Veterinary Services

Continuing problems of diarrhoea and poor postweaning growth due to postweaning multisystemic wasting syndrome (PMWS) were reported on a nursery unit.  Examination of two affected pigs revealed, in addition to histopathological lesions characteristic of PMWS in the lymphoid tissues, evidence of a non-specific bacterial-type typhlocolitis thought to be secondary to the mmunosuppressive effects of PMWS. No significant enteropathogens were isolated from either pig.

The carcase of a 10-month-old boar that had died following a three-day history of vague illness after recent transportation, was submitted for postmortem examination.Gross examination revealed extensive fibrinous peritonitis and inflammation of the scrotal sac, testes and spermatic cords. Escherichia coli and Clostridium perfringens were isolated from the lesions, as well as from the bladder and kidneys. Histopathological findings were consistent with an acute bacterial infection and septicaemia, although the lesions were not considered specific to any particular infection. No further cases of this nature were reported on the unit.

Erysipelas was confirmed within a group of 1000 pigs on a finishing unit. The breeding herd had been vaccinated against erysipelas but there had been an outbreak in the finishers in which approximately 30 sudden deaths had occurred over a two week period. Diamond-shaped skin lesions characteristic of acute erysipelas had been observed in several of the dead pigs and Erysipelothrix rhusiopathiae was isolated from two pigs (50 to 70 kg) submitted for examination. A further 35 pigs died the following week, despite in-feed medication, but mortality declined rapidly after completion of the vaccination course.

Alimentary tract disorders

Rotaviral diarrhoea was confirmed as being the cause of poor postweaning performance and occasional scour on one unit. Gross examination of two affected five-week-old pigs showed normal faecal consistency but an absence of prominent lacteals in the small intestine, suggestive of malabsorption.Histopathological examination of the small intestine revealed lesions of subacute, but ongoing, viraltype enteropathy. Type C rotaviral RNA was detected on polyacrylamide gel electrophoresis (PAGE) testing of caecal contents.

Four six-week-old pigs were submitted over a seven-day period from a unit that had received a batch of pigs weaned at four weeks of age. All the cases, which were reported to become lethargic and fade over 24 to 48 hours,were dehydrated and showed evidence of weight loss since weaning. The stomachs were empty and the fundic mucosa was ulcerated, with bleeding points noted around the rim of the ulcer in the first pig submitted. Although K88-positive E coli was isolated from the intestinal contents of two of the pigs and type A rotavirus was detected by PAGE in one pig, no significant histopathological changes were observed in the small intestine examined. Histopathological examination of the gastric mucosa revealed severe mycotic gastritis and ulceration in three of the four pigs.

Stress and failure to feed were considered the predisposing factors in these cases and advice was provided on appropriate environmental temperature, bedding and palatability of the ration (creep feed was not provided on the breeding unit of origin). Since the changes were made, the feed intakes and weight gain have improved and no further cases have been reported.

Two younger pigs (25 to 35 kg) from the finishing unit experiencing losses due to erysipelas (mentioned previously) were submitted for postmortem examination.  Both pigs showed signs of diarrhoea but a generalised scour problem had not been reported. Lawsonia intracellularis DNA was detected by PCR, and histopathological examination confirmed the presence of porcine proliferative enteropathy (PPE), with marked crypt epithelial hyperplasia and abscessation.

A finishing unit that received notification of level 3 status under the Zoonosis Action Plan (ZAP) Salmonella Monitoring Scheme received an advisory visit in July 2005. Bacterial culture of representative faecal samples at that time showed a 20 per cent prevalence of Salmonella Derby in the growing pigs, with evidence of infection present in all sheds. There was no evidence of any clinical illness and the pigs were achieving target growth rates.  Advice was given on specific measures that could be used to  ontrol salmonella infection on the unit and a series of measures were introduced in line with the DEFRA/Scottish Executive  environment and Rural Affairs Department Code of Practice, including cleaning and disinfection of buildings and feed acidification. Similar bacteriological screening of faecal samples was repeated in November and no Salmonella species were isolated. No positive serological results were recorded in the previous monitoring quarter and the unit currently has ZAP level 1 status.

Respiratory tract diseases

Apparent upsurges in enzootic pneumonia were recorded as the cause of increased levels of coughing and poor growth among growing pigs on two units following postmortem examination of affected animals. The reasons for the upsurges have not been established.  Lesions of PPE were also observed in a scouring pig from one of the units.

Nervous system disorders

Cases of meningitis and sudden deaths among eight- to 10-week-old pigs in a newly established breeding herd prompted submission of one dead and one live affected animal. The live pig was in lateral recumbency, unable to stand and showed classic ‘paddling’ movements, with the neck held in rigid extension. There was also evidence of marked hock joint swelling. Gross  postmortem examination of both pigs revealed meningeal congestion, with fibrin exudation, particularly marked over the cerebellum and brainstem,  and fibrinopurulent polyarthritis.  Streptococcus suis serotype 2 was isolated from the brain, joints and internal organs of both pigs. S suis serotype 2 meningitis had been a problem in the previous herd on the premises and it was not clear whether the source of the current problem was a remnant of the previous herd problem (for example, in the environment or in rodent carriers) or whether it had been introduced in the new breeding stock.

Lesions of viral-type interstitial pneumonia were observed in one of the pigs and while there are several possible viral causes. for example, circovirus or coronavirus, the lesions raised the additional possibility of a porcine reproductive and respiratory syndrome breakdown in the herd.

Cases of arthritis and occasional meningitis-like signs were also reported in three-week-old pigs on another recently established herd. One pig submitted appeared relatively bright, but was unwilling to stand and showed signs of marked neck stiffness. No specific cranial nerve signs were noted. The right hock and carpal joints were also swollen. Postmortem examination revealed fibrinopurulent arthritis in the affected limb joints and also in the atlanto-occipital joint; S suis serotype 1/14 was isolated from all these sites. No gross evidence of meningitis was observed and brain cultures were negative. While meningitis is not such a common feature of S suis serotype 1/14 and 14 infections (compared with serotype 2 infections, for example), atlanto-occipital joint infections appear to be relatively common and such lesions may account for some of the neurological signs reported in the herd.