Pat's Note: This extremely interesting article from Australia, gives a
good insight into much of the confusion surrounding this disease and
rightly emphasises the apparent escape of Australia from this
worldwide epidemic despite having PCV2.

There is no mention of events in Britain, no doubt reflecting the
disinclination of both the government and veterinary industries to
talk much about the problem in public.

There is nothing on the mode of movement of the more virulent strain
between countries and continents. Traditionally Australia, New
Zealand, Britain and North America tend to stress infected meat as
this goes down well with the farming lobby.

New Zealand, having two islands, with a different strain in each (and
I think a ban of the movement on live pigs between the two) is a vast
real life lab that tends to exonerate meat, cooked or raw as a means
of transmission. That, together with Australia's apparent escape and
the dates of spread through Europe and North America should be more
closely examined. It is pointless and damaging to slam the wrong door.

Britain's reluctance to openly admit that mutated MRSA caused an
epidemic in Britain in 1999, possibly even a little earlier in
Northern Ireland, does the world a mis-service. PMWS was roaring
through East Anglia in late 1999 with heavy and increasing losses.
Both CSF (2000) and the catastrophic FMD (2001) arrived into pigs
already seriously sick. Why was this information suppressed?

What is Britain hiding that is so important? Why won't they tell us
whether the pigs have MRSA? We know that vast quantities of
antibiotics have been used for the last nine years - ideal conditions
for antibiotic resistant organisms to develop.

http://www.ferret.com.au/c/Pork-CRC/Dr-Trish-Holyoake-publishes-article-on-PMWS-in-Pork-CRC-s-newsletter-n814557


European Spin on PMWS by Dr Trish Holyoake, University of Sydney

Post weaning multi systemic wasting syndrome(PMWS) affects weaner pigs
and is characterised primarily by non-responsive wasting.
It is now known that Porcine Circovirus Type 2 (PCV2) is necessary for
the syndrome to be expressed.

Australia remains one of the few countries where PMWS has not been
diagnosed, despite PCV2 being widespread in our pigs.

PMWS was first reported in Canada in 1991, with cases subsequently
reported in Europe.

The first cases of PMWS occurred in Denmark in 2001 and in Sweden in
2003. Norway had two cases in 2003 and managed to stamp these out.

More cases appeared in the country following the eradication.
New Zealand had its first case in the North Island in 2003 and
subsequent cases in the South Island in 2006. Finland has only
recently become affected (December 2007).

Disease Syndromes

A number of disease syndromes have recently been linked to PCV2,
including reproductive failure, respiratory disease, enteric disease,
congenital tremors and porcine dermatitis nephropathy syndrome. The
role of PCV2 in these diseases is still under investigation.

In December 2004, a consortium of researchers from 16 organisations
across Europe and North America were funded by the European
Union to study diseases associated with PCV2. The consortium annually
holds a Specific Support Action (SSA) workshop to disseminate
key research findings and I was fortunate to attend the most recent
SSA meeting in Budapest. In this article, I summarise
some key findings from the workshop. 

Immune Activation

PCV2 is a very small virus and, like all viruses, it relies on the
cells of its host (the pig) to multiply sufficiently to cause disease.
The results of genomic studies of PCV2 suggest that the virus only has
DNA to (1) start replicating and (2) to put a capsid (“shell”)
around the end product. 

All other functions must be provided by the host cell.
From several experimental challenge models developed to reproduce PMWS
in the laboratory situation, it is generally accepted that the
presence of PCV2 alone is not enough to reproduce PMWS as seen on
farms.

Other infectious or non-infectious factors are required for the
development of the full clinical disease.

These “factors” can be pig pathogens e.g.parvovirus and porcine
reproductive and respiratory syndrome virus (PRRSV). They can
also be non-infectious immuno-suppressors or immuno-stimulators.

Given the wide range of potential “activators”, the risk of an
individual pig becoming infected with PCV2 is high.

Full-blown PMWS may occur in a herd when many pigs are exposed to the
immuno-modulator. This assumes the “right” strain of PCV2 is present.

Right Strain

There is currently no standard system for classifying different PCV2
strains, with different countries having their own way of naming
them. One of the objectives of the European consortium is to
standardise them.

It appears that differences exist in the virulence of PCV2 strains.
For example, there has been an increase in the incidence of PCV2
strain “321” (“new” strain) in Canada since 2004.

This has been associated with an increase in PCV2-related disease.
However, these virulence differences have not fully explained the
differences in clinical disease observed in the field.

Vaccines Available

There are now four commercially available vaccines against PCV2
disease. The first registered was manufactured by Merial
(Circovac) and is registered for use in sows pre-farrowing to boost
maternally-derived protection in piglets against PMWS.

Approximately 25% of sows in France, where Circovac was first
registered, are vaccinated and 17% in Denmark and Germany.

The growth and reproductive performance in herds is reported to
improve after vaccination commences (i.e. when “before” and
“after” performance is compared).

Independent studies in Sweden, where the progeny of vaccinated and
non-vaccinated sows have grown out at the same time, alsuggest this
vaccine improves the growth performance of pigs in herds with PMWS.

In 2008, Boehringer Ingelheim registered a 1-shot PCV2 vaccine for
piglets (Ingelvac Circoflex) in the EU and this opened the door
for other piglet vaccines to be used in Europe.

Feedback from veterinarians working on-farm is that the vaccines
appear to work
well.

Herd Mentality

Despite extreme research effort, it’s still unclear why some herds get
PMWS and others don’t.

With the heavy reliance of PCV2 on its host for replication, the pig
itself must be very important in determining the ability of the
virus to cause disease.

University of Copenhagen research into the role pig genetics play in
disease susceptibility may help explain Australia’s freedom from PMWS.

The genotypes of early PCV2 isolates in Australia have been sequenced
(Muhling et al.,2006) and appear to fit into the “422” (“old”) family
of PCV2.

It would be useful to know the genotype(s)of more recent PCV2 isolates
to understand why we have not had the “classical” PMWS outbreaks other
countries have had.

Vaccine Option

Vaccines offer an excellent control option for PCV2 disease. Given we
have PCV2 in Australia and the changing nature of the disease, it
would benefit us to consider using these vaccines should PCV2 disease
occur here.

Preliminary discussions now, with relevant government agencies and
pharmaceutical companies, would speed up registration and
importation for the future.

-- 
Regards
Pat Gardiner
Release the results of testing British pigs for MRSA and C.Diff now!
www.go-self-sufficient.com  and http://animal-epidemics.blogspot.com/