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Worming
 Moderated by: DrDeb  
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AuthorPost
Horse Adventurer
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Joined: Tue Nov 30th, 2010
Location: Curlew, Washington USA
Posts: 8
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 Posted: Sun Dec 26th, 2010 03:31 am
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Hi Dr. Deb!  What a find you are...Thank you so much for this classroom ""-D

Your opinion please:

-Chemical wormers can strip the gut of good bacteria so then the gut is out of balance and now an attractive environment for worms and parasites.

-Are there always "some" worms in the gut?

-Only worm when necessary.  Where is the best to get stool samples tested and ask for what?

-Herbal wormers.  Any recommendations?

-Practices to keep the gut in balance.

Best

DrDeb
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Joined: Fri Mar 30th, 2007
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 Posted: Sun Dec 26th, 2010 07:53 am
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Dear Adveturer: Welcome to the Forum.

The question you ask represents a confusion. The usual dewormers used on horses, specifically ivermectin and strongid (pyrantel pamoate, pyrantel embonate), praziquantel, fibantel -- all of these are anti-parasitic agents, not antibiotics, and they have little effect on gut bacteria.

Yes, under normal domestic conditions, adult horses always have some worms in them -- the idea with deworming is not to clean out every single worm until the villi of the gut are as pink and clean as a baby's butt, but to hold the worm population to a low point where the parasites do no discernable harm to the horse.

Efforts to 100% clean out the worms are both unnecessary and unwise -- even unethical; because to do this, daily, low doses of the wormer would need to be administered. Over time this has proven to create "resistance" in the targeted worm species, creating the need for ever stronger deworming chemicals. For example, efforts in the 1990's to market low-dose "daily dewormers" were made by the company that used to own the patent on Strongid (pyrantel pamoate), in the period just prior to the expiration of their patent rights. This was 100% politics -- a greedy effort to get rid of their remaining inventory at the greatest possible profit before other companies gained the right to manufacture it. The harm done was not only to horses but, especially, to the hog industry, because Strongid was the only product effective against worms that parasitize hogs, and they have now had to move to much stronger and more costly agents to get the same job done.

All these chemicals -- Ivermectin, Strongid and so forth -- kill worms by interfering with nervous system and muscle function. Worms are animals, and they have nerves and muscles. Ivermectin (and the related avermectins found in, for example, ant poison) inhibits nerve transmission to muscles. Pyrantel works by paralyzing muscles, thus causing intestinal parasites to "lose their grip" and thus be flushed out of the system with the stool.

Obviously, bacteria have neither a nervous system nor muscles, and these chemicals do not target intestinal bacteria, the one-celled creatures that compose the "gut flora".

The reason that you do not want to over-use these chemicals has, thus, nothing to do with "balancing the gut", but rather out of caution because the horse itself does have a nervous and muscular system, i.e. the very same chemical that kills the worms could, in high enough doses, also kill the horse -- or create milder, yet still troublesome, neuro-toxic effects.

For this reason, for example, ivermectin cannot be given to birds, turtles, and some breeds of dogs that have a genetic mutation -- any amount of the chemical will kill these animals, because in them ivermectin is more readily absorbed from the gut (creating a higher concentration of the chemical in the blood, from which it can reach nerves and muscles) and/or can cross the blood-brain barrier.

Dewormers also need to be administered with caution to horses or donkeys that are suspected of carrying heavy parasite loads. A big single dose of de-wormer will kill most of the parasites all at once, leading to an impactive colic in which the impaction is a ball of dead worms. This is particularly a concern with Strongid/pyrantel. Ivermectin, which is particularly effective against roundworms, can create a colic through causing dead worms to clog the mesenteric and/or hepatic arteries, thus choking off circulation to a section of intestine.

The most sensible way to arrange your de-worming program is, first, to look at the conditions under which the horse is kept. If the enclosure in which he lives has not been grazed by horses for a few years; if your herd are the only horses on it and there are never any "visitors"; and if you make efforts to pick up most of the manure that they drop, then you have less need for deworming.

On the other hand, if you share a paddock with other boarders or agisters, and those horses are swapped in and out at intervals; or if your horse sometimes is put into an "overnight paddock" for example at a show or clinic, or in any other way has frequent access to grass near where horses that you don't know have manured, then you need more frequent deworming.

Exactly how frequent, which chemicals, whether different dewormers are to be alternated, and how strong the dosages are all matters for you and your attending veterinarian to decide.

It is also very sensible to submit a stool sample to your vet. Many equine vets will do a stool evaluation for free. It's a very reliable way to find out what type of worms your horse(s) may have and how heavy a parasite load they may be carrying. -- Dr. Deb

 


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