Ear diseases of the dog and cat. Case studies

to the veterinary surgeon. Although the animal is generally not seriously ill, these conditions are very troublesome and insidious if not treated and managed properly.

This book contains a selection of case studies covering most forms of otitis diagnosed in dogs and cats, including details of the anatomy, aetiopathogenesis, clinical features, tests, and

Pilar Sagredo Rodríguez

Problems involving otitis may be responsible for 20 % of visits

local and systemic treatments relevant to each case.

Ear diseases• Case studies

Ear diseases of the dog and cat Case studies Pilar Sagredo Rodríguez

2

EAR DISEASES OF THE DOG AND CAT

Otitis media can occur with or without rupture of the tympanic membrane. During ear examination, this membrane looks shiny, pearly grey in colour and translucent when in good health, but it can sometimes appear inflamed or deformed, or even show the formation of pseudo-adhesions, which alter its permeability.

The aetiopathogenesis of otitis externa involves primary precipitating causes, as well as predisposing factors and perpetuating factors that encourage it to become chronic.

The following are primary causes of otitis: Atopic dermatitis: This is the most common cause of OE in the dog, but is uncommon in the cat, where it tends to affect only the pinna and the periauricular area. Sometimes OE is the only manifestation of atopic dermatitis (Fig. 1).

Food allergy dermatitis: This is sometimes the cause of unilateral erythematoceruminous OE (Fig. 2).

Flea-bite allergy dermatitis (FAD): This is a much less common cause but should be borne in mind, either on its own or in combination with another allergic condition.

Irritative contact dermatitis.

Pyotraumatic dermatitis: On the pinnae and in the periauricular area.

Foreign bodies: Grass awns are a common aetiology in late spring and early summer.

Mites: Mainly Otodectes cynotis (more common in young animals and those

12

AETIOPATHOGENESIS OF OE

from communal settings such as shelters, breeding establishments or pet shops). The symptoms may be directly caused by presence of the mite or may be due to a hypersensitivity reaction. This parasite can migrate out of the ear to skin elsewhere on the animal. Much less often, other mites may be found, such as: Demodex (in both dogs and cats), Neo­ trombicula autumnalis, Sarcoptes and Notoedres.

Ticks: These can induce hypersensitivity reactions (Fig. 3).

Flies: From a direct bite or because of hypersensitivity reactions. Seasonal dermatitis of the pinna occurs in the form of a papulocrustous reaction with punctate ulcers.

Keratinisation disorders: These cause chronic ceruminous otitis because of impaired keratinocyte production, excessive scaling or a defective epithelial barrier (mainly due to hypothyroidism, but also possible in ovarian imbalance and Sertoli cell tumours) (Fig. 4).

Glandular disorders: Sebaceous or ceruminous gland hyperplasia.

Pathogenic bacteria: E. coli, Pseu­ domonas spp.

Juvenile cellulitis.

Autoimmune diseases: Pemphigus, lupus. In pemphigus foliaceus, pustules and crusts develop on the pinna.

Neoplasms.

Viral diseases: Immunosuppression-associated OE.

Figure 1. Atopic dermatitis: highly intense erythema on the pinna.

Figure 2. Food allergy: intense erythema, crusts and excoriations on the pinna of a 3‑year‑old, mixed‑breed dog.

Figure 3. Ticks on the pinna of a mixed‑breed dog with a free‑roaming rural lifestyle.

13

2

EAR DISEASES OF THE DOG AND CAT

Otitis media can occur with or without rupture of the tympanic membrane. During ear examination, this membrane looks shiny, pearly grey in colour and translucent when in good health, but it can sometimes appear inflamed or deformed, or even show the formation of pseudo-adhesions, which alter its permeability.

The aetiopathogenesis of otitis externa involves primary precipitating causes, as well as predisposing factors and perpetuating factors that encourage it to become chronic.

The following are primary causes of otitis: Atopic dermatitis: This is the most common cause of OE in the dog, but is uncommon in the cat, where it tends to affect only the pinna and the periauricular area. Sometimes OE is the only manifestation of atopic dermatitis (Fig. 1).

Food allergy dermatitis: This is sometimes the cause of unilateral erythematoceruminous OE (Fig. 2).

Flea-bite allergy dermatitis (FAD): This is a much less common cause but should be borne in mind, either on its own or in combination with another allergic condition.

Irritative contact dermatitis.

Pyotraumatic dermatitis: On the pinnae and in the periauricular area.

Foreign bodies: Grass awns are a common aetiology in late spring and early summer.

Mites: Mainly Otodectes cynotis (more common in young animals and those

12

AETIOPATHOGENESIS OF OE

from communal settings such as shelters, breeding establishments or pet shops). The symptoms may be directly caused by presence of the mite or may be due to a hypersensitivity reaction. This parasite can migrate out of the ear to skin elsewhere on the animal. Much less often, other mites may be found, such as: Demodex (in both dogs and cats), Neo­ trombicula autumnalis, Sarcoptes and Notoedres.

Ticks: These can induce hypersensitivity reactions (Fig. 3).

Flies: From a direct bite or because of hypersensitivity reactions. Seasonal dermatitis of the pinna occurs in the form of a papulocrustous reaction with punctate ulcers.

Keratinisation disorders: These cause chronic ceruminous otitis because of impaired keratinocyte production, excessive scaling or a defective epithelial barrier (mainly due to hypothyroidism, but also possible in ovarian imbalance and Sertoli cell tumours) (Fig. 4).

Glandular disorders: Sebaceous or ceruminous gland hyperplasia.

Pathogenic bacteria: E. coli, Pseu­ domonas spp.

Juvenile cellulitis.

Autoimmune diseases: Pemphigus, lupus. In pemphigus foliaceus, pustules and crusts develop on the pinna.

Neoplasms.

Viral diseases: Immunosuppression-associated OE.

Figure 1. Atopic dermatitis: highly intense erythema on the pinna.

Figure 2. Food allergy: intense erythema, crusts and excoriations on the pinna of a 3‑year‑old, mixed‑breed dog.

Figure 3. Ticks on the pinna of a mixed‑breed dog with a free‑roaming rural lifestyle.

13

2

EAR DISEASES OF THE DOG AND CAT

AETIOPATHOGENESIS OF OE

Predisposing factors include:

Figure 4. Seborrhoeic otitis in a Shih Tzu bitch with ovarian imbalance.

