In Memory of Tequilla

The Love of a Horse knows not its own depth until the hour of separation.

April 16th, 2004 at the age of 9

I never dreamed that a swollen sheath and a small patch of ventral edema April 3rd were first signs that I would be writing this article. I thought my biggest struggle this spring was finally realizing that Tequilla and my daughter would go places I could never take him to reach his full potential and he had become her horse. The Eastern Canadian Pony Club Dressage and Show Jumping was to be the finale to our well planned summer. They had been Champion in their division of show jumping and Reserve Champion in dressage last summer at the SLOV Regional finals. Turning him into an Eventer this summer would be more challenging.  Just watching the two of them in a ring of any kind I was over whelmed with pride.

For the first time since we have owned our horses, six years, they were living like kings in a small private barn, never having to worry about where their next meal and drink of water would come from, a cozy clean comfy place to sleep every night and a parasite-free paddock.

Tequilla was a victim of "Larval Cyathostomaisis", in other words encysted small strongyles. The potential for "larval Cyathostomiasis" is something that all horse owners should understand and be aware of. Maybe many do but I didn't. I have researched exhaustively and have place many links at the bottom of this page for anyone interested in learning more.

From the onset, we noticed a small patch of pitting edema on Tequilla's chest,  but his spirit was still good, his coat was healthy and shiny, and his slight weight loss could be attributed to winter muscle loss. He did not have diarrhea and was eating well, so it didn't seem life threatening. Within a few days his sheath swelled and there was a notable rapid weight loss, although he still ate all his feed with vitamins, oil, beet pulp and his 4 flakes of hay every night. Nothing was making sense. Over the past year I had wormed regularily, at two month intervals rather than once every three months, so parasites never occurred to me as the cause. The horses were due to be wormed, along with their regular yearly vaccinations on April 14th.

A blood test showed that he was "hypoalbuminemia", anemic and protein deficient.  His immunity was greatly reduced. A second vitamin and selenium & E supplement was added to his feed and as well as all three of our horses given an ivermectin wormer. Over the next few days Tequilla ate well and during stall cleaning and paddock manure pick up we found a large number of dead small strongyles and blood in his manure, strongly indicating that what we were dealing with was a mass emergence of encysted small strongyles, "larval cyathostomaisis".

 He followed me around in the paddock and when I was bent over inspecting the manure he followed me everywhere and nudged me from behind to let me know he was there. Tequilla never lost his curiosity or our companionship.  He started to refused his feed so we resorted to hand feeding him. He would show excitement and stick his head in the pail then not eat or eat very little. He had spiked a fever and was also laboring to breathe. As a result he was treated intravenously to reduce the fever and with antibiotics to cover any secondary infections that might ensue. His fever continued to climb over the next three days and be treated. When hand feeding with molasses and applesauce-laced feed failed, I began giving him his supplements and meds by syringe with apple sauce twice a day and slivered carrots by hand. He was the most patient horse in the world,  trying as hard as I was to get better and despite everything we did he worsened. Seven short days from the onset, he was going down hill very quickly, hours were making a difference.  He had a hard time walking and the edema was very apparent along his entire abdomen and his gums were now purple. Fluid was leaking into his body cavity and lungs. He was literally drowning in his own body fluids.

I took him to a big hay field where he could eat some fresh grass and sat quietly with him, his coat glistening in the sun, remembering every where we had been and everything we had done. How could this be parasites? I have always wormed regularily on time with rotation. His coat was not dull, he was shedding normally and he had no sign of diarrhea, his ribs were not showing and he looked close to normal, on the outside. Once he staggered and stepped on my ankle, he was so weak and shaky I didn't even feel it. He nibbled and tried to eat but it was so hard for him to breathe and eat. I knew this was it and it was only his spirit that was keeping him going......he was not giving up and neither was I. I ran in the field and he jogged a few steps with me like we used to do. Prognosis from the vet that day was not what I wanted to hear but in my heart I knew it was true...his system was shutting down quickly. I had to say good bye to my "Baby". The pain in my heart while leaving the barn was almost unbearable knowing I would never see him again, those big brown eyes, sweet face, ever be able to hug him or hear his welcoming knicker again.

These silent killers, encysted strongyles, can exist undetected and accumulating in the mucosal lining of the hind gut for a long period of time, up to years according to several studies, waiting for an optimal time to emerge regardless of a regular worming program. Little did I know, I was only remaining one step ahead. I wormed the day before I moved my horses in the fall and thought I was leaving it all behind .....I was wrong.  Apparently the damage was already done. Would a dose of moxidectin or double doses of fenbedazole for five consecutive days have prevented this fate? That I will never know. Fecal tests may or may not have picked up encysted because in this stage they are not laying eggs. A blood test may have given a clue earlier on.

