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SUMMER 2016 ISSUE
EQUINE MATTERS
4
CASE STUDY
There is an infinite number of agents that
can cause allergic disease but the most
common agents and some of the diseases
they cause are summarised in
Table 1
.
Seasonal allergic skin disease can only
happen at certain times of the year in
susceptible individuals. The symptoms include
hives (raised wheals) and severe itching with
self trauma causing skin damage and leaking
of serum (clear, yellow fluid). The inciting
allergen(s) can be very hard to identify
although exclusion or elimination trials and
intradermal skin tests can help identify the
cause. Treatment with topical and oral
anti-inflammatories, and antibiotic medication
if necessary, is often helpful; or a course
of hyposensitisation injections can be
performed.
Veterinary surgeon
Richard Morris
XLEquine practice
Fenwold Veterinary
Group
Seasonal Allergic Dermatitis
An allergic reaction is where an individual’s immune system overreacts to
a harmless agent to which the majority of animals would not react.
Richard Morris BSc BVetMed CertVD MRCVS, Fenwold Veterinary Group
Insect bites (midges/black fly)
Hay moulds, stable dust and dust
mites
Tree, flower and grass pollen
Stable dust, mould spores and dust
mites
Tree, flower and grass pollen
Skin
Respiratory system
Respiratory system
Skin
Skin
Sweet Itch
Recurrent airway obstruction
(RAO)/Equine asthma
Summer pasture associated
RAO/Equine asthma
Year round allergic
dermatitis - atopic dermatitis
Seasonal atopic dermatitis
Agent
Organ Affected
Disease
Table 1. Common equine allergic diseases and implicated allergens
‘Texas’, an eight year old Thoroughbred cross
gelding developed progressively itchy skin
every Spring and would rub himself raw
(figure 1)
. In previous years it had settled
after a few weeks of topical medication but
it became progressively worse each year such
that the owner sought help from the practice.
After taking several laboratory samples to rule
out other diseases such as lice, mange or
ringworm, intradermal skin testing
(figure 2)
was performed which identified pollen from
plants flowering in the nearby hedgerow (tree
pollens, Scotch Pine
(figure 3)
, Meadow
Fescue and Lambs Quarter) as the allergens.
Management involved preventing further
exposure to these plants and so he was
immediately moved away from the hedgerow,
and the existing skin infection was treated with
topical and oral antibiotics and his allergic
reaction was suppressed with topical and
intravenous corticosteroids. After this initial
treatment his condition was managed by
avoiding the plants he was allergic to
and treating any flare ups with appropriate
medication as and when necessary. Linseed
oil supplementation can also be useful in
managing allergic skin disease. His condition
has greatly improved and he no longer has to
suffer the debilitating symptoms that previously
made his life so miserable.
Figure 1. Allergic skin disease with
resultant self trauma causing hair loss
and skin infection.
Figure 2. Intradermal skin testing
Figure 3. Nearby pine trees in bloom
releasing pollen