What’s in an Ear?
An ear smear is a diagnostic tool used to determine if a pet has an ear infection and what kind of infection that might be. It is important to know what the cause of an infection is to determine the best treatment without causing any more harm to the ear or wasting time with a treatment plan that does not work. With dogs, we most often see yeast or bacterial infections. Whereas cats often present with symptoms caused by ear mites; they can also have bacterial or yeast infections.
Obtaining a sample
To accomplish an ear smear, a technician will obtain a sample from each ear with a cotton swab. A lot of pets have no reaction to this, but for some the ears can be raw and overly sensitive, and they might not tolerate it very well. Here we can use distraction to help make the experience less traumatic for the pet by giving treats, praising the animal, or petting them to divert attention away from the ears. The technician will then bring the samples to the laboratory to prepare them for cytology.
Preparing the slide for Cytology
The technician will transfer the samples to a microscope slide, making sure to keep the sample from each ear separate. A lighter will then be used to heat fix the cells to the slide. This is done to help prevent the cells from washing off when staining the slide. We stain the cells by gently dipping the slide multiple times; first in a fixative, which again helps make sure the cells stay on the slide, followed by a red colored stain, and then a blue colored stain. We then rinse the slide very gently with distilled water, making sure to only let water hit the top of the slide with no sample on it, and run down over the rest of the slide, rinsing off any excess stain. Then preferably the slide should air dry to minimize disruption of the cells. The slide can also be dried with a small fan or shaken dry to speed up the process.
Microscopy and Diagnosis
Once the slide is dry, it is placed under a microscope where the technician will examine the entire slide on 10x magnification, then 40x magnification, and lastly 100x magnification using immersion oil. The technician will then write their findings in your pet’s journal and let the veterinarian know what was found, so the veterinarian can diagnose and treat the problem accordingly.
A mite check is another diagnostic tool, most often performed on young kittens or stray cats, to check for the presence of ear mites and ear mite eggs. Samples are collected from both ears using cotton swabs. The sample material is then transferred to a microscope slide and mixed with a small amount of mineral oil. This is done to spread out the debris and make spotting the ear mites and eggs easier. A technician will then examine the entire slide on 4x or 10x magnification. If ear mites are present, they can often be seen in all stages of life and moving around between the debris.
Article written by: Sara