CHAPTER | 13 Diseases of Eyes, Claws, Anal Sacs, and Ear Canals
Blepharitis
Features
Insect Bite/Sting Hypersensitivity
Onset of eyelid erythema, with swelling (angioedema) or raised focal masses, is acute.
Diagnosis
2 Cytology (pustule, abscess): suppurative inflammation and bacterial cocci, if primary or secondary bacterial blepharitis is present. Malassezia organisms, if secondary yeast dermatitis is present.
3 Bacterial culture (pustule, abscess): Staphylococcus is usually isolated, if primary or secondary bacterial blepharitis is present.
Treatment and Prognosis
4 Warm water compresses should be applied to affected areas two to three times daily to decrease swelling and remove exudate.
5 If bacterial infection is present, a topical antibiotic-glucocorticoid ophthalmic preparation should be applied to the affected eye every 8 to 12 hours for 2 to 3 weeks. Effective preparations include those containing the following:
6 For bacterial blepharitis, appropriate systemic antibiotics should be administered for at least 3 weeks.
7 For autoimmune blepharitis, treatment with immunosuppressive medications should be provided (Tables 8-1 and 8-2).
8 Symptomatic treatment with topical ophthalmic preparations that contain glucocorticoids or antihistamines may be helpful in cases of allergic blepharitis.
FIGURE 13-1 Blepharitis.
Discoloration and matting of the hair around the eye in a dog with bilateral blepharitis.
FIGURE 13-2 Blepharitis.
Close-up of the dog in Figure 13-1. Discoloration and matting of the hair around the eye caused by the copious ocular discharge are apparent.
FIGURE 13-6 Blepharitis.
Same dog as in Figure 13-5. The “marginal blepharitis” caused a bilateral, alopecic, papular dermatitis.
FIGURE 13-8 Blepharitis.
Same dog as in Figure 13-7. Alopecia, erythema, and tissue swelling of the periocular skin.
(Courtesy S. McLaughlin.)
FIGURE 13-9 Blepharitis.
Alopecia and erythema affecting the periocular skin caused by a secondary bacterial pyoderma.
(Courtesy E. Willis.)
Otitis Externa
Features
Otitis externa is an acute or chronic inflammatory disease of the external ear canal. Its causes are numerous and almost always have an underlying primary disease (Table 13-1) that alters the normal structure and function of the canal, resulting in a secondary infection (Table 13-2). Otitis externa is common in cats and dogs, with Cocker spaniels especially at risk for developing severe and chronic disease.
TABLE 13-1 Primary Causes of Otitis Externa
| Primary Factor | Characteristics | Comments |
|---|---|---|
| Parasites | Otodectes cynotis | Cause approximately 50% of otitis cases in cats and 5% to 10% of otitis in dogs. Dogs and cats can be asymptomatic carriers |
| Demodicosis | Can cause a ceruminous otitis in dogs and cats | |
| Sarcoptes scabiei | Typically, the ear margin and ventral third of the outer ear pinna are affected. Otitis externa is not usually a feature of this disease | |
| Hard ticks, chiggers | May affect ear pinnae and external ear canal | |
| Spinous ear ticks | An uncommon cause of otitis externa in dogs and cats | |
| Hypersensitivities | Atopy | Otitis externa is seen in 50% to 80% of atopic dogs. (In 3%–5% of them, otitis externa is the only symptom.) Usually, bilateral otitis |
| Food hypersensitivity | Otitis externa is seen in up to 80% of dogs with food hypersensitivities. (In more than 20% of these dogs, otitis externa is the only symptom.) | |
| Contact dermatitis | Otic medication (e.g., neomycin, propylene glycol) can cause irritant reactions in the ear. Should be suspected any time ear disease worsens significantly while animal is undergoing topical treatment | |
| Endocrine Disorders | Hypothyroidism | Bilateral ceruminous otitis externa. Most common in middle-aged to older dogs. Usually, skin involvement |
| Foreign Bodies | Usually present as unilateral otitis externa. Look for plant material, dirt, small stones, impacted wax, loose hair, and dried medication. Often, the inciting foreign body is not identified because it becomes so coated with cerumen that, when removed during ear flushing, it is not recognizable | |
| Keratinization Disorders | Canine primary seborrhea | Bilateral ceruminous otitis. Usually have other skin involvement, especially Cocker spaniels |
| Facial dermatosis of Persians | Bilateral ceruminous otitis externa and seborrheic facial dermatitis. Secondary malasseziasis is common. Uncommon to rare in Persian cats | |
| Sebaceous adenitis | May cause dry, scaly ears and mild inflammation. Usually other skin involvement. Rare in dogs, with highest incidence in Standard Poodles, Akitas, and Samoyeds | |
