Veterinary Services

Nutritional and metabolic disorders

Histopathological examination of tissues from pigs from three separate units revealed lesions of acute degenerative cardiomyopathy consistent with inadequate dietary vitamin E intake. Two unrelated cases involved "sudden deaths" in finishing pigs while a third case involved an indoor unit reporting several unexplained deaths amongst three-week-old unweaned piglets. Attention to dry sow feed vitamin E levels was suggested in this case.

Generalised and systemic conditions

Three new outbreaks of post-weaning multisystemic wasting syndrome (PMWS) were diagnosed this month. In one case, a single animal was examined from a finishing unit reporting widespread coughing and diarrhoea in twelve-week-old pigs. Histopathological lesions of lymphoid depletion were observed in lymph nodes together with low-grade viral-type pneumonia and a superimposed extensive bacterial bronchopneumonia (Pasteurella multocida isolated). No significant enteric pathogens were isolated from areas of congested colon and although suitable material was not available for histology, a non-specific bacterial-type colitis associated with the PMWS was suspected. It is not clear whether this individual case was representative of the clinical problem described on the unit.

Poor growth rate on a farrow-to-finish unit, apparently associated with scour in some cases, prompted the submission of four affected twelve-week-old growers. Post-weaning mortality on the unit had also increased from 3.3% to 4.2% over the last year, with the most recent three-month figures at around 6.6%. Extensive lesions of proliferative enteropathy (Lawsonia intracellularis infection), most marked in the caecum and colon, were detected on gross and histopathological examination of three of the pigs. Lesions consistent with spirochaetal colitis (Brachyspira pilosicoli infection) were also observed in some sections, although no Brachyspira spp. were isolated on culture. Normal lymphoid histological morphology was observed in all three of these pigs. Lymphoid depletion in the spleen and mesenteric lymph node consistent with PMWS was however detected in one pig in very poor body condition. The pig also showed lesions of focal exudative epidermitis (Staphylococcus hyicus isolated), viral-type pneumonia with bacterial bronchopneumonia and a fibrous pleurisy and pericarditis. Evidence suggestive of spirochaetal colitis was also observed in this case.

In the third case, an outbreak of meningitis and "sudden deaths" was reported in seven to eight-week-old pigs, in which six of a group of 250 had died. The gross post mortem findings of generalised lymphadenopathy, hydropericardium and hydrothorax with generalised pulmonary consolidation and marked interlobular oedema were highly suggestive of PMWS. Only mild meningeal congestion was noted on examination of the brains. Lesions of lymphoid depletion and histiocytic infiltration in lymph nodes and viral type pneumonia were detected on histopathological examination. Streptococcus suis serotype 1/2 was isolated from the brain and internal organs of two pigs examined. This was a high health status outdoor breeding / indoor rearing herd on which neither streptococcal meningitis nor PMWS had been diagnosed previously. No possible source of recent introduction of virulent S. suis could be identified and it seems most likely that immunosuppression due to PMWS had predisposed to septicaemia involving a "strain" (or possibly "strains") of S. suis of relatively low intrinsic virulence that had been in the herd for some time.