Water mold infection, or pythiosis, in cats is a type of infection caused by the fungus-like pathogen Pythium insidiosum. Pythium insidiosum is a spore that is found in areas of standing water, typically in late summer or early fall. This hazardous spore is found in bodies of poorly draining, standing water in many parts of the United States, but especially in the Midwest, Southeast and South, such as in the Gulf of Mexico. Infection by this spore can be a life-threatening condition in your cat, and it’s important that the condition is caught early for a good prognosis.

Depending on the location where the spore enters your cat’s body, symptoms of water mold infection may manifest in a variety of different ways. Below are some of the most common indications your cat may be suffering from an infection. 

Cats can become exposed to the pathogen that causes water mold infection by swimming, bathing, walking, ingesting or otherwise coming in contact with bodies of standing water that contain the spore Pythium insidiosum. The risk of infection is especially high in late summer and early fall and occurs most commonly in Midwest, Southern and Southeastern regions of U.S. Water mold infection cannot be transmitted between pets or between pets and humans.

Diagnosis of water mold in your cat can be a complicated process. The first step will be to provide a complete history of your cat’s symptoms to your veterinarian. You should document any outside activity, note whether your cat is an indoor or indoor and outdoor pet, and generally provide timelines regarding progression of any symptoms. 

After a thorough physical exam of any lumps, sores or other problematic areas, there are several tests your veterinarian will order. First, your vet will want to biopsy any easily accessible affected areas such as cysts, open sores or putrid tissues. If your cat is experiencing abdominal discomfort, your vet may order imaging such as x-ray or ultrasound, to determine if any masses or obstructions, caused by the spores, are present. While your vet will be able to review biopsied tissue in office for a preliminary diagnosis, they will most likely recommend that tissues be sent to an outside lab specializing in fungal, bacterial and other spore based infections, so that a definitive diagnosis can be made and the correct treatment prescribed.

The first recommended course of treatment will be the removal of any infected mass or surrounding tissue, both for biopsy and to prevent any further spread of the pathogen. Water mold infection is caused by an organism that invades healthy tissue in your cat, therefore it is critical that all traces of the organism be removed in order for proper healing to occur. 

After biopsy and removal of mass or areas of open wound, your veterinarian may recommend following up with laser therapy that further targets the affected areas. This will guarantee that any remaining spore cells are destroyed and cannot cause further harm to your pet. 

Your vet will schedule follow up appointments at regular intervals of three to six months in order to ensure that no remaining spores have spread to healthy tissue and to identify if additional tissue removal is needed. It is important during this time that you notify your vet of any new instances or areas of infection.

Depending on the nature of the water mold infection in your cat, your veterinarian may choose to prescribe a systemic antifungal-type drug to help treat the condition, such as  itraconazole. This is not typically the primary form of treatment, and medication is usually given in connection with removal of affected tissue on your cat.

Water mold infection in cats can be a life threatening condition if not caught early. In cases where symptoms are identified quickly and early treatment is sought, most of the affected tissue is able to be removed, which greatly increases your cat’s chance of a full recovery. Complete removal of all the affected tissue is an important factor in determining how quickly and thoroughly your cat will recover.

Proper management and follow up with additional veterinarian exams is critical to prevent recurrence of infection. In addition to revisiting your vet, you should also pay attention for any recurrence of lumps, sores or other symptoms. Finally, you should keep your cat away from any standing bodies of water that may have been the source of contamination, especially if you live in an area of the U.S. especially prone to the spore that causes Pythiosis. If the infection is caught early and the affected tissues are completely removed, your cat’s prognosis for a full recovery is very good.