Breeds with narrow ear canals: Chow Chow, Shar Pei. Auricular hypertrichosis: Bichon, Poodle, Shih Tzu (Fig. 5).

Previous episodes of otitis, causing stenosis.

Seborrhoeic conditions: German Shepherd.

Breeds with pendulous ears: Cocker Spaniel, Basset Hound.

Excess moisture: Dogs that swim, damp climates.

Polyps: In cats, nasopharyngeal polyps.

Ceruminous gland neoplasms.

A long, narrow horizontal canal: German Shepherd.

Apocrine cysts: In dogs.

Apocrine cystadenomatosis: In cats.

Poor care: Baths without protecting the EEC, over-zealous cleaning of the EEC with cotton buds or similar.

Perpetuating or secondary factors include:

Figure 5. Obstruction of the canal by knotted hair.

Photograph courtesy of Dr Ana Ríos.

14

Secondary infections by bacteria and/or yeasts: The most commonly isolated bacteria are Staphylococcus intermedius, Streptococcus, Proteus spp., E. coli, Klebsiella and Pseudomonas spp. Ulcers and a yellowish-white exudate are common with Gramnegatives. The most important yeast is Malassezia pachydermatis. Overgrowth tends to be found in cases of allergy, damp environments, and after antibiotic treatment.

Otitis media: Inflammation of the tympanic bulla can cause recurrent OE with an apparently healthy eardrum.

Pathological changes to the external ear: Closure of folds and accumulation of scales and secretions, causing a reversal of epithelial migration.

Drug reactions: Reactions to neomycin are the most common; gentamicin and vehicles such as propylene glycol are less commonly involved.

15

2

EAR DISEASES OF THE DOG AND CAT

AETIOPATHOGENESIS OF OE

Predisposing factors include:

Figure 4. Seborrhoeic otitis in a Shih Tzu bitch with ovarian imbalance.

Breeds with narrow ear canals: Chow Chow, Shar Pei. Auricular hypertrichosis: Bichon, Poodle, Shih Tzu (Fig. 5).

Previous episodes of otitis, causing stenosis.

Seborrhoeic conditions: German Shepherd.

Breeds with pendulous ears: Cocker Spaniel, Basset Hound.

Excess moisture: Dogs that swim, damp climates.

Polyps: In cats, nasopharyngeal polyps.

Ceruminous gland neoplasms.

A long, narrow horizontal canal: German Shepherd.

Apocrine cysts: In dogs.

Apocrine cystadenomatosis: In cats.

Poor care: Baths without protecting the EEC, over-zealous cleaning of the EEC with cotton buds or similar.

Perpetuating or secondary factors include:

Figure 5. Obstruction of the canal by knotted hair.

Photograph courtesy of Dr Ana Ríos.

14

Secondary infections by bacteria and/or yeasts: The most commonly isolated bacteria are Staphylococcus intermedius, Streptococcus, Proteus spp., E. coli, Klebsiella and Pseudomonas spp. Ulcers and a yellowish-white exudate are common with Gramnegatives. The most important yeast is Malassezia pachydermatis. Overgrowth tends to be found in cases of allergy, damp environments, and after antibiotic treatment.

Otitis media: Inflammation of the tympanic bulla can cause recurrent OE with an apparently healthy eardrum.

Pathological changes to the external ear: Closure of folds and accumulation of scales and secretions, causing a reversal of epithelial migration.

Drug reactions: Reactions to neomycin are the most common; gentamicin and vehicles such as propylene glycol are less commonly involved.

15

3

EAR DISEASES OF THE DOG AND CAT

General clinical and dermatological examination A full general clinical examination must then be carried out to determine whether the animal is in good health. This is followed by a thorough dermatological examination to see whether or not there are any skin lesions elsewhere on the animal’s body, noting

CLINICAL ASPECTS OF OTITIS

primary and secondary lesions and their distribution.

Otoscopic examination includes: Checking the healthy ear (in cases of unilateral otitis).

Examining the affected ear(s) with the aid of a veterinary otoscope.

Before otoscopic examination begins, it may be apparent whether the animal tilts its head, or has any neurological abnormality suggestive of otitis media. Gently palpating the external ear canal may reveal whether there is any pruritus, pain or hypertrophy, as well as the presence and amount of exudate. The existence of any hearing deficit should also be assessed.

Otoscopic examination

Figure 1. Five-year-old male cat with a food allergy. Intense pruritus. Self-inflicted lesions on the pinnae.

Figure 2. Dermatophytosis: scaly lesions on the pinna of a young cat from a shelter.

20

During this examination, the pinna and external canal may exhibit changes that can guide diagnosis: Primary and secondary dermatological lesions: Such as hyperplasia (chronic conditions), erythema (allergic conditions) or keratoseborrhoeic lesions (Fig. 3).

Material resembling coffee grounds: Otodectes cynotis otoacariasis (the pedal pinna reflex is almost always present in these cases).

Moist brown exudate: Bacteria (cocci) and/or yeasts (Malassezia).

Purulent yellowish exudate: Gram-negative bacteria.

Greasy yellow to greyish-brown content: Ceruminous otitis.

Cheesy greyish exudate and rancid odour: Malassezia.

Abnormal odour.

Presence or absence of ulcers.

Presence or absence of nodular lesions.

Presence or absence of foreign bodies (grass awns).

Appearance of the tympanic membrane.

Spring/summer sees the flowering of a grass distributed all over Europe, the flower spikes of which are the “awns” often removed from dogs’ ears. Its Latin name is Hordeum murinum, and it has various common names: wall barley, false barley, mouse barley, etc. The most important property of these awns is that their cells expand and contract with changes in environmental humidity, which means they can move of their own accord, and because of their shape, they always move forwards.

Sometimes it will be necessary to clean or flush the external canal before conducting a good otoscopic examination. This occurs when: There is very marked stenosis of the external canal.

The tympanic membrane cannot be seen in cases of severe and/or recurrent otitis and otitis media is suspected.

21

3

EAR DISEASES OF THE DOG AND CAT

General clinical and dermatological examination A full general clinical examination must then be carried out to determine whether the animal is in good health. This is followed by a thorough dermatological examination to see whether or not there are any skin lesions elsewhere on the animal’s body, noting

CLINICAL ASPECTS OF OTITIS

primary and secondary lesions and their distribution.

Otoscopic examination includes: Checking the healthy ear (in cases of unilateral otitis).

