Postings & Discussion: 

Subject:          ERU and De-wormers

Date:               October 25, 2006      

This discussion is in an attempt to resolve the questionable connection between ERU & de-wormers.  Please consult your veterinarian for the latest in update information.  If you would like to post your findings to this subject, please feel free to email the information, all in an effort to communicate knowledge for the individual reader to determine the most conducive results for them and their equine partner(s).

"I would encourage you to establish a relationship with

an equine veterinarian in your area and support them fully".

JP B. DVM,  PhD

Diplomate ACT

College of Veterinary Medicine

University of Illinois

From: Janice from Texas

To: Dr. B from University of Illinois

I am still looking for a simpler but effective way to protect my mare from worms & not compromise her vision. I do not know if she is predisposed or not and do not want to find out the hard way.  I have also read that leptospirosis is a possible cause.  Before I have a vet here for shots etc, I want to be fully armed with information.  With my gelding,  we went thru ointments, drops, masks, daily bute with flares.

To: Janice

From: Dr. B

Basically, the association between flare ups of ERU and de-worming is due to a microfilaria of the parasite Onchocerca cervicalis commonly known as the threadworm. Aberrant larvae migrate in the conjuctiva, scelera and occasionally cornea of horses. When a de-wormer is used, ivermectin kills the larvae and body mounts an immune reaction to the dead parasite. 

To prevent or minimize this reaction, the recommendation is to premed the horse with anti-inflammatory drugs, before administering the de-wormer.

Recommendations are to administer a corticosteroid (prednisolone) before and for 5-7 days after de-worming to minimize the inflammation. I additionally administer the nonsteroidaly drug, flunixin/banamine as well. I would encourage you to discuss this with your regular veterinarian to work out a treatment plan. 

Dr. B. DVM, PhD

Questions/Concerns from Janice:

Answers/Suggestions provided by Dr. B:

Q: Is the prednisone available to mix into grain?

A: Yes

Q: How many days prior to worming is it to be administered?

A: Start the day of de-worming.

Q: Dosage? 
A: Consult your veterinarian

Q: Is it injectionable only?

A: NO

Q: Would oral bute work as well?

A: Banamine is thought to be better for reducing ocular inflammation

Q: Is the flunixin injectable only?

A: Banamine is the trade name for flunixin meglumine

Q: Is it to be done for the full 5-7 days afterward also? 

A: Generally treat for 5 days with decreasing doses. Consult your veterinarian

Q: Should the banamine be injected into the vein or do you think IM is okay?  Do you think im banamine is predisposed to cause an abscess?

A: I NEVER recommend administering BANAMINE or Butazolidin IM. Both are very low pH and quite irritating. The parenteral forms should only be administered by careful IV injection by someone trained and qualified to give that type of injection.

Q: Do you suggest rotating dewormers on 2-3 mo bases? When ivermection came out, I used it regularly with occasional rotation with safeguard & dropped tube worming.  All before I learned the connection with eru & then it was too late.

A:It is an interesting debate about rotating or not. Good evidence to support not rotating until resistance is demonstrated…but this requires routine fecal examinations to detect resistance. I still rotate with my horses as well as do regular fecal exams.

No real need to tube worm horses in my opinion.

Q: Are the milder wormers unlikely to cause the eru response?  Is moxidectin a trigger also? Are their possibly any others likely to stimulate the response?

A: Any dewormer that has efficacy against the microfilaria of Onchocerca can be a trigger.

Q: Do you think leptospirosis is a causative factor?  Should vulnerable breeds get vaccinated against it?  It currently appears to be approved for bovine, but many horse farms use it with no problems.

A: Lepto has been associated with ERU. No lepto vaccine is currently approved for use in horses.

"I would encourage you to establish a relationship with an equine veterinarian in your area and support them fully".