Health Guide: Otitis Media, Otitis Interna / Labyrinthitis

Otitis Media, Otitis Interna / Labyrinthitis

Definition

Ot=ear + itis=inflammation.
Otitis media=inflammation of the middle ear.
Otitis interna/Labyrinthitis=means inflammation of the inner ear and structures.

Clinical Signs

Head tilted or rotated to side, rubbing head against floor of cage, scratching at ear, poor balancing, and circling.

May have foul or sweet smelling drainage from ear in more advanced infections.

May involve facial nerve paralysis, blinking of eye, or enophthalmos (recession of eye) on the side affected.

Signs and symptoms of an external otitis may also be present.

Etiology

Inflammation of the middle and inner ear, known as otitis media and otitis interna, respectively, is often associated with upper or lower respiratory infections, or in some instances may be an extension of an external otitis (inflammation of the outer ear).

Otitis media and interna often develop when bacteria, such as Mycoplasma pulmonis, Streptobacillus moniliformis, or Psuedomonas aeruginosa, and viruses, travel from the naso-pharynx through the eustachian tubes, to involve the lining of the ear. As the infection progresses to involve the labyrinth structure of the inner ear inflammation to the vestibular nerve, and swelling of the surrounding tissues, results in “torticollis” or a tilting of the head. This tilting is most often directed towards the side of the affected ear. It is sometimes referred to as “Head Tilt,” or “Wry Neck” (a neuro-muscular response seen primarily in rabbits).

In most cases, when treated promptly with systemic antibiotics to combat infection, as well as a corticosteroid to reduce the swelling of tissue, the head tilt will disappear in a matter of days. However, it is not unusual in some cases for the head tilt to remain throughout the rat’s life. This permanent “tilt” does not seem to pose a significant problem for rats, as they are able to adjust to it very quickly. Where left untreated, the condition could worsen resulting in the loss of balance for the rat, rolling rather than being able to stand or walk, and the inability to feed or care for itself.

It is important to note that there are other conditions that can result in “head tilt” besides infections of the ear, such as, brain injuries (e.g. strokes), pituitary tumors, or trauma. Any disease process which can cause obstruction or inflammation of the inner ear can lead to head tilt.

A final note, when attempting to resolve otitis media or interna, the underlying cause should be determined and treated if possible.

Case histories and photo examples of head tilt resulting from inflammation in the inner ear have been provided in the following figures.

Fig. 1: Widget’s inner ear infection and resulting head tilt.
Fig. 2: Photos of head tilt due to a variety of causes.
Fig. 3 M�ski’s inner ear infection and resulting head tilt.
Fig. 4a: Inner ear infection as a result of ulcerated, abscessed, squamous cell lesion. Includes link to cleaning of wound and supplies used.

Diagnostics

Obtain history to determine underlying cause.

Assess rat’s balance. Head will often be tilted towards side of affected ear.

Visualization with otoscope may show discoloration, bulging, or rupture of the tympanic membrane. Fluid or exudate/pus may be present in the tympanic cavity. A foul or sweet smell may indicate the presence of bacteria or yeast.

If possible obtain exudate for culture and sensitivity.

Treatment

Refer to the Rat Medication Guide, for medication information and dosages.

For Topical Treatment

If exudate is present and tympanic membrane intact, an ear wash such as Epiotic, OtiClens, OtiRinse, or warmed normal saline (preservative-free sterile saline for contact lenses may be used, or for a saline solution at home mix 1 teaspoon of salt in 1 pint of warm water) may be used to flush ear.
If an acetic acid is required in the solution the following may be used: Otic Clear, Otocetic, or AloCetic.

*Note: If planning to use an aminoglycoside, it is necessary to cleanse or remove exudate since drugs in this group are inactivated in the presence of pus.

Be sure to dry ear before applying cream or ointment.

Topical agents are varied and use may be based on the organism(s) or condition being treated.
Some of those that one may see the Vet select are topical otic antibiotics or antifungals that may include a steroid such as: Treasaderm (containing neomycin sulfate, thiabendazole, and dexamethasone), or Gentocin Otic (containing gentamicin sulfate, and betamethasone valerate), or topical otics that may require an addition of a systemic or topical steroid such as: Baytril Otic (enrofloxacin/silver sulfadiazine) primarily used for gram neg. infection, or Silver sulfadiazine (Silvadene).

In addition an agent such as Tris-EDTA may be instilled in the ear canal prior to the use of topical otic antibiotics to enhance their activity.

For Systemic Treatment:

Begin long term systemic therapy for 3-6 weeks, with broad spectrum antibiotics such as enrofloxacin, doxycycline , amoxicillin , chloramphenicol, or azithromycin.
If combination antimicrobial therapy is required, the following may be used:
enrofloxacin and doxycycline
enrofloxacin and amoxicillin
enrofloxacin and chloramphenicol
azithromycin and doxycycline

In addition, systemic corticosteroids such as prednisone may be given. Corticosteroids along with a systemic antibiotic should be started as soon as clinical signs of the illness first begin. Doing so can help to decrease the chance of the head tilt becoming permanent.

*Note: The use of a corticosteroid either topically or systemically can aid in reducing exudate and tissue growth as well as relieve itching. Its use may predispose to yeast infections; however, the benefit in many cases with rats far outweighs the risk. If yeast is present or of concern, the Vet may choose to include a topical or systemic antifungal medication (already included in some topical medications) such as ketoconazole or metronidazole.

Nursing Care

When cleaning ear of debris, or to soak up any drainage, a wick may be fashioned of cotton balls or absorbant towels. Care should be taken if using Q-tips in order to prevent abrasions to the tissue in the ear, and the packing of wax or debris against the ear drum.

Give medications for the length of time prescribed. When administering topical agents: instill medicine, gently hold ear closed, and massage ear canal 30 to 60 seconds to ensure dispersion of medication.

Maintain clean cage environment.

Maintain safe environment, particularly if head tilt is severe.

Keep food and water within easy access to rat.

Provide high calorie foods (e.g., avocado), or food supplements such as Nutri-Cal Paste, canned Ensure, Soy or soy formula, along with a multi-vitamin and mineral supplement (can be found in pet store) if weight loss or food intake is poor.

Observe and contact vet if infection does not resolve or if worsens, or if there is decreased appetite and or significant weight loss.

Outcomes

Infection and inflammation resolved.

Underlying conditions determined and treated.

Head tilt minimized.

Prevention

Treat any respiratory illnesses promptly.

Treat underlying diseases as appropriate to reduce tilting.

Posted on June 25, 2003, 09:28, Last updated on October 12, 2006, 14:13 | Auricle / Ear