The first "Ask the Buckeye Vet" Contest winner, for May 2010 is:
Kim Cronenwett from Woodview Farm in Sandusky , Ohio.
Congratulations Kim, and thank you for your question!
ASK THE BUCKEYE VET:
What are your thoughts on the newest deworming recommendations in the horse publications (Thoroughbred Times, Practical Horseman), ie selective deworming based on results of fecal examinations, geographic location and parasite life cycles vs. routinely scheduled (every 8-12 weeks) rotational deworming programs? Cost considerations vs. effectiveness? Is worm resistance a big factor in this area of the country?
ANSWER:
This is a complex question that is being widely discussed. Resistance to dewormers is known to be increasing in the United States, especially in the south. This “new” awareness about resistance is something that we in routine practice have been concerned about for a long time. Many anti-parasite medications have long been ineffective and are still on the market for the unaware horse owner. There are no new anthelminthics in the “pipeline”: certainly none that will be available within the next ten years.
In order to decrease resistance to the anti-parasite medications, selective deworming is obviously the optimal choice. However, research labs have some advantages in this area over a “real world “practice. Based on the life cycles of the majority of the parasites we are concerned with, fecals would need to be examined on a monthly basis to determine whether horses are newly infested or not. That is part of “research” in a lab, but would be cost prohibitive to a client!
A negative fecal egg count doesn’t necessarily mean that your horse is parasite free, either. While it is the best diagnostic indicator we have, it may be that the worms were not shedding eggs on that day. The quality of the sample is important as well: “old” feces will not be as likely to give accurate counts as the eggs may have hatched. Tapeworms are a significant concern, as they do not shed eggs at all times, are notoriously difficult to pick up on a fecal exam, and can be a cause of colic.
Each farm has different exposure risks. A large boarding facility with small paddocks used by many horses has a greater chance of spreading parasites than a few horses in a large pasture. Because desiccation of the eggs in the sunshine kills the larva, it is thought that mowing may help destroy the parasites. (It is now believed that freezing may not be vey effective in killing them). We do know that frequent removal of feces from pastures greatly decreases exposure.
If label instructions were followed, we would be deworming very frequently. Strongid (pyrantel pamoate) is labeled for use every six weeks. Panacur (fenbendazole) is labeled for treatment every two months (with double dose, multi-day treatment twice a year). Neither of those recommends “rotation” with other dewormers, even though they are not effective against all worms. Overuse of any product is definitely not recommended, and leads to resistance.
As a practice, we are trying to use the available, effective products in a minimal and responsible way. After much discussion, we have decided to be proactive by promoting and monitoring fecal egg counts: twice a year in our wellness programs (a fall exam was added this year at no additional cost) and recommended at least once a year for all horses. Of course, we can read them as often as is needed in problem cases, or at the clients’ request.
In our wellness programs, rotational deworming will be continued four times a year, including the use of Equimax (ivermectin and praziquantel) twice a year for control of tapeworms. Horses with resistant worms (as identified by fecal egg counts) will be treated specifically. By doing more fecal egg counts, we hope to be able to identify and address trends or problem areas.
Of course, there are exceptions. For instance, this discussion does not apply to foals, which have a separate, specific set of recommendations. Please consult your veterinarian about appropriate use of dewormers for your specific circumstances.
Our June 2010 winner is Cheryl Fazio! Congratulations Cheryl, you've won a free farm call!
ASK THE BUCKEYE VET:Do you often see leptospirosis as the cause of uveitis in horses?
ANSWER: This is a great question, Cheryl. Equine Recurrent Uveitis (ERU) is an aggravating problem that affects many of our clients’ horses. Also known as “moon blindness”, it is an auto-immune reaction that involves damage to the “uvea” (the iris, ciliary body,etc) inside the eye. Typical symptoms are swollen eyelids, red conjunctiva, tearing, light sensitivity, and pupil constriction. Sometimes there will be fibrin or clusters of cells floating in the eye chambers. This is an emergency situation. The inflammation needs to be controlled and the pupil, if constricted, needs to be opened as soon as possible. Even when the eye appears asymptomatic, there is a low level of inflammation within the eye. Stress, illness, or an unknown cause allows the inflammation to flare up, often within a very short time. If one eye is affected, there is a 50/50 chance that the other eye will have similar issues at some time.
