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What are Pythiosis?

Pythium insidiosum can cause infections in dogs and horses that are life-threatening. It can also cause infection in cattle, cats, equines, captive polar bears and even humans. It is most commonly found in tropical regions or subtropical regions. Pythiosis is typically found in states along the Eastern coastal areas and the Gulf of Mexico. Most cases of pythiosis are diagnosed in the fall or early winter and usually after a summer of flooding and large amounts of precipitation. 

Pythiosis in dogs is a gastrointestinal infection that will cause the gastrointestinal tract to thicken. Eventually, an abdominal mass or intestinal obstruction will develop. The dogs that are most at risk of infection include Labrador Retrievers, Cavalier King Charles Spaniels and German Shepherd Dogs. Young dogs are most often affected by pythiosis.

Other types of pythiosis include cutaneous pythiosis and canine lagenidium. Cutaneous pythiosis is when pythiosis is transmitted through an open wound. Lesions will usually form near the perineal area on the tail, the thorax, abdomen, face and legs. 

Canine lagenidium is very similar to cutaneous pythiosis except dogs that present with lagenidium will many times have involvement of distant sites and the lesions will appear on the mammary glands, groin, near the tail, trunk and/or legs. It also will disseminate to other organs and can cause an aneurysm and sudden death.

Pythiosis is also called water molds and is caused by pythium which is a genus of parasitic oomycetes. There are around 200 species of pythium that can cause disease to fish, crops and plants. There is only one species of pythium, pythium insidiosum, which can infect plants and animals, including dogs.


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Symptoms of Pythiosis in Dogs

It is important that your dog be treated quickly to give them a better chance of surviving pythiosis. This is an infection of the gastrointestinal tract that will cause your dog to develop an intestinal obstruction or abdominal mass as the intestinal tract thickens. Do not wait to seek veterinary attention when you notice symptoms, early diagnosis and treatment is important when dealing with pythiosis. 

  • Diarrhea, many times bloody
  • Loss of appetite
  • Vomiting
  • Weight loss
  • Enlarged lymph nodes
  • Lethargy
  • Fever
  • Excessive drooling 
  • Palpable abdominal mass

Cutaneous pythiosis

  • Draining sinus cavity
  • Skin lesions 
  • Swollen wounds that will  not heal
  • Pus filled nodules
  • Chewing or scratching 

Canine lagenidium

  • Skin lesions
  • Swollen wounds that will not heal
  • Pus filled nodules
  • Chewing or scratching
  • Sudden weight loss
  • Sudden death

Causes of Pythiosis in Dogs

Pythiosis is caused by pythium, a genus of parasitic oomycetes. Commonly called water molds, there are about 200 species of pythium. There is only one pythium, pythium insidiosum, which will infect plants and animals.

Your dog can become infected with pythium insidiosum by either ingesting it or by getting the spores into a break in the skin. Most cases of pythiosis in the United States occur along the Eastern coastal region or the Gulf of Mexico where winters are mild and there is a lot of precipitation during the summer and fall months. Dogs that are used for hunting, especially in swampy areas are at a higher risk of contracting pythiosis.

Diagnosis of Pythiosis in Dogs

It is important that pythiosis is quickly diagnosed and treated. It is a rapidly progressive illness and many dogs do not survive because diagnosis and treatments begin too late. Your veterinarian will begin by doing a full physical examination and ordering a complete blood count, biochemistry panel, urinalysis and fecal exam. 

If there are lesions on the skin, a skin scraping will be taken and a biopsy conducted. A special stain will be required to properly diagnose pythiosis. Many veterinarians will need to send the samples to a laboratory for the biopsy.  

Your veterinarian will also want to have abdominal radiographs taken. This is done to look for any intestinal obstruction or thickening of the intestinal wall. It will also verify the presence of an abdominal mass. Ultrasounds can also show any thickening of the intestinal wall. 

Treatment of Pythiosis in Dogs

For most dogs, they will have a natural resistance to pythium insidiosum. Dogs that do contract the infection pythiosis will probably already have a weakened immune system and will be unable to fight the infection. 

There are treatments available that have been effective in treating pythiosis when the infection is caught early enough. One such treatment is the PAVLAB Immunotherapy treatment. It will strengthen your dog’s immune system and allow them to be able to fight the infection with the use of anti-fungal medications, low doses of prednisone and antibiotics. 

Dogs that have an intestinal blockage or abdominal mass will require surgery. Wounds on the skin will need to be debrided to remove any dead or dying tissue. Your veterinarian will discuss all surgical options with you.

Recovery of Pythiosis in Dogs

Your dog’s chances of survival will strongly depend on how quickly pythiosis is diagnosed and treated. Be sure to follow your veterinarian’s treatment plan and any post-surgical instructions. 

Many dogs are not diagnosed in time since pythiosis is a rapidly progressive infection. Euthanasia is generally recommended if your dog’s condition has already deteriorated to the point where treatments will not be helpful.