| Autoimmune/Immune-Mediated Diseases | Juvenile cellulitis | Acute cellulitis of muzzle and periocular regions with marked submandibular and prescapular lymphadenomegaly. Exudative otitis externa, fever, and depression may also be present. Uncommon in puppies 3 weeks to 6 months old, with highest incidence in Golden retrievers, Labrador retrievers, Dachshunds, Pointers, and Lhasa apsos |
| Inflammatory Polyps (cats) | May present as recurrent, unilateral otitis externa. Polyps may originate from lining of tympanic cavity, auditory canal, or nasopharynx | |
| Neoplasia | Cats | Ceruminous gland adenomas and adenocarcinomas, sebaceous gland adenomas and carcinomas, squamous cell carcinomas, papillomas |
| Dogs | Ceruminous gland adenomas and adenocarcinomas, papillomas, basal cell carcinomas, squamous cell carcinomas | |
| Conformation | Heavy, pendulous ears | May result in decreased air circulation, increased heat, and moisture |
| Narrow ear canals Retention in the ear canal | Nidus for infection | |
| Hair in ear canals | ||
| Increased glandular tissue |
TABLE 13-2 Secondary Causes of Otitis Externa
| Secondary Factors | Comments |
|---|---|
| Bacterial infection | Include Staphylococcus spp., Streptococcus, Pseudomonas spp., Proteus, and Escherichia coli. Recurrent bacterial otitis is often associated with underlying allergies. |
| Yeast infection | Malassezia pachydermatis. Recurrent yeast otitis is often associated with underlying allergies. |
| Otitis media | Chronic otitis externa (2 months’ duration or longer) often results in extension of the disease into the middle ear. The otitis media can then be a source for recurrent otitis externa. |
| Chronic pathologic changes | With chronic inflammation, the dermis and the subcutis become fibrotic, leading to permanent stenosis of the canal lumen. The auditory cartilage may become calcified and ossified. Secretions, desquamated cells, and proliferating microorganisms become entrapped. Calcified ear cartilage is a permanent change that cannot be resolved with medical therapy. |
Diagnosis
2 Otoscopic examination: assess degree of inflammation, ulceration, stenosis, and proliferative changes; amount and nature of debris and discharge; presence of foreign bodies, ectoparasites, and masses; and integrity of tympanic membrane.
4 Cytology (ear swab): look for bacteria, yeasts, fungal hyphae, cerumen, leukocytes, and neoplastic cells.
5 Bacterial culture (external or middle ear exudate): indicated when bacteria are found on cytology in spite of antibiotic therapy, or when otitis media is suspected.
6 Fungal culture: indicated when dermatophytic otitis is suspected, especially in long-haired cats that have ceruminous otitis.
7 Radiography (bulla series), computed tomography (CT), magnetic resonance imaging (MRI): evidence of bullous involvement (sclerosis, opacification) is seen in approximately 75% of otitis media cases.
Treatment and Prognosis
2 For swimmer’s ear, maceration of ear canals can be prevented by prophylactic instillation of a drying agent after the dog gets wet (swimming, bathing), or two to three times per week in very humid climates. Effective products are ear products that contain astringents/alcohol.
3 For allergic otitis, long-term management includes control of underlying allergies, resolution of any secondary bacterial and yeast otitis, and institution of ear cleaning and treatment every 3 to 7 days to prevent recurrence. In animals whose underlying allergies cannot be identified or completely controlled, judicious use of steroid-containing otic preparations as infrequently as needed may prevent otitis flare-ups.
4 For mild/acute otitis, at home, the owner should perform ear cleaning every 2 to 7 days with a ceruminolytic agent (that does not need to be flushed out) to prevent earwax and debris from accumulating. Lifelong ear cleaning every 3 to 7 days may be necessary to prevent relapses of otitis. The use of cotton swabs (which may damage the epithelium) is not recommended.
5 For severe/chronic otitis, in-hospital ear cleaning and flushing should be performed to remove accumulated exudate and debris from the vertical and horizontal ear canals (under sedation or anesthesia if necessary). The procedure should be repeated every 2 to 7 days until all debris has been removed.
Products that can be used for ear flushing include the following:
6 Systemic glucocorticoids should be administered if the ear is painful or the canal is stenotic from tissue swelling or proliferation. For dogs, prednisone 0.25–0.5 mg/kg PO should be administered every 12 hours for 5 to 10 days. For cats, prednisolone 0.5–1.0 mg/kg PO should be administered every 12 hours for 7 to 14 days.
