Veterinary Services

Generalised and systemic conditions

Four pigs were submitted in response to increased mortality rates on two organic outdoor finishing units. Post-weaning multisystemic wasting syndrome (PMWS) had been present within the enterprise for over four years. Post mortem examination revealed a number of problems. Examination of two four-month-old pigs, found dead without any previous clinical signs, revealed lesions of hepatosis dietetica and acute degenerative cardiomyopathy (consistent with vitamin E / selenium deficiency) in one of the pigs, while a large haemorrhagic ulcer of the pars oesophagea of the stomach was noted in the other. Findings in two three-month-old pigs that had been losing condition prior to death were consistent with PMWS, with one of the pigs showing concomitant lesions of porcine dermatitis and nephropathy syndrome. Once PMWS has been diagnosed on a unit, there is often a tendency to attribute increases in mortality rates to "upsurges" of the syndrome. However these cases highlight the importance of post mortem examination in identifying other conditions as contributory causes of such increases.

One unit reported a problem with two-day-old pigs presenting with swollen, apparently bruised, heads, which then died within 24 hours despite treatment. Two or three piglets per litter among several litters were reported to be affected. Necropsy revealed subcutaneous oedema and dark skin discolouration over the head, most marked over the cranium and eyelids. There was evidence of longitudinal splitting of the clipped incisor and canine teeth in both piglets but no evidence of localised infection. No other significant gross lesions were observed. Zinc sulphate turbidity testing revealed adequate colostral immunoglobulin absorption. Pasteurella multocida was isolated from the subcutis and livers of both animals but no significant organisms were isolated from intestinal contents. Histopathological examination revealed evidence of acute cellulitis with congestion and dermal haemorrhage. In one of the pigs there was evidence of exudative epidermitis and mites within the keratin layer indicating very early infestation. The relationship of these lesions to the cellulitis is unclear.

Three eleven-week-old pigs from a finishing unit, where pigs appeared "drunk and staggering" before dying, were submitted for post mortem examination. The pigs were receiving in-feed medication with chlortetracycline and tiamulin and there had been no response to penicillin treatment of individual cases. On gross examination, all three pigs had severe interlobular pulmonary oedema and marked oedema of the mesentery and mesocolon. There was evidence of lung consolidation suggestive of enzootic-type pneumonia. One pig also had oedema in the musculature of the cranial neck/laryngeal region. Another pig had a marked hydrothorax. Histopathological examinations of the brains of all three pigs revealed similar changes comprised of multiple areas of cerebellar haemorrhage associated with foci of necrotic neuropil, and more generalised mild meningo-encephalitis with pleomorphic 'cuffing' reaction. Theses changes were consistent with a vasogenic meningoencephalitis of viral origin. There was no evidence of lesions suggestive of oedema disease, bacterial meningitis or water deprivation/salt poisoning. Visceral samples from one of the pigs were examined and showed marked lymphoid depletion of spleen, lymph node and gut-associated lymphoid tissues, with histiocytic infiltration at all sites consistent with lesions of PMWS. The liver showed widespread hepatocellular degeneration and lymphocytic infiltration consistent with sub-acute hepatitis and there was subacute viral-type interstitial pneumonia and pulmonary oedema. The findings in this case certainly indicated significant PMWS involvement. It was considered that the neurological lesions could be directly related to porcine circovirus 2 (PCV2) infection or possibly due to viraemia with a different virus, perhaps enabled by PMWS immunosuppression.

Sixteen finishing pigs had become recumbent and died over a two week period, having shown no response to antibiotic treatment. They were housed on loose straw bedding in three sheds holding approximately 300 pigs each, with open sides and no means of artificial ventilation. Outdoor temperatures had been exceptionally high over the previous week. Two 20-week-old pigs showing typical signs were sacrificed and submitted for post mortem examination. Gross examination revealed petechial haemorrhages over the flanks, scrotum and the distal forelimbs in one of the pigs and hyperaemia of the scrotal skin in the other pig. In one of the animals there was also a dramatic fibrinous peritonitis with extensive adhesion formation and a serosanguinous effusion. In both pigs there was bilateral renal enlargement with cortical thickening and petechial haemorrhages suggestive of porcine dermatitis nephropathy syndrome, which was confirmed on histopathological examination.

Alimentary tract disorders

Three piglets from a 260-sow unit were submitted for post mortem examination to investigate a significant scour problem in three to four-day-old piglets. Mortalities of 26% in the current batch and 38% in the previous batch were reported. The cleansing, disinfection and down-time regime in the farrowing house appeared to be adequate. Although there had been an apparent response of cases to parenteral treatment with penicillin and streptomycin, no gross evidence suggestive of a bacterial enteritis was noted. Rotavirus was detected by polyacrylamide gel electrophoresis in intestinal contents of two out of the three piglets and histopathological examination confirmed a viral-type enteropathy.

Type A rotavirus RNA was also detected by PAGE in two faeces samples from a newly repopulated indoor unit reporting scour in five to six-day-old pigs.

A four-week-old piglet was submitted from a unit suffering from a spreading scour condition immediately prior to weaning. Evidence of dehydration, ventral oedema and enteritis were observed on gross examination and haemolytic E. coli isolated from the intestine was identified as Abbotstown serotype (0149:K91,K86a,c). Subsequent histopathological examination confirmed mucosal congestion, pronounced oedema of the villus lamina propria and coliform attachment within the small intestine; all changes consistent with acute colibacillosis.