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Aural Abscesses

BASICS

DEFINITION/OVERVIEW

Aural abscesses are a common presentation of captive chelonians. They can be sterile but the majority are associated with bacteria, usually of digestive origin. May be observed in turtles suffering from subclinical hypovitaminosis A.

ETIOLOGY/PATHOPHYSIOLOGY

Otitis in chelonians is often due to secondary infections as result of squamous metaplasia from hypovitaminosis A leading to blockage of the auditory ducts causing lack of drainage.

Poor husbandry conditions and trauma may also be contributing factors.

Otitis caused by nematodes (due to internal duct migration) has also been described in Testudo graeca.

In box turtles, (Terrapene carolina), a possible correlation between the occurrence of otitis and environmental levels of organochlorine pesticides acting as immunosuppressive agents has been suggested, but the link is not definitively proven.

SIGNALMENT/HISTORY

Aural abscesses are observed almost exclusively in chelonians, with more frequent occurrences in American species (Trachemys sp., Graptemys sp., Pseudemys sp., Terrapene sp.) followed by European species (Testudo sp.).

There are some cases in saurians, but they are much less frequent.

Primarily seen in captive animals or wild‐caught animals that have been kept as pets and fed an inadequate diet.

CLINICAL PRESENTATION

Animals present with unilateral or bilateral swellings of the tympanic membrane.

These swellings can cause severe external and internal deformations of the era canal.

The swelling may start with a soft consistency but quickly becomes firm to hard as the material becomes caseous.

In extreme cases, abscesses can progress towards the inside of the skull and affect internal structures (brain, mandibular base, etc.).

Some animals may also present with conjunctivitis, blepharedema, nasal discharge, and overgrown beak and nails.

Some of these signs may suggest a concurrent respiratory infection.

RISK FACTORS

Husbandry

Poor hygiene and inappropriate diet (low in vitamin A) are the main contributing factors.

Others

Exposure of animals to toxins such as organochlorines, which inhibit the synthesis of vitamin A, or have an immunosuppressive effect must also be considered.

DIAGNOSIS

DIFFERENTIAL DIAGNOSIS

Nutritional secondary hyperparathyroidism

Neoplasia

Parasites

Upper respiratory tract disease

DIAGNOSTICS

Cytology

A cytological imprint or aspiration of the abscess helps in determining whether bacteria and/or fungi are involved.

Microbiology

Culture and sensitivity of the abscess material is recommended for proper identification of the bacteria involved (usually Staphylococcus, Streptococcus or Pseudomonas) and to ensure a proper antibiotic was selected.

Imaging

In cases with perceived skull deformities or non‐responsive to therapy, radiographs or CT are recommended to determine whether osteolytic changes are present.

Histology

If the material extracted from the site does not have the appearance of an abscess or is closely attached to the bone, it should be submitted for histopathological evaluation to rule out neoplasia.

PATHOLOGICAL FINDINGS

Lesions of the tympanic epithelium include hyperplasia, squamous metaplasia, hyperemia, cellular sloughing, granulomatous inflammation, and bacterial infection.

Histopathologic changes in turtles with aural abscesses are consistent with a syndrome involving hypovitaminosis A.

TREATMENT

APPROPRIATE HEALTH CARE

Aural abscesses require a dual approach of surgical debridement and medical therapy.

Ophthalmic antibiotic drops may be instilled in the canal for local therapy in addition to the use of systemic antibiotics.

The use of ointments should be reserved for the period when all the material can be easily flushed out of the canal.

Some may elect to administer vitamin A (5,000–10,000 iu IM as a single dose), but this should be reserved for the most severe cases, as hypervitaminosis A from parenteral administration is a concern.

NUTRITIONAL SUPPORT

Natural sources of vitamin A in the diet (herbivorous—parsley, carrot, tomato, spirulina; carnivorous—liver, fish, eggs).

CLIENT EDUCATION/HUSBANDRY RECOMMENDATIONS

Ensure a proper balanced diet for the species and consider oral vitamin A supplementation at a rate of 2–8 iu/g of feed.

Improve hygiene to decrease bacterial load in the water/enclosure.

Avoid fights or scratches among animals housed together.

SURGICAL CONSIDERATIONS

The debridement must be performed with the animal under sedation or anesthesia with proper analgesia (NSAIDs and opioids, local block, etc.).

The tympanic membrane can then be incised either in a vertical or horizontal manner.

A horizontal incision on the ventral aspect of the membrane may allow for better drainage postoperatively.

The tympanic membrane is usually edematous and vascularized leading to appreciable bleeding upon incision.

If excessive bleeding occurs, topical hemostatics (silver nitrate) may be used.

Once an opening is made, the caseous material must be removed in its entirety via manual manipulation and flushing.

Chelonian ears have an inverted L shape, which means that there is often a dorsocaudal pocket that harbors more material.

A cotton‐tip applicator can be placed on the dorsocaudal aspect of the head/ear followed by applying pressure in a cranioventral direction, to help expel the material.

Forceps are also helpful to remove excess material.

It is not uncommon to remove a volume of material two to three times the size of the external swelling.

Once the material is removed, the ear canal can be flushed with a disinfectant solution (iodine, chlorhexidine, etc.) and saline.

The membrane is left open to heal by secondary intention.

The ear canal can continue to be flushed once to twice daily until it closes.

MEDICATIONS

DRUG(S) OF CHOICE

Antibiotics: broad‐spectrum antibiotics (fluoroquinolones, cephalosporins) until resolution of clinical signs.

Preventive vitamin A is recommended at 1000–2000 iu/kg every 7 days, but is best done by dietary supplementation at 2–8 iu/g of feed) to avoid overdosing.

PRECAUTIONS/INTERACTIONS

With preventive vitamin A it is advisable to use a minimum dose.

Overdosage of oily vitamin A causes exostosis, hepatomegaly, and skin lesions.

FOLLOW‐UP

PATIENT MONITORING

A thorough physical examination will confirm the healing of the tympanic membrane.

It usually takes between 2 and 4 weeks.

If vitamin A has been provided, no further relapses are expected.

EXPECTED COURSE AND PROGNOSIS

Generally carries a good prognosis.

Balance is not usually affected, although cases may be observed depending on the degree of injury to the inner ear.

MISCELLANEOUS

COMMENTS

Recent research suggests that 6 months of exposure to selected organochlorine compounds (chlordane, aroclor, lindane), or similar duration of reduced dietary vitamin A concentrations, did not influence the formation of squamous metaplasia and aural abscesses in red‐eared sliders (Trachemys scripta).

Although the etiopathogenesis of otitis is known, there are probably more factors involved in the onset of this disease.

ZOONOTIC POTENTIAL

N/A

SYNONYMS

Otic abscess

Otitis

ABBREVIATIONS

IM = Intramuscular

NSAIDs = nonsteroidal anti‐inflammatory drugs

INTERNET RESOURCES

Center for Avian and Exotic Medicine. Aural Abscesses in Aquatic Turtles. http://avianandexoticvets.com/aural‐abscesses‐in‐aquatic‐turtles

Kik, M JL. Adenovirus infection in reptiles. EAZWV Transmissible Disease Fact Sheet, sheet no. 2, April 2009. https://www.eazwv.org/page/inf_handbook

PetMD Editorial. Ear Infections in Turtles and Tortoises. PetMD July 24, 2008. http://www.petmd.com/reptile/conditions/ears/c_rp_ear_infections