Examining the affected ear(s) with the aid of a veterinary otoscope.

Before otoscopic examination begins, it may be apparent whether the animal tilts its head, or has any neurological abnormality suggestive of otitis media. Gently palpating the external ear canal may reveal whether there is any pruritus, pain or hypertrophy, as well as the presence and amount of exudate. The existence of any hearing deficit should also be assessed.

Otoscopic examination

Figure 1. Five-year-old male cat with a food allergy. Intense pruritus. Self-inflicted lesions on the pinnae.

Figure 2. Dermatophytosis: scaly lesions on the pinna of a young cat from a shelter.

20

During this examination, the pinna and external canal may exhibit changes that can guide diagnosis: Primary and secondary dermatological lesions: Such as hyperplasia (chronic conditions), erythema (allergic conditions) or keratoseborrhoeic lesions (Fig. 3).

Material resembling coffee grounds: Otodectes cynotis otoacariasis (the pedal pinna reflex is almost always present in these cases).

Moist brown exudate: Bacteria (cocci) and/or yeasts (Malassezia).

Purulent yellowish exudate: Gram-negative bacteria.

Greasy yellow to greyish-brown content: Ceruminous otitis.

Cheesy greyish exudate and rancid odour: Malassezia.

Abnormal odour.

Presence or absence of ulcers.

Presence or absence of nodular lesions.

Presence or absence of foreign bodies (grass awns).

Appearance of the tympanic membrane.

Spring/summer sees the flowering of a grass distributed all over Europe, the flower spikes of which are the “awns” often removed from dogs’ ears. Its Latin name is Hordeum murinum, and it has various common names: wall barley, false barley, mouse barley, etc. The most important property of these awns is that their cells expand and contract with changes in environmental humidity, which means they can move of their own accord, and because of their shape, they always move forwards.

Sometimes it will be necessary to clean or flush the external canal before conducting a good otoscopic examination. This occurs when: There is very marked stenosis of the external canal.

The tympanic membrane cannot be seen in cases of severe and/or recurrent otitis and otitis media is suspected.

21

3

EAR DISEASES OF THE DOG AND CAT

CLINICAL ASPECTS OF OTITIS

Figure 3. Leishmaniosis: Keratoseborrhoeic lesion on the pinna of a 2-year-old Brittany dog.

Otitis media is suspected when: There is chronic, suppurative otitis externa, with or without rupture of the tympanic membrane.

The tympanic membrane is seen to be thickened, and is discoloured or opaque.

The tympanic membrane is missing and there are visible contents in the bulla.

The animal tilts its head because of vestibular disease.

The animal shakes its head, has a hearing deficit, and is lethargic and in pain.

The facial or sympathetic nerves that pass alongside the middle ear are affected. The palpebral reflex is diminished. Horner’s syndrome.

There is keratoconjunctivitis sicca because of the involvement of parasympathetic branches.

22

In extreme cases, otitis externa can lead to otitis media and develop into otitis interna involving the cochlea, vestibule and semicircular canals. The signs that may be encountered on examination are as follows: The animal tilts its head.

There is horizontal or rotatory nystagmus.

The animal remains standing but has asymmetrical ataxia.

Vomiting in acute stages, the animal walks in circles and falls over.

Direct microscopic examination includes looking for parasites (eggs, larvae and adults of Otodectes cynotis and Demodex canis or cati). If sarcoptic mange is suspected several scrapings should be taken from areas of the pinnae bearing lesions (it has been shown that this is where the probability of finding the mite is highest) (Fig. 4).

Cytological examination of the exudate may reveal yeasts (mainly Malassezia pachydermatis), cocci (especially Staphylococcus intermedius) and bacilli (most often Pseudomonas aeruginosa). In cases of suppurative otitis externa the presence of neutrophils is observed.

In both suppurative chronic otitis and severe recurrent otitis, an exudate sample should be sent to the laboratory for bacteriological and mycological examination. The

antibiotics included in antibiotic sensitivity tests should be those that prove effective against bacteria commonly diagnosed in otitis. This information is particularly important for using a systemic antibiotic, but is less critical for application of a topical treatment (antibiotic concentrations used in topical treatments are much higher than those employed in the in-vitro laboratory test).

In suspected cases of otitis media radiographs should be taken of the tympanic bulla, and a myringotomy should be performed in order to inspect the appearance of the bulla.

If the tympanic membrane is ruptured or a myringotomy has been performed, a sample should be obtained with a sterile swab for culture and antibiotic sensitivity tests (bacteriology and mycology), and the bulla should then be flushed.

Other tests After the otoscopic examination has been performed, samples should be taken for mycology and/or bacteriology. This should always be done with the aid of a sterile swab.

If the animal is uncooperative, it should be tranquillised for this procedure.

Figure 4. Siberian Husky puppy purchased from a pet shop with sarcoptic mange.

Scaly lesions on the pinna.

23

3

EAR DISEASES OF THE DOG AND CAT

CLINICAL ASPECTS OF OTITIS

Figure 3. Leishmaniosis: Keratoseborrhoeic lesion on the pinna of a 2-year-old Brittany dog.

Otitis media is suspected when: There is chronic, suppurative otitis externa, with or without rupture of the tympanic membrane.

The tympanic membrane is seen to be thickened, and is discoloured or opaque.

The tympanic membrane is missing and there are visible contents in the bulla.

The animal tilts its head because of vestibular disease.

The animal shakes its head, has a hearing deficit, and is lethargic and in pain.

The facial or sympathetic nerves that pass alongside the middle ear are affected. The palpebral reflex is diminished. Horner’s syndrome.

There is keratoconjunctivitis sicca because of the involvement of parasympathetic branches.

22

In extreme cases, otitis externa can lead to otitis media and develop into otitis interna involving the cochlea, vestibule and semicircular canals. The signs that may be encountered on examination are as follows: The animal tilts its head.

There is horizontal or rotatory nystagmus.

The animal remains standing but has asymmetrical ataxia.

Vomiting in acute stages, the animal walks in circles and falls over.

Direct microscopic examination includes looking for parasites (eggs, larvae and adults of Otodectes cynotis and Demodex canis or cati). If sarcoptic mange is suspected several scrapings should be taken from areas of the pinnae bearing lesions (it has been shown that this is where the probability of finding the mite is highest) (Fig. 4).

