Polynephritis in cattle
Contagious bovine polynephritis is a specific infection of urinary tract of cattle. The causative agent is Corynebacterium renale, a rod shaped gram-positive bacteria which occurs in groups and bundles. The organism can be isolated from urine, vagina and male genital tract of healthy cattle. Cattle are seldom affected before maturity and cows appear to be much more susceptible than bulls. Sheep are also occasionally affected.
Transmission: It is thought that infection is not through blood but ascending from urethra and ureters, to the urinary bladder and kidneys. It may be possible that cattle may be symptom less carriers and under favourable conditions infection is established in upper parts of urinary tract. The incidence is highest in females during or immediately after pregnancy.
Symptoms: The first sign observed may be passing of blood-stained urine in an otherwise normal animal. In some animals there is acute colic, fluctuating temperature (39.5°C), capricious appetite, loss of condition or fall in milk yield. The urine contains albumen, red blood cells and pus. Urination may be frequent and painful. There may be apparent recovery followed by remissions. The course of the disease may be several weeks to even months. The terminal signs are uraemia.
Lesions: Polynephritis appears to develop as an ascending infection of urinary bladder, ureters and pelvis of kidney. The kidneys are usually enlarged and lobulation less evident than normal. Necrotic areas may be observed on the surface of pelvis. The ureters may contain blood, pus and mucus. The bladder and urethra are haemorrhagic, oedematous and eroded.Diagnosis: The diagnosis can be made on symptoms and post-mortem lesions.Confirmation is obtained by isolating the causal organism from urine or the lesions.
Treatment: Several antibiotics inhibit C. renale but penicillin appears to be the drug of choice. In well-established cases where there is extensive tissue damage, the recovery is temporary.
Control: The isolation of affected animals and destruction of infected litter and bedding reduce the bacterial population of the local environment and the opportunity of transmission.