Worming
Equine worming and the development of resistance to wormers is a hot topic these days. Here are a few of the most commonly asked questions answered.
Do I need to worm my horse or pony?
Worm egg counts should be performed to assess whether or not worming is essential for your horse or pony.
Unfortunately, worms are becoming increasingly resistant to the wormers available on the market today. Targeted worming will help to slow this growing resistance.
If you wish to perform a worm egg count, please submit a nugget of fresh faeces to our in-house laboratory. Please make sure it is labelled with your horse’s name when you drop it off at reception!
What is a worm egg count?
A worm egg count is used to determine the number of worm eggs in a small proportion of your horse or pony’s faeces. These are detected via use of a microscope following suspension of the faeces in a solution. A worm egg count can detect the presence of redworms and roundworms.
The presence of tapeworm can be detected by a blood test or a saliva test.
Which wormer should I use?
The advice we give will be determined by a combination of worm egg count result, time of year, age of horse and previous worming history.
Typically we will advise different worming strategies for youngsters (< 2 year olds) and broodmares, in comparison to the general horse population.
We offer a worm egg count service with free worming advice, and stock a range of wormers.
Worming Resistance
Unfortunately due to the presence of wormer resistance, wormers are not always as effective as we hope for.
It is not too late for veterinary surgeons, horse owners, educators and pharmaceutical companies to take responsibility for this issue and safeguard the health of our horses.
Poor pasture management, under-dosing of wormers and repetitive excessive dosing with wormers all contribute to the development of this resistance.
The interval dosing programme that was first developed more than 40 years ago increases the chances of anthelmintic resistance, resulting in an increased burden of eggs in the environment.
The majority of wormers will only kill the adult stages of the worm. and not the larval stages that are responsible for clinical disease.
Horses are variable in their susceptibility to parasite infection resulting in significant differences in parasite burdens among horses kept under similar management conditions, therefore worm egg counts for individual horses are so important.
The main parasitic pathogens affecting mature horses now are the cyathostomin (small strongyle) and the tapeworm.
We can all take several steps to help reduce the worm population and therefore improve our horse’s health:
- Understand the life cycle of the worms that you are dealing with
- Know at what stage of the lifecycle you should worm your horse
- Know which wormers to use
- Worming in response to worm egg counts
- Biosecurity for new horses coming onto the farm
- Pasture related tactics to reduce the pasture contamination
- Don’t aim to reduce the worm population to zero
What can we do?
- Worm egg counts are our most valuable ally, as they will indicate whether you need to worm and which worm species is involved.
- Worm egg reduction counts after worming will indicate the level of resistance in your population.
- Worm egg reappearance counts will help to formulate a plan and can help in detecting early signs of resistance.
- By adopting a strategy of pasture management, testing and timing the worming regime we can help to reduce the amount of resistance that is developing in our horse population.
- Pasture management includes removing the droppings, cross grazing, resting the ground and taking hay off the paddock.
Testing involves the use of worm egg counts, and although they are only a snapshot of the actual state, and may well have inaccuracies, they will indicate horses that do have a worm burden and these horses can then be treated, thus reducing the number and cost of treatments. Remember that the worm egg count does not detect the encysted larval stage.
Structured worming
Structured worming to take into account the time of the year, the age of the horse, pregnant mares or horses recovering from an illness.
By adopting a more structured approach, we can reduce the treatments given to horses relying more on management of individual cases and a knowledge of the local factors on the farm. This approach to worm management requires advice and support from vets, suppliers and land management experts.
This will lead to an economy with less use of wormers that are more effective and increased food utilisation.
If you recognise that worming your horse does not appear to be giving the results expected, then it is wise to check that the worm egg count is still high and that there are no other reasons for the signs that you are seeing.
If there appears to be a resistance problem, contact your vet or retailer to discuss the recent wormer history and get advice on what wormers appear to be working best in your situation and area.
Wormer resistance varies between horse, yard and area of the country and advice as to what strategy to use must be tailored to your horses’ specific requirements.
- Blindly worming with several different wormers will only increase the resistance in the local worm population.
- The inclusion of refuge horses that have a population of worms that are not exposed to wormers is important.
- Dose correctly for body weight.
- Consider the age range and mobility of the population and pasture hygiene.
- Non-uniform dispersal of parasite population (80/20)
- Immunity will never be 100%
- Most (80%) adult horses will have low level infection
- Variable parasite susceptibility
- Target treatment of animals based on FWEC
- Actively look for AR with FECRT
- Select products carefully and ‘rotate’ annually.
Tapeworm tests
With the increasing prevalence of worm resistance to worming treatments, it is highly recommended that you perform a faecal worm egg count prior to worming your horse.
Unfortunately, a faecal worm egg count is not a reliable test to see if your horse has tapeworms or not. Currently there are two methods available to horse owners in order to determine their horse’s exposure to them. Both test the level of antibodies in your horse, the higher the level the higher the likelihood that your horse may need an anti-tapeworm treatment. This would be dependent on your horse’s previous worm treatment as both tests are more accurate if your horse has not had an anti-tapeworm treatment in the last 4 months.
One test is an Equisal saliva test which costs £17.95 plus post and packing. We can either send you one in the post or they can be purchased directly from the Equisal website – www.equisal.co.uk. This is an easy test that you can perform at home. It requires a swab from the inside of your horse’s mouth (full instructions are provided with the kit) which is then sent to the lab in a postage-paid envelope. Typically results are given within four working days of the lab receiving the test. Some considerations to bear in mind when using this test; as mentioned above ideally your horse should not have had an anti-tapeworm treatment within the last four months. Also your horse should not have food, water or exercise for at least 30 minutes prior to the test being performed.
The other test available is a blood test. The blood is sent to an external lab for testing which costs approximately £30 (please remember that you will also need to have a vet visit to take the blood sample or it can be done on your next routine visit or here at the clinic). Typically we will receive the results back here at the clinic in one – five working days whereupon your vet will phone you with the result and advice on any further course of action.
Please give us a call if you would like any further information on anything you have read. We are happy to talk to you about worming your horse or you can read more on our Equine Fact Sheets linked below.