Veterinary Services

A major problem of selenium toxicity was confirmed in twelve-week-old pigs in one herd. Fifty pigs out of a batch of 280 pigs developed acute-onset paralysis. The affected pigs were bright, alert, in sternal recumbency and most were still able to eat and drink, but required assistance as they were unable to access the usual feed and water provided to the groups. The first cases of paralysis occurred two days after the introduction of a new batch of feed supplemented with a product said to aid in the control of tail biting. The liver selenium levels in the first three carcases received  were 13.2 mg/kg DM, 9.49 mg/kg DM and 10.1 mg/kg DM (reference range 0.7 to 1.8mg/kg DM). Blood samples collected from a further two cases prior to euthanasia, had selenium levels of 1.62 ug/ml and 1.37 ug/ml (mean selenium in healthy pigs usually around 0.13ug/ml).  Selenium toxicity in pigs was reported with a mean blood selenium level of 0.57 +/- 0.06 ug/ml in cases of toxicity (Can J Com Med 1983; 47:412-421) . Histopathological examinations revealed bilateral, roughly symmetrical lesions of poliomyelomalacia affecting the cervical and lumbar enlargements of the spinal cords, consistent with those described in selenium toxicity. Acute necrosis, haemorrhage and cavitation were present in the worst affected areas (Figure 2 - see top right-hand side). The ration being fed to the pigs was analysed and was found to have a selenium level of 42.6 mg/kg which is approximately 100 times higher than the maximum recommended level. After reporting this case to the Food Standards Agency (FSA), it was discovered that a batch of the feed supplement was subject to a manufacturer’s recall. When the recalled batch of supplement was analysed it was found to contain a selenium level of 3,090 mg/kg and this was being incorporated in the ration at five kg per tonne. In total, 461 pigs received feed containing the recalled batch of product. The FSA stipulated the need for a 114 day withdrawal period and, should any of the pigs be slaughtered before this period, the liver and kidneys were to be removed at slaughter and discarded. The remaining paralysed pigs were killed for humane reasons as the farmer was unable to sustain the level of individual nursing care that the pigs required. Ultimately, all of the remaining pigs that received the recalled batch of product were killed on farm and disposed of as fallen stock, as the abattoir was not prepared to accept the pigs under the conditions stipulated by the FSA.

Polyarthritis due to Streptococcus suis serotype 14 and ulcerative stomatitis were diagnosed in a two-week-old piglet. The herd had a higher than expected pre-weaning mortality rate. The piglet had a necrotic ulcerated area in the mouth on the left cheek. S. suis serotype 14 was isolated from both elbows, the right stifle and the atlanto-occipital joint.

Alimentary tract conditions

Swine dysentery was diagnosed in grower pigs on four units. Affected pigs ranged between 11 and 15 weeks of age and showed acute diarrhoea. The morbidity rate was between ten and 20 percent in affected batches and mortality rate between two and seven percent. In all instances, the postmortem examinations showed typical lesions of typhlocolitis with watery haemorrhagic colonic contents and large spirochaetes in the colonic crypts. The diagnosis was confirmed by PCR testing and bacterial cultures.

Swine dysentery and infection with Salmonella Rissen were identified in a batch of 11-week-old gilts with a history of diarrhoea, recumbency, paddling and shaking. The clinical signs were acute in onset and the pigs died rapidly. Postmortem examination showed severe diphtheritic typhilitis associated with these combined infections.

Salmonellosis was diagnosed in three further pig units with histories of diarrhoea in grower pigs.  S. Typhimurium and S. Derby were identified in one outbreak, S. Brandenburg in another and S. Rissen from the third outbreak. No other recognised enteropathogens were detected in these instances.

Respiratory tract disease

Pleuropneumonia due to Actinobacillus pleuropnemoniae was diagnosed in a 15-week-old gilt, which died suddenly. The finishing unit had experienced an ongoing pneumonia problemwith four deaths since the batch moved into the finishing shed two weeks previously. There was severe extensive pleuropneumonia affecting both lungs with yellow fibrinous exudates covering the right apical lobe and dark areas of consolidation affecting both diaphragmatic lobes. A profuse growth of Actinobacillus pleuropneumoniae was isolated in culture from the lung.  Serotyping of the isolate gave positive reactions to serotypes 3, 6, 8.