Veterinary Services

Generalised and systemic conditions

Failure to thrive was investigated on a unit with 2500 five-month-old pigs. The morbidity was five to 10 per cent and mortality over the previous few weeks was approximately 1.2 per cent. Some of the dead pigs were in good condition. One such well-thriven pig had porcine dermatitis and nephropathy syndrome (PDNS) combined with extensive suppurative pneumonia from which Strep dysgalactiae subsp equisimilis was isolate in profuse growth. Another had fibrinous pleuropneumonia associated with Actinobacillus pleuropneumoniae and Arcanobacterium pyogenes infections. A poorly-thriven pig submitted at the same time had lesions consistent with postweaning multisystemic wasting syndrome (PMWS). No vaccination against porcine circovirus type 2 had been used in the farm up to then.

Respiratory tract conditions

There were several investigations into outbreaks of respiratory diseases this month. An outbreak of enzootic pneumonia (EP) complicated by bacterial infections was diagnosed in a High Health herd free from EP belonging to a small producer who had sold gilts to another farmer several months previously. The latter farmer kept other pigs of unknown health status and all were housed together. However, this farmer decided to cease pig production and returned the gilts in question to the original producer. Shortly after the pigs were returned, all ages of pigs on the original High Health farm developed acute respiratory disease. Two boars aged five and eight months were submitted for postmortem examination. Polyserositis and anteroventral consolidation of the lung lobes was evident in both cases. Figure 2 (see top right-hand side) shows the opened thorax of the older boar. Liquid was present in the pericardial sac with fibrinous adhesions between the pericardium and epicardium. Mycoplasma hyopneumoniae PCR performed on lung tissue from both carcases proved positive. A linear oesophagitis was noted in the younger boar and Mannheimia haemolytica was cultured. Although Haemophilus parasuis was not recovered from tissues from these boars the gross pathology strongly suggested Glasser's disease. Unfortunately, neither producer appeared to have been aware of the biosecurity risks involved in moving and mixing pigs in this way.

Other respiratory disease outbreaks involved enzootic pneumonia flare-ups in non-EP vaccinated herds complicated by secondary bacterial infections including Pasteurella multocida and Streptococcus suis. Severe chronic suppurative pneumonia was diagnosed in an adult female pot – bellied pig from an animal sanctuary in Ross. Multiple pulmonary abscesses containing grey to green coloured pus were found on gross postmortem examination. Arcanobacterium pyogenes and Fusobacterium necrophorum ssp necrophorum were recovered from cultures.

Alimentary tract disorders

Porcine colonic spirochaetosis was diagnosed in a herd that reported diarrhoea affecting ten-week-old pigs. The large intestines of two pigs were thickened and had a diphtheritic membrane. Although only Brachyspira innocens/murdochii species were isolated in culture, histopathology provided evidence of chronic colitis. There was marked goblet cell hyperplasia, crypt extension, mononuclear cell infiltration and submucosal lymphoid aggregates with in situ lymphoid follicle formation. On silver staining there were large, fine spirochaetes in the colonic crypts suggestive of Brachyspira pilosicoli infection. There was no evidence of PMWS involvement.

A diarrhoea problem of two to three weeks duration, some deaths and also loss of condition were reported on a unit. Necropsy of two ten-week-old pigs revealed typhlocolitis. B. pilosicoli was isolated in culture from the colonic contents of one pig. Histopathological examination of both pigs confirmed sub-acute to chronic colitis. Numerous large spirochaetes were detected in the colonic crypts on silver staining. Combined infections with Lawsonia intracellularis and Brachyspira pilosicoli were diagnosed in a batch of 12 to 14-week- old pigs suffering from diarrhoea and ill-thrift in a herd in Sutherland. Gross post mortem examination and histopathology showed changes consistent with these infections, and their presence was confirmed by PCR testing.