Fall Deworming

Why do we wait until after the first frost to deworm in the Fall?

With the cooler temperatures setting in it’s time to start thinking about fall deworming protocols. The life cycle for most equine internal parasites involves eggs, immature larvae, and adult worms that then release more eggs into the environment through manure. Eggs or larvae shed in manure will accumulate in the environment, and if horses are turned out on these same pastures throughout the grazing season they can acquire large parasitic burdens by ingesting the eggs and larvae on the grass.  The goal of any deworming protocol is to focus treatments at times of the year that are most optimal for larval development and egg transmission, ultimately reducing the parasite load both internally and in the grazing areas. As temperatures cool down and we start to see frost, the eggs on the ground are no longer viable, and this is an ideal time to deworm because the horses won’t pick up more live parasite eggs and larvae and carry them through the winter. A few weeks after the first frost we recommend using an ivermectin or moxidectin product that also contains praziquantel to additionally target tapeworms – a serious internal parasite that is widespread and has the potential to cause disease (including colic).

Red Urine

We started see red urine in a new gelding. What is causing this? 

Horses often have quite a bit of sediment and occasionally some dark pigment in their urine. In addition, a dehydrated horse will produce very concentrated urine, resulting in a darker looking fluid (and often a stronger smell), a common situation in the wintertime due to reduce voluntary intake. Even perfectly normal, well-hydrated horses can produce very dark urine, particularly during the end of the stream when voiding the “dregs” at the bottom of the bladder.

This is usually not an indication of serious problems, but occasionally very dark urine can be a signal of health issues. Muscle damage, typically tying-up, releases pigment called myoglobin into the bloodstream that is subsequently filtered by the kidney and excreted in urine. Excessive levels of myoglobin will cause the urine to look like Coke and can cause serious damage to the kidney, which is why we will put a severely affected horse on IV fluids to help dilute and flush out this toxin. Blood in the urine, from trauma, infection, kidney/bladders stones, or invasive tumours can also appear quite dark. Even components of normal coloured urine will metabolize into a dark rusty coloured substance after voiding, which can look like blood when they pee on something light coloured like snow. This phenomenon causes lots of phone calls to the vet the day after a good snowfall.

If your horse seems healthy and normal otherwise, I would keep an eye on things but not worry too much. If you have any suspicion of a health problem, a physical exam with bloodwork and urinalysis can determine the source of the unusual colouring.

Melissa McKee DVM

COPD and Exercise

My horse was just diagnosed with COPD, he was in quite a state when the vet came out. I have spent hours and hours educating myself on the topic as this is one I do not have experience with. While I understand the condition can be managed and dealt with my concern is more of a humane one. I have my horse to enjoy and ride. While he is feeling better is it humane to ride him? He can’t tell me how he’s feeling and the thought of him not being able to breath breaks my heart and I can’t stand the thought of making him do something he’s not able. I am doing everything possible to keep him happy but is it fair? I know this is partially a personal question but in all the reading I have done there is no mention of exercise or what physically is good for horses with COPD. 

COPD is a gradually progressive respiratory condition that occurs when exposure to environmental irritants and allergens triggers inflammation in the lungs, causing thickening of the air passages and increased mucus secretions. Over time, oxygen exchange gets less efficient and the horse has to make an increased effort to breathe because of the excess mucus and loss of airway elasticity. Some horses are more susceptible to this condition and acute attacks of wheezing and coughing can be triggered by exposure to an allergen that they are particularly sensitive to. It sounds like this is what happened with your guy.

While we cannot reverse or cure the effects of COPD, the good news is that we can significantly help horses suffering this condition through environmental management and judicious medication. There are several COPD Q&A files on our “Ask The Vet” archive that cover various current treatment and management strategies.

Although COPD is a chronic condition, the good news is that a horse can usually continue to enjoy their regular activities once the acute attack has resolved and an appropriate management plan has been instituted. As long as those small airways are protected from irritation, mild to moderately affected horses generally perform quite comfortably. One of my own COPD affected horses was still able to compete at the advanced level in three day eventing once we had successfully identified and controlled his triggers and the associated inflammation. In his case we gave him as much turnout as possible, changed to dust-free bedding, provided soaked hay and hay cubes, and treated him with inhaled medication which directly treats the irritated airways with a relatively tiny dose of drug.

The best plan for you is to talk to your vet about the stable management and medication strategy that best suits his environment and routine. Once he’s past the acute event, start riding again and monitor his performance carefully. Signs that he’s not coping well would include increased recovery time after exertion, coughing, lack of desire to go forward, and increased respiratory effort with flaring nostrils. You will probably find he has great days and some off days, usually when the heat or environmental conditions hit extremes. But please don’t think it is cruel to continue enjoying your time together on the trail or schooling ring. It’s overall much healthier for a horse to have some exercise and it should not trouble him as long as you have adequately addressed the underlying condition.

Rain Rot Scar

My horse had rain rot this summer, not terrible, mostly under his chest and near his legs only. I noticed a tiny little bump, hard, doesn’t seem to be attached to anything (no root) looks like a rain rot scar. Is this possible?

