Your Handy Guide to Diagnostics in Canine OE

Otitis externa (OE) in canines is one of the most common dermatological complaints presented to the companion animal veterinarian. An accurate diagnosis of OE – including the pathogens causing it – can aid in better treatment and a swifter recovery. Cytology is a crucial step in identifying the causative pathogens. By adding good imaging, sampling, staining and microscopy techniques, we can get a more accurate picture. Neptra is a great choice for the common acute OE pathogens, which can be revealed using best-practice cytology methods.

Imaging 101

Imaging is your first step towards effective treatment of OE cases. Basic ear examinations reveal an abundance of information, enabling you to tell the chronicity of the problem and rule out other possible causes of the ear discomfort. Begin the ear exam by looking at the external ear pinnae and canal opening, checking for erythema, self-trauma or signs of scratching, polyps or discharge. Next, use the otoscope to visualise inside the external ear canal, and establish if the tympanic membrane is intact. Other notable observations are canal stenosis, foreign bodies, ear mites (Otodectes cynotis), and ulceration of the external canal.

Getting a good sample

Obtaining a useful sample is crucial for cytology – all you need is a cotton ear bud, a glass slide, lead pencil, immersion oil, Diff-Quik stain and a microscope. Gently insert the cotton bud into the vertical ear canal to the junction to the horizontal ear canal and rotate the cotton bud to retrieve your sample. Some handy tips: label your slide in advance, start with the less affected ear, and roll the cotton bud onto the slide rather than sliding it.

No stain, no gain

Following a standard Diff-Quik staining procedure is best for evaluating ear smear cytology. A handy tip to avoid damaging the sample during rinsing is to only expose the underside of the slide to the running water. Keeping separate staining pots for ear slides also reduces the need to replace stains due to contamination with ear debris. Alternatively, source individual pipette bottles for each stain and apply stain using the pipette.

Under the microscope

A microscopic examination of your sample reveals a lot about how to proceed with OE treatment – here are three key things to look out for. Inflammatory cells or neutrophils indicate the strength of anti-inflammatory needed. The type (cocci or rods), number and intracellular status of bacteria determine necessary antibiotics. Finally, the presence of yeasts and their number tells you what anti-fungal to use. You will be able to identify the typical ‘peanut-shaped’ Malassezia yeast organisms at 40x magnification, however bacteria can only be identified under the 100x lens. Remember that when changing magnification lenses the light needs to be gradually increased, but the condenser and diaphragm should remain untouched.

A trusted treatment

Seeking a trusted and efficient treatment for OE? Neptra^TM is a fantastic comprehensive option. As the only single dose vet-administered ear treatment available on the market, it eliminates stress and non-compliance on the part of pet parents – so it’s easy, effective and proven safe¹.

References

1. Claro FOI study, NADA141-440, 2015. Always read and follow label recommendations. Neptra is not recommended in cases with rod-shaped bacteria present on cytology sample, as these may represent gram negative Pseudomonas aeruginosa. This product should NOT be used in dogs with perforated/ruptured tympanic membranes. Culture and sensitivity testing should be performed when appropriate to determine susceptibility of the causative organism(s). Empirical therapy may be instituted before susceptibility results are known, however once results become available, the antimicrobial treatment should be adjusted accordingly. Not for use in cats. © 2022 Elanco or its affiliates.

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