helping anxious pets cope

Own A Horse With A Skin Lesion? What You Need To Know About Potentially Deadly Pythiosis

8 May 2018

Aatu Leppo

An organism living in standing water and moist soil can cause a skin infection in horses and other large animals. The organism is called Pythium insidiosum, and a skin infection from it is called pythiosis. The condition is also referred to as swamp cancer. Unfortunately, if the skin infection is left untreated, the infection could spread and develop into a multi-system disease that affects vital organs. If this happens, death could occur. Here's what you need to know if you have a horse that you think may have pythiosis. 

What does pythiosis look like? 

Pythiosis typically develops on lower limbs, but lesions can be found anywhere on the body. The lesions from the infection form a grainy surface during the healing process. The granulation looks similar in appearance to coral and is called "kunkers." The lesions grow and expand similar to the growth of cancerous tumors as more of the organisms enter into the opened skin. Your horse will likely attempt to scratch at the lesions or rub them on hard surfaces such as fencing or rocks. The lesions drain a serosanguineous fluid, which typically has a strong odor. 

How is pythiosis diagnosed and treated? 

Pythiosis is diagnosed through an enzyme-linked immunosorbent assay test for pythiosis antibodies. This test is done by drawing blood from the horse and sending it to the lab. A biopsy may also be done to rule out any other causes of the lesions, but the organism itself is difficult to identify in biopsy samples. 

Depending on the test results, treatment involves immunotherapy via subcutaneous injections. If the initial series of injections does not improve the infection, another round may be given. Sometimes, after the end of the treatment course, larger lesions need to be surgically removed. If the treatment isn't done as soon as possible, the organism could enter the bloodstream and adversely affect the vital organs. 

Will your horse need to be hospitalized? 

Of course, if your horse's infection has spread to their vital organs, it will need to be admitted to a large animal hospital for IV immunotherapy and IV antibiotics. Additionally, horses with large lesions may also need to be admitted for intensive treatment and frequent vital sign testing. 

Due to the rapid destruction of tissue, it is highly recommended to confine your horse to a dry location away from standing water or moist soil. If this is not possible, consider admitting your horse to a veterinary hospital.  

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