Veterinary Services

Meningitis due to Streptococcus suis serotype 2 infection was diagnosed as the cause of neurological signs in ten-week-old gilts. Fifteen pigs had been affected over a two week period and response to antibiotic treatment had been slow. Clinical signs were seen around one week after the pigs were moved and about two weeks after their medicated feed was stopped. S.suis serotype 2 was isolated from the brain, lung, liver and joints of an affected pig with Pasteurella multocida also isolated from lung tissue.

A combination of enzootic pneumonia and post-weaning multisystemic wasting syndrome/porcine circovirus 2 (PMWS/PCV2) was diagnosed in a four-month-old pig from a batch with a history of wasting. The animal submitted was in an emaciated condition and findings at necropsy included subacute peritonitis, lymphadenopathy and severe chronic pneumonia. Grey consolidation affected around forty percent of the lung field with an anteroventral distribution evident. Histologically the lymph nodes and spleen showed lymphoid depletion and histiocytic infiltration consistent with PCV2-type changes. The lung findings were consistent with enzootic-type pneumonia and the presence of Mycoplasma hyopneumoniae was confirmed by PCR testing. The unit had not been using vaccines against M.hyopneumoniae or PCV2.

Erysipelas infection was confirmed as the cause of death of a two-month-old Gloucester old spot pig from a litter of three on a small outdoor unit. At necropsy there was generalised carcase congestion and fibrinous pleurisy. Erysipelothrix rhusiopathiae was isolated from lung and brain tissues.  Several other piglets on the holding had displayed pyrexia and inappetance a few weeks previously however these animals had responded to treatment with penicillin. No erysipelas vaccination was being used.

Alimentary tract disorders

Gastric ulceration and chronic pleurisy and pericarditis were diagnosed in a nine-week-old pig. It was one of five pigs to be submitted for postmortem examination to investigate an increase in the mortality rate in growers on the unit. Another three pigs submitted from the same unit had septic pericarditis and pleurisy. Pasteurella multocida was isolated in systemic distribution from one of these. Another pig had skin lesions on the face, suggestive of early stage greasy pig disease, from which Staphylococcus chromogenes was isolated. All of the pigs had been tail bitten. A fifth pig was suspected to have died from an intestinal torsion. SAC C VS concluded that the increased mortality rate was associated with a range of common problems rather than a single disease process.

Proliferative enteropathy was diagnosed in a 14-week-old boar submitted as part of an investigation into loss of condition and scour. At necropsy sections of the large intestine had yellow fibrinous diphtheritic material adherent to the mucosa while other parts had mucosal thickening and corrugation. Histopathology revealed widespread lesions of proliferative enteropathy involving almost all of the crypts in representative sections of ileum and large intestine. There was also crypt epithelial hyperplasia, crypt abscessation and foci of exudative inflammation.

Skin conditions

ctoparasitism associated with midge species was suspected as the cause of skin lesions in approximately 25 percent of slaughtered pigs from a mange-free unit. The presence of the lesions had resulted in significant financial loss to the producer. The lesions were comprised of multifocal flat red spots varying from 0.5 – 1.5 cm diameter that were widely distributed across the backs and sides of the pigs (Figure 5 - see top right-hand side). The skins were not thickened and all other organs were unremarkable. Insect bites were suspected and by way of investigation, a series of ground traps and aerial traps were sited in the finishing sheds for a two week period. The ground traps yielded only a low number of spiders and non-biting insects. The aerial traps yielded large numbers of flying insects and the relative proportions are shown in Figure 6 (see top right-hand side). Of the insects trapped, the two species of midge were the only ones capable of biting and feeding from pigs. Culicoides obsoletus is a species complex of four different subspecies that are known to feed from pigs and Culicoides impunctatus (the ‘Highland biting midge’) will feed from a variety of large mammals including pigs (A.Blackwell, personal communication). The unit is not in a highland area and the number of midges was surprising as they were not evident in the unit by day. Possible means of controlling midges in the buildings are under consideration.