Toxoplasmosis: A Master of Disguise That Mimics EPM
- Heather U
- Jun 11
- 3 min read
Toxoplasmosis cases are on the rise, and while many are overlooked or confused with EPM (Equine protozoal myeloencephalitis), knowing about this disease, how it is caused, and how to detect early symptoms are paramount to your equine partner’s safety and well-being.
What is Toxoplasmosis (“Toxo”)?
Like EPM, Toxo is an infection caused by a protozoan parasite known as “toxoplasma gondii”. Horses serve as intermediate hosts by ingesting contaminated food or water. While infection is generally asymptomatic in healthy adult equines, it can often rear its ugly head in immune-compromised horses. Sound familiar? That’s because like EPM, toxoplasmosis will occur (and does often) in equines that have experienced “stressors” or in those that have lowered immunity because of things like environment (toxins), glyphosate exposure, over-vaccination, leaky gut syndrome, ulcers, hind-gut acidosis, and so many more causes. Toxo can cause neurological issues, severe fetal malformations, or abortion.
How is toxoplasmosis transmitted?
Horses typically become infected by consuming feed, hay, or water contaminated with parasite oocysts shed in the feces of infected cats (the definitive host). When we consider how many equines are stabled with or kept near barn cats or even feral cats, it isn’t so surprising that these oocysts are spreading everywhere. Toxo doesn’t discriminate. It is in every state, and all around the world. It is not "rare" in equines in reality; case reporting may be limited but active cases are seen on a regular basis.
For humans, toxoplasmosis can be life-threatening, but it is not directly contagious to humans via touching or caring for our horses. (It would be transmitted via accidental ingestion of the parasite so it is important to wash your hands when handling anything related to your pets). Pregnant women are generally advised to avoid cleaning litter boxes for this reason. It is considered rare in humans.
What are the Symptoms of Toxoplasmosis?
Learning to recognize symptoms, is important, especially because once the disease becomes neurological, it mimics EPM. Knowledge is power. Knowing that the symptoms can be subtle at first is key.
A few early-stage symptoms (there are many more) can be:
- Change in energy level or appetite
- Droopy lip or penis
- Mild toe drag
- Mild Fever
- Standing camped out often, with hind legs stretched behind horse
- Trouble backing
- Tripping or stumbling
- Hair-coat changes (new patterns, dull, patchy or fungal issues)
- Performance issues – just doesn’t seem right under saddle
- Horse just seems “off” in general
Later stage symptoms often progress to neurological. Some signs of progressive toxoplasmosis include:
- Vision impairment or issues – problems with depth perception, trailer loading, etc
- Spooky, reactive behavior
- Dull disposition
- Weight Loss
- Ataxia (lack of coordination, balance, falling down, stumbling, etc)
- Head Tilt
- Difficulty with leads
- Cross-firing in canter
How Can We Help These Horses?
Prevention: First, let’s talk about prevention. Healthy barn cats are far less likely to spread toxoplasmosis. It is not possible to rid cats of the protozoa with regular deworming. Instead, fostering a good immune system through decent food, proper care, and regular deworming will lessen a barn cat’s chances of spreading disease. Feline population control is also prudent. Spay or neutering barn cats around your property can help reduce the spread of the disease.
Management: Helping your horse by boosting its immune system is a critical component. Just as with EPM, the gut plays a significant role. Reduce vaccinations (see recent research on the over-use of vaccines in canines) as vaccines immediately trigger an immune response. Ensure you are feeding a well-balanced diet free of leaky gut / malabsorption triggers like soy, molasses, other sugars, corn, and heavy starches. Reduce heavily processed feeds that are likely to contain mycotoxins and heavy metals. Choose cleaner hay, that has less exposure to glyphosate. (See my separate article on glyphosate concerns for equines). And choose management practices that promote a healthy environment, emotional wellness, and overall, a strong immune system.
Testing: If your horse is acting strange, and you don’t have another reasonable explanation, and he shows any of the symptoms I described earlier, consider testing for toxo with UC Davis. Obviously, testing for EPM at that point may become useful as well as the symptoms mimic each other. I have provided their test form, interpretation instructions, and general toxoplasmosis information in full article linked below.
Treatment: Toxoplasmosis can be treated with a variety of protocols both western and eastern or “alternative”. I have successfully treated toxo in multiple equines and with the right approach, your horse can heal. Remember not to hyper-focus on symptoms, but to provide systemic support that helps heal all systems of the body…and THAT begins with a healthy equine gut.
How To Test for Toxoplasmosis?
UC Davis can run a blood test for you for under $100. Their lab forms are linked below.
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