Rain rot actually tends to affect the back and sides of the horse, where moisture due to rain and sweat tend to keep the skin chronically damp and less resistant to fungal and bacterial invasion. Your horse probably has another form of skin infection, but either way it is unlikely that it is related to the nodule you have recently noticed. This probably a small collagen granuloma (often called nodular necrobiosis). Skin irritation from a bug bite is one cause, and they often also occur under pressure points- mainly in the saddle and girth area. The compression and friction that occurs from tack can rupture the hair follicle, releasing collagen and stimulating a local inflammatory response. I often compare it to an ingrown hair. This causes a palpable lump, which over time may calcify. If the bump is in an area that is becoming rubbed or irritated  I usually have very good results by simply injecting a tiny bit of triamcinolone (a type of light steroid) into the lump, which then goes away after a few days. There are some horses that will develop these lumps repeatedly but they always respond very well to injection if you catch them before significant scar tissue has formed. If the nodule is not growing in size, not painful or ulcerated, and does not get rubber by tack, I would simply keep an eye on it for now.

Melissa McKee DVM

Locking Stifles

Grooming before ride, noticed my 15 yr gelding seemed to not be fully weight baring on right hind. Appears to walk and trot fine. Asked him to step back, left hind he picks up normally, right hind he doesn’t – slides it back. I don’t feel any swelling or heat in that leg. I am wondering where the problem is, my next steps…

If your gelding seemed totally fine while being ridden, and did not show the same awkwardness on the right hind after you were finished your ride, I wouldn’t get too worried about this yet. Horses can effectively lock their stifles so they can relax and doze while standing up. Sometimes that system malfunctions temporarily, resulting in a leg that can’t flex right away when the horse tries to move. It’s possible that he was dozing a bit on the cross-ties and had trouble unlocking the stifle on that side when you tried to back him up. Fortunately it’s not painful and once the ligament releases it’s business as usual. Keep an eye on him, if this continues to happen or he starts to feel off under saddle then I would call your vet to take a look in case something else is going on.

Keeping Horses Cool in Hot Weather

Having just been to visit the barns at the Pan Am Games (congrats to all involved again!!) we noticed that when the temperatures spiked the grooms all ran out and purchased fans to hang around the stalls to cool the horses. We are wondering if this is necessary at a certain point? Or beneficial for competition horses over pleasure horses? As barn owners/managers, what is the best way to ensure the horses in our care stay cool during these heat waves?

Horses have a small surface area relative to their body mass so they tend to have more difficulty cooling off in hot humid weather, especially when exercising. Horses competing at the Pan Ams had to be in top physical condition and feel fresh and energetic on event day, so every precaution was taken to ensure their comfort. This included special misting/cooling fans, electrolytes, lots of cool baths, timing their workouts during cooler hours of the day when possible, and if necessary, intravenous fluids to replenish losses after extreme exertion.

Although horses under less demanding athletic conditions don’t necessarily require this level of preventative management, you can still take some simple measures to ensure their comfort during a heat wave. This includes:

  • Lots of fresh clean water available at all times. Dehydration is the most significant concern due to sweat losses, so it is important that they have water both in the stalls and on turnout.
  • Electrolyte supplementation- horses that are working in extreme heat will lose electrolytes in their sweat so replacement therapy is helpful.
  • Switching to overnight turnout keeps horses safe from direct sun and flies while allowing them to enjoy turnout in the cool hours overnight. Then they can loaf in a shady, well-ventilated stall during the day.
  • Placement of fans in doorways, windows, and in front of stalls will ensure good ventilation and help with cooling because air movement enhances the cooling effect of sweat through evaporation.
  • Alcohol or witch hazel baths are more cooling than a straight water bath.
  • Good fly control. Horses get very hot, cross, and fussy to work with if they have to spend the whole day stomping and swishing to dislodge flies. Not to mention the wear and tear on their legs from these activities.


Runny Eye

My horse has a red runny eye. Can I use sterile 0.9% normal saline,or what do u suggest?

It sounds like your horse may have conjunctivitis (inflammation of the tissue that lines the eyelid and eye socket), which is a common occurrence in the summer due to dust, allergies, and flies. Sterile saline is very benign and there is no harm in flushing the eye with this, it will help to rinse out any foreign material that could be causing the problem. There are medicated drops available from your veterinarian that contain lubricants and medication that are even more effective for treating conjunctivitis, however, an inflamed and watering eye can be a sign of more serious issues such as uveitis (moon blindness) or a corneal ulcer, and in some cases a steroid eye drop can make the condition far worse. Your horse may also have a blocked tear duct that requires flushing with a special catheter so the eye can drain normally again, otherwise you could have persistent tearing and irritation. If this eye problem persists for more than a day in spite of saline rinses, you should have your vet examine the horse to determine if there is a more serious underlying problem and prescribe the correct treatments to alleviate the situation.

