Equine Disease Quarterly | EQUINE
autoimmune disease.
management is needed to best control clinical
disease.
In all cases of pruritic dermatitis, managerial
procedures to decrease exposure to exciting agents
as well as symptomatic therapy to reduce pruritus is
warranted. In IBH procedures to decrease exposure to
insects should be fully implemented. Farm sanitation
to compost manure properly, eliminate wet areas with
decomposing vegetation, and the use of fly predators
or feed through fly inhibitors can greatly reduce
fly populations. Heat, humidity, and solar radiation
exacerbate pruritus, thus the provision of shade and
wind currents by fans provide relief. Stabling to avoid
the most significant insects (Table 1) and the use
of fly sheets and face masks are helpful. Because
some horses develop contact allergies to topical
products, judicious and cautious use of fly repellants
is advisable. Simple feeds and whole grains are better
than mixed, multiple-grain sweet feeds. Cool-water
rinses and shampoos can rehydrate and sooth dry
skin as well as reduce the amount of allergens on the
skin. Colloidal oatmeal, pramoxine, and 1 percent
hydrocortisone shampoos or leave-on hydrocortisone
rinses may reduce pruritus and minimize or reduce
the amount of systemic antipruritic medication
needed. Systemic medications (steroids and
antihistamines) may help interrupt the itch-scratch
cycle, however long term use, particularly of
steroids, should be avoided. A complete and detailed
investigation into the etiology of the disease should
occur simultaneously with general symptomatic
care. Intradermal skin testing to determine antigens
for allergen specific immunotherapy may be helpful,
particularly in young animals with atopy. Clients
should understand that hypersensitivities and atopy
are lifelong. Affected horses will need continuous
management and/or therapy. Often a patient may be
symptom-free with low exposure to inciting antigens
and symptomatic as the antigen load increases.
Antigen exposure is additive, thus comprehensive
CONTACT: Susan L. White, DVM, MS, DACVIM, [email protected],
(706) 296-8607, Department of Large Animal Medicine, College of
Veterinary Medicine, University of Georgia Athens, GA
Theiler’s Disease
Theiler’s disease, or equine serum hepatitis, is an
infrequent but sometimes life-threatening liver disease
of adult horses. Sir Arnold Theiler first described the
disease in the early 1900s as a form of highly fatal
acute liver failure that occurred 4-12 weeks after
administration of equine antiserum, which was used
as part of a vaccination strategy for African Horse
Sickness. Since then, many additional cases of serum
hepatitis have been reported, and a variety of blood
products of equine origin have been associated with
the disease. In North America, the majority of recent
cases have been associated with the administration
of tetanus antitoxin, although commercial plasma
products also have been incriminated. The number of
horses that become ill following administration of a
specific lot of incriminated blood product is estimated
at 1 to 2 percent, although more horses might have
sub-clinical disease. An infectious agent, such as a
virus, has long been suspected to cause this condition,
and a new equine parvovirus was recently discovered
in a horse with a fatal case of serum hepatitis. The
parvovirus was present in the diseased horse and in
the biologic product that it had received nine weeks
earlier. Inoculation of experimental horses with the
commercial product resulted in transmission of this
newly discovered virus and in liver disease. Variation
in individual immune responses to the virus could
explain the low percentage of clinically affected
horses.
An identical disease, both in terms of clinical signs
• Volume 20 Issue 3 | October 2018 •
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