Porcine cystitis-pyelonephritis complex is a leading cause of mortality in sows. Increased incidence appears to be related to changes in management, particularly the adoption of confinement housing for gestating sows; however, incidence has decreased after adoption of artificial insemination breeding techniques. Distinguishing features of endemic cystitis and pyelonephritis include lack of a temporal relationship between the vulvar discharge and the estrous cycle, minimal effect on herd fertility, low morbidity, and high mortality in advanced-parity (6+) sows.
Etiology and Pathogenesis of Porcine Cystitis-Pyelonephritis Complex
A wide variety of bacteria have been isolated from cases of porcine cystitis and pyelonephritis, including Escherichia coli, Arcanobacterium pyogenes, and Streptococcus and Staphylococcus spp. These endogenous and opportunistic organisms typically inhabit the lower urinary tract and are often referred to as being responsible for nonspecific urinary tract infections. Actinobaculum suis, a specific urinary pathogen, is an important cause of ascending infection in swine. Formerly classified in the genera Eubacterium and Actinomyces, A suis is a gram-positive, rod-shaped bacterium that grows well under anaerobic conditions and is a commensal organism of the porcine urogenital tract. A suis is fimbriated, and the short, wide urethra of the sow enhances accessibility to the bladder.
Once within the bladder lumen, the alkalinity of the environment increases due to the cleavage of urea into ammonia via the urease enzyme. The increased pH enhances bacterial proliferation and inflames the mucosal surface. The alkaline environment also inhibits the growth of competitive microflora and promotes precipitation of urinary salts and crystals, particularly struvite. Such precipitates not only further increase inflammatory changes in the bladder mucosa but also provide a nidus for bacterial growth and protection from antibiotics and host defense mechanisms. Although the primary means of accessibility to the kidneys is not yet completely understood, it is hypothesized that damage to the ureteric valves secondary to bacterial products (possibly originating from E coli) may predispose affected animals to pyelonephritis.
Epidemiology of Porcine Cystitis-Pyelonephritis Complex
Risk factors that hasten the development of porcine cystitis are the reduced availability of water, increased fecal contamination of the perineal area, excessive weight gain, and leg injuries, all of which result in a reduced frequency of urination and enhanced bacterial survival in the urogenital tract. A suis has been isolated from the preputial cavity of boars at slaughter, the vaginal tract of neonatal piglets sampled immediately after parturition, and the vaginal tract of sows sampled throughout all stages of production. It may also be isolated from voided urine, contaminated parturition sleeves of farrowing attendants, pen floors of farrowing and nursery rooms, and the boots of stockpersons working in the breeding area. The organism is ubiquitous, and the vaginal tract can become colonized anytime during the life of the pig. The incidence of the problem has decreased with the wide-scale adoption of artificial insemination.
Clinical Findings of Porcine Cystitis-Pyelonephritis Complex
In acute and severe cases of porcine cystitis and pyelonephritis, affected pigs may be found dead, likely from acute renal failure. Symptomatic animals are usually afebrile and may show anorexia, hematuria, and pyuria. The urine is typically reddish brown, with a strong odor of ammonia. Urinary pH may increase from normal values of 5.5–7.5 up to 8–9.
Pigs that survive the initial infection frequently experience weight loss and reduced productivity secondary to end-stage renal disease, resulting in premature removal from the breeding herd. Inflammatory reaction on the mucosal surface of the bladder may be catarrhal, hemorrhagic, purulent, or necrotic, and the bladder wall may be thickened. Struvites can also be found in the lumen. The ureters often fill with exudate, and their diameter may increase to as much as 2.5 cm.
Unilateral or bilateral pyelonephritis or pyelitis is the primary lesion in the kidneys. The pelvic region of the kidney, frequently distended with blood, pus, and foul-smelling urine, often shows irregular ulceration and necrosis of the papillae.
Diagnosis of Porcine Cystitis-Pyelonephritis Complex
Culture of Actinobaculum suis requires anaerobic conditions and is the confirmatory means of diagnosis
Clinical signs of hematuria along with lesions of cystitis and pyelonephritis are characteristic of A suis infection
Cystitis and pyelonephritis in live animals can best be presumptively diagnosed when frequent micturition of bloodstained and cloudy urine can be observed. Examination of urine sediments may reveal the presence of inflammatory cells, RBCs, granular renal casts, bacteria, and crystals. Because of the striking gross lesions, confirmation of the diagnosis is usually not difficult.
To properly isolate the causative organism, care must be taken during sample collection to minimize exposure to oxygen. In the field, the bladder should remain unopened, and the neck of the bladder should be sealed with umbilical tape. Similar care should be taken with renal tissue. Lesions of pyelonephritis can be demonstrated by examination of one kidney; the other should remain unopened with the ureter sealed as previously described.
Cultures should be grown on colistin nalidixic acid agar at 37°C (98.6°F) under anaerobic conditions for 5–7 days. If the culture is to be done at a distant location, swabs can be placed into Kary Blair anaerobic transport media for shipment. A PCR test for A suis has been described and appeared to have better sensitivity than direct culture.
Treatment and Prevention of Porcine Cystitis-Pyelonephritis Complex
Injectable antimicrobials that target gram-positive organisms, are active under anaerobic conditions, and are excreted via the urinary tract are effective options
Prevention by acidifying the urinary tract with appropriate dietary supplementation and by use of artificial insemination breeding techniques are effective means of prevention
Treatment of urinary tract infections may be successful if the correct antimicrobial is administered early in the disease course. Penicillin and ampicillin are often the drugs of choice because of their effectiveness in alkaline conditions and their propensity for excretion via the urinary tract. Dosages of 6.6 mg/kg, IM, every 12–24 hours are typically administered for 3 days. Ampicillin can be administered at 11 mg/kg, PO, every 12 hours for 5 days; however, bioavailability is questionable, and cost may become an issue. Acidification of the urine through oral administration of feed-grade citric acid has been reported.
Maintaining excellent hygiene during breeding and parturition, as well as throughout the gestation period, is critical to prevent urinary tract disease. Facilities must be properly designed to reduce the spread of pathogens within the breeding herd and to allow for efficient removal of feces from the environment. Free-choice water should be available at all times, because restricting water availability through use of intermittent delivery systems or poor husbandry results in an increase in abnormal urine parameters in gestating sows, including decreased urine output, increased specific gravity (>1.026), and increased creatinine concentration. Finally, because a higher degree of urinary tract disease can be seen in older sows, proper culling procedures are important to ensure that an optimal parity distribution is maintained within breeding herds.
Key Points on Porcine Cystitis-Pyelonephritis Complex
Actinobaculum suis is the primary pathogen involved in cystitis and pyelonephritis in sows.
A suis is an obligate anaerobe; therefore, culture and sensitivity of this organism must be performed anaerobically.
Injectable medications, such as penicillin, are effective means of treatment.