Pythiosis

Recently, a reader wrote us, greatly concerned because her two dogs were stricken by the Pythiosis parasite which can be deadly to animals. Below is her letter to us.

We contacted Dr. Jacqueline Brewer of Maybank Animal Hospital who informed us she was unaware of local cases that could be considered an outbreak. To further check on the status of the occurance of Pythiosis in this region, Dr. Brewer consulted with Dr. Amy Grooters, Professor of Veterinary Medicine at LSU. Below is her reponse:

What is Pythiosis?Pythiosis

Pythiosis is an infectious disease caused by a fungus-like organism, Pythiuminsidiosum, that naturally inhabits wetlands, ponds, and swamps.  In dogs, the disease usually is manifested by gastroenteritis or dermatitis.  Presumably dogs become infected by ingesting, or swimming in contaminated water.  Pythiosis is endemic in states that border the Gulf of Mexico, but has been diagnosed in dogs from southern Indiana (with no history of travel outside the state).  Dogs with gastrointestinal pythiosis often have a history of retrieving objects, such as sticks, from water and then chewing on them; young male retriever-type dogs are particularly at risk.  Dogs with open skin wounds are probably predisposed to acquiring cutaneouspythiosis. Gastrointestinal pythiosis is usually a fatal disease.
Excerpted from Purdue University Newsleter on Pythiosis in Dogs.

A concerned reader writes:

For those of you who have not been following the medical odyssey of my little dog Lila, this is to let everyone who swims their dogs in lakes and ponds;to reconsider exposing their beloved pets to the possibility of this deadly pathogen. I lost one perfectly healthy dog to pythiosis;6 years ago and because of it's;rarity in our area at the time,;I was told it was just an unfortunate fluke that my dog contracted it. Now,;6 yrs later, I've had another seemingly healthy dog also contract pythiosis, so it isn't a fluke, the pathogen is definitely present in at least some of the lakes and ponds in our area.

Considered a tropical pathogen (I guess we are becoming more tropical what with global warming), pythium is a parasite of grasses at the edges of water with fluctuating levels. When infected plants are inundated, the pythium, considered a "pseudo-fungus", releases reproductive bodies into the water to infect other plants. These cells can also infect animal tissue thru breaks in the skin, or if swallowed, thru any irritation in the gastro-intestinal tract. Once in the tissue the organism grows while the body has a localized inflammatory reaction to the invading cells;and a cancer-like mass develops, and like a cancer it will spread to surrounding tissue. If in the GI tract, the mass will finally block the gut and the dog will starve.;Infection in the GI tract;is usually asymptomatic untill significantly advanced, and complete surgical removal is the only cure as medications are ineffective.

Very few dogs diagnosed with pythiosis survive it. Six years ago my whippet Breezy did not, the infection was beyond complete;excision by the time she had surgery. Last week Lila underwent an extreme surgical procedure;to remove the mass found in her large intestine (lost the whole colon) but biopsy results indicate surrounding tissue seems to be clear of pythium. I am hopeful it was completely removed, but we won't know for sure for some time. Lila will have life-long consequences though, living without a colon has it's problems. For more details about pythiosis, you can go to this site:;;http://www.pythiosis.com/

Both of my dogs seemed to be perfectly healthy when they became infected, and each summer they were exposed, several of my other dogs were also swimming in the same waters at the same time or even more frequently, and those dogs were unaffected, so there is no way to predict which dog(s) will be susceptible to pythiosis. All three bodies of water that my dogs have been swimming in have many other dogs swimming regularly as well, and one even has human swimmers, so there is no way to tell which places are safe and which are not. My dogs will never swim in lakes or ponds again! I'm not telling anyone else not to swim their dogs, just to think about what could possibly happen.

Feel free to contact me if you have any questions!

Kathleen Cole


From Dr. Amy Grooters

;I would definitely not call this an outbreak - based on data from my lab, rates of pythiosis in South Caroline are similar to what they have been for the past 15 years. It does occur in the state, but MUCH less often than it does in states like Louisiana and Florida. In fact, other than the dog described in your email, I only diagnosed pythiosis in one other dog from the Charleston area in 2011, and looking back, it's been 2 per year or less for years.

My best recommendation for owners who are worried that their dogs might get pythiosis is to bathe them with some type of soap/shampoo after they swim (the infective zoospores are killed by soaps) and to test dogs early in the course of disease. That doesn't mean that every dog that vomits a couple of times should be tested, but if vomiting, weight loss, diarrhea, or skin wounds don't resolve within a week or two, and no alternative diagnosis is made, testing for pythiosis should be considered. This would apply mostly to dogs at higher risk (young to middle aged dogs that spend a significant amount of time outdoors, especially large breed dogs).

Since we have a blood test that is close to 100% accurate, testing for pythiosis is pretty easy and inexpensive ($40 at my lab). I would warn you that there is a lab in Texas that offers pythiosis testing that has a problem with false positive results - I have retested at least a dozen dogs that had no clinical signs but had tested "positive" at that lab, and none of them actually had pythiosis, so if folks go looking around the internet for pythiosis testing they could end up making an incorrect diagnosis through that lab.

I would discourage anyone from testing dogs that have no clinical signs at all, as the likelihood of getting a false positive result is MUCH higher than getting a true positive result, and then people panic and treat their healthy dogs unnecessarily.

Any lab that offers testing for any infectious disease should be able to show published results for sensitivity (how well a test detects a disease) and specificity (how reliable a positive test result is) - if they can't, there's no way to know what their results mean.

Amy M. Grooters
Professor of Veterinary Medicine
LSU School of Veterinary Medicine
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