Little did I know the true full risks of heavy parasite exposure over a period of several years, I would never have been so patient and would have moved my horses several years before I did. I was under the misconception that worming every two months with a rotation of ivermectin, fenbendazole and pyrantel tartrate would protect him. Although I was covered for adult small strongyles among other species, I had never heard of encysted small strongyles. Many studies conducted on this number-one enemy are still inconclusive about the cause of a mass emergence or why they encyst in the mucosal lining of the cecum. There is one product on the market that claims to kill the encysted stage of these parasites, moxidectin gel, although it may not be 100% effective either. I gave a moxidectin gel wormer when I first bought Tequilla in 1998 and not again since. I was afraid to use that particular wormer.  Now knowing the consequences, I no longer feel that way and highly recommend it once a yearat least. There is no way of knowing if it would have saved my horse.

The only sure way is prevention through proper pasture management. This larvae is not killed by frost; that is one of those old wives tales. Frequent harrowing and or at least manure pick up weekly, or more frequent depending on the space and number of horses confined, is a MUST.  Several years worth of manure can be lethal. Over crowded pastures and irregular feeding creating a feast-famine situation and feeding off the ground greatly increase the risk.  Horses prefer not to graze around feces but are forced to when in an overcrowded pasture.  The horses' water supply must be clean and free of feces or run off from infected pastures. The quarantine and management of new arrivals can not be taken lightly.  Fecal counts and deworming before introducing new horses to the herd is critical in controlling this parasite. Worming all horses on the premises on the same day with a proper rotational program is very important.  Avoid creating "super" worms. The small strongyle is one parasite that is said to always be one step ahead of drug company scientists and there are said to be over 40 species of them that effect the equine. These points are just the tip of the ice burg.

The majority of horses are not likely to be effected, depending on where they have been stabled. There is also no rhyme or reason as to why horses can have the same exposure yet never have this happen to them. I am incredibly happy to say that the results of blood tests and fecal on our other two horses, Suni "Bullwinkle" and Shadow "Excalibur or Rocky", indicate they were caught in time and are now being treated to replace and build the red blood cells lost from these voracious feeders.  I do suspect in this case the mass emergence may have been brought on by a change in feeding, making their body an optimal host with abundant nutrients. However that is just my own suspicion. I do not want to present myself as an expert or veterinarian professional in any way. Just my point of view. I strongly recommend anyone who owns a horse should take the time to read some of the articles I have linked to below. I have search exhaustively for information on this subject and rather than quote directly I have supplied the links. Online veterinarian university sites world wide offer a wealth of valid information on this and many other issues effecting horses.

If one horse can be saved as a result of an owner reading this article then it is not in vain.

"Larval cyathostomiasis.

Lyons ET, Drudge JH, Tolliver SC.

Department of Veterinary Science, Gluck Equine Research Center, University of Kentucky, Lexington, Kentucky, USA.

Over the past few years, cyathostomiasis has become increasingly recognized as a clinical problem of horses in the United States. Clinical cyathostomiasis has been reported frequently in Europe for a considerable time. This clinical syndrome is usually related to the sudden release of large numbers of the larval stages of small strongyles from the mucosa of the large intestine. Typical clinical signs include diarrhea, ventral abdominal edema, pyrexia, colic, weight loss, and poor body condition. Hypoalbuminemia and the presence of large numbers of small strongyles being passed in the feces are also characteristic features of the disease. The disease may occur seasonally in late winter and early spring or after drug treatment to remove the luminal stages of small strongyles. Two commercially available drugs, moxidectin and fenbendazole, have been shown to be effective against the encysted larval stages of the parasites. Drug resistance of small strongyles to all classes of currently available antiparasitic compounds except the macrocyclic lactones (ivermectin and moxidectin) is a limiting factor in controlling these parasites and may result in an increased prevalence of clinical cyathostomiasis over time."

2.University of Pennsylvania - Photos of encysted http://cal.vet.upenn.edu/merial/Strongls/strong_9b.htm

3. University of Kentucky http://horseproducts.stablemade.com/news/Parasitism_in_Horses.htm  Article "Parasitism in Horses"

4. University of North Dakota http://www.ext.nodak.edu/extpubs/ansci/horse/v543.pdf

5. University of Georgia 

6. University of Missouri http://muextension.missouri.edu/explore/agguides/ansci/g02854.htm

7. University of Missouri http://www.dutchhorsesunlimited.com/Cgi-bin/PDF_Documents/G02854.pdf  "Controlling Internal  Parasites in Horses"

8. University of Nebraska http://ianrpubs.unl.edu/insects/g1095.htm

9. Oklahoma State University  

"Small strongyles (Cyathostomum, Cylicocyclus and Cylicostephanus spp.; Gyalocephalus
capitatus) are considered especially dangerous because of their ability to burrow
into a horse's intestinal wall, where they further develop.  At this stage, they are
referred to as "encysted cyathostomes," and can remain in these fibrous bubbles in an
inactive state from several weeks up to one year or more.