Cytological examination of the exudate may reveal yeasts (mainly Malassezia pachydermatis), cocci (especially Staphylococcus intermedius) and bacilli (most often Pseudomonas aeruginosa). In cases of suppurative otitis externa the presence of neutrophils is observed.

In both suppurative chronic otitis and severe recurrent otitis, an exudate sample should be sent to the laboratory for bacteriological and mycological examination. The

antibiotics included in antibiotic sensitivity tests should be those that prove effective against bacteria commonly diagnosed in otitis. This information is particularly important for using a systemic antibiotic, but is less critical for application of a topical treatment (antibiotic concentrations used in topical treatments are much higher than those employed in the in-vitro laboratory test).

In suspected cases of otitis media radiographs should be taken of the tympanic bulla, and a myringotomy should be performed in order to inspect the appearance of the bulla.

If the tympanic membrane is ruptured or a myringotomy has been performed, a sample should be obtained with a sterile swab for culture and antibiotic sensitivity tests (bacteriology and mycology), and the bulla should then be flushed.

Other tests After the otoscopic examination has been performed, samples should be taken for mycology and/or bacteriology. This should always be done with the aid of a sterile swab.

If the animal is uncooperative, it should be tranquillised for this procedure.

Figure 4. Siberian Husky puppy purchased from a pet shop with sarcoptic mange.

Scaly lesions on the pinna.

23

4

EAR DISEASES OF THE DOG AND CAT

TAKING SAMPLES

Figure 1. Taking samples by scraping the ear margin.

Sampling with adhesive tape This technique can be used when Cheyletiella, Neotrombicula or Notoedres is suspected, or to confirm the presence of flea excrement.

The material collected is placed on a slide and observed under the microscope.

Taking a cerumen sample This is done when Otodectes cynotis infesta­ tion is suspected, and always before cleaning the external canal. The sample is taken with a moistened cotton bud and spread onto

28

Figure 2. Taking a sample with a swab.

a slide (Figs. 2 and 3). The cotton bud is used to distribute the sample evenly, and a cover slip is added for observation under the microscope.

Cytology Ear cytology is a quick, easy method for diag­ nosing and treating otitis. During microscopic examination the micro­organisms present can be identified. This not only allows the correct diagnosis to be made, but also ena­ bles the treatment response to be assessed.

Figure 3. Spreading the sample obtained with a damp cotton bud onto the microscope slide.

29

4

EAR DISEASES OF THE DOG AND CAT

TAKING SAMPLES

Figure 1. Taking samples by scraping the ear margin.

Sampling with adhesive tape This technique can be used when Cheyletiella, Neotrombicula or Notoedres is suspected, or to confirm the presence of flea excrement.

The material collected is placed on a slide and observed under the microscope.

Taking a cerumen sample This is done when Otodectes cynotis infesta­ tion is suspected, and always before cleaning the external canal. The sample is taken with a moistened cotton bud and spread onto

28

Figure 2. Taking a sample with a swab.

a slide (Figs. 2 and 3). The cotton bud is used to distribute the sample evenly, and a cover slip is added for observation under the microscope.

Cytology Ear cytology is a quick, easy method for diag­ nosing and treating otitis. During microscopic examination the micro­organisms present can be identified. This not only allows the correct diagnosis to be made, but also ena­ bles the treatment response to be assessed.

Figure 3. Spreading the sample obtained with a damp cotton bud onto the microscope slide.

29

4

EAR DISEASES OF THE DOG AND CAT

Samples from the external ear canal should be taken with a cotton bud first moistened in physiological saline, and always before cleaning the external canal. The cotton bud should be gently rotated onto a slide to depo­ sit a small amount of the material collected.

If the sample looks purulent it is left to air dry, but if greasy or ceruminous it should be dried with a gentle heat source, e.g. a hair dryer. It is then stained.

Staining the sample The most widely used stains are May­Grün­ wald/Giemsa and rapid stains such as modi­ fied Wright’s stain (Diff­Quick). Diff­Quick stain has the advantage of being easy to use. The sample should be dipped 5 to 10 times into each solution, starting with the fixative solu­ tion, followed by Solution 1 (eosin) and Solu­ tion 2 (methylene blue). It is then washed with water and left to air dry or dried with gentle heat. It is advisable to wear gloves to avoid staining the hands.

During microscopic examination it is best to start at low magnification, choose an area displaying plenty of purple­coloured material, and then switch to higher magnification. An examination should also be done at ×1000 with immersion oil to look for cells and micro­ organisms. In order to obtain an image of the highest quality, a drop of mineral oil or immer­ sion oil is placed over the stain and the cover slip is put in place.

30

TAKING SAMPLES

Interpreting the results In order to identify inflammatory cells (mainly neutrophils and macrophages) it is advisable to use the ×400 objective. For viewing coc­ ci, bacilli and yeasts, the ×2000 objective is used with immersion oil.

It is important not to confuse cocci with melanin granules. The former always appear round, purple in colour, and all very similar in size, whereas the latter are black, brown or yellow (Figs. 4 and 5).

It is a good idea to examine the cytology of healthy ears, in order to gain experience and learn to tell the difference easily be­ tween healthy and abnormal ears. Cytologi­ cal specimens from healthy ears often display large, polygonal cells containing no nucleus (keratinocytes, Fig. 6).

In cases of bacterial otitis, degenerate neutrophils are visible, with intracellular and extracellular cocci, mainly Staphylococcus intermedius.

Bacterial overgrowth can sometimes be seen, with large numbers of cocci but no in­ flammatory reaction.

In cases of bacterial otitis caused by Pseudomonas spp. large numbers of degenerate neutrophils and intracellular and extracellular bacilli are observed. In these cases, culture and antibiotic sensitivity tests are indicated, in order to confirm/rule out Pseudomonas aeruginosa (Fig. 7).

Figure 4. Keratinocytes with melanin granules (×1000).

Photograph courtesy of Dr Jaume Altimira (Histovet).

Figure 5. Keratinocyte with bacteria (cocci) (×1000).

Photograph courtesy of Dr Jaume Altimira (Histovet).

Figure 6. Normal keratinocytes (×1000). Photograph courtesy of Dr Jaume Altimira (Histovet).

In cases of Malassezia pachydermatis oti­ tis, which are very common and sometimes occur in combination with Staphylococcus intermedius, yeasts can be seen in the shape of a “footprint” or “peanut” (Fig. 8). Malassezia otitis is a common finding in patients with

atopic dermatitis. The exudate has a cerumi­ nous appearance and gives off a characte­ ristic odour.

