Pythiosis, a rare, but rapidly developing disease, affects dogs, horses, humans, and other mammals. British veterinarians first described the illness in 1884 when they studied horses suffering from skin lesions in India. Since then, it has been recognized as an endemic disease that affects tropical and subtropical areas of the globe, including Thailand and India and Brazil. It can cause non-healing sores or rapid growth of lesion in the stomach and intestine, which quickly obstruct the intestinal tract.
What causes pythiosis?
Pythiosis can be caused by Pythium insidiosum, an oomycete. Oomycetes, pronounced “oh-uh MY-seats”) are organisms that look and act like fungus, but are closer to algae. They are sometimes called “water molds.”
To complete its life cycle, P. insidiosum requires water. P. insidiosum is most commonly found in stagnant water such as those found in bayous, swamps, and ponds. However, it can also be found in moist soil. P. insidiosum likes grasses, other aquatic vegetation, horse hair and skin of mammals.
Pythium insidiosum, a form of Pythium, is most common in the United States. It can be found in the southeast region, which includes Florida, Texas and Louisiana as well as Alabama and North and South Carolina. There have been cases of pythiosis in other areas of the country as well, including Wisconsin and California. The number of Pythiosis cases has increased significantly over the past decade.
This organism can be found in bayous, swamps, and ponds. It makes sense considering the typical subtropical geographical distribution of pythiosis. We don’t know why we find pythiosis in animals who live in colder or arid regions of the country. They also have no travel history. Some speculate that exposure to P. insidiosum may be linked to agricultural irrigation practices in these areas.
Pythiosis can affect any breed of dog. Most dogs who develop pythiosis in their young years are less than three years old. They are often hunting or sporting dogs that spend time near water or marshy areas. The United States has shown a higher incidence of the disease in German Shepherds. It is unknown why German Shepherds are so prevalent.
Dogs with pythiosis symptoms
Two types of pythiosis are known to occur in dogs: the skin and the digestive. The cutaneous form can be contracted by dogs if a cut or wound is made to their skin. Oomycetes can not invade healthy skin. Dogs that ingest oomycetes in water or aquatic plants can contract the gastrointestinal form.
Dogs with cutaneous disease will develop a non-healing wound, which is resistant to antibiotics. It can grow in size and develop pustules. It can appear similar to an acute acral-lick granuloma. However, tissue death (necrosis), will follow, and the skin will turn black.
Buster was in perfect health and has had a lot of energy until recently. He was adopted as a puppy at the shelter when he was just 10 weeks old. His playful antics have made him a delight to his parents. He is fighting for his life, seemingly in a matter of hours. He is scheduled to have surgery to remove the intestine masses and will be receiving powerful antifungal medications. Megan Rawie.
Dogs with gastrointestinal pythiosis may experience vomiting or diarrhea. If the small and large intestines are affected, vomiting may occur. If the colon is affected, diarrhea may occur. Diarrhea may become watery or bloody stool. As the disease progresses, dogs may lose their appetite or stop eating altogether. Dogs with the disease will experience weight loss due to a reduced ability to absorb nutrients.
Pythiosis may lead to abnormal thickening or swelling of the small and large intestines, stomach, and esophagus. These sites may become infected with masses. Your veterinarian may feel these masses on abdominal palpation.
How can pythiosis be diagnosed in dogs?
If your veterinarian suspects that you have pythiosis, she may order two tests. First, a Pythium Insidiosum ELISA blood test is performed. This test looks for antibodies in the blood of your dog, which could indicate that they have been exposed to the P. insidiosum organism.
Histopathology is the second test. This involves a biopsy taken from one or more lesion. The cutaneous form requires biopsy samples from one or more of the skin lesions. The gastrointestinal form requires an abdominal exploratory procedure. Biopsy samples are taken from any abdominal mass or thickened areas. To see the P. insidiosum organism under a microscope, the biopsy samples must be stained with a special stain called GMS.
Dogs suffering from pythiosis can be treated
The treatment involves extensive surgical excision of the affected skin and/or a section of the gastrointestinal tract. The skin lesions may be on the limbs or the tails. In these cases, the limbs or tails might need to be amputated. The gastrointestinal condition requires that the affected sections of the small and large intestines be removed. After the lesions have been removed surgically, dogs are treated with antifungal medication for up to four months. Sometimes, lesions can be so severe that surgery is impossible.
Dogs are given antifungal medication to help them if surgery is not an option. Itraconazole and Terbinafine are frequently combined with amphotericin A. P. insidiosum, although not a fungus, is effective in treating approximately 20% of dogs suffering from pythiosis.
In a case report published in 2019, it was reported that three dogs suffering from pythiosis were successfully treated with a combination of itraconazole and terbinafine. The clinical signs of the three dogs were completely resolved. They also experienced regression in their colonic masses and had negative titers of P. insidiosum.
A 2011 case report described the successful treatment for a dog suffering from pythiosis in the stomach and small intestinale. Itraconazole was combined with terbinafine and mefenoxam. Mefenoxam can be used as an agricultural fungicide. It is used to combat oomycetes, which can be pathogenic to crops, ornamental plants, and grasses. As part of its approval process, the Environmental Protection Agency (EPA), had to conduct safety studies on mefenoxam in mammals. This was what inspired the authors to test mefenoxam.
In 2020, a case report also looked at the treatment protocols of mefenoxam, terbinafine and itraconazole. This protocol was used to treat five dogs suffering from gastrointestinal pythiosis as well as one dog suffering from cutaneous pythiosis. The results of dogs suffering from gastrointestinal pythiosis may be improved by mefenoxam, according to this report.
You are desperate to find better treatments
The University of Florida College of Veterinary Medicine has begun recruiting dogs with pythiosis to participate in a pilot study of mefenoxam as of the publication of this article. People interested in enrolling their dogs in this study should contact the University of Florida Small Animal Hospital at (352) 392-2235 or complete the study interest form at https://research.vetmed.ufl.edu/clinical-trials/contact-us/ to see if their dog qualifies.
For dogs suffering from pythiosis, there is an immunotherapy option. The Pythium Insidiosum Antigen (PIA), a therapeutic vaccine, causes a change in the dog’s immune response to P. insidiosum. This vaccine is only used to treat symptoms and not to prevent infection by Pythium insidiosum. PIA works best when administered early in the disease’s course. In 55% of the dogs that were treated, PIA was effective.
The University of Florida College of Veterinary Medicine also studies heat-killed bacteria, Actinomycetales. People interested in enrolling their dogs in the study can either contact the UF CVM Small Animal Hospital or fill out the interest form online.
What is the maximum lifespan of a dog with a Pythium infection? Dogs with pythiosis are not expected to live long, particularly in advanced cases. A study of 10 cases found that the median survival time after diagnosis was 26 days. All 10 dogs died from the condition. New treatments are on the horizon, however, which could change the outlook for dogs suffering from this condition. Early diagnosis is key to successful treatment. Your veterinarian should be contacted immediately if your dog has suffered from a non-healing sore or lost weight, vomiting, or diarrhea after visiting the wetlands.
Whole Dog Journal: Pythiosis: An Emerging and Scary Disease
