Should you exercise a horse with possum disease?

Answer 1

"Possum disease" is Equine Protozoal Encephalytis. It is contracted by eating feedstuffs or drinking water contaminated by possum feces. There are several treatment options including Marquis, Navigator, diclazuril and a combination of pyrimethamine and sulfadiazine marketed as Rebalance. However, Navigator is no long in production and Rebalance tends to be out of stock so vets and owners go through compounding pharmacies to have pyrimethamine and sulfadiazine compounded for use. Diclazuril has never been mass produces in a formula for treating EPM because the cost of doing so and the fact that an already effective treatment (Marquis) is on the market would likely lead to the same fate as that of Navigator---a product that doesn't sell enough to warrant production. Marquis is labelled for use for 28 days and actually kills the parasite. This product is more expensive than the Rebalance but it requires a much shorter treatment time. Marquis also has a low incidence of adverse effects. Rebalance (pyrimethamine/sufladiazine) prevents reproduction of the parasite and treatment must be continued for a minimum of 3 months to allow for the parasites that are present to all die without leaving new generations in the central nervous system of the horse. It is often recommended that this product be given for 6 months or more. Rebalance must be given on an empty stomach. About 70% of horses recover with any of these treatments. Recovery is considered a 1 grade improvement of neurological deficits as graded on the Mayhew scale 1 month after treatment ends. However, horses who are recovering from EPM can improve for more than a year after treatment. But rehabilitation must be slow and cautious for the safety of the horse and the handlers. Recovered horses also can have days when they appear to relapse and neurological symptoms reappear or worsen. This may actually be from a reinfection or it may be from an inability to compensate for neurological deficits left over from their initial infection. Horses will over time learn to compensate for neurological deficits and appear normal or at least more normal, but overwork, illness, injury, excessive heat and humidity or anything else which affects their energy level or concentration may lead to a reappearance or worsening of neurological deficits. When considering EPM as a possible cause of neurological deficits, it is very important to get an accurate diagnosis. There are many other diseases/causes that present with similar symptoms to EPM so a full physical examination and appropriate diagnostic testing including blood tests for exposure to S. neurona, x-rays of the head/neck, testing for other diseases such as West Nile Virus, Eastern Equine Encephalytis, etc.

Answer 2

Possums disease in horses is called EPM Equine Protozoal Myeloencephalitis. It is a neurological disorder. It affects the central nervous system in horses. Double check with your vet though.

Answer 3

This will depend upon what you are referring to as "possum disease". This may be equine protozoal myeloencephalitis, a central nervous system disorder caused by aberrant migration of S. neurona protozoa that are commonly thought to be transmitted through opossum urine. However, you could also be referring to hypokalemic periodic paralysis, a genetic defect in certain bloodlines of Quarter Horses and horses derived from Quarter Horse stock, in which the horse is unable to regulate potassium correctly.

In either case, your veterinarian is your best source of information about this, because the risk of injury due to exercise will depend upon the severity of the condition and your horse's individual health and fitness. However, in general terms, a horse that is mildly affected with EPM can be exercised at mild to moderate rates, but rider safety should be carefully considered before under saddle work is started. Horses with EPM typically have variable limb weakness and can suddenly buckle or fall without warning, posing significant risk to the rider. They can also be extremely sensitive to pressure along the spine, making saddling a difficult to impossible task. Horses with mild HYPP can often be worked as normal, although they need to be carefully monitored for stressful events so they can be treated properly for a HYPP event. These horses can also suddenly collapse, trip or fall, which can be very hazardous to the rider.