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JULY 2019
Animal Health Focus
www.irishfarmersmonthly.com
41
JULY 2019
www.irishfarmersmonthly.com
Animal Health Focus
Figure 1. Development of latent carrier cattle following initial infection
and recovery of susceptible (na´ve) animals.
Reactivation
and
secondary
infection
Virus shedding
Virus shedding
Stress can cause
reactivation
Na´ve animal
Primary
infection
Latent
infection
while others have approved eradication programmes
underway. In both cases, these countries are granted
additional guarantees in relation to intra-community
trade. One consequence of these guarantees is that they
e ectively stop live exports from other member states
that are not recognised as free or that cannot satisfy
requirements for isolation and testing prior to export.
These requirements are in the process of being updated,
with the EU currently consulting on new rules in relation
to surveillance, eradication programmes and disease
freedom as part of the Animal Health Law (Regulation
(EU) 2016/429).
In the absence of a national programme, herd owners
should take the decision to implement a control
programme in a breeding herd following discussion with
their veterinary practitioner. A decision will be influenced
by a number of factors, including herd specific goals
(e.g. obtaining or protecting a high health status,
production of potential AI sires and sale of IBR-free
stock) and the levels of clinical and subclinical disease.
Where a decision is taken to implement a control
programme, the three recommended steps are:
investigate, control and monitor.
INVESTIGATE:
where the level of infection is unknown,
strategic testing will indicate if there is no current
evidence of infection, a low prevalence or a medium/
high prevalence. This in turn can help when selecting
the relevant control options.
CONTROL:
There are 3 general principles that can be
included in herd control strategies for IBR. The most
suitable control strategy will vary with the herd status
and should be decided under veterinary guidance.
Bioexclusion: this is an essential component of all IBR
control strategies, aiming to put in place farm-specific
measures to prevent introduction of infection. These
should address the highest risk activities first, with a
focus on introduced animals and direct or indirect
contact with cattle in other herds.
CULLING/ISOLATION:
In herds that start with, or
achieve a low prevalence of infection, this can be used
to remove the last remaining latent carriers.
VACCINATION:
complete and regular herd vaccination
makes it less likely that a latent carrier will reactivate
and shed the virus and reduces the likelihood that
a susceptible animal will become ill and transfer