Fungal diseases in dogs are caused either by the animal inhaling the fungal spores or from contamination of the dog's skin by the fungi. Fungal spores are a normal inhabitant of the environment and, when in contact with cells of the dog, will release enzymes that produce toxins and kill, digest and invade the host cells. A fungal infection can start out superficially, but then spread throughout the body. Treatment can be prolonged and expensive.
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Types
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Antifungal drugs are a type of veterinary antimicrobial medication used to treat both skin and systemic fungal infections in dogs. Superficial mycoses (fungal skin infections) such as ringworm, and deep mycoses (systemic fungal infections within the body) such as histoplasmosis, cryptococcosis, candidiasis and aspergillosis have all been successfully treated with this group of drugs.
Ketoconazole, itraconazole and amphotericin B are synthetically produced antifungals used to treat animals with systemic mycoses. Systemic fungal infections can invade the dog's lungs, lymph system, deep skin tissues and heart, causing edema (an accumulation of fluid) in all of these organs. These are potentially fatal diseases. The veterinarian will usually recommend that owners give the first two drugs in pill form while amphotericin B must be administered intravenously in a clinical setting. Ketoconazole may also be recommended for ringworm disease in dogs.
Griseofulvin is also commonly used in dogs to treat dermatophytes (ringworm). This drug is normally given in pill form along with other topical antifungal medications to be prescribed by the veterinarian. The vet may also recommend that the animal receive a medicated bath one to two times a week until the dematophytes can no longer be seen microscopically on slides from the infected skin areas.
Function
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Antifungal drugs work by binding to a specific spot on the cell membrane of the fungi, causing the cell to leak critical components and damaging its living mechanism. This effect is called either fungicidal (meaning the fungi cell will die) or fungistatic (the fungi cell will neither grow nor reproduce), depending on the concentration of the drug at the infection site.
Benefits
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Antifungal drugs have proven to be the most effective treatment for fungal infections in dogs that are diagnosed correctly and given the right drug. Most of these dogs can recover from both superficial and systemic infections with time. Side effects may be minimized and easily treated with consistent monitoring by the veterinarian and the dog's owner.
Considerations
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Some veterinarians may recommend using a combination of medications to treat all the forms of the diagnosed fungal infection. Most dogs will require treatment over time--ranging anywhere from several weeks to several months. Particularly severe cases may require treatment for up to a year. With long-term treatment, the veterinarian will usually recommend a series of blood tests to determine liver or kidney function as well as to monitor success of the treatment. Skin and hair cultures may also be taken to check for fungal growth in the case of a dog with ringworm. Even with a good response to treatment, relapses are common, and some dogs may need to have life-long treatment to stay in remission.
Warning
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Pregnant dogs should not be given antifungal drugs, as they have been shown to cause abortions and birth defects in laboratory animals. They are also usually not recommended for breeding dogs because they may be related to lowered testosterone and cortisol levels in males. Side effects may include nausea, vomiting, and anorexia with some impairment of the liver and/or kidneys.
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