If a fungal infection is suspected, it is advi­ sable to perform a fungal culture with identifi­ cation of macroconidia.

31

4

EAR DISEASES OF THE DOG AND CAT

Samples from the external ear canal should be taken with a cotton bud first moistened in physiological saline, and always before cleaning the external canal. The cotton bud should be gently rotated onto a slide to depo­ sit a small amount of the material collected.

If the sample looks purulent it is left to air dry, but if greasy or ceruminous it should be dried with a gentle heat source, e.g. a hair dryer. It is then stained.

Staining the sample The most widely used stains are May­Grün­ wald/Giemsa and rapid stains such as modi­ fied Wright’s stain (Diff­Quick). Diff­Quick stain has the advantage of being easy to use. The sample should be dipped 5 to 10 times into each solution, starting with the fixative solu­ tion, followed by Solution 1 (eosin) and Solu­ tion 2 (methylene blue). It is then washed with water and left to air dry or dried with gentle heat. It is advisable to wear gloves to avoid staining the hands.

During microscopic examination it is best to start at low magnification, choose an area displaying plenty of purple­coloured material, and then switch to higher magnification. An examination should also be done at ×1000 with immersion oil to look for cells and micro­ organisms. In order to obtain an image of the highest quality, a drop of mineral oil or immer­ sion oil is placed over the stain and the cover slip is put in place.

30

TAKING SAMPLES

Interpreting the results In order to identify inflammatory cells (mainly neutrophils and macrophages) it is advisable to use the ×400 objective. For viewing coc­ ci, bacilli and yeasts, the ×2000 objective is used with immersion oil.

It is important not to confuse cocci with melanin granules. The former always appear round, purple in colour, and all very similar in size, whereas the latter are black, brown or yellow (Figs. 4 and 5).

It is a good idea to examine the cytology of healthy ears, in order to gain experience and learn to tell the difference easily be­ tween healthy and abnormal ears. Cytologi­ cal specimens from healthy ears often display large, polygonal cells containing no nucleus (keratinocytes, Fig. 6).

In cases of bacterial otitis, degenerate neutrophils are visible, with intracellular and extracellular cocci, mainly Staphylococcus intermedius.

Bacterial overgrowth can sometimes be seen, with large numbers of cocci but no in­ flammatory reaction.

In cases of bacterial otitis caused by Pseudomonas spp. large numbers of degenerate neutrophils and intracellular and extracellular bacilli are observed. In these cases, culture and antibiotic sensitivity tests are indicated, in order to confirm/rule out Pseudomonas aeruginosa (Fig. 7).

Figure 4. Keratinocytes with melanin granules (×1000).

Photograph courtesy of Dr Jaume Altimira (Histovet).

Figure 5. Keratinocyte with bacteria (cocci) (×1000).

Photograph courtesy of Dr Jaume Altimira (Histovet).

Figure 6. Normal keratinocytes (×1000). Photograph courtesy of Dr Jaume Altimira (Histovet).

In cases of Malassezia pachydermatis oti­ tis, which are very common and sometimes occur in combination with Staphylococcus intermedius, yeasts can be seen in the shape of a “footprint” or “peanut” (Fig. 8). Malassezia otitis is a common finding in patients with

atopic dermatitis. The exudate has a cerumi­ nous appearance and gives off a characte­ ristic odour.

If a fungal infection is suspected, it is advi­ sable to perform a fungal culture with identifi­ cation of macroconidia.

31

5

EAR DISEASES OF THE DOG AND CAT

Systemic treatments 1. Micro-environment modifiers:

Glucocorticoids, prednisone/prednisolone: 1-2 mg/kg/day. Reduce inflammation and exudate, which encourages a response to topical treatment.

Ciclosporin: 5 mg/kg/day. Especially indicated in chronic otitis with severe stenosis of the canal.

TREATMENTS

2. Antibiotics: The antibiotics listed are those usually employed in otitis media. It is always advisable for antibiotics to be administered according to the results of sensitivity tests.

Sulfadiazine/trimethoprim: 25 mg/kg q12h. Do not use in dehydrated animals, kidney disease or pregnant females. Do not use by the oral route in cats.

Clindamycin: 10 mg/kg q12h, p.o. For use in dogs and cats.

Cefalexin: 22 mg/kg q12h, p.o. For use in dogs and cats.

Enrofloxacin: 5-10 mg/kg q12h, p.o. (dogs); 5 mg/kg q24h, p.o. (cats). Do not use in growing animals, pregnant or lactating females, or kidney disease.

Marbofloxacin: 2 mg/kg q24h, in dogs and cats (i.v., s.c., p.o.).

Tobramycin: 2-4 mg/kg q8-24h, in dogs and cats (i.v., i.m., s.c.). Dosing every 24 hours is considered more effective.

Gentamicin: 5-10 mg/kg q24h, in dogs and cats (i.v., i.m., s.c.). Nephrotoxic and ototoxic. Do not use in dehydrated animals.

Ticarcillin: 40-100 mg/kg q4-6h, in dogs and cats (i.v., i.m.).

3. Antifungals:

Ketoconazole: 10 mg/kg q12-24h, for 4 weeks. Another option is to treat at a dose of 5 mg/kg q24h for 10 days and then switch to alternate days for a further 10 days. Do not use in pregnant females.

May cause a rise in liver enzymes.

Itraconazole: 5 mg/kg/day, alternate weeks.

4. Acaricides:

Ivermectin: 300 µg/kg/week, for 3 weeks. Do not use in breeds with mutations in the MDR1 gene.

Selamectin spot-on: One pipette every 3 weeks.

Owner’s instruction sheet The owner plays a key role in ensuring good progress and cure in cases of otitis in dogs and cats. He or she therefore needs to be educated appropriately. A good method is

to provide a printed sheet of instructions explaining the right way to administer treatments prescribed by the veterinary surgeon.

Date: Case No.: Animal’s Name: Owner’s Name: Applying your animal’s ear treatment properly is extremely important.

External ear canal:

Vertical part

Horizontal part

The external ear canal in dogs and cats is not straight like in humans, but Lshaped or elbow-shaped. The first part of this canal runs vertically, whereas the second part runs horizontally and ends at the eardrum.

