Treating Systemic Fungal Infections With Better Options

There are more options today for treating systemic fungal infections in foals and horses, but owners should be prepared for a long haul--treatment takes a long time, it's expensive, and the infection can reoccur.

Fungal infections can cause a host of systemic problems, such as pneumonia, meningitis, and aggressive sinusitis and rhinitis, and they can cause abortions in pregnant mares. Some diseases are so aggressive, horses have to be euthanized.

Early treatment is best, but clinical signs can be vague, and the infection might not be diagnosed until the horse is very ill and teaming with fungi.

"Often the first signs are weight loss, anorexia, fever, and diarrhea," said Allison J. Stewart, BVSc (hons), MS, Dipl. ACVIM, Dipl. ACVECC, of Auburn University, at the ACVIM Forum 2010 veterinary meeting held in Anaheim, Calif.

Once recognized and diagnosed, treatment can take months, and the infection can reoccur. Still the treatment options are better than ever before, she said. Antifungal agents such as amphotericin B, itraconazole, fluconazole, and voriconazole, are viable choices for treating systemic fungal diseases. An older therapy, iodine, is not very effective, she added, and should no longer be used as the sole treatment for systemic fungal infections. Veterinarians will prescribe an antifungal based on the infection site and type of fungus.

"The duration of therapy is always the tricky decision," said Stewart. "When do we start? How long do we keep going? It really depends on the organism."

Most horses are treated from three to 12 months, and she recommended that veterinarians do blood tests to monitor the disease.

Some fungal infections (i.e., those caused by Aspergillus, Candida, Fusarium, Emmonsia, and Pneumocystis) occur in horses with compromised immune systems. Stewart recommended veterinarians check the immune status of the horse to make sure he doesn’t have other problems before making an investment of several hundred to thousands of dollars a day (one drug, fluconazole, has decreased the price of treatment to about $200-$300 per month).

Other infections, such as those caused by Blastomyces, Histoplasma, Coccidioides and Cryptococcus, affect immunologically normal horses; these horses are more likely to recover.

"Until recently, the prognosis for systemic fungal infections has been guarded to poor," said Stewart, but the newer antifungal drugs have increased the chances of recovery for these horses.

About the Author

Marie Rosenthal, MS

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