A veterinarian presented with a cat that is scratching and biting at her skin and losing hair, is weak, has developed raised red skin bumps and is showing evidence of flea feces and/or eggs in her coat, will quickly recognize the classic signs of flea infestation. He will conduct a thorough physical examination to look for adult fleas and to take samples of flea feces, which look like pepper, and/or eggs, which look like salt. Usually, flea infestation is easily diagnosed based on the cat’s history and results of the initial physical examination. Depending on the severity of the cat’s symptoms, further diagnostic procedures may be appropriate, especially to figure out whether the kitty is actually allergic to flea saliva.
If there is visible evidence of flea feces in a cat’s coat, it can easily be collected by brushing or combing it onto a damp paper towel. Flea fecal matter looks like black pepper particles and is little more than digested blood. It will turn a reddish brown when smudged onto a wet paper towel. Observance of adult fleas meandering around on a cat’s skin and through its fur is of course one of the best ways to diagnose a flea problem.
Itchy cats can be tested to determine whether they are allergic to flea saliva (this is called “flea bite hypersensitivity”). Unfortunately, skin allergy tests are not especially reliable for flea allergies in cats, especially if the tests turn out to be negative. The veterinarian will try to rule out other causes of itchy skin (pruritus) to diagnose flea bite hypersensitivity. A fecal examination can be done to determine whether the cat has Dipylidium caninum tapeworms. These internal parasites can be transferred from infected fleas to the cats and other animals that they feed upon, when the host ingests the fleas during grooming, biting or chewing episodes.
Usually, the most effective way to definitively diagnose flea infestation in cats is to find adult fleas or evidence of flea fecal matter on the cat’s skin or in its fur. Another good way to diagnose a flea problem is to observe a cat’s response to flea eradication efforts. In other words, if topical or oral flea treatments are used in the affected cat and all other household pets, combined with well thought out environmental flea management protocols, and if the cat’s symptoms go away, it almost certainly had a flea burden to begin with.