Individual Diseases
7 For ear mites, affected and all in-contact dogs and cats should be treated. When otic treatments are used, additional treatment to eliminate ectopic mites should be concurrently administered. Effective therapies for ear mites include the following:
Otic miticide as per label directions (ivermectin and milbemycin products are safe and highly effective)
Otic miticide as per label directions (ivermectin and milbemycin products are safe and highly effective)
8 For demodectic otitis, effective therapies for ear mites include the following:
9 For yeast otitis, antifungal-containing ear preparations should be repackaged into a bottle to provide more accurate dosing—dropper bottle, brown amber bottle, etc. Then, 0.2 to 0.5 mL (
dropperful) should be instilled in the affected ear every 12 hours for at least 2 to 4 weeks. Treatment should be continued until follow-up ear smears are cytologically negative for microorganisms, the external canals are no longer edematous or inflamed, and the ear canal epithelium has normalized.
dropperful) should be instilled in the affected ear every 12 hours for at least 2 to 4 weeks. Treatment should be continued until follow-up ear smears are cytologically negative for microorganisms, the external canals are no longer edematous or inflamed, and the ear canal epithelium has normalized.Effective products include the following:
10 For severe refractory yeast otitis externa or otitis media, in addition to topical antifungal treatment, systemic antifungal therapy may be helpful if administered for at least 3 to 4 weeks, then continued 1 to 2 weeks beyond complete clinical cure. Effective therapies include the following:
11 For bacterial otitis, antibiotic-containing ear preparations should be repackaged into bottles to provide more accurate dosing—dropper bottle, brown amber bottle, etc. Then, 0.2 to 0.5 mL (
dropperful) should be instilled in affected ears every 8 to 12 hours for at least 2 to 4 weeks. Treatment should be continued until follow-up ear smears are cytologically negative for microorganisms, the external canals are no longer edematous or inflamed, and the ear canal epithelium has normalized.
dropperful) should be instilled in affected ears every 8 to 12 hours for at least 2 to 4 weeks. Treatment should be continued until follow-up ear smears are cytologically negative for microorganisms, the external canals are no longer edematous or inflamed, and the ear canal epithelium has normalized.Effective products include the following:
12 For bacterial otitis media, systemic antibiotics may not achieve sufficient tissue concentrations to kill Pseudomonas and to prevent antibiotic resistance; the highest possible dose of antibiotic that is safe should be administered with concurrent high-concentration topical therapy of the same antibiotic. If topical treatment has been used aggressively and has been unsuccessful, systemic antibiotics may be indicated, based on culture and sensitivity results, for a minimum of 4 weeks, and continued 2 weeks beyond complete clinical cure.
Antibiotics include the following:
13 For Pseudomonas otitis, aggressive treatment should be provided for at least 2 to 4 weeks, then continued 2 weeks beyond complete clinical cure. All underlying/primary diseases should be identified and addressed. Currently, the most effective treatments include tris–ethylenediaminetetraacetic acid (EDTA) solutions with high concentrations of antibiotics instilled in high volumes (to ensure deep penetration and prevent dilution by exudate). Antibiotics should be selected according to culture and sensitivity results. Systemic antibiotics may not achieve sufficient tissue concentrations (mutation prevention concentration) to kill Pseudomonas and prevent antibiotic resistance. If systemic antibiotics are used, the highest possible dose that is safe should be administered, along with concurrent high-concentration topical therapy of the same antibiotic.
The EDTA solution should be combined with enrofloxacin to make a 10- to 20-mg/mL solution. The solution should be used q 12–24 hours to completely fill the ear canal. Even as the sole therapy, the surfactants in T8 Solution act to clean the ear while allowing the high concentration of enrofloxacin to penetrate into the deep canal. This treatment is 80% effective in chronic, recurrent otitis cases, even if the bacteria are reported to be resistant to enrofloxacin (because of the tris-EDTA and high concentration of antibiotic).
The EDTA solution should be combined with enrofloxacin to make a 10- to 20-mg/mL solution. The solution should be used q 12–24 hours to completely fill the ear canal. Even as the sole therapy, the surfactants in T8 Solution act to clean the ear while allowing the high concentration of enrofloxacin to penetrate into the deep canal. This treatment is 80% effective in chronic, recurrent otitis cases, even if the bacteria are reported to be resistant to enrofloxacin (because of the tris-EDTA and high concentration of antibiotic).
tsp]) of Silvadene Cream with 13.5 mL distilled water, or mix 0.1 g silver sulfadiazine powder with 100 mL distilled water), and instill 0.5 mL q 12 hours
For End-Stage Ears
14 For chronic proliferative otitis, aggressive medical therapy is needed. Weekly ear cleaning should be instituted. For bacterial/yeast otitis externa and media, long-term (minimum, 4 weeks) systemic and topical antibiotics or antifungal medications should be administered and continued beyond complete clinical resolution of the infection. To reduce tissue proliferation, prednisone 0.5 mg/kg PO should be administered every 12 hours for 2 weeks; then followed by 0.5 mg/kg PO every 48 hours for 2 weeks. These ears rarely return to complete normalcy, so long-term maintenance therapy with steroid-containing otic preparations, as described for allergic otitis, is almost always necessary.
