Veterinary Services

Generalised and systemic conditions

Significant mortality occurred on a unit that fed free-access whey to all pigs over 15 to 20 kg, as part of their diet. Pigs developed diarrhoea the day after being fed a new batch of whey. Over the next 48 hours 100 grower and finisher pigs died and a further 80 became moribund and were euthanized. Gross necropsy findings in four pigs submitted for postmortem were unremarkable. However neuropathology showed acute cerebrocortical necrosis, cortical oedema and cerebral perivascular eosinophil infiltrates consistent with a diagnosis of salt poisoning. All intestinal tissues showed subacute granulomatous enteritis with widespread plasmacytic and lymphocytic infiltrates suggesting an allergic type enteritis. The whey supplied contained 24 per cent protein. This was much higher than the usual concentration of six per cent. The interaction between the concentrated whey, the diarrhoea and the eventual diagnosis of "salt poisoning" is not fully understood at present.

Vaccination against enzootic pneumonia at weaning failed to prevent widespread coughing and poor growth rates in a batch of replacement gilts weighing approximately 60kg. Postmortem examination of a sacrificed gilt showed extensive lesions of chronic, active enzootic-type pneumonia. The efficacy of vaccination was questioned.

A breeding boar was euthanized following a period of weight loss during which pyrexia and a cardiac murmur had been identified. Postmortem examination revealed an enlarged heart with dilation of the right ventricle. Valvular endocarditis and vasculitis affected the base of the pulmonary artery, causing significant vascular occlusion (Figure 4 - see top right-hand side). Pasteurella multocida and Streptococcus suis type II were isolated from the affected valve.

Another boar was submitted following treatment for general illness and severe left hindlimb lameness. Necropsy revealed a consolidated right lung and extensive chronic peritonitis affecting the entire abdomen. The left hip had chronic osteomyelitis associated with fracture of the femoral head (Figures 5 and 6 - see top right-hand side). Arcanobacterium pyogenes was isolated from the fractured hip joint and other chronic inflammatory lesions.

Lesions suggestive of greasy pig disease were noted in an adult sow and boar that were unsuccessfully treated for mange. The Gloucester Old Spot pigs were kept on a small 'hobby' farm. However Thurso isolated Staphylococcus chromogenes rather than Staphylococcus hyicus, the recognised cause of greasy pig disease. The VLA has also isolated Staphylococcus chromogenes from pigs with skin disease but in that case the pathology was complicated by the presence of pig pox virus.

Alimentary tract disorders

Acute post-weaning colibacillosis was diagnosed when 12 of the best, eight-week-old pigs in a batch of 90 lost condition and developed diarrhoea over two to three days. Atypically the pigs were weaned over four weeks earlier. Three pigs submitted for necropsy showed acute enteritis. Widespread coliform attachment to the surface mucosa in all sections of small intestine resulting in destruction and disruption of the microvilli was noted on histopathology. In two pigs the coliform attachment continued into the large intestine. Severe depletion of lymphocytes and lymphoid follicles in lymphoid tissues suggested that subclinical post-weaning multisystemic wasting syndrome (PMWS) was involved despite vaccination against PCV2 as weaners. The SAC VS considered PMWS allowed the establishment of the E.coli infection in the pigs of this age.

Reproductive disorders

Abortion due to Bacillus licheniformis infection appears to be rare in pigs but it was diagnosed in three late term fetuses and placentas from a gilt. It was uninterested in food but bright. On gross examination, the fetuses were unremarkable with no evidence of serositis. Two placentas were thick, spotty and opaque. Bacillus licheniformis was isolated in heavy, pure growth from pooled stomach content and all three placentas. Histology revealed inflammation of all three placentas. The gilts were housed and given straw that sometimes contained stones and soil that they took into their mouths and "chewed". The SAC VS considered that this was a possible source of the infection.