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We all hear about how important it is to worm our donkeys, but very few people know how these parasites affect your donkey.  This article, I hope will help you understand some of these parasites and how they  multiply..  


Nematodes are the most important group of internal parasites in donkeys.  Most nematodes have a similar lifecycle.  The female lives in the donkey’s intestines, she lays eggs, which pass out in the manure, if the environment is warm and moist, the eggs hatch.  The larvae grow and develop until they reach the infective stage, then the infective larvae move onto blades of grass.  The donkey eats the grass with the larvae on it.  Then the larvae migrate and burrow through the donkey’s body.  The larvae return to the donkey’s intestines, mature, mate and the females start to lay eggs.  It is like a revolving door, unless the cycle can be broke!


Some of the more common nematodes parasites are ascarids, strongyles, lungworms, bots and oxyuris. 


Ascarids are primarily a problem in young donkeys.  Donkeys usually develop a resistance to ascarids by  the age of two then they carry a small number.  In foals, ascarids may cause weight loss, rough hair coat, coughing and nasal discharge (because they migrate through the lungs).  Sometimes when foals with a very large number of ascarids are dewormed, the dead worms may pack into a large ball and obstruct the foal’s intestines.  This causes colic and even death.    By the time a foal is two/three months old, they will have some mature worms in their intestines already laying eggs.  This part is really important; foals should be dewormed for the first time at six months of age to avoid a large accumulation of worms in their intestines and the environment.  If a foal is thought to be heavily infested with ascarids, the foal should be dewormed with half the regular dose of dewormer.  Then in two/three weeks the foal should be dewormed again at the proper dose.   This method will decrease the risk of obstruction of the foal’s intestines with dead ascarids, because only the ascarids most sensitive to the dewormer are killed at the first deworming.  The remaining ascarids are removed with the correct does later.  My donkeys have always been wormed in this manner and I have never had a problem.


Strongyles, there are two types large and small.  The small strongyles stay in the gut and gut wall and do not cause much damage.  The large strongyles do a lot of damage because of their type of lifecycle.  The larvae migrate and develop in the blood vessels.  This damages the blood vessel walls, so instead of being smooth the walls have adherant debris, worm larvae and blood clots.  Pieces of damaged vessel and blood clots sometimes break loose and the flow of blood carries these pieces along until they come to a blood vessel that is too small for them to pass through.  These pieces block off the blood vessel and stop the flow of blood.   If that blood vessel leads to the intestine, that piece of intestine will start to die due to lack of oxygen and nutrients.  If only a small amount of gut is affected the nearby blood vessels enlarge to carry blood to the affected area of the gut.  If the amount of gut affected is large this collateral circulation cannot compensate for the blocked vessel.  The section of gut dies and becomes gangrenous.  The donkey depending on the amount of gut affected may develop anything from mild colic to severe fatal colic.  Because of this it is important to worm your donkey, as strongyles do not usually cause weight loss or poor hair coat.  


Lungworm can infect both horses and donkeys but the effects are very different.  Donkeys usually show little or no clinical signs of their infection, while infected horses show obvious respiratory signs.  Horses usually develop a chronic cough when infected with even small numbers of lungworm larvae.  Most standard wormers have little effect on lungworms and that was why many people stated and still do that donkeys and horses should never be pastured together.   This is not true if your animals are wormed with invermectin dewormer.  My horses and donkeys are pastured together and I have never had a problem.


Bots, any donkey that is outside during the summer is likely to have bots.  Bots are not in the nematode category but very important to be aware of.  The bot flies attach their eggs to the donkey’s hair  usually on the legs, but could be anywhere.  The eggs either hatch on their own or are stimulated to hatch by warmth                

and moisture when the donkey scratches.  The larvae then burrow into the donkey’s mouth and stay there for three/four weeks.  Then the larvae move down to the donkey’s stomach and stay there until spring.  In the spring the bots release their hold on the stomach wall and are passed out in the manure.  They then burrow into the ground to continue development and in two/three weeks hatch as flies.   Bots do not usually cause a serious problem unless the donkey has a very heavy infestation.  It is a good idea to remove the eggs, if you see them.  Pot knives can be purchased to remove the eggs from the donkeys hair. 


Oxyuris is another nematode that infects donkeys; the common name is pinworm.  This worm does not do as much harm to donkeys but is more of a nuisance.  Instead of the eggs passing out in the manure like most nematodes, the female of this species move to the rectum when she is ready to lay eggs.  She extends her long tail out and deposits a sticky fluid containing the eggs on the skin just under the donkey’s tail.  This fluid causes irritation and the donkey tries to scratch the spot where the eggs have been deposited.  When the fluid dries, the eggs drop off and the donkey eats any that happen to fall into its hay or water.  If you see your donkey rubbing his hid end on a fence,  or has hair missing from the top of its tail your donkey probably  has pinworms.  Pinworms are very common in donkeys. 


There are many types of deformers on the market and each has a varying degree of effectiveness against different worms.  To decrease the development of resistance to a particular dewormer by the worms, it is recommended that different dewormers be used in rotation.  If you use the same wormer the probability is that the worms will develop a resistance to it.    I do suggest that invermectin (Zimecterin or Eqvalan)  is used in the fall after several good frosts because of bots.


I hope this information is informative and will help you understand how worms affect your donkeys and how important it is to worm them.





Yvon & Nancy Leduc
RR #4,
Tweed, Ontario K0K 3J0
Phone:  613-478-1367