Pythiosis Questions and Advice from Veterinary Professionals

4 Years
Moderate condition
0 found helpful
Moderate condition

My daughter's dog had a bowel resection due to partial obstruction. Prior to surgery he had anorexia,lost aprox 10 pounds, diarrhea and occasional vomtiting. Pathology of mass detected no cancer but showed "spore like"fetaures.. Blood test sent to Pavlab showed level of 278 pythium and 207 lag. Would you interpret these as positive test for pythium? Many vets do not about this disease and we are trying to educate our vet about it because she doesn't want to order the immunotherapy for it until she knows more. From what we have read and have been told by Bob Glass at Pavlab it is critical that this treatment be started immediately. It has been 2 1/2 weeks since surgery was done.Since a vet must order the immunotherapy serum, do you have any suggestions if our vet still doesn't want to order it. My daughter is a health professional and would be comfortable giving the injections - we just need the serum!! It has been very frustrating. Thanks and will be awaiting your reply.

Dr. Callum Turner, DVM
Dr. Callum Turner, DVM
3319 Recommendations
In many cases surgical removal of a gastrointestinal mass and long term treatment with antifungal medications are the treatment of choice for Pythiosis, however immunotherapy has shown a greater success rate in some studies. If your Veterinarian is unsure about ordering or using immunotherapy, speak with another Veterinarian at the practice or another Veterinarian in your area; also speak with your nearest Veterinary School as they may be able to help you, without examining Marley I cannot do anything, Regards Dr Callum Turner DVM

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Border Collie
6 Years
Serious condition
0 found helpful
Serious condition

Has Symptoms

Nasal Discharge

Our dog, Jet, a 6 1/2 year old Border Collie, was diagnosed with gastrointestinal pythiosis. He almost died. We had him to a local vet 4 times in a month and a half with 4 different meds and no results. We finally, out of sheer desperation, took him to another vet who immediately did surgery (called us during the surgery to tell us that he thought it was pythiosis and took out 12 inches of his colon). Luckily for our Jet the deposits were in a section of the colon that was very easy to remove. Our new vet had only experienced two other cases of pythiosis!! He went to vet school in Louisianna and his professor wrote the book on pythiosis so he was all about the immunotherapy injections from the PavLab out of Texas. We did get a positive pythiosis reading on the pathology so we started the injections. We will take the third shot of the first round of injections this coming Friday. Jet has gained 11 pounds (Jet had lost half his body weight going from 60 pounds to 30 pounds before we could find out what was wrong) since his surgery 3 weeks ago. Our new vet feels positive that the colon resection probably cured Jet of his problem. We are doing the injections simply as a precaution. Here are my questions: 1. Jet has HORRIBLE gas. I mean like nothing I have ever experienced in my life! Is this common with the injections or with the gastrointestinal type of pythiosis? Will this get better? 2. He has a nasal drainage. His nose is draining like a facet. This has been non-stop even pre and post surgery. His nose runs all the time. I noticed here that was a sign or symptom of pythiosis. Should we be worried about this? Will this get better? The vet said he may do xrays of his sinuses when he comes in for his third shot on Friday. 3. He is itching like crazy as well. I also saw where that was a sign/symptom. Will this get better? I guess I'm just worried that maybe we are not out of the woods yet! He acts like our old ball loving and frisbee catching Border Collie. He is active and eating like a horse. His stools go from solid to very loose, but we are also feeding him ANYTHING he will eat- which means he is getting some people food too! We are just trying to get some weight back on him. The vet said not to worry too much about diet right now. He says feed him whatever he will eat for now and we can focus on good diet later. 4. Finally my last question - What will prevent Jet (and our other two dogs for that matter) from getting this again?

Dr. Michele King, DVM
Dr. Michele King, DVM
1610 Recommendations
Thank you for your email. Your veterinarian sounds like they are doing a great job managing this uncommon disease. Most dogs are not affected by Pythiosis, and it may be a sign of a compromised immune system that he was affected originally - that may be part of the rest of his signs, but it would be a good idea to check with your veterinarian regarding the gassiness, the nasal discharge, and the itching. They may be unrelated to the disease, but they may be ongoing signs. As far as avoiding the disease, if areas of warm, stagnant water are avoided, the areas that tend to harbor the fungus can't make contact with any open wounds or be ingested. I hope that Jet makes a full recovery!

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4 Years
Serious condition
0 found helpful
Serious condition

Has Symptoms

Licking at Genitals
Foamy throw up with blood
Hardened and twisted intestines,

Medication Used

Sucralfate 1 gr

Our 4 year old boxer was diagnosed with pythiosis his intestines have hardened and twisted! Do you think he would since he’s far into disease benefit from having intestine removed and then the immunotherapy too?? Please we’re desperate the vet said he may have a month left!! He’s still a baby!! Thanks

Dr. Callum Turner, DVM
Dr. Callum Turner, DVM
3319 Recommendations
Unfortunately gastrointestinal pythiosis carries a grave prognosis, attempts at surgical resection and aggressive therapy are treatments of choice but still there is an unfavourable prognosis. You should discuss Tyson’s condition with your Veterinarian and decide on whether the surgery is worth the risk or not. Regards Dr Callum Turner DVM

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