NADIS disease forecast – pigs (July)

July 2004

By Mark White BVSc DPM MRCVS

NADIS Pig Disease Forecast

It was no surprise to find that PMWS/PDNS dominated the programme at the recent International Pig Veterinary Society Meeting in Hamburg and, whilst research work continues to concentrate on Porcine Circovirus Type II and development of vaccines against the organism (one of which may not be too far off becoming available) there were a number of clinical reports which add to our knowledge and understanding. 

3 items stand out:

1. 
   
   The so called “litter effect” – where the majority of affected pigs arise from a limited numbed of litters – could not be confirmed in a number of detailed studies.
   
   
2. 
   
   Other studies, however, demonstrated a tendency for more losses to come from litters of older sows, with the incidence in Parity 1 and 2 progeny the lowest. This would be consistent with observations in the UK over the last 3 years in herds disrupted by Foot and Mouth Disease restrictions.
   
   
3. 
   
   The recent appearance of the disease in New Zealand and the behaviour of the disease there supports the clinicians view that PMWS is caused by a novel infectious agent entering a herd (and spreading between herds) and “activating” Porcine Circovirus Type II to cause its damage, rather than there being specific nutritional, genetic, environmental or managemental factors triggering this apparent change in pathogenecity.  This does not mean to say that vaccinations against Porcine Circovirus Type II will not be effective but it continues to leave it unclear as to the true primary cause.  There is circumstantial evidence in New Zealand to suggest that the “new” agent may have been introduced via infected meat products, acquired by waste feeders from airports.  This is an alarming reminder of Foot and Mouth Disease 2001 introduction in the UK.

Adults
Many farms are reporting improved productivity this year which would be consistent with a 2 year programme of restoring herd age structure after the 2001, 2002 disruptions. 

It is interesting to read in the latest MLC pig year book that the average production for all breeding herds over 2001, 2002 and 2003 has been virtually constant (~21.2 pigs reared per sow per year) and does not show the drop in output expected following the fertility problems in late 2002. 

This figure is, however, 1 pig per sow per year less than average herd achieved in 2000 before serious disruption occurred.

Individual herds do still suffer production problems, particularly where old sows remain and age structure has not been restored. 

Semen quality has also been called into question in at least one reported farm with the herd struggling to achieve 72% farrowing rates.

The dry early spring followed by more recent rain has created unusual ground conditions for outdoor sows – hard ground followed by mud and this appears to have been associated with an increase in lameness. 

Observation has been difficult in the wet weather as sows and boars are reluctant to leave arcs.

There are also early signs of the usual summer problems outdoors of litter desertion, poor feed intake and heat stroke.

Growers
Scouring continues to be a pre-dominant feature of the growing pigs with many farms seeing a fall off in growth with low-grade scour associated with the low levels of copper now used in diets. 

Accurate figures in one herd show a loss of 100g per day liveweight gain over the finishing period.

Post weaning scours have also been seen where Zinc Oxide has been withdrawn from diets in an experiment to anticipate the probable ban on this cheap and effective medication next year.

Skin lesions have been widely reported in May with mange, fight wounds, pityriasis rosea and other unspecified problems reported. 

Erysipelas has also been seen (its usual warm weather rise?) and PDNS has shown a blip over the month.

Respiratory diseases inevitably continue with mixed infections.  One herd experiencing the twin effects of PRRS and Actino pleuropneumoniae was particularly severely affected.

Tail biting was widely reported in highly variable temperatures.

Piglets
Scouring continues to dominate reports in the pre-weaning period with rotavirus and coccidiosis widely seen. 

It is questionable, however, how many of these are confirmed diagnoses and how many are presumed from the clinical presentation.

Hernias, both inguinal and umbilical, appear to have increased in a number of farms.

In July, watch out for:

• 
  
  Erysipelas
  
  
• 
  
  Farrowing house scours
  
  
• 
  
  Heat stroke and sunburn, especially in gilts.
  
  
• 
  
  Grower scours
  
  
• 
  
  Returns to service

While every effort is made to ensure that the content of this forecast is accurate at the time of publication, NADIS cannot accept responsibility for errors or omissions. All information is general and will need to be adapted in the light of individual farm circumstances in consultation with your veterinary surgeon

Copyright © NADIS 2002