Protocols Based on Findings of the Ear Swab Stain and Physical Examination
Ceruminous Otitis Externa
Otoscopic examination shows that the exudate is mostly on the outer portions of the ear canal. The deeper vertical and horizontal ear canal are affected but there is no ulceration and the eardrum can be visualized. The exudate is golden to brown and creamy in appearance. There seems to be generalized seborrhea (excessive production of flake and scale) or allergic disease affecting the pet’s skin as well.
Ear Swab Stain Findings
The ear swab stain shows normal epithelial cells but no other inflammatory cells such as neutrophils. There are a few yeast cells that are usually attached to the epithelial cells, but their number is less than four per high power field. There are bacteria present but they are cocci (spherical-shaped) and are scattered about.
This ear disease is typical for a pet with an underlying skin problem. Because the ears are lined with skin they are affected as well. The structure of the dog ear is such that excessive wax production accumulates and results in reduced drying to the ear canal. This creates a high moisture environment that can lead to bacterial and yeast infections. These infections are secondary to the wax and moisture. We recommend thyroid tests and allergy tests as needed to find if the seborrhea has and underlying cause that can be managed.
The ears should be flushed to clean the debris and the client is instructed on home flushing and cleaning of the ears.
Medications are used to reduce the inflammation in the ear canals, cause atrophy of the wax-producing glands and to control or prevent infection. This can be accomplished with Liquichlor®, which contains prednisolone to control inflammation, as well as squalene, which is ceruminolytic, and chloramphenicol, which is effective against cocci bacteria.
Discussions should be held with the client informing them that the ear disease described above is most likely the result of a more generalized condition that is affecting the pet. This ear disease can be managed but will reoccur once the management or medications have stopped. These ears tend to eventually have severe infections that are difficult to resolve because of the chronic inflammatory response of the ear canal and resistance to medications that the organisms develop. Therapy should be directed at the underlying skin disease with the preparation for chronic management of the ear problem. Periodic flare-ups are expected even with diligent home care.
A series of re-check examinations are scheduled to adjust the therapy protocol.
Allergic Otitis Externa
The pet presents with a history of shaking the head and scratching the ears. The earflaps are red and inflamed and hot to the touch. They may have a flaky scale, typical of a seborrhea secondary to inflammation. Both ears are equally affected. The otoscopic examination shows that the deep vertical and horizontal canals are normal. The eardrum is intact and has the normal glossy appearance. The pet usually has signs of atopic (allergic) disease on the skin as well. This is most commonly seen as bronzing (color change of the hair coat from saliva) of the feet and rubbing of the face and eyes. Flea allergies are evidenced by loss of hair on the rump and down the back legs.
Ear Swab Stain Findings
The ear swab stain was difficult to acquire because of lack of exudate deep in the ear canal. The material that is in the outer ear canal is therefore stained instead. There are stacks of epithelial cells. A few inflammatory cells are seen as well and rare yeast and cocci bacteria are found. More chronic allergic otitis external cases will have more wax, yeast and bacteria.
A diagnosis of allergic otitis is made with secondary seborrhea.
This pet will need systemic therapy to control the itch reaction. An injection of cortisone followed by administration of oral prednisolone is usually indicated.
Synotic® is usually used for allergic otitis. If the ear has secondary infections, then anti-bacterial or anti-fungal medications are added to the Synotic®.
The client is advised that the ear disease is secondary to the allergic disease. Allergy testing is recommended as well as a blood screen and a thyroid test to identify any underlying cause to this problem.
If exudate is accumulating in the ear canal, then home flushing is recommended and demonstrated to the client.
A re-check examination is scheduled.
The physical examination shows a pet with very itchy ears. The ears are not painful and the ear pinna is usually not affected. When the ear canal is massaged externally the pet leans into your hand indicating that it feels good. The ear canal makes a squishy sound when it is squeezed and massaged. This reaction of the pet indicates that the ear canal is itchy and not very painful, yet has copious exudate. There may be a significant, sweet smelling odor to the ears. This characteristic odor is common in yeast infections. The ear canal is difficult to examine because of the quantity of brown, waxy exudate. The entire ear canal is involved. The eardrum is most likely intact but is difficult to visualize. There are not ulcers in the ear canal and both ears seem to be equally affected. If only one ear is affected, suspect eardrum rupture in this ear.
Ear Swab Stain Findings
The stain shows epithelial cells and large numbers of budding yeast. These yeast cells stain purple or dark blue and are footprint shaped. There are clusters of them on the epithelial cells as well as scattered about the slide. More than five yeasts per high power field indicate active infection. More than twenty indicates moderate infection and too numerous to count indicates a severe infection.
Mild infections can be managed with medications alone. These medications need to have a combination of anti-inflammatory and anti-fungal activity. Most, first-time infections may be managed with Otomax®, Mometamax®, or Panalog®, but moderate or severe infections should be managed more aggressively with a Lotrimin® containing solution. Hydrocortisone with 3 cc Lotrimin® is recommended in these cases. Synotic® with Lotrimin® may be used in pets with allergic otitis and secondary yeast infection.
The ears need to be cleaned prior to therapy. This cleaning may require sedation depending on the nature of the pet and severity of the disease. Most severe or reoccurring infections should be thoroughly cleaned under general anesthesia to allow complete examination of the ear canal and eardrum for underlying causes.
Exposure to water is the most common predisposing cause of yeast infections. These are common in Labrador and golden retrievers. Client education involves proper ear care after swimming or bathing. The proper care involves application of a drying solution to the ears just after swimming or bathing. In dogs with pendulous ears, it is advantageous to keep the earflaps on top of the head while drying. Some clients use soft ponytail holders around both ears during the drying process. “Swimmers ear” drying solutions usually contain alcohol and can be used effectively if there is not ulceration in the ear canal. Ulcerated ears require a more soothing astringent solution such as Epi-Otic®. The client is notified that these conditions are a byproduct of the moist environment in the ear canal and the infection will return periodically despite diligent maintenance at home.
