organisms such as Staphylococcus, Proteus, Streptococcus, and Trueperella species may also be involved. These bacteria are often environmental or part of normal genital tract flora, but they can become pathogenic when the urinary tract lining is irritated or damaged.

Risk factors in sheep may include poor perineal hygiene, difficult lambing, urinary catheterization, dehydration, concurrent illness, and urinary stasis or obstruction. Rams and wethers with lower urinary tract disease may be at risk if urine flow is reduced. Your vet may also look for underlying problems such as bladder infection, stones, congenital abnormalities, or chronic kidney disease that allowed the infection to take hold.

Diagnosis usually starts with a physical exam and a close review of the sheep's history, including recent lambing, urinary signs, appetite changes, and flock management factors. Your vet may check temperature, hydration, body condition, abdominal comfort, and whether the bladder feels enlarged or painful.

A urinalysis is one of the most useful first tests. It can show blood, white blood cells, bacteria, protein, and urine pH changes that support urinary tract infection. A urine culture and susceptibility test is especially helpful because it identifies the bacteria involved and helps your vet choose an antibiotic with the best chance of working.

Bloodwork may be recommended to assess kidney values, hydration, and the degree of systemic illness. In more involved cases, ultrasound can help evaluate the kidneys, ureters, and bladder for enlargement, inflammation, stones, pus, or structural changes. Your vet may also work through other causes of similar signs, including cystitis, urolithiasis, leptospirosis, reproductive tract disease, or generalized infection.

Prevention focuses on lowering the chance of bacteria entering and ascending the urinary tract. Good lambing hygiene, clean bedding, prompt attention to difficult births, and careful handling of the perineal area all matter. If urinary catheterization is ever needed, sterile technique is important because instrumentation can introduce bacteria.

Keep sheep well hydrated, especially during hot weather, transport, illness, or diet changes. Adequate water intake supports normal urine flow, which helps flush the urinary tract. In males, work with your vet on prevention of urinary obstruction where that is a flock concern, because poor urine flow can increase infection risk.

Watch for early urinary signs such as straining, frequent urination, blood in the urine, or reduced appetite after lambing or illness. Early veterinary evaluation can prevent a lower urinary infection from progressing to the kidneys. If one sheep develops urinary disease, it can also be worth reviewing housing cleanliness, nutrition, mineral balance, and handling practices across the group.