There was a slight, but not statistically significant, fall in diagnoses of PMWS (as a percentage of relevant diagnostic submissions) during the quarter compared with the same quarter last year (see histogram). Nevertheless this is set against an overall steady quarter-by quarter downward trend in diagnoses of PMWS after 2001.

The high percentage (11.6%, revised) of diagnoses of PDNS, from relevant submissions, noted in the first quarter this year was not sustained in the second quarter (2.7% provisionally). Only in the last quarter of 1999 and the first quarter of 2000 has the percentage of PDNS diagnoses reached over 11%. For all but one other quarter (8.4% fourth quarter 2000), commencing with the second quarter of 1999, PDNS diagnoses have varied from 0.5% to less than 6% of relevant submissions. There is no simple underlying explanation for these observations, although disease incidents at the time may well have influenced decisions to have more PDNS-related incidents investigated thus resulting in a higher proportion of diagnoses of PDNS.

Much of the porcine circovirus 2 (PCV2) related disease this quarter was in association with respiratory disease and increased mortality in growers and finishers - see respiratory disease section below. The clinical expression of PCV2-associated disease in pigs can result in several distinct syndromes including PMWS and PDNS. A review of these syndromes is given by Chae (Chae C, 2005, The Veterinary Journal 169: 326-336).

Incidents investigated included a 215-sow breeding/finishing unit with mortality increasing in weaners from 2% to 11% since January 2005. Unthriftiness, mild respiratory signs, and diarrhoea were also noted. Necropsy findings included enlarged lymph nodes, cachexia, fibrinous peritonitis and lobar pneumonia. Histopathological examination of lymphoid tissue showed typical signs of PMWS. Bacteriology was unrewarding; probably as a result of antimicrobial treatment prior to death.

On a second farm the presence of PCV2 was confirmed on histopathology in one of three pigs and suspected in another two on a unit where 10% of a group of 1030 were scouring. In a third incident, cases of wasting and death were starting to increase on an organic breeding/finishing unit. PMWS was diagnosed at least two-years previously. Total mortality from birth to finishing was subsequently maintained, until recently, below 8% following management changes, including introducing vaccination against porcine reproductive and respiratory syndrome (PRRS) and enzootic pneumonia.

Histopathological changes typical of PMWS were seen in all pigs examined. One pig also had a bacterial pneumonia from which Pasteurella multocida and Streptococcus suis serotype 3 were isolated. Porcine proliferative enteropathy, due to Lawsonia intracellularis, was confirmed in another by histopathology. There was also histopathological evidence in another pig of spirochaetal colitis.

An 8-week-old piglet was submitted from a fourth unit where reported signs included loss of condition, coughing, and diarrhoea. Histopathology revealed changes in lymphoid tissue typically associated with PCV2. Acute fibrinous meningitis was also present and another manifestation of PMWS was suspected.

PDNS was diagnosed in 16-week-old housed finishers. Seventeen of 1500 pigs were reported as affected and PDNS was confirmed in three pigs examined, two had gastric ulceration and two had pneumonia from which P.multocida was isolated.