Hyperplastic Otitis Externa
The pet will present with a chronic history of ear disease that may or may not have been managed in the past. There is usually some predisposing cause such as breed predisposition, or chronic exposure to water or chronic seborrhea or allergies. In Hyperplastic Otitis Externa, the ear canal is noticeably thickened and the surface varies from a mild cobblestone appearance to severe deep folds. The exudate is usually creamy tan to whitish and may be thinner in consistency than typical earwax. The ear canals are thick and firm when palpated through the skin. Palpation may elicit a painful reaction form the pet. In severe cases, the pet may have facial nerve paralysis (evidenced by lack of sensation to pinprick of lip or facial skin) and subsequent keratoconjunctivitis sicca (dry eyes from lack of nerve function to the tear glands). These signs indicate severe secondary inflammation, possible bone infection and middle ear disease.
Ear Swab Stain Findings
The appearance of the ear swab stain varies greatly with hyperplastic otitis. This emphasizes the need for these stains to guide therapy. Many clients will not accept the fact that surgery is necessary to control their pet’s disease. They might want to delay the surgery as long as possible. Accurate diagnosis is crucial in formulating medications that will be effective in abating the signs, while not curing the disease. The ear swab stain will contain epithelial cells as well as bacteria. In a few pets with early hyperplastic disease, yeast will be the predominate organism. This type of presentation is uncommon in chronic infections because yeast cannot grow in an acid environment. The hyperplastic conditions favor bacterial colonization and this bacterial growth causes the pH to decrease to a more acid environment causing the yeast infections to disappear. Inflammatory cells are prevalent but not predominant. Bacteria are prevalent usually a mixed population of cocci and rods. Bipolar rods indicate Pasturella spp. infection. Other rods are usually seen that may indicate infections with E.Coli, proteus spp or Pseudomonas spp. Cocci in chains indicate streptococcus and larger cocci in clusters indicate staphylococcus infection.
Medical management is palliative only in this disease. The symptoms can be reduced but not controlled. Pets with this severe disease have usually adapted to the chronic pain and discomfort. They have learned not to shake their head because it is too painful and are “head shy” from chronic medication. Surgery is recommended once hyperplastic otitis is noticed. The degree of the hyperplasia only determines the type surgical procedure not the decision to recommend surgery.
Oral medications will be recommended in all cases because of the reduced effectiveness of topical medications. Topical medications cannot penetrate or coat the redundant folds of tissue that are present in this condition. Oral medications usually include antibiotics such as cephalexin or Baytril®. Corticosteroids may also be used to reduce the inflammatory reaction and make it easier for the client to medicate the ears.
Topical medications should be used aggressively and should be used based on culture and sensitivity results. Initial medications based on the ear swab stain are used while waiting on the culture and sensitivity.
Gram positive infections are treated with Baytril Otic®.
Gram negative infections are treated with hydrocortisone and Baytril® or gentamicin.
Mixed infections are treated with Baytril Otic®.
If yeast is involved, use Mometamax®.
Surgery is always recommended, but ear flushing should be done at a minimum. The ear canal will be very narrow and flushing will require general anesthesia. Examination of the ear canal will reveal the severity of the condition and degree of necessity for surgery. The eardrum is usually not intact if there have been chronic infections for any period of time. The ear canal is frequently lined with nodular cysts created by dilated ceruminous glands.
Surgical correction for mildly affected ears involves lateral ear resection where hyperplastic changes have not occurred to the base of the pinna and secondary middle ear disease is not present. More aggressive surgeries are preformed in an effort to remove all the diseased tissue. These surgeries culminate in total ear removal or ablation. Ablation is the removal of all structure of the ear including opening the tympanic bulla to establish drainage and healing.
The pet is presented with acutely painful ears. The dog cries when someone touches the ears. The pet has a desire to shake his head but does so very slowly because of the pain. Examination of the ear canal shows a red, inflamed ear pinna and canal that is warm to the touch. Ulceration will be present on otoscopic examination. The pet may not allow you to examine these ears without prior sedation. The exudate is thin and yellow – typical of pus. This infection may have appeared to come on very quickly. Predisposing causes are bathing, grooming, swimming or other wet trauma to the ear. Strongly consider foreign object, tumor or ruptured eardrum if only one ear is affected.
Ear Swab Stain Findings
The predominant cell type is the neutrophil, with most of the neutrophils being degenerate (their nucleus is dissolving because of the release of the chemicals that fight the infection). Degenerate neutrophils indicate bacterial presence. The bacteria type is usually cocci but you may also see rods if the infection is recurrent to chronic or cause by contamination from ear cleaning or grooming.
Therapy is initiated by a gentle therapeutic flushing under general anesthesia. This ear canal is very fragile when ulcerated like this. Antibiotics are given systemically as well as topically. This type of infection will also need an anti-inflammatory medication to allow the owner to medicate the ears without undue pain to the pet.
Chronic bacterial otitis occurs due to rupture of the eardrum and is also seen in immunocompromised patients. Cats with feline leukemia or pets with diabetes, cancer or other serious internal dysfunction are prone to these types of infections. Surgical drainage of the ear canal is often recommended in chronic bacterial otitis.
Bacterial infections with Pseudomonas spp are common and can be difficult to control. Pseudomonas bacteria have a slime coating that prevents most antibiotics from gaining access to the cell wall or internal organelles where the antibiotics work. EDTA is a chemical agent that helps antibiotics break through the slime it is used in severe Pseudomonas infections with gentamicin or Baytril®.