Leptospirosis is a zoonotic disease caused by a spirochete, typically shed in the urine of infected animals. It is able to survive in water for long periods, and is usually transmitted through skin or mucus membranes. In horses, infection is typically associated with abortion and uveitis, but most of the time it is mild and self-limiting. Infections may be asymptomatic, or show fever and being “off feed”. It is not easily cultured. In our practice, Lepto is a rare diagnosis.
Multiple causes of ERU have been determined. According to the Merck Veterinary Manual, the list includes: Leptospirosis, Brucellosis, strangles (Strep equi), onchocerciasis (aberrant parasite larval migration), influenza, tooth root abscesses, and hoof abscesses. It states that up to 67% of uveitis is caused by Leptospirosis. Unfortunately, the inflammation in the eye does not happen until an extended period of time AFTER the horse has recovered from the inciting cause. This makes finding a definitive diagnosis challenging as the cause is long gone. Drawing fluid directly from the eye to search for the cause is extremely dangerous to the horse, and not practical. We can pull serum titers a few weeks apart to determine recent infection, but the cost/benefit ratio may not be worth it. With many potential tests to run, and an answer not likely to be determined, typically we treat the symptoms and make owners aware of the recurrent nature of the disease.
Treatment typically is aimed at reducing the inflammation inside the eye. Banamine (flunixin meglamine) is the first line of defense. A topical nonsteroidal anti-inflammatory like diclofenac, or Optimmune (cyclosporine) is frequently used. Oral aspirin may be used prophylactically. Often, we reach for a topical corticosteroid as the most potent anti-inflammatory. A solid diagnosis of ERU is necessary, as putting a steroid in an eye with a scratch can lead to a devastating fungal infection.
Within the last twenty years, a surgical approach for treatment has been steadily improved and is very effective. An implant embedded with cyclosporine is actually surgically inserted in the eye, suppressing the auto-immune reaction and quieting the flare-ups. We have multiple horses within our practice that have had this procedure, and it has been successful in dramatically improving the recurrence in most cases.
Remember, DO NOT put steroids in an eye unless it has been determined that there is no ulcer (scratch). Flourescein stain and careful examination will usually identify an ulcer.
Here's another great question from Cheryl Fazio!ASK THE BUCKEYE VET: My question is about enteroliths in horses. Well, kind of a three fold question. How often do they cause colic in horses, what causes them and can they be prevented?
ANSWER:Enteroliths (also known as intestinal stones) are masses composed of mineralized material (primarily magnesium, aluminum, and phosphate) that form around sand, stone, nail, rope/twine, wood, even hair, ingested by the horse. Individuals affected are typically greater than 10 years of age and are fed a diet high in alfalfa hay. Geographic location (due to soil composition) can also be a contributing factor with the highest incidence of enterolithiasis seen in California and other parts of the south west.
Certain breeds, Arabians and Arabian crosses for example, may also be more likely to develop this condition.
Clinical signs vary depending upon the size and location of the enterolith. The horse may have mild and intermittent episodes of colic to severe pain/discomfort, decreased to no appetite, weight loss, passing a small amount of manure or diarrhea.
Enteroliths are usually located in the right dorsal colon, transverse colon, and small colon so are not likely to be palpated on a rectal exam. The diagnosis can be made based upon abdominal radiographs, but is more frequently confirmed at surgery, as well as at necropsy. And, horses that develop an enterolith may be predisposed to forming them again.
To reduce the risk of formation, certain management strategies are recommended, such as: feeding grass hay instead of alfalfa, increased grazing time for horses with limited pasture access, feeding psyllium, and increasing turn out and exercise for stalled horses. Any dietary changes should be made slowly.
Small colon enterolith
Researched by Dr. Amy Rennie
