06/03/2022
Apparently it’s March?
Our wonderful, tidy calendar says it’s autumn now too. And so here is my annual “It’s not actually autumn yet – don’t deworm your horses straight away!” spiel.
Autumn is the No. 1 time of year to worm your horses, because it ties in best with breaking the bot-fly life cycle. A bot fly’s lifecycle is 12 months, so treating just once a year will break that lifecycle (and overtime decrease bot fly populations). By mid-autumn/early winter, the entire population of bot flies will be inside your horse, which means you can target all the bots on your property with a single dosage of a boticide dewormer (ivermectin, abamectin, moxidectin).
If you deworm your horses too early in autumn, you will not be targeting all the bot flies. For example, just this morning, I had to rescue my ponies from three of them. Had I dewormed on the 1st of March, there are three bot flies and all their subsequent offspring I did not control.
Hold off a little longer, if your horses are in good condition. Wait until the nights cool down and the bot flies disappear before deworming – and make sure that the dewormer you purchase is active against bots, otherwise it will all be in vain. If your horses need to be treated now, do so, but make sure you target bot flies again in early winter.
So that’s my bot-fly spiel. Normally I write about strongyles (my favourite), and so I shall of course make a mention of them here too.
I always recommend a mid-late autumn deworming for ALL HORSES because it a) cleans out any bots and b) all horses really should have a strongyle clean out once a year as well. I may be against deworming for the sake of deworming, however that is only if you are doing it 3 or 4 or more times a year.
Strongyles can have a lifecycle of as little as 6 weeks. In addition, at any one point, about 90% of the strongyle population is living on the pasture, not in the horse. Therefore, the concept of using chemical dewormers inside the horse to break the lifecycle of strongyles would not work. At all. So, we chose our annual deworming-clean-out to line up with as many other parasites as possible.
All boticide dewormers are also effective against strongyles so deworming in autumn is a 2 for 1 type deal. You should also consider using a dewormer that also contains praziquantel to treat for tapeworms to get a complete clean out, just in case tapeworms are present. If your horses are only being treated once a year, it is good to do as complete a treatment as possible.
Lastly… wait, second lastly.. this is a topic to complex to get into here, but: this time of year is key for larval cyathostomins, where encysted larvae have mass emergences from the intestine wall, in response to changes in weather (eg in VIC as it cools and becomes wetter again). Deworming and removing adult populations of worms can act as a trigger for larval re-emergence, which is also why I often baulk at deworming horses now. The larvae may slowly re-emerge coming into the cooler weather and treating in mid-late autumn may be a safer bet to remove adults and emerged larvae. The research on this is sketchy as best, however these are patterns shown in cattle and hypothetically should translate over into horses.
And lastly (pat on the back for reading this far): just because I’m recommending deworming all horses does not mean I am not recommending FECs in autumn. A FEC will tell you important things about your horses health, and pick up anything odd that may be happening (eg tapeworm you didn’t know about). It will also allow you to test drug efficacy. Autumn should be a key time for everyone to do a FECRT (faecal egg count reduction test), where you get FECs done before and after deworming to make sure that it worked. If you only deworm once a year, then you’ve only got one chance for a FECRT, and you cannot, I repeat, you CANNOT do a FECRT without a FEC before to compare to.
If you’d like to organise FECs and FECRTs for your horses this autumn, check out the website (link on the FB page) for postal submission and drop off points.
Happy autumn! I am now going to spend some time crying over the winter coats my ponies are already growing.
