What are Tapeworms?
Colic, a leading cause of death in horses, has long been traceable to equine parasites. One of the key parasites that cause severe infections in most animals, the tapeworm, is increasingly selecting horses as their hosts of choice. Tapeworms are increasing in number across the United States, primarily because they have been gaining resistance to the medications that have resolved infections in the past. New treatments, education about the life cycle of the tapeworm, and strategies for eradication are all being sought within the veterinary community, and also by horse owners who have watched their horses suffer from colic caused by parasitism.
Tapeworm infestations can be tricky because horses may be asymptomatic for some time. However, obvious signs of gastric distress such as flatulence and subtle signs like the sudden dullness of a previously healthy coat eventually point to the presence of these parasites. More severe symptoms of tapeworm infestation, such as weight loss and fecal impaction, warrant an immediate call to an equine veterinarian for examination and treatment. Young horses are particularly at risk of developing anemia and losing weight due to nutritional deficits caused by parasites. While tapeworms are best diagnosed by the presence of their eggs in fecal matter, not all fecal examinations will prove diagnostic. A horse owner may be forced to bring several samples to the veterinarian in order to get a certain diagnosis. Sometimes, owners or veterinarians may find extremely small segments of worms around the base of the tail, but such findings are unlikely. Owners often instead assume the presence of a tapeworm and treat with a deworming product. Many choose the preventive measure of adding a tapeworm product to their annual or bi-annual deworming schedule according to veterinary advice.
Increasingly, however, tapeworms are becoming resistant to deworming preparations, which is alarming because their presence is increasing. While three forms of tapeworms are found in horses (Anoplocephala magna, A perfoliata, and Paranoplocephala mamillana), only Anoplocephala perfoliata is prevalent in the United States. Current high-growth areas for tapeworms include the upper Midwest, where 80% of the horse population has been exposed to tapeworm infections. Some horses are barely able to fight the extreme colic that can accompany a parasitic infection, while others experience a milder form of illness. In all cases of tapeworm infestation, the tapeworm enters the area around the small intestine, and causes enough inflammation for the horse to become painfully and dangerously impacted. Most horses, though, experience a milder form of colic that results from the increase in bacteria typically found in the large intestine. The worst effects of mild colic include gas, bloating and discomfort, but such problems typically resolve upon treatment. A recovering horse may appear lethargic while regaining strength and performance.
A particular emphasis must be placed on the incidence of tapeworm infestations in young horses. In this case, the tapeworm prevents the proper absorption of nutrients, which, in small, more vulnerable horses, often results in acute weight loss. The young horse may not develop properly as a result of malnutrition.
Tapeworms are parasites that cause infections and incidences of colic in their equine hosts.
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Symptoms of Tapeworms in Horses
- Diminished performance
- Pain and discomfort
- Increased flatulence
- Trying to lie down
- Nipping at sides
- Refusal to eat
- Weight loss
- Nutritional deficiency
- Dull coat
- Lack of shedding in warmer weather
There are three forms of tapeworms:
- Anoplocephala magna – the only tapeworm prevalent in the United States
- A perfoliata
- Paranoplocephala mamillana
Causes of Tapeworms in Horses
- Tapeworms are becoming resistant to deworming preparations
- Horses may be asymptomatic
- The tapeworm enters the area around the small intestine and can cause pain in some horses
- This parasite may cause more issues for young horses than mature ones
Diagnosis of Tapeworms in Horses
It is difficult to get a certain diagnosis when it comes to tapeworms. Fecal flotations tests are often unreliable or unremarkable due to fluctuations of the amount of tapeworm eggs in the feces. Because of this, testing may need to be repeated more than once in order to definitively diagnose the presence of the parasite. Blood testing may be helpful if offered by your horse’s veterinarian. One particular test screens for a tapeworm antigen, but this testing is not always available. A palpation of the abdomen which may reveal a mass, in addition to clinical signs such as lethargy and a dull coat, may point to a diagnosis of tapeworm infestation.
Treatment of Tapeworms in Horses
Medications commonly used to eradicate tapeworm infections include combinations of moxidectin and praziquantel (the latter kills tapeworms), marketed as Quest Plus and ComboCare; combinations of ivermectin and praziquantel marketed as Zimecterin Gold or Equimax Paste; and pyrantel pamoate paste. Veterinarians recommend that horse owners alternate products due to the growing incidences of treatment-resistance in tapeworms.
Recovery of Tapeworms in Horses
A full recovery is expected for the average horse treated for a tapeworm infection. Symptoms associated with colic are likely to resolve in most cases. Consult with your horse’s veterinarian to come up with the best annual or bi-annual deworming schedule in order to prevent future incidence of worms.