PMWS Solution Found on UK Study Farm

By Michael R Muirhead., BVM&S, DPM, FRCVS - This case history summary describes the appearance in April 2001 of PMWS and PDNS in a 240 sow breeding/finishing herd located in a pig dense area in the UK and reports on the numerous procedures that were tried in, what appears to be, an eventually successful attempt to bring the problem under control.
calendar icon 4 April 2002
clock icon 6 minute read
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Farm History

Biosecurity on the farm is considered to be good and only AI has being used for genetic improvement over the past 3 years (no live pig imports).

The pigs are weaned each week at a mean age of 24 days to all-in/all-out self-contained groups of approximately 110 pigs. Each batch is held in this group for 2-4 weeks when they are moved into 2nd stage, continually used, grower accommodation in small groups of 25-30 (without doubt the continual use of this accommodation has been a contributing factor to the development and severity of the disease).

Health and performance of the herd had been excellent over the previous 3 years with 2.3 litters per sow per year and 24 pigs weaned. Weaner mortality (7 to 35kg) averaged 2.3% with finishing mortality at 1.8% and feed efficiency to 95kg at 2.20.

PMWS emerges

Pig with PMWS and PDNS In early 2001 the owner reported some inappetence in a few sows at farrowing and poor milking but no increase in piglet mortality.

Post mortem examinations of pigs in April showed severe pneumonia with pericarditis, epicarditis, pleurisy, severe consolidating pneumonia and oedema (fluid) on occasions and peritonitis. Samples were taken from lymph glands for histological and biochemical analysis. These confirmed the presence of inclusion bodies in lymphoid tissues in the cells, typical of PMWS.

Action taken

Commencing in early June it was decided to totally depopulate the second stage accommodation, steam clean the whole of the building, disinfect using Virkon S and rest it for 2 weeks. Repopulation of this building them commenced late in June.

The farm has generally followed the rules and points explained in the article "Controlling PMWS". Approximately sixteen of the twenty "Madec principles" have been adopted. Generally, it has to be said that this has had limited effect on this farm.

The table below summarises the specific actions taken to try to control the outbreak of PDNS/PMWS and is broken down into two columns. On the left are a list of procedures that were applied and do not appear to have given a response to the incidence of PMWS. On the right are the list of procedures that do appear to have had an effect in some form or another. Specifically, the combination of two of the procedures appears to have resulted in very significant improvements.

Procedures and their effect on the incidence of PMWS
No discernible response
Appears to have helped
All in all out - No reduction in PMWS incidence. All all out - Improved general health but not PMWS incidence.
Reduction in group sizes at weaning from 100 to 50. Improved diet using natural supplement with increased levels of dietary antioxidants
Altered timing of piglet vaccinations Serum inoculation - This was tried at 5 days of age and at weaning.
Immune stimulation of the sow and gilt. Serum treatment of sick pigs.
Depopulation, cleaning, disinfection and repopulation of the stage 2 housing Good hospital pens.
Improved hygiene, teeth clippers etc. Prompt removal to hospital pens.
Any form of treatment, individual or group (except serum treatment of diseased pigs). Aerial disinfection with Virkon S - Reduced secondary pneumonias
Improved environments and management Glässers Disease vaccination
Vaccinations at weaning against parvovirus.

Two Procedures appear to have worked

As mentioned, two specific procedures appear to have had a significant effect in reducing the devastating effects of PMWS.

These procedures are the introduction of a natural feed supplement high in antioxidants and the use of serum to both treat affected pigs and "immunise" piglets and/or weaners at weaning time.

Initially, a nutritional supplement called Vira-Matrix comprising a mixture of natural nutritional ingredients containing high levels of antioxidants, was added to the feed of all pigs on the farm from weaning to 14 weeks of age. After 6 - 8 weeks of use the number of pigs affected with PMWS fell from a high of 23% to 13%.

After this initial period and in addition to the feed supplement, serum was given to piglets at 5 days of age. This procedure was subsequently revised with the serum being given at weaning time. The use of enhanced nutrition and serum appears to have had further benefits with PMWS affected pigs currently running at less than 4% in these groups.

Results from the use of Vira-Matrix and serum.
Pre Feed and Serum Changes: 3082 pigs - 21% av. affected (Apr-Dec 01).
Feed changes only 655 pigs - 13% affected (all pigs now over 18 weeks old)
Feed + Serum (5 days) 398 pigs - 3.3% affected to date (pigs now 15-18 weeks old)
Feed + Serum (weaning) 591 pigs - 3.4% affected to date (pigs now 8-14 weeks old)


The most remarkable clinical observations are the changes in health, general demeanor, activity, feed intake and growth rate of the pigs, first seen with the introduction of Vira-Matrix. In the Vira-Matrix plus serum groups this response had been even more striking.

This is the first time since PMWS became evident, back in April 2001, that there has been a dramatic response.

If you have an intractable problem with PMWS try the following regime:
  1. Fortify the feed fed to pigs from weaning to 14 weeks of age by adding Vira-Matrix at the rates recommended by the manufacturer.
  2. Treat all pigs at either 5 days or weaning with 5ml of serum.
  3. Promptly move any pigs that show signs of developing PMWS to a suitable hospital pen. Feed rations fortified with Vira-Matrix and treat the pigs with 10ml of serum.
I can not say with any certainty this will work on other farms due to the vagaries of PMWS, all I can say is that significant benefits have accrued from its use on this farm.

NOTE: Discuss the implementation of this procedure and specifically the use of serum with your Vet prior to taking any action.

Further Information

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Source: Michael R Muirhead., BVM&S, DPM, FRCVS - 4th April 2002
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