The role of Porcilis® AR-T in an Atrophic Rhinitis eradication programme
By Marc Martens, Intervet - Before 1960, it was assumed that pig farms once infected with Atrophic Rhinitis (AR) would always remain that way. Depopulation followed by complete repopulation with new AR-free animals was the only means to become free of AR. The problem of AR was addressed in this way by state-run programmes in many European countries (East and West).
The aetiology of AR was first clarified after
1975 when publications appeared showing
that it was not Bordetella bronchiseptica,
but the Dermo-Necrotic Toxin (DNT)-
forming strains of Pasteurella multocida,
that caused AR.
These DNT-forming P.multocida strains
(Pm+) were isolated on only a few pig
farms, by contrast with B.bronchiseptica.
Furthermore it was possible to reproduce
the disease, and the subsequent economic
damage, by infection with these Pasteurella
species alone.
In the Netherlands at that time, the initial
eradication programme based on depoprepop
was brought to a halt and a
certification programme, organised by the
regional Animal Health Institutes, took its
place. It was then found that farms that
had been vaccinating for years with Nobivac
AR had become free of the Pm+bacteria.
The Dutch experience has been the basis
for a new eradication programme in Austria,
which involves vaccination over several
years and removing only the Pm+
individuals.
The certification programme of the Animal Health Institute in the Netherlands
Farms infected with AR were eligible for a
sustainment programme. Advice was given
on epidemiology, housing, climate control
and management. The DNT-pasteurella
was isolated in the laboratory, its resistance
pattern determined, and medication
regimes proposed. In 1985, Intervet was
the first company to introduce an ARtoxin
vaccine (Nobivac AR-T) onto the
market. As soon as it was available, it was
used on these farms.
Figure 1. Percentage certified PM+ free-farms in the Netherlands
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Figure 2. Sales of AR-vaccine (million doses) by year (75-85% Porcilis ART)
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Pm+-free certification programme was
begun. Initially it was only for breeding
and rearing farms, but now piglet
producers can participate as well. Early
on, vaccination was allowed on some farms
belonging to breeding companies that
were so concerned about the disease that
they were unwilling to stop vaccinating,
but later, vaccination was completely
forbidden under the rules of the
programme.
The conditions for the Pm+-free certificate
are:
- Swabs must be taken from nose and tonsils three times a year, for two years. All samples must be examined in the laboratory and must all be free of toxin-producing P.multocida.
- No AR vaccination is allowed.
- Only Pm+-free animals and/or animals from certified Pm+-free farms may be introduced.
In fact, over 90% of breeding farms are
now certified, and over 95% of replacement
gilts are sold with a Pm+-free certificate.
Recently, also piglet producers have joined
the programme in order to be able to offer
Pm+-free finishers.
At first an ELISA test was used for routine
diagnosis, but this has been replaced by
PCR techniques with a far greater
sensitivity. The advantage of the PCR is
that, even on farms which vaccinate, the
chances of missing Pm+ bacteria are very
small.
Eradication
Dr M de Jong from Animal Health Institure
Deventer / Holland found that AR-infected
farms that had been vaccinating for a
number of years with Porcilis AR-T had become
Pm+-free. Neither the ELISA nor with
the PCR tests were able to demonstrate
any DNT-Pasteurella on these farms (ref.3).
Investigation of these particular farms
revealed that:
- Herds had been vaccinated for at least 3 years with Intervet's Porcilis AR-T
- Replacement gilts (7 months of age) had come from certified Pm+-free farms, were housed for 6 weeks in quarantine and vaccinated twice with Porcilis AR-T before introduction to the herd. They were then vaccinated for the third time, 4 weeks before farrowing.
- A strict "all in-all out" procedure had been followed in the farrowing and growing units.
Factors with a negative influence on Pm+ eradication were:
- Purchasing boars or gilts from infected farms.
- Introduction of piglets from around 12 weeks of age that could not be vaccinated beforehand.
- Immediate introduction into the infected herd without a quarantine period, so vaccination was started too late.
- Replacement gilts taken from own breeding stock.
These findings led to the conclusion that
it was possible to clear AR-infected and
vaccinating farms of Pm+ by identifying
and eliminating carrier sows only, avoiding
the cost of complete depopulation.
Figures 1 and 2 show that with the increase
of certified Pm+-free farms in the
Netherlands, the overall use of AR-vaccine
has decreased.
AR eradication in Austria
At the moment, 300 farms in Nieder Thann Oberösterreich are involved in an eradication programme based on the system already described (intensive vaccination and screening using PCR). The samples are taken by local practitioners. Dr Martin de Jong from AHI Deventer is the AR expert for this programme.
Discussion and conclusions
Porcilis AR-T not only protects pigs against
the clinical symptoms of Atrophic Rhinitis
but also reduces the transmission of the
toxin-producing Pasteurella multocida
within the herd. This property of Porcilis
AR-T has not yet been elucidated.
Intensive vaccination with a potent vaccine
and a test and remove protocol are ideal
tools for an eradication programme, and
bear similarities with Aujeszkys Disease
eradication. In the Netherlands, as the
percentage of certified Pm+-free farms has
increased, sales of Porcilis AR-T have gone
down.
Porcilis AR-T DF
The above results have been achieved with
Porcilis AR-T, which will soon be replaced
by an improved version of the vaccine
named Porcilis AR-T DF. Porcilis AR-T DF is
already officially registered by the
centralised EU procedure and will soon be
launched in several countries. The adjuvant
in Porcilis AR-T DF is Diluvac forte which is
more tissue-friendly than an oil adjuvant.
In addition, the PMT toxin is now produced
in a very pure form, in E coli bacteria
producing a non-toxic recombinant
derivative of PMT. The new vaccine also
contains inactivated cells of B. Bronchiseptica.
The improved vaccine will be able to
produce the same results as reported
above.
Further information
Click the links below for additional information:
- More information on Porcilis AR-T
- More information on Intervet and their pig products
References
1. Meyer K. and Schöss P.
Eradication of Progressive Atrophic
Rhinitis by bacteriological and
serological examination. Proc. IPVS
Bologna 1996 p246
2. De Jong M.F. Kamp E. and Bokken G.
Selecting sows harboring AR toxigenic
Pasteurella multocida by a PCR test to
eliminate PAR in a breeding herd. Proc.
IPVS Bangkok 1994 p167
3. De Jong M.F. Kamp E. van der Schoot
A. and von Banniseth T. Elimination of
AR toxinogenic Pasteurella from
infected sow herds by a combination
of AR-T vaccination and testing sows
with a PCR and ELISA test. Proc. IPVS
Bologna 1996 p245
4. De Jong M.F. Fortschritte in der Rhinitis
Atrophicans Bekaempfung. BgVV
symposium 2000 Jena Germany
Source: Intervet UK Ltd - November 2005