Large numbers of encysted small strongyles can suddenly and unexpectedly emerge from
the intestinal wall, releasing into the horse's system metabolic excretory products
that the larvae have been producing within the cyst.  According to parasitologists,
the release of these dangerous toxins can cause a variety of intestinal problems,
including: diarrhea, anemia, severe and rapid weight loss, colic, fever and even death."

11. Great Article in "The Horse" called "No More Hitch Hikers"  

"Small strongyles infect virtually all pastured horses

Intestinal parasites remain an ongoing threat to the health and happiness of all horses that set a hoof down in a pasture. And, the cast of characters in the intestinal parasite drama is changing, according to equine parasitology experts.

Until the mid-1980s, parasitology experts estimated that large strongyles (commonly known as "blood worms" or "red worms") infected more than 50 percent of all adult horses. Thanks to the widespread availability of ivermectin and paste dewormers, large strongyles have been nearly eradicated in well-managed horse herds, according to Craig Reinemeyer, DVM, PhD, Associate Professor at the College of Veterinary Medicine at the University of Tennessee.

This virtual elimination of large strongyles in the population has, by default, left small strongyles with the distinction of being the most common and economically devastating internal parasite of adult horses, Reinemeyer says. He notes that despite their diminutive name, small strongyles can severely impact the health and well-being of adult horses and should be the primary concern of horse owners and veterinarians in most parasite control programs.

"Small strongyles are found universally wherever horses are pastured. Virtually all horses on pasture are infected with them," says Reinemeyer. He adds, "Although severe clinical infection with obvious symptoms that we associate with a 'wormy' horse may occur, most horses infected with small strongyles do not display symptoms. It's difficult to document, but subclinical effects still occur." Reinemeyer says subclinical infection impacts horses in areas not typically measured-feed efficiency, rate of daily gain and performance.

Life Cycle

The life cycle of small strongyles begins when horses swallow infective larvae (third-stage or L3 larvae) on grass contaminated with feces.

After L3 larvae are ingested, they burrow into the wall of the large bowel, where they develop into L4 larvae - commonly referred to as "encysted cyathostomes" by parasitologists and veterinarians.

Reinemeyer says encysted cyathostomes may remain in the tissue of the mucosa (enclosed in fibrous cysts or bubbles) in an inactive state from several weeks up to one year or longer.

While they are in the encysted- stage, small strongyles appear to cause very little inflammatory reaction in the horse, Reinemeyer says. However, severe intestinal problems can occur - when large numbers of encysted cyathostomes begin emerging from the gut wall at once.

"When encysted cyathostomes emerge, the mucosal lining of the gut becomes inflamed, because the horse is being exposed to all of the metabolic excretory products the larvae have been producing within the cyst," Reinemeyer says. The level of damage and disease varies with the level of infection and can include mild to severe colic, anemia, severe diarrhea and weight loss, he says.

The timing of emergence of encysted cyathostomes from the gut wall continues to be studied by parasitologists. "We don't know enough about the timing of emergence of encysted cyathostomes, or why large numbers tend to emerge all at once," says Reinemeyer. He adds, "We do know that in the northern United States, encysted cyathostomes tend to emerge in the late winter or early spring. In the southern United States, the reverse may be true, with large numbers of encysted cyathostomes emerging during summer and early fall."

After encysted cyathostomes emerge, they mature into adults and produce eggs which are excreted by the horse in feces. After the eggs hatch, the larvae go through two molts and become third-stage or L3 larvae, which attach themselves to grass and are ingested. This cycle of infection continues as long as horses remain on pasture.

Reduce Pasture Contamination

Reinemeyer says completely eliminating small strongyle infection is unrealistic and even undesirable. "A low or mild level of infection is actually desirable, to help the horse maintain acquired immunity," he says. Reinemeyer recommends the following to help reduce pasture contamination and subsequent reinfection:

Work with your veterinarian to develop a regular deworming program that will kill adult small strongyles before they have the chance to lay eggs. Although encysted small strongyles typically survive repeated treatments with single-dose dewormers, suppressing the number of eggs produced by adults will cut down on the level of pasture contamination.

Group pastured horses by age, to avoid exposing youngsters to heavy larval populations. A good place to start: pasture mares and foals away from other horses less than 2 years of age.

Allow an adequate number of acres for the number of horses being pastured. Although horses prefer not to graze near feces, overcrowding may force them to do so, increasing the likelihood of ingestion of larvae.

Isolate and deworm new horses that are arriving on the farm.

If feasible, remove manure from pastures at regular intervals. Twice-weekly removal is optimal.

Rotate sheep or cattle in horse pastures, as these species are not infected by small strongyles. Grazing these species helps reduce pasture contamination by removing the L3 larvae, thus breaking the cycle of infection."