Ear problems are one of the most common health problems seen in dogs and cats and ear infections are the most common ear problem diagnosed. However, before ear infections can be treated, the source of the infection needs to be determined.
Determining the Source of Canine and Feline Ear Infections
Once an ear infection has been diagnosed, the most valuable test to determine the source of the infection is known as ear cytology. Performing ear cytology involves using a swab to obtain a sample of the debris in the infected ear. Once the sample is obtained, it is placed on a microscope slide and distributed evenly across the slide and then treated with special stains, each of which adheres to specific types of cells, organisms and/or parts of cells. The slide is then examined under a microscope under a high power, magnified by 10-40 times initially and then magnified by a higher factor, usually 100.
Ear Cytology Aids in Diagnosing the Source of Ear Infections in Dogs and Cats
Ear cytology can be used to determine the individual cell types which make up the debris found in the infected ear of the dog or cat. Organisms which contribute to infection of the ear canal are readily identified on ear cytology and may include:
- bacteria
- yeast
- parasites
Other cells frequently seen on ear cytology include neutrophils, which are a type of white blood cell which is often present in active infections and epithelial cells, which often slough from the lining of the ear canal.
Bacteria and Their Role in Canine and Feline Ear Infections
Bacteria are commonly found on ear cytology and can often be found in small numbers even in normal ears. When present in moderate to large numbers, bacteria are usually considered to be pathogenic (causing disease), especially if the pet is also exhibiting symptoms of an ear infection.
Bacteria seen on ear cytology slides are classified as rods or cocci, depending on the shape of the bacterial organism. They are further characterized as gram positive or gram negative, depending on which stains adhere to the bacterial organisms.
Yeast Infections in the Ear of the Dog and Cat
The most common yeast organism found in the ears of dogs and cats is known as Malassezia. Malassezia is seen as a club shaped organism on ear cytology slides and is easily recognized. Normal dog and cat ears may contain a few Malassezia organisms without being abnormal. In larger numbers, this yeast is pathogenic and is a frequent cause of ear problems.
Parasites in Canine and Feline Ear Problems
Ear mites are by far the most common type of parasite seen infecting the cat ear. Dogs can also be infested with ear mites, although ear mites are less common in dogs than in cats. Ear mites are insects which are large in comparison to bacteria and yeast and are easily seen on ear cytology studies.
Naturally, ear cytology must be performed by a veterinarian or veterinary staff and is usually performed once a diagnosis of ear infection is reached and other causes of ear problems in dogs and cats, such as foreign objects, have been ruled out.
The results of the ear cytology study must be evaluated in light of the clinical signs that the pet is experiencing. For instance, small numbers of bacteria or yeast in the canine or feline ear of a pet with no evidence of clinical disease may be insignificant. However, the same results in a dog or cat who is experiencing symptoms characteristic of ear infections may be more significant.
Ear cytology is the most commonly used diagnostic tool in determining the source of infection within the canine or feline ear. Properly performed, ear cytology can help direct treatment of an ear infection for the dog or cat and can also help evaluate whether treatment has been effective in alleviating the infection for the affected dog or cat.
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