Veterinary Services

Generalised and systemic conditions

Increased mortality in eight to twelve-week-old pigs on one unit was attributed to an upsurge in post-weaning multisystemic wasting syndrome (PMWS) and porcine dermatitis and nephropathy syndrome (PDNS). Most cases were in reasonable body condition and had been found dead without any clinical illness noted. The two PDNS cases did not show any obvious skin lesions but there was evidence of severe glomerulonephropathy, interstitial nephritis and renal vasculitis characteristic of the syndrome. In the PMWS cases, there was marked lung pathology and severe hydrothorax, a feature frequently seen in such "sudden death" PMWS cases. In addition to the characteristic lesions of lymphoid depletion and histiocytic infiltration in lymphoid tissues, histopathological examination of lung revealed extensive acute interstitial pneumonia with marked oedema and fibrin exudation. The pathogenesis of the severe oedema in such cases is poorly understood, but degeneration of vascular endothelium observed in some of these lung sections may be a significant factor.

Examination of two pigs from a neighbouring unit (not directly associated but located 1.5km away) experiencing a similar increase in mortality due to "sudden deaths" in 12 to 14-week-old pigs, revealed more classic skin and renal lesions of PDNS. The reasons for these upsurges in disease and possible relationship between the two cases are not clear.

PMWS was diagnosed in an eight-week-old pig from a unit reporting losses among weaned pigs in apparently good body condition. Coughing was reported in the group. Characteristic lesions of PMWS were observed in lymphoid tissues, while in the lungs there was interstitial pneumonia with bronchiolar necrosis suggestive of swine influenza. Viral isolation was not performed to confirm the diagnosis.

Alimentary tract disorders

Swine dysentery was confirmed as the cause of haemorrhagic scour and death in an eight-week-old pig on a nursery unit reporting a sudden increase in mortality. The mucosa of the colon showed extensive ulceration and diphtheresis and Brachyspira hyodysenteriae was isolated from colon contents. Confirmatory testing by polymerase chain reaction (PCR) also identified B. hyodysenteriae-specific DNA.

A problem with scour and decreased growth rate was reported in a group of 140 weaners housed in a straw court. Twenty pigs had either died or been destroyed over a one-week period. The scour was black, watery and granular and the pigs appeared to be very thirsty. Post mortem examination revealed distension of the colon and caecum with very watery contents and a large quantity of dark grey-black silt. In some cases examined the caecum was half full of the silt material. Apart from the distension, no other significant gross intestinal lesions were observed. Histopathological examination revealed no evidence of significant pathology in the intestine, liver, kidney, spleen or lymph nodes. The findings were suggestive of management problems in relation to feeding, possibly insufficient trough space or insufficient feed available which could have been causing the smaller pigs to fall behind and search elsewhere for food. The source of the silt in the building was not determined.

Musculo skeletal conditions

A 14-week-old Tamworth gilt was one of a litter of ten in which seven pigs had shown similar clinical signs over a short period. After handling, the hindquarters would collapse and the pigs would appear paralysed. No lordosis or kyphosis was reported. The pig submitted for examination showed spastic paralysis of the hindlimbs. On section of the vertebral column, a deformation of the vertebral body of L5 was detected. This consisted of a "V" shaped distortion of the dorsal surface of the ventrum which was projecting into the ventral spinal canal and causing stenosis. There was evidence of haemorrhage beneath the dura mater in this region and the spinal cord showed evidence of compression. No evidence of spinal abscessation was detected. While a developmental abnormality was suspected in this pig, further investigation of the lesion was not performed. It is not clear whether this was representative of the remainder of affected animals.

Nervous system disorders

Progressive hindlimb paresis in an eight-week-old pig over a four-day period prompted euthanasia of the animal and submission for post mortem examination. The pig, housed in a group of four on solid flooring with wood shavings, had been able to move using its forelimbs and was still eating. There had been no similar problems in other pigs. Gross examination revealed a fibrinous peritonitis and ulceration of the pars oesophagea of the stomach (thought likely to be due to short-term anorexia). No bacteria were isolated from the peritoneal fluid. Histopathological examination of brain and spinal cord identified perivascular mononuclear cerebellar meningitis and mild encephalitis. The likely aetiology was thought to be viral, porcine circovirus 2 (PCV-2) or porcine reproductive and respiratory syndrome (PRRS) virus being possible causes, however this was not confirmed.