Pyoderma literally means “pus in the skin.” It can be caused by infection, inflammation, or cancer and is common in dogs.
Most cases of pyoderma are caused by bacterial infections. Most of these are superficial and secondary to a variety of other conditions, such as allergies or parasites. Pyoderma that occurs in otherwise healthy animals usually resolves completely with appropriate antibiotics. Warm, moist areas on the skin, such as lip folds, facial folds, armpits, feet, and neck folds, often have higher bacterial counts than other areas and are at an increased risk for infection. Pressure points, such as elbows, are prone to infections due to repeated pressure. Any skin disease that changes the normally dry, desert-like environment to a more humid environment can cause overcolonization of the skin with bacteria.
The most common sign of bacterial pyoderma is excessive scaling. Scales are often pierced by hairs. Itching is variable. In dogs, superficial pyoderma commonly appears as bald patches, welts around hairs, and scabbing. Shorthaired breeds often have multiple welts that look similar to hives because the inflammation in and around the follicles causes the hairs to stand more erect. These hairs are often easily removed, which distinguishes pyoderma from hives. Hair loss leads to small bald patches in affected areas. At the margins of the hair loss, there may be redness and welts but these signs are often absent in shorthaired breeds. The signs of deep pyoderma in dogs include pain, crusting, odor, and secretions of blood and pus. Redness, swelling, ulceration, scabs, and blisters may also be seen. The bridge of the muzzle, chin, elbows, hocks, knees, and spaces between the toes are more prone to deep infections, but any area may be involved.
Diagnosis is based on signs. Diagnosis of pyoderma must also include steps to identify any underlying causes. These include fleas, allergies, hypothyroidism, Cushing disease, and poor grooming. Multiple deep skin scrapings are needed to exclude parasitic infections. Bacterial and fungal cultures may also be taken.
The most common causes of recurrent bacterial pyoderma include failure to treat underlying causes, use of glucocorticoid drugs, and inappropriate treatment with prescribed antibiotic medications. You may contribute to a recurrence of pyoderma in your dog if you don’t carefully follow your veterinarian’s treatment directions. Even though your dog may seem better after only a few days or a week, it is still very important for you to continue the prescribed treatment program for the full length of time. The bacteria causing pyoderma can still be present and ready to multiply again if the complete course of medication is not given.
Antibiotic treatment should last for at least 3 weeks and preferably for 4 weeks. All signs (except for hair regrowth and resolution of increased pigmentation) should be gone for at least 7 days before antibiotics are discontinued. Longterm, recurrent, or deep pyodermas typically require 8 to 12 weeks or longer to heal completely. Topical antibiotics may also be used in some cases.
Attention to grooming is crucial. The hair coat should be clipped in dogs with deep pyoderma and a professional grooming is recommended in medium to longhaired dogs with superficial pyoderma. This will remove excessive hair that can trap debris and bacteria and will help grooming.
Dogs with superficial pyoderma should be bathed with a shampoo recommended by its veterinarian. Baths should be given 2 to 3 times per week during the first 2 weeks of treatment and then 1 to 2 times per week until the infection clears. Dogs with deep pyoderma may require daily baths with medicated shampoos diluted to one-half or one-quarter strength. Shampooing will remove bacteria, crusts, and scales, and reduce itching, odor, and oiliness. Improvement may not be evident for at least 14 to 21 days, and recovery may not be as rapid as expected. Your veterinarian can recommend the appropriate bathing program for your pet’s condition. Medicated shampoos usually need to remain on the coat for 10 minutes in order to be effective.
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