What can go wrong with worm control; a veterinary view
08 June 2016
from Westgate vet Carolyn Cummins
For the third installment of our 'ask the expert' series we go to Carolyn Cummins MVB Phd MRCVS, consultant vet to Westgate Laboratories to get a veterinary view on the importance of good parasite control:
Why do you think good worm control is important?
Working as a first opinion equine vet I see a wide and varied caseload. Every year this includes horses that are suffering from a severe worm burden. In some this is due to neglect or other underlying illnesses. More worryingly in others, these are horses with owners who believe that they are worming their horses appropriately and have measures in place to prevent worm related issues.
Problems can arise from worming at the wrong times of year, not using the appropriate wormer, under-dosing, or overuse of a particular wormer leading to resistance so that the drugs we have are no longer effective against the parasites that are a threat to horse health.
Unfortunately there is a lot of misinformation and contradictory advice out there which can lead to confusion for the horse owner. That is a problem for the horse world in general but it is even more important at the individual horse level.
How does parasite control fit into the bigger picture of a healthy horse?
Parasite control should be high up on the list along with vaccinations, dental and hoof care when it comes to routine care of your horses. It can be easy to forget worming as it is generally a hidden issue until it becomes a problem.
A horse suffering with a severe worm burden can go from an apparently healthy horse to a severely ill one in a very short space of time, hence the importance of a regular testing regime using worm egg counts and the saliva test for tapeworm.
What do you think the biggest challenges are that horse owners face in managing worm control?
I think it is all the information that’s out there that can make the subject seem very confusing. You can walk into a shop and ask for a wormer, but which one do you want, an ivermectin, a benzimidazole, how about a combination wormer, are you treating for tapeworm, what time of year is it, are there encysted redworms, what about roundworms?
How often do you dose when information on the back of the wormer box can say suitable for worming every 6-8 weeks! Then there's the information about rotating wormers, whether to worm before you move field or after. Worming every 6-8 weeks may make some people feel that they are safe and can't possibly have a worm issue, however they are setting themselves up for a resistance problem and if their horse does become ill with worms, they will have limited treatment options.
The big challenge facing us all is wormer resistance. Unfortunately we are seeing increasing levels of resistance to wormers on the market with no sign of any new ones coming in the near future. This means that we have to look at our methods of worm control and our reliance on wormers.
Old information was to dose every 6-8 weeks, worm horses and then move horses on to new grazing immediately. We now know that this is only helping to increase resistance to wormers. Fortunately there are things that can be done to help prevent this, or at least slow the process down, poo picking regularly, targeted worming programmes that include worm egg counts, saliva tests and worming only at certain times of year.
This is where Westgate Labs can help to give best practice impartial advice to the horse owner to help them navigate the worming maze.
What are the dangers of getting it wrong?
The dangers are increased resistance and even worse very sick animals. While you may not have an issue with worms (that you know of) you may be setting yourself up for a serious issue a few years down the line. As I said before, I have seen horses lost to severe worm burdens and it is very sad. These are not all the neglect cases that have never had a wormer in their life, they can be well loved, well cared for animals who have been given the wrong wormer at the wrong time, under dosed or are carrying resistant worms.
What does worming responsibly mean and why is it important?
Worming responsibly means only using a wormer when really necessary and at the appropriate time of year for the worms you are treating. Luckily there are tests you can do to check if your horse needs a wormer. Worm egg counts and the tapeworm saliva test should be used regularly and routinely to see if your horse is carrying worms. If he's clear, then he doesn't need a wormer. The caveat with this being encysted redworms which will not show up on a worm egg count.
This is usually counteracted by treatment with moxidectin, but again this must be the right time of year (late winter, early spring). Following this type of plan will keep your horse healthy not only today but hopefully long into the future as well.