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Cats are frequently presented to the
clinic when their owners notice that the cat is scratching its ears or
there is discharge or an odor from the ear. It is important to
establish the cause of the condition to select the proper therapy. The
primary cause may be ear mites or allergies and these are frequently
complicated by secondary infections. Therapy is based on ear cytology.
Samples of material are collected from the ear canal to identify
parasites, bacteria, yeast, or tumor cells that might be involved.
Blood tests (CBC, Feline leukemia and FIV tests) help identify
systemic causes of ear disease.
Ear disease in cats is different that
that in dogs. Some of the important differences are:
- Cats are much more likely to develop
ototoxicity (head tilt, ataxia, deafness) when topical medications
are used.
-
Cats do not tolerate ear drops well
and inflamed ears are frequently treated with systemic medication.
-
Cat ear canals are shorter than dogs
and more debris is removed by shaking – may not need to be flushed.
-
FIV and Feline Leukemia virus
infections may predispose cats to refractory ear disease.
The most common primary causes of ear
disease are:
-
Ear mites (Otodectes
cynotis) cause almost 50% of feline ear
infections. Revolution® is an excellent therapy for these patients.
Rarely, other mites may be seen. The ear may have secondary
bacterial or yeast infections.
-
Allergies (inhaled
allergens)
a. Usually both ears are involved and frequently they are secondarily
infected with yeasts and/or bacteria.
b. Allergies are a common cause of ear hematomas.
c.
Referral to a veterinary dermatologist for allergy testing and
desensitization will benefit 70% of patients with inhalant allergies.
d. Antihistamines and omega 3 fatty acids may help some patients and
cyclosporine or prednisolone may be needed for others.
1.
Food allergy
a.
Otitis
may be the only sign and some times one ear is more severely affected
due to secondary infection, most commonly with yeast (Malassezia).
b.
The infections must be treated at the beginning of the food trial and
then treatment is gradually stopped as the food trial continues.
c.
The food trial must continue for 8 to 12 weeks.
2.
Idiopathic ceruminous otitis externa
a.
Some cats produce excessive cerumin (wax).
b.
They are predisposed to infections.
c.
May be associated with allergies
3.
Tumors
a.
Most commonly seen in older cats
b.
History usually includes recurrent ear infections in one ear
c.
90% are malignant
d.
Complete diagnostics including blood tests, CT or MRI are needed to
determine prognosis
e.
Treatment is total ear canal removal by a surgical specialist.
4.
Ceruminous
cysts
a.
Cerumin
glands become dilated with fluid and look dark blue
b.
May be found any where in the ear canal
c.
May predispose to ear infections
The clinical signs seen are frequently
the result of secondary factors
1.
Yeast
infections
–malassezia
a.
Secondary to
one of the primary conditions- - may be recurrent
b.
May respond to
topical medication
c.
May need oral
itraconazole 5mg/kg/ day for 2-4 weeks or fluconazole 5mg/kg/day for
2-4wks
2.
Bacterial
infections
a.
Generally
secondary to primary disease.
b.
Antibiotic
treatment is needed.
c.
Treatment needs
to continue for at least two weeks and then a medical progress exam
with ear cytology will help determine the need of additional therapy.
3.
Wax (ceruminoliths)
a.
This debris may
be irritating or the source of infection.
b.
Anesthesia is
frequently needed to safely irrigate an ear to remove large balls of
wax.
c.
Medication to
soften and lubricate the mass may be applied prior to irrigation with
sterile saline.
Ear disease is a common and painful
condition in cats. Appropriate diagnostics and therapy are important
for the comfort of our feline companions.
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