Also known as 'pyoderma' (which stands for pus in the skin) skin infections are relatively uncommon in cats. Most are secondary, which means they are caused by an underlying disorder. Anything that affects the integrity of the skin has the potential to lead to a skin infection. Most often this is caused by trauma (such as a bite or scratch), self-mutilation (over grooming but more often than not, damage due to biting or scratching itchy skin due to an allergic reaction, hypersensitivity, parasites), endocrine disorders and poor immunity.
Pyoderma can affect the superficial or deeper layers of the skin. It can affect any part of the body, however, it is most commonly seen on the cat's trunk. Staphylococcus pseudointermedius is the most common of bacteria to cause pyoderma in cats, other bacteria include Pasteurella multocida.
Shorthaired cats are more prone to developing skin infections, however, there is no age or sex predilection.
What are the causes of pyoderma in cats:
As we have already mentioned, anything that irritates the skin can potentially lead to pyoderma. Common causes include:
- Allergy - Particularly food, inhalant or contact allergy which result in itching and irritation to the skin.
- Fleas - Some cats are particularly sensitive to the saliva of the flea, which results in a breakout of itchy papules on the skin.
- Ear mites - Spider like mites which live in the ears of cats causing intense itching and discomfort.
- Ringworm - A fungal infection of the skin and claws, most cases of ringworm aren't particularly itchy, but it can and does occur in some cats.
- Seborrhea - A condition caused by the overproduction of sebum, an oily substance produced by the sebaceous glands in the skin to protect and lubricate the skin.
- Hypothyroidism - A disease caused by an underactive thyroid gland.
- Cushing's syndrome - A disorder caused by excessive production of cortisol by the adrenal gland. One symptom is a thinning of the skin, which can make it much vulnerable to damage.
- Diabetes - Type 2 diabetes is a condition in which the body's cells don't respond to insulin, a hormone which is required to enable glucose to enter the cells. A side effect of diabetes is poor circulation and dry skin, both of which can cause itching, making it more vulnerable to infection.
- Demodicosis - Another type of mite which lives in the skin follicles or the surface layers of your cat's skin. Immunocompromised or malnourished cats are most at risk. Itching leads to damage to the skin, making it prone to infection.
- Feline acne - Characterised by the presence of blackheads (comedones), particularly around the chin. These can become inflamed, leading to folliculitis, which is a form of skin infection of the hair follicles.
- Skin folds - Less common in cats than dogs, breeds with skin folds can develop pyoderma due to the skin trapping in moisture, in areas of folds, which provides the perfect environment for bacteria to proliferate. Prone areas include the nasal fold, vulval fold, and tail fold.
What are the symptoms of skin infection in cats?
Symptoms can vary between superficial and deep pyoderma. Also, the underlying cause will play a factor in how symptoms present. The symptoms below relate to skin infection only. Onset may be acute or slow to progress.
- Crusting and scaling, often with shortened hairs which can easily be pulled out
- Papules or pustules on the skin
- Alopecia (baldness)
- Ulcerations or erosions which may ooze
- Unpleasant odour
- Pruritis (itching) may or may not be present, this can depend on the underlying cause
How is a skin infection diagnosed?
Your veterinarian will perform a complete physical examination of your cat and obtain a medical history from you, including accompanying symptoms you have noticed. He may be able to make a tentative diagnosis based on presenting symptoms alone. Tests your veterinarian will perform may include:
Cytology - A small amount of the cells within a pustule will be examined under a microscope. This can help to identify the infectious organism, which may be bacterial or fungal.
Culture and sensitivity - If bacteria is identified, a culture and sensitivity will be recommended. The bacteria are grown in a medium and then exposed to several types of antibiotic to determine which is the most effective in killing the bacteria.
Diagnosing the underlying cause:
Skin scrapings - To check for the presence of mites.
Fungal culture - To look for ringworm.
Hypoallergenic food trial - If a food allergy is suspected, your cat will be placed on a special diet see if the allergy clears up, if it does, he will then be put back on his normal diet to see if symptoms return.
Skin prick tests - A number of pricks are made in the skin containing allergens to common substances. The skin is then evaluated for a reaction to one or more of the allergens to identify possible allergies.
Endocrine tests - To evaluate for hypothyroidism or Cushing's syndrome.
Complete blood count to evaluate the general health of your cat.
How is a skin infection treated?
Treatment is aimed at addressing both the underlying cause and the skin infection. If the underlying cause isn't treated, recurrence is likely.
Skin infections are treated as follows:
- Oral antibiotics will be prescribed to treat the infection. The course will usually run for 3-4 weeks.
- Topical antibiotics or antibiotic shampoos may also be necessary to help soften the crusts and treat infection.
Treating underlying causes:
- Avoidance of the allergen, if possible. Cats with food allergies will need to go on a 'hypoallergenic' diet.
- Diligent flea control, not only should all pets in the house be treated, but the environment too. Most of the flea life cycle is spent OFF the cat.
- Anti-parasitic medications to treat ear mites and demodicosis.
- Anti-fungal medications to treat ringworm.
- Medicated "antiseborrheic" shampoos given every three days until the condition is brought under control.
- Hypothyroidism is treated with synthetic hormones to replace those not being produced by the thyroid gland.
- Cushing's syndrome is treated by surgical removal of the adrenal gland if a tumour is involved, or gradual withdrawal of corticosteroids if they are to blame.
- Diabetes is managed with dietary changes and/or insulin injections.
- Feline acne should be managed by keeping the area clean and switching to glass or metal bowls.