What To Do

Eardrum

Pull the pinna (ear) upwards with one hand to straighten the second part of the external ear canal into a vertical posit ion as far as possible. Then, insert the prescribed treatment (drops or ointm ent) and, without letting go of the ear, mas sage vigorously with the thumb of the other hand along the entire course of the external ear canal. It is very important to perfo rm the massage before the animal shakes its ears, so that the medication applied spreads right along the canal.

Recommended Treatment Apply Come back for a check-up on

40

,

time(s) daily daily. .

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EAR DISEASES OF THE DOG AND CAT

Systemic treatments 1. Micro-environment modifiers:

Glucocorticoids, prednisone/prednisolone: 1-2 mg/kg/day. Reduce inflammation and exudate, which encourages a response to topical treatment.

Ciclosporin: 5 mg/kg/day. Especially indicated in chronic otitis with severe stenosis of the canal.

TREATMENTS

2. Antibiotics: The antibiotics listed are those usually employed in otitis media. It is always advisable for antibiotics to be administered according to the results of sensitivity tests.

Sulfadiazine/trimethoprim: 25 mg/kg q12h. Do not use in dehydrated animals, kidney disease or pregnant females. Do not use by the oral route in cats.

Clindamycin: 10 mg/kg q12h, p.o. For use in dogs and cats.

Cefalexin: 22 mg/kg q12h, p.o. For use in dogs and cats.

Enrofloxacin: 5-10 mg/kg q12h, p.o. (dogs); 5 mg/kg q24h, p.o. (cats). Do not use in growing animals, pregnant or lactating females, or kidney disease.

Marbofloxacin: 2 mg/kg q24h, in dogs and cats (i.v., s.c., p.o.).

Tobramycin: 2-4 mg/kg q8-24h, in dogs and cats (i.v., i.m., s.c.). Dosing every 24 hours is considered more effective.

Gentamicin: 5-10 mg/kg q24h, in dogs and cats (i.v., i.m., s.c.). Nephrotoxic and ototoxic. Do not use in dehydrated animals.

Ticarcillin: 40-100 mg/kg q4-6h, in dogs and cats (i.v., i.m.).

3. Antifungals:

Ketoconazole: 10 mg/kg q12-24h, for 4 weeks. Another option is to treat at a dose of 5 mg/kg q24h for 10 days and then switch to alternate days for a further 10 days. Do not use in pregnant females.

May cause a rise in liver enzymes.

Itraconazole: 5 mg/kg/day, alternate weeks.

4. Acaricides:

Ivermectin: 300 µg/kg/week, for 3 weeks. Do not use in breeds with mutations in the MDR1 gene.

Selamectin spot-on: One pipette every 3 weeks.

Owner’s instruction sheet The owner plays a key role in ensuring good progress and cure in cases of otitis in dogs and cats. He or she therefore needs to be educated appropriately. A good method is

to provide a printed sheet of instructions explaining the right way to administer treatments prescribed by the veterinary surgeon.

Date: Case No.: Animal’s Name: Owner’s Name: Applying your animal’s ear treatment properly is extremely important.

External ear canal:

Vertical part

Horizontal part

The external ear canal in dogs and cats is not straight like in humans, but Lshaped or elbow-shaped. The first part of this canal runs vertically, whereas the second part runs horizontally and ends at the eardrum.

What To Do

Eardrum

Pull the pinna (ear) upwards with one hand to straighten the second part of the external ear canal into a vertical posit ion as far as possible. Then, insert the prescribed treatment (drops or ointm ent) and, without letting go of the ear, mas sage vigorously with the thumb of the other hand along the entire course of the external ear canal. It is very important to perfo rm the massage before the animal shakes its ears, so that the medication applied spreads right along the canal.

Recommended Treatment Apply Come back for a check-up on

40

,

time(s) daily daily. .

41

6

EAR DISEASES OF THE DOG AND CAT

Pinnal lesions in a cat with seasonal atopic dermatitis PILAR SAGREDO

Pinnal lesions in a cat with seasonal atopic dermatitis

CASE STUDIES

General clinical examination

Differential diagnosis

Examination detected no abnormality.

Based on the animal’s intense pruritus, the main things to consider were allergic condi­ tions (atopic dermatitis, food allergy, FAD) and parasitic diseases (Otodectes, Demodex, Notoedres, Cheyletiella). Diagnoses of parasitic diseases were not the first thought, because the cats living with the patient displayed no

Dermatological clinical examination Lesions present on both pinnae consisted of alopecia, erythema, excoriations and crusts (Fig. 1).

Figure 1. Image of the patient. The cat had pinnal alopecia, erythema and crusts.

Figure 2. Another cat with seasonal atopic dermatitis displaying skin lesions very similar to those seen in this case. Alopecia, erythema, excoriations, crusts and ulcers.

Clinical history A 4-year-old, female, Siamese cat. For the past 2 years, always in the spring months, the animal has had continuous, intense pruritus of the pinnae. When summer arrives, the pruritus disappears and does not recur until spring the next year.

The animal has been treated with injections (probably corticosteroids), which resolve the symptoms for approximately 10 days. It is fed on premium pet food. Internal and external parasite control programmes are correct, and vaccinations are up to date. There is no history of previous disease and, apart from the skin problems, the cat is well. It lives with three other cats of the same breed, which have no skin lesions or pruritus, and no symptoms have been noticed in the people living with it. It lives in a house with a garden in a rural area and has access to the outdoors.

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Figure 3. A 3-year-old Siamese cat with nonseasonal atopic dermatitis.

Facial erythema and intense pruritus.

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6

EAR DISEASES OF THE DOG AND CAT

Pinnal lesions in a cat with seasonal atopic dermatitis PILAR SAGREDO

Pinnal lesions in a cat with seasonal atopic dermatitis

CASE STUDIES

General clinical examination

Differential diagnosis

Examination detected no abnormality.

Based on the animal’s intense pruritus, the main things to consider were allergic condi­ tions (atopic dermatitis, food allergy, FAD) and parasitic diseases (Otodectes, Demodex, Notoedres, Cheyletiella). Diagnoses of parasitic diseases were not the first thought, because the cats living with the patient displayed no

Dermatological clinical examination Lesions present on both pinnae consisted of alopecia, erythema, excoriations and crusts (Fig. 1).

Figure 1. Image of the patient. The cat had pinnal alopecia, erythema and crusts.

Figure 2. Another cat with seasonal atopic dermatitis displaying skin lesions very similar to those seen in this case. Alopecia, erythema, excoriations, crusts and ulcers.

