Download Infectious Bovine Rhinotracheitis (IBR)

Infectious Bovine Rhinotracheitis (IBR)
Phil Scott DVM&S, DipECBHM, CertCHP, DSHP, FRCVS
Infectious bovine rhinotracheitis (IBR, BHV 1)
Introduction
IBR is a highly contagious and infectious viral disease
that affects cattle of all ages. Infection occurs by
inhalation and requires contact between animals
spreading quickly through the group. The disease is
characterised by severe inflammation of the upper
respiratory tract. Bovine herpes virus 1 (BHV 1) also
causes infectious pustular vulvovaginitis in the female,
and infectious balanoposthitis in the male.
Clinical signs
Clinical signs generally first appear two to three weeks
following transport, sale, housing or other stressful
event such as calving. During an outbreak of IBR, the
morbidity rate may be 100% but the mortality rate is
generally less than 2%. The first two or three cattle
affected often develop the most severe clinical signs.
The conjunctivae are oedematous and there is partial
prolapse of the third eyelid. Tear staining of the face,
quickly turning purulent, can be pronounced. There
may be small erosions on the nasal septum
progressing to diphtheritic plaques. There are no oral
lesions but there is drooling of saliva due to ruminal
stasis. There is halitosis from pus in the larynx and
trachea, and varying degrees of dyspnoea. Affected
animals cough frequently and palpation of the larynx is
resented. There is an increased respiratory rate but no
abnormal lung sounds except sounds referred from the
upper respiratory tract. After several days,
inappetance leads to a shrunken rumen giving affected
cattle a gaunt appearance. Body condition loss can be
pronounced. Death is unusual but is caused by severe
damage, necrosis and secondary bacterial infection of
the trachea with accompanying inhalation pneumonia.
Affected cattle lose their appetite, develop a high fever
(41-42°C) with purulent ocular and nasal discharges. Severely affected animals are very depressed, slow to
rise, and stand with the head held lowered.
Purulent nasal discharge in a purchased steer with
suspected IBR.
Much milder clinical signs with conjunctivitis,
occasional coughing and poor milk yield can occur.
IBR virus enhances the pathogenicity of Moraxella
bovis and severe infectious keratoconjunctivitis lesions
can develop in calves.
Differential diagnoses in individual cattle
Suspected IBR in a recently purchased Charolais bull. The bull was febrile (41.5°C). The lungs were also
scanned to check for chronic suppurative pneumonia.
-
Recrudescence of chronic suppurative pneumonia
-
Malignant catarrhal fever
-
Mucosal disease
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Recrudescence of chronic suppurative pneumonia in
a dairy heifer two weeks after calving
Foot and mouth disease
Differential Diagnosis in a group of cattle
-
Bluetongue.
-
Foot and mouth disease
Diagnosis
Malignant catarrhal fever should be differentiated
from IBR.
Diagnosis can be established after careful
inspection of all the animals in the group. Fluorescent antibody test (FAT) requires ocular
swabs (rub vigorously as test needs cells) from
affected febrile animals avoiding samples from
cattle with purulent ocular discharges. If the
veterinary laboratory is not local, make smears on
glass slides and dry in air before posting. Note that
false negatives are not uncommon.
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Necropsy findings of severe tracheitis in a beef steer
that had died from IBR.
MSD Animal Health
At the start of an IBR control programme,
measuring bulk milk antibody titres can be a very
useful means of determining IBR status of the
herd. However, a negative bulk milk result does not
necessarily indicate that a herd is IBR-free as up to
20% of the milking herd can be latently infected with
IBR before the bulk milk result will become positive,
therefore blood testing is essential to confirm
IBR-free status. Once the veterinary health plan is
in place bulk milk antibody testing can be a simple
means of confirming the absence or low prevalence
of IBR.
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Treatment
Vaccinate all animals in the group immediately IBR
is suspected on clinical findings. Sick animals
should be treated daily for five to seven days with
parenteral procaine penicillin. There is little benefit
gained from administering much more expensive
antibiotics. NSAIDs can be used as supportive
therapy; never use corticosteroids.
Management/Prevention/Control measures
IBR vaccination is inexpensive, either by single
intranasal or intramuscular injection and is
incorporated into veterinary herd plans. Marker gE
vaccines are available for more sophisticated
control programmes. Purchased beef cattle of
uncertain status should be vaccinated as soon as
they arrive on farm, and are often turned out to
pasture for three to six weeks in the autumn before
housing.
Purchased beef stores vaccinated against IBR and
turned onto stubbles for several weeks before
housing in November.
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