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Dedicated to effective

parasite control


With the advent of widespread worm resistance to the commonly used dewormers, the term BROAD SPECTRUM DEWORMER is now a myth.  We are in real danger of landing up with worms that are multi drug resistant.  Just as medical doctors are concerned about antibiotic resistance bringing back old long forgotten diseases into our midst, so too we as horse owners need to be concerned about parasites that are flourishing in spite of our efforts at eradicating them. 


The minute brain of the parasite is beginning to outsmart the shrewdest horse owner and his veterinarian! 


Our team at Worm-Ex Lab will put you, your horses and your regular vet in an informed position to manage the increasing complexity of equine parasites better and cheaper than regular across the board deworming. 


It really does pay to count your eggs before they hatch!

About us
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The Worm-Ex Lab exists to assist the owner and their regular veterinarian to cost effectively implement modern evidence based preventative veterinary medical guidelines to enhance equine (and livestock and wildlife) health.


The Lab was founded on the passion and wide experience of Dr Karl van Laeren and his veterinary practice partner, Dr Jane Howes, and the widely recognized Danish veterinary deworming system.

Latest News 

Deworming strategies where worms are rarely encountered

In adult Sport-horses in Gauteng,  we are seeing less than 4% of horses needing deworming.  This means horses with 350 or more worm eggs noticed per gram of dung tested by McMaster slide examination. 


So about 96% of horses appear to not need deworming! 


Does this mean it’s safe to break away from regular deworming as has been drummed into us for years?  Indeed it does!  We have a small yard that has not had to deworm any of their horses in eight years with no ill effects.


However, owners are getting jittery.  They feel they need to deworm even if a single worm egg is encountered! 


What is a good policy and what is a safe, scientific, well thought out approach to deworming? 

It is hard to get owners to be comfortable with low counts of 50 to 300 and doing nothing at all.   It is very easy indeed to create a zero WEC sheet.  Just deworm repeatedly till the horse is zero.  Simple!  

Wrong answer! 

Parasite resistance in our horses is what we should be aiming for AS WELL AS minimizing paddock contamination.  Achieving the latter is labour intensive but achievable, especially in yards with small paddocks.  Achieving the former, resistance to parasites, may be manageable in most horses over time by low parasite exposure. 


Resistance is more likely in older horse than young stock.  We are thinking 10 to 12 years of age as there are a lot of species of worms that horses are exposed to.  Eighty three species in 29 genera on last count! Imagine if horses had to develop immunity to 83 strains of African Horse sickness!


That won’t happen overnight.   


This is a big ask and will take time, but many horses’ wonderful immune systems are up to this challenge!   They do develop a solid immunity and ultimately can cope without deworming.    Well, there are a few exceptions.  There are always outliers and exceptions to every scenario.  Nothing is cast in concrete in biology.  I see a few horses with presumably a weak immune system that are always wormy but I can count the number I am aware of on one hand (out of tens of thousands tested over the years!).  This is especially true where less than meticulous paddock management is also at work.


So back to the main concern.  Should one deworm horses with ivermectin if they are worm free?


In essence, a strong No!


You are simply wasting money deworming such a horse with, for example, ivermectin, as you can’t expect any gain from such a practice, especially if no immature worms are present either. 


However, there is a slight amount of merit in doing this seemingly senseless act once every two or three years!   To make this point clearer I wish to take you back to the findings of the research groups in Denmark and in Kentucky, the home of the flat racehorse breeding industry and where most of the first class equine parasite research is coming from.


So, as you may be aware, Denmark has started to make deworming of horses illegal unless a competent lab has found worms to be present in sufficient numbers.  This is called the Selective  or Targeted approach  and was adopted into law in Denmark 20 years ago.  Since then a few forward thinking individuals, like you reading this article, and in countries like Holland , Sweden and Finland have followed suit.  Hooray, these people are thinking about the consequences of excessive, uncalled for, deworming.


Kentucky by contrast deworm by calendar month.  This is called Strategic or Seasonal deworming.  However, this is largely a system based on the needs of foals and young horses and this should not apply to adult horses. 


There is a new type of test called PCR testing where one can look for a genetic finger print of a specific pathogen, bacteria, virus or, in this case, worms.  This specific PCR test has been set up to look for the Strongylus vulgaris (large strongyle) parasite egg in particular.  What has been uncovered is that this “bad boy” parasite, whose lifecycle includes time inside the arteries of horses, is not present in Kentucky, but is present in small numbers (14.1%) in Denmark.  So, while Kentucky may have a dangerous deworming policy, they can show some definite positive effects of this system, whereas Denmark may have the gold standard ideal in mind but there is a draw back.  The bad boy parasite S vulgaris is raising its ugly head here!


So, WORM-EX LAB has come out with a largely unique solution.


We have married the two systems into one unit to get the best of both worlds.  We don’t want to over deworm and neither do we want the bad boy parasite to get a toe hold in our clients’ horses.  Also, current testing methods for stomach bots and tapeworm diagnosis are mildly flawed as they under-represent the actual incidence in horses, and perhaps gives a false sense of security.  We need therefore to counter this by taking precautions against possible infection.


So, we are saying that clients who feel uncomfortable not deworming at least once in a while may want to consider meeting on neutral ground.   We are suggesting that, once every two years, all the horses in your yard get dewormed with an ivermectin dewormer plus praziquantel.   This will cover tapeworms, stomach bots (Gasterophilus) and Strongulus vulgaris but will not destroy the small strongyle refugia  (dormant worms in the gut lining), so immunity development to these more common parasites will continue, unabated.    


And what is the best time to do this?  Autumn is supposedly the best time to get rid of tapeworms which generally have a single cycle per year with the highest prevalence at the tail end of summer.   However, winter is the best time to clear horses of bots when the free flying bot fly is at its least prevalent.  So, doing one broad spectrum dewormer in winter will cover all these bases adequately. 


As most Gauteng horses have been experiencing regular unnecessary deworming we feel that one should deworm only based on WEC results for now.    Then, come Winter 2020, that one embarks on an “entire yard” deworming spree with ivermectin plus praziquantel that will last till  2022 for large strongyle, tapeworm and bots.


Regular WEC testing between these dates remains important to pick up the individuals with counts of 350 and above.