Clinical history A 4-year-old, female, Siamese cat. For the past 2 years, always in the spring months, the animal has had continuous, intense pruritus of the pinnae. When summer arrives, the pruritus disappears and does not recur until spring the next year.

The animal has been treated with injections (probably corticosteroids), which resolve the symptoms for approximately 10 days. It is fed on premium pet food. Internal and external parasite control programmes are correct, and vaccinations are up to date. There is no history of previous disease and, apart from the skin problems, the cat is well. It lives with three other cats of the same breed, which have no skin lesions or pruritus, and no symptoms have been noticed in the people living with it. It lives in a house with a garden in a rural area and has access to the outdoors.

78

Figure 3. A 3-year-old Siamese cat with nonseasonal atopic dermatitis.

Facial erythema and intense pruritus.

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EAR DISEASES OF THE DOG AND CAT

symptoms, the owners had no skin lesions (Cheyletiella), and the lesions seen were not compatible (Notoedres, Cheyletiella).

Further investigations Skin scrapings taken from both pinnae proved negative for mites. Otoscopic inspec­ tion of the external ear canal was negative.

Food allergy was ruled out by confirming that the animal ate exactly the same food all year round. Flea­bite allergy was also ex­ cluded from differential diagnosis, on the basis that the animal was treated correctly against ectoparasites (fipronil pipettes every 3 weeks).

Diagnosis Seasonal atopic dermatitis.

Food allergy-associated bilateral otitis externa in a dog

Treatment The owner was completely opposed to cor­ ticosteroid therapy, so it was recommended starting chlorphenamine treatment at a dose of 1 mg/kg b.i.d., warning him that a treat­ ment trial would be necessary because effi­ cacy is not 100 % in cats.

Progress At the 15­day check­up appointment, the cat still had pruritus and the lesions had not im­ proved. It was recommended discontinuing the above therapy and starting alimemazine treatment at a dose of 0.1 ml s.i.d.

After 15 days of treatment the animal was much better. There was an 80 % reduction in pruritus, as judged by the owner, and the le­ sions looked better (less erythema).

It was recommended continuing alimema­ zine treatment at the prescribed dose until the end of spring.

CASE STUDIES

Food allergy-associated bilateral otitis externa in a dog PILAR SAGREDO

Clinical history

Remarks The absence of mites in the skin scrapings, the negative otoscopic examination of the ex­ ternal ear canal, the age of presentation, and the seasonal onset of the problem pointed to a suspected diagnosis of seasonal atopic dermatitis.

It is possible that this animal may have a food allergy that does not reach the itch threshold, but that when spring arrives, with the addition of outdoor allergens typical of that season (tree, grass or weed pollens), the threshold is reached and symptoms appear.

The same thing could happen with a flea­bite allergy that does not reach the itch thresh­ old until the addition of outdoor allergens.

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A large, 3-year-old, male, black, mixed-breed dog, weighing 28 kg. Approximately a year and a half ago, the animal began to display intense generalised pruritus (according to its owner, it scratches itself a lot on the face, ears, axillae and ventral abdomen). The owner has also noticed hair loss, red skin and pimples. The problem has gradually been getting worse, and is unrelated to the time of year. The animal has had short courses of antibiotic therapy and prednisolone at a dose of 1 mg/kg s.i.d., for several weeks. These treatments helped improve the pruritus and the appearance of the skin, but the animal is still scratching. It is fed on supermarket pet food and kitchen scraps. It is not regularly treated against either internal or external parasites. Vaccinations are up to date. There is no history of previous disease, and the dog is currently normal apart from the skin problems. It lives with two other adult dogs, which have no skin lesions. There are also no skin lesions in the people living with the animal. It lives in the country, and is kept outdoors.

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EAR DISEASES OF THE DOG AND CAT

symptoms, the owners had no skin lesions (Cheyletiella), and the lesions seen were not compatible (Notoedres, Cheyletiella).

Further investigations Skin scrapings taken from both pinnae proved negative for mites. Otoscopic inspec­ tion of the external ear canal was negative.

Food allergy was ruled out by confirming that the animal ate exactly the same food all year round. Flea­bite allergy was also ex­ cluded from differential diagnosis, on the basis that the animal was treated correctly against ectoparasites (fipronil pipettes every 3 weeks).

Diagnosis Seasonal atopic dermatitis.

Food allergy-associated bilateral otitis externa in a dog

Treatment The owner was completely opposed to cor­ ticosteroid therapy, so it was recommended starting chlorphenamine treatment at a dose of 1 mg/kg b.i.d., warning him that a treat­ ment trial would be necessary because effi­ cacy is not 100 % in cats.

Progress At the 15­day check­up appointment, the cat still had pruritus and the lesions had not im­ proved. It was recommended discontinuing the above therapy and starting alimemazine treatment at a dose of 0.1 ml s.i.d.

After 15 days of treatment the animal was much better. There was an 80 % reduction in pruritus, as judged by the owner, and the le­ sions looked better (less erythema).

It was recommended continuing alimema­ zine treatment at the prescribed dose until the end of spring.

CASE STUDIES

Food allergy-associated bilateral otitis externa in a dog PILAR SAGREDO

Clinical history

Remarks The absence of mites in the skin scrapings, the negative otoscopic examination of the ex­ ternal ear canal, the age of presentation, and the seasonal onset of the problem pointed to a suspected diagnosis of seasonal atopic dermatitis.

It is possible that this animal may have a food allergy that does not reach the itch threshold, but that when spring arrives, with the addition of outdoor allergens typical of that season (tree, grass or weed pollens), the threshold is reached and symptoms appear.

The same thing could happen with a flea­bite allergy that does not reach the itch thresh­ old until the addition of outdoor allergens.

80

A large, 3-year-old, male, black, mixed-breed dog, weighing 28 kg. Approximately a year and a half ago, the animal began to display intense generalised pruritus (according to its owner, it scratches itself a lot on the face, ears, axillae and ventral abdomen). The owner has also noticed hair loss, red skin and pimples. The problem has gradually been getting worse, and is unrelated to the time of year. The animal has had short courses of antibiotic therapy and prednisolone at a dose of 1 mg/kg s.i.d., for several weeks. These treatments helped improve the pruritus and the appearance of the skin, but the animal is still scratching. It is fed on supermarket pet food and kitchen scraps. It is not regularly treated against either internal or external parasites. Vaccinations are up to date. There is no history of previous disease, and the dog is currently normal apart from the skin problems. It lives with two other adult dogs, which have no skin lesions. There are also no skin lesions in the people living with the animal. It lives in the country, and is kept outdoors.