Melissa McKee DVM


I have a horse (2005 Appaloosa/Thoroughbred mare) who has become “suddenly” blind. She was diagnosed with cataracts (at 10 years old – no signs of uveitis) that she may have been born with, but have progressively gotten worse over time. Over the last 9 years of ownership, there have been no obvious signs of vision trouble until summer this year.
At this time, I know that surgery is the only option for restoring sight, however I’ve just read a news article that scientists have developed an eye drop (lanosterol) that can dissolve cataracts. These are still in trials, so  it is unknown when they may be widely available.
Having said that, someone has told me that there is apparently already available a drop that claims to dissolve cataracts in humans and dogs. It is an N-acetylcarnosine drop. What are your thoughts on this and would it be worth asking my local vet to investigate this further?

Cataracts occur when there is scarring in the lens of the eye. The lens serves to transmit and focus light that enters the eye onto the retina, and if there is an opaque region in this structure it interferes with normal vision. Cataracts can be congenital, or they can form later in life due to injury or inflammation of the eye.

Your mare is half Appaloosa, and this breed has a very high rate of uveitis when compared to the average horse population. Even if there were no immediate clinical signs of uveitis, it can be difficult to evaluate the retina and optic nerve if a cataract is obscuring the lens without specialized examination equipment and techniques, so I would not yet rule out episodes of uveitis as the inciting factor for the worsening of her cataracts.

Since bilateral vision loss is a severe issue in horses, I suggest you consult a board certified veterinary ophthalmologist for a full evaluation of her eyes in order to develop a plan to address the cataracts and prevent further loss of sight. I would certainly obtain a leptospirosis titer to determine if this infection is present, which is a high risk factor for uveitis and the associated complications. Identifying and treating any predisposing factors in her case will help to prevent or at least slow the onset of further lens scarring.

Surgery is still the most effective treatment for mature cataracts. There has been some investigation in the use of N-Acetylcarnitine drops for reduction of mild immature cataracts, but the evidence for their effectiveness even in these cases is weak. They would not have a useful effect on a mature established cataract.

Melissa McKee DVM

Duration of Lameness After a Hoof Abscess

How long does it take for a horse to return back to soundness after the abscess has burst? 

For most horses, once an abscess ruptures the relief from acute lameness is almost instantaneous, and residual tenderness will disappear in about 24 hours. For severe and more chronic abscesses though, recovery time can be several days and even a few weeks. This is because the abscess pressure creates a lot of local inflammation and also can compress and deform the adjacent tissues, which then take a while to bounce back to normal condition. Other horses suffer from lingering soreness because the abscess does not drain completely before closing over, resulting in repeat episodes of pain and drainage. In some instances, there is necrotic tissue or a damaged spot of coffin bone that forms a nidus of infection and will continue to drain until the revitalized tissue is gone. Your veterinarian can assist this process by surgically opening and scraping away the problematic tissue. If your horse has ruptured and drained an abscess but is still significantly lame, it may be worth having your vet take look and obtain some X-rays to see if there are any additional problems in the foot.

Melissa McKee DVM


How do you diagnose for PSSM? What are tell tale signs that I should be looking for that will tell me we need to start to treat and test?

PSSM is short for “polysaccharide storage disease”. It is a muscular condition that predominantly affects horses with draft or warmblood ancestry. Affected horses are unable to utilize dietary carbohydrates for energy to contract the skeletal muscles; they tend to store up large globules of carbohydrates in the muscle cells but cannot break them down for consumption- hence the name of the disease. Draft horses are the most severely affected by this condition and in some cases can die from it, while lighter breed horses have  milder and more nebulous symptoms. The usual complaint is that the horse is “stuck” or won’t go forward, has become grumpy and muscle sore, resents grooming, may show signs of shivers or muscle cramping, and lacks energy despite an increase in the grain rations. This is a separate syndrome from “tying up” seen in lighter breeds although the clinical signs and some of the bloodwork findings are similar. Quarter horses also have a cluster of breed-specific muscle disorders that are not exactly the same as PSSM. In fact, further research has shown that there are several variations of equine muscle storage disease that affect different breeds, and horses are so highly interbred that they can be affected by any of these conditions.

Diagnosis is based on a combination of history and physical exam, blood tests for muscle damage enzymes, muscle biopsy, and genetic testing. Horses affected with PSSM will often show a mild and persistent elevation in certain enzymes on blood tests, particularly after strenuous exercise. A muscle biopsy taken from the hindquarters can be examined for characteristic polysaccharide clumps in the muscle cells. Recently, a blood test for a particular gene associated with PSSM had been developed, but this will only detect one of several possible genes for the disease.

If PSSM is diagnosed, the treatment is to change the diet so that most of the energy is provided in a non-carbohydrate form. In most cases, this is the “high fat high fibre” ration that is becoming increasingly mainstream in the feed tubs. The fact is that many horses respond well to this diet, even those that suffer from other problems such as tying up or gastric ulcers.

If you suspect PSSM in your horse, you may wish to talk to your veterinarian about the various diagnostic options.

Dr Stephanie Valberg of the University of Minnesota specializes in neuromuscular disorders in horses, and has a very informative website. Here is a link to the PSSM page: http://www.cvm.umn.edu/umec/lab/PSSM/home.html