Prior to the introduction of vaccination against this virus, many herds suffered losses well in excess of 10 per cent of pigs weaned. On a national basis mortality peaked in 2004 at 6.7 per cent. (BPEX Pig Yearbooks 2008 and 2010.)

The NADIS recording system in its current form began in spring of 2007 just as the first sow vaccines had been introduced. By 2008, piglet vaccination was starting to become widespread and the BPEX research programme, which provided subsidised vaccine, began.

Graph 1 shows a trend in mortality over the last four years with 2007 being very erratic and a steady decline within the monitored population through 2008/9 as vaccine use became widespread.

Of course, PCVAD is only one of many causes of loss of pigs in the feeding herd and in many herds nowadays, the disease is clinically silent. It should be noted, however, that whilst mortality in the last year has hovered around the 3.5 per cent level, which is half of that, nationally, in 2004, that decline did start before vaccination became widespread.

Within Graph 1 a noticeable jump around in the winter of 2009/10 is consistent with the cold weather in December and January and losses only steadily reduced through the year. It remains to be seen if a similar jump occurs at the end of 2010 when the weather was even worse.

Looking at the recent analytical data based on pig-keeping systems, a number of interesting features can be noted.

Graph 2:

1. Within the monitored population, mortality in slatted systems is almost double that of straw based systems.
2. Losses in indoor produced pigs are 25 per cent higher than in outdoor derived pigs.
3. Continuous flow systems experience approximately 20 per cent higher mortality than batch systems. The expected benefits of batch production does not always manifest in other parameters.

Graph 3:

Mortality in breeder/feeder and nursery/finisher herds is comparable with a small benefit seen in the latter. However, there does not seem to be any improvement in mortality in the monitored population by separation of weaner and finishing pigs. Breeder/weaner or nursery plus finishing mortality exceed that of the breeder/feeder or nursery/finisher herds.

Graph 4:

Geographically, the Midlands and North East England experience the highest losses whilst the South West of England records the lowest, within the monitored population.

Graph 5

The pattern of losses by feeding herd size follows a steady progression with a tendency for mortality to increase as herds get bigger, with a particularly sharp rise in the largest herds.

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