Age affected: Sows.
Causes: Bacteria e.g., E. coli, Actinobaculum suis; water deprivation; urinating while lying.
Effects: Illness, pus in urine, weight loss, sudden death.
Cystitis (inflammation of the bladder) is most common in sows and is caused by infection of the bladder by bacteria which usually reach it by ascending the urethra (the tube leading from the bladder to the exterior), but which may come from the kidneys. Most cystitis is caused by the common gut bacterium Escherichia coli (E. coli). It travels up the urethra, particularly when the sow has not urinated from some time or when little urine is being produced because of low water intake. Lying in dirty conditions can also predispose to cystitis. Once in the bladder, the organisms multiply. If flushing occurs sufficiently frequently, no disease results. If not, bacteria may reach levels of 5 million per ml at which level they cause inflammation of the bladder wall. They may then erode the valves controlling the entry of urine from the kidneys via the ureters and cause inflammation all the way up to the kidney. Once there, they erode the kidney pelvis and produce pus (pyelonephritis), destroying the ability to retain sodium and resulting in death. The bacterium Actinobacutum suis can also cause haemorrhagic cystitis and pyelonephritis. It is usually introduced by the boar at service.
Mode of transmission
Most cystitis and pyelonephritis is ascending. The predisposing conditions have been listed above, but the bacteria involved are usually from the environment of the sow. E. coli strains involved in cystitis and consequent pyelonephritis may have similar properties and may persist in the sow’s environment to cause cystitis. Transmission is therefore via the environment. Two other mechanisms exist. Systemic infections with bacteria such as Trueperella pyogenes can cause abscesses in the kidneys which subsequently give rise to ureter infections and cystitis; and service by a boar carrying Actinobaculum suis can result in a cluster of cases of A. suis cystitis and pyelonephritis. As this organism can contaminate concrete, bedding and the clothing of workers, infection may also follow when the vulva of a sow is in contact with such materials.
Cystitis is usually first noticed as an increased frequency of urination in sows or by the presence of blood and/or pus in the urine. The animal may have a hunched back. There may be mucoid discharge of bladder origin on the vulva and this may be smeared across the hindquarters by the tail. The appetite is depressed and the rectal temperature is occasionally raised. When pyelonephritis is present body temperatures may fall. Affected animals may die suddenly without clinical signs having been observed, or as a result of chronic disease. Infection may not be apparent and may only be found after laboratory examination of the urine. Where the causal organism is A. suis, cystitis and pyelonephritis occurs as an outbreak in a small group of sows or gilts. They may die suddenly or be found ill, depressed, thirsty with hunched backs and passing blood stained urine containing pus and sometimes have a vulval discharge. Clinical signs often occur 2-3 weeks after service by a particular boar or may be delayed until farrowing. Affected sows frequently die. Mild cases may occur in which inappetence and vulval discharge is the only obvious sign. High blood urea levels are present in affected sows.
The urine of sows can be inspected by making resting sows stand, following which they frequently urinate. The clinical signs of E. coli cystitis (frequent urination, pus in urine) are sufficiently distinctive to enable a diagnosis of urinary tract infection to be reached. Cystitis caused by A. suis frequently follows recent service and blood in the urine is more common. Urine samples from sows may be examined for the presence of pus cells and bacteria. Both organisms can be seen easily in smears viewed by microscopy and the organisms responsible cultured. A. suis may take 4 days to grow and requires the absence of oxygen. Developing kidney failure in pyelonephritis can be confirmed by the presence of high levels of urea in blood samples.
Post mortem examination of casualties or at slaughter confirms the presence of cystitis and pyelonephritis. The bladder contains urine, pus and varying amounts of blood and the lining is thickened and covered with pus and is sometimes bleeding. The changes may be restricted to the bladder or affect the ureters (the rubes between the kidneys and the bladder) and the kidneys which can contain abscesses. E. coli or A. suis can be demonstrated in the urine unless treatment has been given.
Treatment and prevention
Antimicrobial treatment must be given by injection early in the condition to be successful. Once the kidneys are damaged, recovery is rare. Where A. suis is the cause of the cystitis and pyelonephritis, penicillin or ampicillin treatment for 7-10 days will cure early cases. E. coli requires daily injection with tetracyclines, ampicillin, enrofloxacin, other broad-spectrum antimicrobials or with streptomycin. Affected sows should be encouraged to drink by placing meal on water in front of them in a trough at least 4 cm deep. In A. suis infection, sows served by the same boar and the boar itself should be treated with penicillin, and penicillin injections after service should continue for 2-3 weeks after the outbreak has subsided. Enrofloxacin or ampicillin have been shown to be effective. A. suis is commonly found in a bag-like part of the boar's sheath – the preputial diverticulum. Some people ‘flush’ the sheath and diverticulum with antimicrobial drugs when there is an outbreak of infection in sows. Contaminated areas should be disinfected. Clean boars used on gilts may prevent further outbreaks. To reduce E. coli infection, any stalls present should be cleaned of faeces. Water intake can be encouraged by increasing the salt concentration of the ration to 1% but water must be freely available. Sows should be encouraged to rise by feeding them twice daily. Badly affected sows should be culled and not presented for slaughter for human consumption.