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EAR DISEASES OF THE DOG AND CAT

General clinical examination

Further investigations

Progress

Examination detected no abnormality.

The scrapings taken proved negative for Sarcoptes scabiei and Demodex canis.

Cytology of a pustule from the glabrous part of the abdomen revealed degenerate neutrophils with intracellular and extracellular cocci.

Ear cytology detected Malassezia.

Fifteen­day review appointment: The superfi­ cial pyoderma was resolving and there were no new papules or pustules. The pruritus was still very intense. It was recommended continued treatment and another review in 15 days.

Dermatological clinical examination The lesions present were: alopecia, erythe­ ma, papules, pustules, epidermal collarettes, crusts, hyperpigmentation, hyperkeratosis and lichenification. These lesions were found mainly on the face, pinnae, cubital fossae, axillae, interdigital spaces and the entire ven­ tral aspect of the trunk (Figs. 1, 2 and 3).

The pinnae displayed intense erythema and lesions caused by the chronic nature of the condition (hyperkeratosis, lichenification). Otos­ copic inspection revealed bilateral erythemato­ ceruminous otitis.

The pruritus was so intense that the animal scratched itself even on the consulting table.

Differential diagnosis Based on the animal’s highly intense pruritus, the distribution of the lesions, and the pre­ sence of erythemato­ceruminous otitis, the first things to consider were allergic disease (atopic dermatitis, food allergy, FAD) and sar­ coptic mange. Differential diagnosis also had to include pruritic superficial pyoderma, sec­ ondary to demodicosis or otherwise. A diag­ nosis of sarcoptic mange was considered less likely than allergic disease, because the two dogs living with the patient had no pru­ ritus or skin lesions, and nor did the owners.

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Food allergy-associated bilateral otitis externa in a dog

CASE STUDIES

By then, the lesions of superficial pyo­ derma had disappeared, but the pruritus and associated lesions persisted. The ear ery­ thema had subsided greatly. It was continued the oral antibiotic treatment and ear drops for just another 15 days, and the rest of the treatment as before. At the same time, it was

Diagnosis Probable allergic condition (atopic dermatitis, food allergy).

Treatment It was began treatment for the superficial pyoderma with: Cefalexin: 25 mg/kg b.i.d., treatment not to stop until veterinary review in 15 days.

Essential fatty acids: 3 capsules s.i.d. for 2 months.

Twice­weekly baths with antiseptic, anti­ seborrhoeic shampoo, to be massaged into the affected areas, left in contact for 10 minutes, then rinsed, followed by dry­ ing in the sun and/or with towels.

Figure 1. Alopecia, erythema, hyperkeratosis and lichenification around the eyes, on the muzzle and on the pinna.

Figure 2. Generalised lesions: alopecia, erythema and hyperpigmentation.

Figure 3. Marked erythema on the pinnae.

Figure 4. Chronic otitis. Photograph courtesy of Dr Cristeta Fraile.

And for the otitis: Ear cleanser. Both ears cleaned before starting ear­drop treatment.

Gentamicin, betamethasone and clotri­ mazole: 6 drops in each ear canal, twice daily, with vigorous massage after each application.

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6

EAR DISEASES OF THE DOG AND CAT

General clinical examination

Further investigations

Progress

Examination detected no abnormality.

The scrapings taken proved negative for Sarcoptes scabiei and Demodex canis.

Cytology of a pustule from the glabrous part of the abdomen revealed degenerate neutrophils with intracellular and extracellular cocci.

Ear cytology detected Malassezia.

Fifteen­day review appointment: The superfi­ cial pyoderma was resolving and there were no new papules or pustules. The pruritus was still very intense. It was recommended continued treatment and another review in 15 days.

Dermatological clinical examination The lesions present were: alopecia, erythe­ ma, papules, pustules, epidermal collarettes, crusts, hyperpigmentation, hyperkeratosis and lichenification. These lesions were found mainly on the face, pinnae, cubital fossae, axillae, interdigital spaces and the entire ven­ tral aspect of the trunk (Figs. 1, 2 and 3).

The pinnae displayed intense erythema and lesions caused by the chronic nature of the condition (hyperkeratosis, lichenification). Otos­ copic inspection revealed bilateral erythemato­ ceruminous otitis.

The pruritus was so intense that the animal scratched itself even on the consulting table.

Differential diagnosis Based on the animal’s highly intense pruritus, the distribution of the lesions, and the pre­ sence of erythemato­ceruminous otitis, the first things to consider were allergic disease (atopic dermatitis, food allergy, FAD) and sar­ coptic mange. Differential diagnosis also had to include pruritic superficial pyoderma, sec­ ondary to demodicosis or otherwise. A diag­ nosis of sarcoptic mange was considered less likely than allergic disease, because the two dogs living with the patient had no pru­ ritus or skin lesions, and nor did the owners.

82

Food allergy-associated bilateral otitis externa in a dog

CASE STUDIES

By then, the lesions of superficial pyo­ derma had disappeared, but the pruritus and associated lesions persisted. The ear ery­ thema had subsided greatly. It was continued the oral antibiotic treatment and ear drops for just another 15 days, and the rest of the treatment as before. At the same time, it was

Diagnosis Probable allergic condition (atopic dermatitis, food allergy).

Treatment It was began treatment for the superficial pyoderma with: Cefalexin: 25 mg/kg b.i.d., treatment not to stop until veterinary review in 15 days.

Essential fatty acids: 3 capsules s.i.d. for 2 months.

Twice­weekly baths with antiseptic, anti­ seborrhoeic shampoo, to be massaged into the affected areas, left in contact for 10 minutes, then rinsed, followed by dry­ ing in the sun and/or with towels.

Figure 1. Alopecia, erythema, hyperkeratosis and lichenification around the eyes, on the muzzle and on the pinna.

Figure 2. Generalised lesions: alopecia, erythema and hyperpigmentation.

Figure 3. Marked erythema on the pinnae.

Figure 4. Chronic otitis. Photograph courtesy of Dr Cristeta Fraile.

And for the otitis: Ear cleanser. Both ears cleaned before starting ear­drop treatment.

Gentamicin, betamethasone and clotri­ mazole: 6 drops in each ear canal, twice daily, with vigorous massage after each application.

83