We are searching data for your request:
Upon completion, a link will appear to access the found materials.
Pictures of miliary dermatitis in cat. Image courtesy of Cat Health Network.
By Susan Kowalik, DVM, Dipl. ACVS
The use of the term “dermatitis” does not cover a variety of conditions that occur in the skin of cats. These skin diseases are different in appearance, cause and course, but the word is often used interchangeably. Although they all cause itchy, inflamed skin and sometimes hair loss, the most common cause is fleas, flea bites and/or flea-derived materials.
The following pages provide a broad-based overview of the clinical characteristics of these skin diseases. They are by no means complete or even exhaustive, but the information that follows will give you a foundation for recognizing, diagnosing and treating these skin diseases in your clients.
Dermatitis is defined as the term applied to any inflammation of the skin or hair and is divided into two basic categories: allergic dermatitis and infectious dermatitis.
Allergic dermatitis, which is more common in cats than in dogs, is triggered by contact with an allergen. The term allergy is defined as a disorder in which the body’s immune system makes antibodies against substances or cells in the body that are normally harmless. Once an allergen is introduced into the body (e.g., by contact with dust, food, a drug or another animal), the immune system produces an antibody against it (antigen-antibody reaction).
Allergic dermatitis is more common in indoor-housed cats, but in cats with outdoor access, allergies are more likely to occur when fleas are prevalent in the cat’s environment.
It’s been estimated that up to 70 percent of all cats are sensitive to fleas, and 10 to 20 percent of indoor-housed cats develop allergies to their fleas. There are many ways fleas can affect cats, including irritation of the skin or respiratory tract, causing coughs, sneezing and nasal discharge. The skin of cats is very thin, and fleas, when they bite and feed, leave behind a feeding tract that may contain a combination of their saliva and the saliva of their host. It’s thought that this mixture of flea and cat saliva is the basis for the allergenic reactions that occur.
Flea allergy dermatitis occurs when a cat’s immune system begins to make antibodies against the flea saliva, but only the saliva of cat fleas, so most cat owners will recognize the dermatitis as a type of flea allergy that is limited to cat fleas.
There are two main types of allergic dermatitis, called flea allergy dermatitis (FAD) and flea dermatitis (FD).
Flea allergy dermatitis occurs in cats that are bitten by fleas that are infected with a bacterium called Bartonella henselae. The bacterium is found only in cat fleas, not in dog fleas or fleas of other species. In fact, cat fleas are unique in that they don’t have to bite dogs and other cats to survive. B. henselae bacteria that live in cat fleas cause a serious disorder of the body that can affect the heart, brain, spleen, liver and kidneys.
The first stage of FAD is usually a few days after the cat flea bite. The cat flea’s saliva, containing the bacteria, is usually the cause. Symptoms include itching, especially over the tail, belly and legs, and sometimes over the eyes and ears. These symptoms can lead to scratching, which can then be followed by bald patches on the skin.
In the second stage, cats begin to experience a worsening of the symptoms, including more scratching and increased hair loss. In addition, some cats develop a severe pruritic skin disease. The third stage is called chronic stage and is characterized by persistent pruritus, alopecia, and pruritic skin lesions, usually on the tail, belly and legs. This can be quite painful and can lead to more hair loss. In the last stage, the cat begins to experience weight loss.
The cat is affected only when it is infected by fleas with the bacteria, so if your cat has been exposed to fleas but has not yet been infected, it will not have FAD. Even if your cat is infected with the bacteria, FAD cannot be passed from cat to cat, so if you have two cats in the household, only one can develop FAD. If both are infected, they will have similar symptoms that usually appear one to three weeks after the initial infection. If one is infected with the bacteria, it may take up to a year for the symptoms to appear.
Because cats with FAD often lose hair, they may appear “toddlerish,” which is why it is often difficult for owners to tell the difference between a cat with FAD and one with a hair loss disorder. In fact, some cats with FAD actually develop hair loss. However, hair loss tends to be very patchy.
Because it is an autoimmune disease, FAD usually affects both the skin and the hair. If a cat has hair loss, it is likely that the skin will also be affected, as hair follicles and skin follicles are made of the same tissue.
There is no cure for FAD. Medication is generally not effective, and the only way to effectively manage this disease is to prevent new flea bites. There are several ways to accomplish this. The most important is to ensure that your cat has a well-sealed, clean and dust-free environment, to ensure that your cat doesn’t have access to fleas and to prevent your cat from picking up fleas from other cats and household members. You may consider using flea-repellent sprays on your cat’s skin, but many cats do not respond to flea sprays. If you find that your cat has a sensitive reaction to a particular product, don’t use it.
To prevent flea allergy dermatitis in the future, you should work with your veterinarian to