Veterinary Services

Generalised and systemic conditions

No new outbreaks of post-weaning multisystemic wasting syndrome (PMWS) were recorded this month, although histopathological evidence suggestive of the disease was detected in one pig from a unit which had not previously submitted material.

Several units known to have PMWS reported upsurges in disease problems and mortality associated with the disease.

On one of these units, the appearance of a diarrhoea problem in six to eight-week-old pigs prompted the post mortem examination of four affected pigs euthanased on-farm. In addition to lymphoid lesions consistent with PMWS, a viral-type enteropathy was noted in all four pigs. The effects of PMWS itself (through porcine circovirus 2), or perhaps the involvement of rotavirus may have been responsible for these lesions.

On two other PMWS-affected units, complex pneumonic problems, involving viral-type, enzootic-type and bacterial bronchopneumonia appeared to be responsible for increased respiratory disease reported.

Alimentary tract disorders

Porcine haemorrhagic enteropathy was diagnosed as the cause of haemorrhagic diarrhoea and deaths among finishing pigs on one unit. The risk factors involved in this outbreak were not identified with certainty. However a partial depopulation programme to eliminate enzootic pneumonia, conducted seven months previously, may have caused altered infection dynamics in the herd, leading to delayed exposure to Lawsonia intracellularis. In addition, strategic medication of the finishing herd had been withdrawn following the programme, which may have allowed buildup of Lawsonia intracellularis in the accommodation.

Examination of an 88kg pig from a finishing unit experiencing signs of scour and weight loss (approximately 20% morbidity) and some deaths (2% mortality) revealed a necrotising colitis suggestive of swine dysentery. This was confirmed by detection of Brachyspira hyodysenteriae-specific DNA in colon contents by polymerase chain reaction (PCR).

Reproductive tract conditions

Increased irregular returns to oestrus in one herd prompted the submission of sow reproductive tracts for examination. Of the seven tracts examined, one was pregnant, two had ovarian cysts and two showed histopathological evidence of mild bacterial-type endometritis. The two remaining tracts showed evidence of recent ovulation. A combination of husbandry problems, older sows and possible artificial insemination hygiene problems were suggested.

Musculoskeletal conditions

Severe, acute, suppurative arthritis of the stifle joint was found at post mortem examination of an adult sow that had been euthanased because of a suspected fracture of the affected leg. Staphylococcus hyicus was isolated from the synovial membrane in sparse but pure growth. Although more frequently associated with exudative epidermitis, S. hyicus is an uncommon, but recognised, cause of septic arthritis in pigs.

A complaint was received by an abattoir/pork processor concerning lesions resembling abscesses in the necks of approximately 70% of pigs from two unrelated units. Similar lesions had been reported previously in small numbers of pigs from other herds. Grossly, the lesions were comprised of numerous firm yellowish nodules ranging from 3 to 10mm in diameter within an area ranging from 5 to 15cm diameter. The nodules contained caseous or oily-looking material and some of the nodules appeared to be mineralised. The lesions were situated in superficial musculature and in the intermuscular fascia in most cases although in some they were present in the deep musculature close to the vertebral column (C2-C4). All lesions that were submitted for examination were sterile by aerobic and anaerobic cultures. Microscopic examinations for parasites and bacteria, including mycobacteria, were all negative. Histologically, the lesions resembled foreign body granulomata and further investigations into possible causes are in progress.

Nervous system disorders

Water deprivation ("salt poisoning") was diagnosed in two unrelated herds this month. Clinical signs in both cases involved apparently sudden onset nervous signs and recumbency in several pigs in each group. Some deaths had occurred but some of the affected animals had recovered following treatment and general nursing. Histopathological examination of brains revealed meningoencephalitis with eosinophilic infiltration, oedema and in one case, extensive polioencephalomalacia. Histopathological evidence of PMWS was also observed in lymphoid tissues of a nine-week-old pig from one of the herds.