Sunday, March 11, 2012

Ivermectin usage

One of my pet peeves in the husbandry of rabbits is the overuse of medications OR the wrong use of medications in rabbits.   One should always breed for health and good immune systems.

One of these meds was recently discussed over at the meat rabbits board.

People use ivermectin as a wormer for rabbits.  There are better known and rabbit safe meds out on the market.   People will use it as a preventative medication.  People will use it as a first drug of choice.

Panacur for one.  Easy to use, easy to treat, out of their system in two weeks.  and there are other ones out there.

But no.. people like to use Ivermectin as it's an over-the-counter medication and easily available in a handy little tube for administration.   So no need for fecals, no dealing with vets, etc.

But no fecals means no certainty in what you are treating either so it's a bit of a catch 22 right?

Personally I only worm when I KNOW I have a problem, and then I get a fecal done at the local vet.  Costs me $5 for the fecal, $5-8 for the wormer.  No issues.

Ivermectin is being over used.  People use it for their dogs, their horses, their cattle.  People don't pay attention to strength differences.

So easy to over medicate.
So easy to give via the wrong methodology.
People think because it's over the counter that it's a safe medication.  It isn't.

Ivermectin overdoses can cause seizures and whole host of other issues.  Such as
  • Lethargy
  • Tremors
  • loss of coordination of the muscles, mainly in the extremities
  • Drooling
  • Tachycardia
  • Excessive dilation of the pupil of the eye
  • Stupor
  • Coma
  • Depression 
  • Death
  • Fluctuating blood pressure
  • Birth defects in kits (aka cleft palates)
  • Temporary Blindness
If you ever send your rabbits out as critter food do make sure that none of them have an ivermectin sensitivity.   OR make a point of NEVER giving your rabbits ivermectin. 

Some animals have a genetic mutation that weakens the molecular pump that keeps ivermectin out of the brain.  With this mutation, the drug freely enters the brain's blood supply and the animal seizures to death.  This can also happen with a massive overdose of the drug in an animal without the mutation.  This mutation has been found in many animals, but is mostly commonly found in some herding dogs, particularly the collies. 
The second issue is that, as with all antibiotics and diseases and dewormers and weedkillers and so forth - some organisms are more sensitive to ivermectin than others.  If you give ivermectin to an animal, particularly to a whole herd, even if given at the right dose to treat those animals, some of the parasites will survive.  The tougher ones will go on to reproduce, and pass on those ivermectin resistant genes. 

Resistance is thought to grow any time a dewormer is used, and the more often it is used, and at the lower dose, the faster the resistance grows. So if a producer is using too low a dose (half the amount, in order to save money and treat twice as many animals) and is using the formula wrong (there are pour on vs oral vs injectable solutions) even fewer of the worms will be killed and the population of resistant worms in the pasture will grow even faster. 

Rabbits have so few meds that can be used on them.  Why would you want to encourage drug resistance when there are better meds out there that do the job properly?

The third problem is that ivermectin stays in an animals system for a pretty long time, from 14 to 60 days, depending on the species and the formulation used.  So care must be taken to know just how long to wait until slaughtering the animals, in order to keep the drug out of the food supply. 

If you don't know for sure how long it will be in their system (and remember, rabbits eat their fecals thereby keeping the meds in their systems longer) then how long do you know to hold back that rabbit in order to keep it out of the food system?  
For more information, you can check out:

American Consortium on Small Ruminants Parasite Control (discusses FAMACHA)

FARAD (Food Animal Residue Avoidance Database) -

Minor Species Drug Act -

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