Vulval Discharge

Occurrence: Worldwide.
Age affected: Gilts, sows.
Causes: Poor hygiene; genital infections; urinary infections; oxalates / phosphates in urine; normal discharges.
Effects: White, yellow or grey discharge from vulva, maybe infertility.


Discharges from the vulva may be normal e.g. in the first few days after farrowing or mating, but may also be pathological. They may originate from the uterus, vagina, and vulva or from the urinary tract in cystitis and pyelonephritis. Post-farrowing discharges contain a number of bacteria including ß-haemolytic streptococci, Trueperella pyogenes, Actinobacillus suis, Bacteroides spp. and Clostridium spp. The bacteria appear to colonise the physiologically-disturbed uterus and vagina and give rise to inflammation in the walls of the vagina and/or endometritis.

The discharge eventually resolves but may be accompanied by mild cystitis or by metritis. Infection is probably ascending and often follows interference at farrowing. Post-weaning (or post-mating) vulval discharges can be caused by E. coli at high numbers (10 organisms) and by S. hyicus. The source of infection may be faecal contamination of the vulva, cystitis, uterine infection or service by dirty boards kept under poor hygienic conditions. Rising levels of progesterone as the animal enters metoestrus towards the end of the service period, reduce clearance of bacteria. Vaginitis may result or infection may progress to endometritis. Uterine infection may result in death of the eggs or developing embryos and delay return to service.

Mode of transmission

The bacteria causing this discharge are frequently present in the sow’s environment, and there is usually a predisposing cause for infection to take place. There is no specific means of transmission, but infection discharges can be initiated by the venereal route, through contaminated semen in AI and through service by a boar with local infections, especially if there is damage to the vulva and vagina. Infection can also be transmitted by poor hygiene at farrowing and when heavily pregnant animals lie on infected concrete in such a way that their vulvas are pressed open. 

Clinical signs

Post parturient vulval discharge occurs initially as a clear mucoid, serous or bloody discharge and normally dries up. It may persist for 5-7 days. Pus may then be seen during urination or may be found on the floor behind the sow. Extended weaning to service intervals may be recorded. Subsequent fertility may be reduced by 10% in animals recovered from discharge. Post-mating vulval discharge appears first as tacky mucus on the vulval lips 15-20 days post-service.

A creamy discharge then develops and may persist until at least 80 days post-service. Returns to service usually follow. Discharge is more common in older sows and rare in gilts of first parity animals. Endometritis, vaginitis and cystitis may all occur and may be distinguished by endoscopy. Volumes of discharge are usually highest (90ml) in endometritis and fertility is lowest (farrowing rate 14%) and depression of appetite is most severe. Vaginitis occurs in fewer cases of PMD than endometritis, has a later onset (12-30 days) produces lower volumes of discharge (14-26 ml) has a 70% farrowing rate and is not fatal.

Post-partum vulval discharge is easily seen in the early stages, but a speculum or endoscope may be required to see pus or inflammation later in the disease and it is relatively easily distinguished from cystitis. In early cases, incomplete parturition should be considered. Late cases or those with a closed endometritis may only be suspected when systemic signs develop. Swabs for bacteriological examination should be guarded or a speculum used to reduce vulval contamination.

Post-mating vulval discharges are identified by inspection The presence of blood or mucus in the discharge indicates cystitis or pyelonephritis. Frequently found during investigation of high rates of return. Discharge may be visible only on the underside of the tail, on faeces or on the backplate of the crate. It is difficult to detect in loose-housed sows. Discharge may pool in the anterior vagina and be visible only through a speculum or endoscope. Bacteria may be identified in culture. Levels of 2% post-mating discharge are acceptable on a herd basis, but levels of 3-5% require treatment.

Postmortem lesions

Vulval discharge can be identified in unwashed pigs presented for examination, but once slaughtered or washed, external signs disappear. Examination of the lips of the vulva and the vagina may allow pus, inflammation or other damage to be seen and endometritis and an open cervix may also be present.

Treatment and prevention

Antimicrobial therapy may be injected for post-farrowing discharges and post-mating discharges, given by irrigation of the vagina, placement of pessaries or by treatment in the feed over the period of farrowing and for 7 days afterwards. Control of post-farrowing discharges has been achieved by routine antimicrobial injection at farrowing with tetracyclines, ampicillin, ceftiofur and trimethoprim sulphonamide. Hygiene is important in prevention.

Faecal accumulations behind sows should be removed before and after farrowing, all interference at farrowing should be carried out using clean hands and antimicrobial treatment should be considered immediately interference has been carried out. Sows with endometritis should be culled at the next opportunity after confirmation. Prevention of post-mating discharges involves injection at weaning followed by feed medication with oxytetracycline at therapeutic level for 21 days.

Boars should be treated also by washing the preputial sac and instilling an oxytetracycline intramammary preparation daily for 5 days. Treatment should be accompanied by rigorous cleaning and disinfection of sow and boar accommodation and consideration should be given to lowering slurry levels in dry sow houses and to altering the back plates of stalls where these are still in use. The poor farrowing rate of endometritis affected sows makes culling advisable.