Bovine Cystitis and Pyelonephritis

Formerly, the most common causative agents were the Corynebacterium renale group of bacteria, including C renale, C cystitidis, and C pilosum, as well as Escherichia coli; however, E coli and Trueperella (formerly Arcanobacterium or Corynebacterium) pyogenes are now the bacteria most frequently isolated from cows with pyelonephritis. Other opportunistic and environmental bacteria may be involved, including staphylococci and streptococci.

The most common causative bacteria are ubiquitous in the environment and are common inhabitants of the vagina and prepuce. Pyelonephritis develops from an ascending infection from the bladder. Cystitis may be present without involving the ureters or ascending to the kidney until some event occurs that compromises the defense mechanism of the ureteral mucosa. The organisms attack or colonize the mucosal lining of the bladder and ureters usually after some traumatic insult (such as parturition or abnormal deformity of the vaginal tract). The stresses of parturition, peak lactation, and a high-protein diet (which increases the pH of the urine and is therefore conducive to colonization of the urinary tract by Corynebacterium spp) are all contributing factors. Routine catheterization of the bladder with nonsterile catheters may facilitate transmission of Corynebacterium spp from cow to cow. The decrease in the frequency of urinary catheterization has been associated with a decreased prevalence of Corynebacterium spp as a cause of pyelonephritis.

The first sign observed may be the passage of blood-stained urine in an otherwise healthy cow. As the infection proceeds up the ureters, causing inflammation and subsequent involvement of the kidney, the animal exhibits discomfort manifest by frequent attempts to urinate, anorexia, a slight fever, loss of production, colic with restlessness, tail switching, polyuria, hematuria, or pyuria. In chronic cases, the animal may show colic, diarrhea, polyuria, polydipsia, stranguria, and anemia. As the disease progresses, the bladder becomes thickened and inflamed. The ureters become thickened and dilated with a purulent exudate. The involved kidneys develop multiple small abscesses on the surface that may extend into the cortex and medulla.

Diagnosis is based on clinical signs; hematuria; a history of recent parturition; palpation of the left kidney for enlargement, loss of lobulation, and pain; ultrasonographic inspection of the kidneys, ureters, and bladder; endoscopic inspection of the bladder for detection of cystitis; microscopic examination of the urine for WBCs and bacteria; dipstick screening for proteinuria and hematuria; and quantitative urine culture to identify the organism. The right kidney cannot be palpated per rectum, except for the caudal pole in Jersey cows and heifers. In early acute cases of pyelonephritis, enlarged ureters and involvement of the kidney may not be detectable on palpation per rectum. Typically, only one kidney is affected.

Early diagnosis and prompt, sustained treatment are needed for a successful recovery. A catheterized urine sample should be taken for culture and antimicrobial susceptibility testing. The treatment of choice for pyelonephritis due to Corynebacterium spp is penicillin (22,000 IU/kg, IM, bid) or trimethoprim-sulfadoxine (16 mg combined/kg, IM, bid) for ≥3 wk. The dosage, frequency, and length of administration for both of these drugs is extra-label, and adequate precautions must be taken to prevent antibiotic residues from entering the human food supply. E coli infections require a broad-spectrum antimicrobial. Ceftiofur (1.1–2.2 mg/kg/day, IM or SC) or gentamicin (2.2 mg/kg, IM, bid) for ≥3 wk have been used successfully in some cases. Because of the extremely long tissue-depletion time, the aminoglycosides may not be indicated in food-producing animals. Manipulation of urine pH may theoretically be of value because E coli grow best in acidic urine (pH <7), whereas Corynebacterium spp grow best in alkaline urine (pH >7). Nonazotemic animals with pyelonephritis confined to one kidney may benefit from unilateral nephrectomy.

Even though the organisms are ubiquitous in the environment, affected animals should be isolated from the herd to restrict buildup of organisms. Because of suspicion that bulls may act as mechanical vectors of Corynebacterium spp, artificial insemination in herds with multiple animals affected may be considered.