It’s the first half of the year, and around here that means it’s everyone’s favorite time of year: Fecal Egg Count Season! I know, my humans are weird. They celebrate strange things, and they are very, very passionate about their fecal egg counts. Let me tell you all about the strange rituals involved, and the deep meaning behind all of it. Get ready for me to drop some serious knowledge on you, and save you some money. Learning, and saving? Sounds like a great combination!

First, the Bad News

The bad news is the deworming drugs on the market now are all we’ve got. There are no new ones in the works, which means a minimum of 10 years before we could even see a new drug. Even more bad news: there’s resistance reported to every one of those drugs right now. This means you humans better be good users of the drugs you’ve got! Most of you aren’t old enough to remember what it was like before easy, safe dewormers were available, but I hear it involved some seriously scary colics, and some pretty toxic chemicals. None of you want to go back there, I promise, so read the rest of this week’s blog very carefully.

Let’s talk life cycle

We’re going to mostly talk about the two biggies: small strongyles, and ascarids. These are the ones fecal egg count season revolves around. I’m also going to touch on tapeworms, large strongyles, and onchocerca and haemophilus. I’m a very knowledgeable cat. 

Small strongyles begin life as an egg in the pasture. They enjoy cool, but not cold temperatures, reasonable to high humidity, and really don’t like temperatures over 85F. When the weather meets these requirements, they hatch and crawl to the top of some nice tasty grass in a drop of dew. Here, your horse eats them, giving them a free ride to the intestinal tract. Once in the large intestine, the baby worms crawl into the lining to grow up. Here they have choices. If they can’t handle the pressure of growing up to be an adult, they can hibernate in the mucosa for a while as an encysted larvae. If they’re ready to make grown-up choices and have kids, they can mature to adults and head to the intestinal lumen. Once there, the adults do what adults do and make eggs. These eggs exit in the manure so that the circle of life can continue on. The adults carry on until they die of old age at about 8-10 months. 

Ascarids are the big reason for the fecal egg count season, although they allow us to carry the joy on for the entire year! Yay!! Ascarids start their life as eggs in the pasture, as well. These guys are the Ironman of the parasite world, though. Nothing kills these eggs. They handle heat, cold, dry, wet. You name it, they’ll survive. They also take a much more scenic route to adulthood than the small strongyle. 

After being eaten, ascarid larvae migrate from the intestinal tract through the body to the lungs or liver. If they are lucky enough to make it to the lungs, they cause the horse to cough them up, where they are then swallowed back into the intestines. Now they are ready to grow up to be adults and have kids. And boy do they have kids. They aren’t as reliable as small strongyles at constant egg laying. This means a few fecal egg counts may be necessary to find them. Fun ascarid fact: they kinda look like short, fat spaghetti noodles. You won’t miss these guys when they die and come out in the poop! 

The important thing about the life cycle of ascarids and small strongyles is they’re really fast! They can happen multiple times during a year. For tapeworms and large strongyles, life moves at a more cat-nap-like pace. This will be important later! Onchocerca and heamophilus get their eggs laid by flies in open wounds so fecal egg count season doesn’t apply to them. They get their own season called Summer Sore Season. You can look that one up in the search bar above. Trust me, I’ve blogged on it several times. 

Just deworm all the horses

“Well Tony,” you say, “sounds like I should just throw wormer at everyone!” First, it’s dewormer. We are taking the worms out, not putting them in. Second, under no circumstances should this be your thought process! This is why I have to save you humans from yourselves all the time. Do you remember earlier when I said we only have the drugs we have, and the parasites have learned how to evade all of them? The way you guys keep those drugs lasting as long as possible is to only deworm the horses that need it. Guess how you know which horses need it? Fecal egg counts! Here’s the fecal egg count rules:

1. Everyone over the age of 12 months gets one between January and July.
2. Everyone under the age of 12 months gets one at about 6 months, and again around 9 months. 
3. If anyone has a high fecal egg count, they get dewormed with an appropriate product (stay tuned for more on that), and then recheck in 14 days to be sure there’s none of that dreaded resistance. 

Simple, right? Yep. Super simple. Side note from my humans: when bringing them a sample to test, they want ONE, and only ONE fecal ball taken from a fresh pile, and placed in a plastic baggie in a cool, dry place until it can be delivered to the clinic. As long as it is kept cool in your fridge (the butter spot in the door works great) you can take up to 7 days to get it to them. 

You may now deworm… Maybe

Now that you have results, you may deworm the horses that have more than 350 eggs per gram of poop. Now, most of the time in an adult, you’re going to use plain old ivermectin. It still works great most of the time, it hits all the bugs we want, and it’s pretty safe. The rest of the drugs out there just don’t work very well on small strongyles, so don’t waste your money or your time. 

Notice in the rules I said if you’re under 12 months, you get a fecal twice! That’s because ascarids are generally only found in horses under 18 months old, and usually under 12 months. Once the adult immune system kicks in, it gets to work kicking those ascarids out of town! That same adult immune system is why some horses don’t have high strongyle egg counts. Their immune system kills the little buggers before they can lay eggs. 

Back to ascarids. My docs do start deworming foals for ascarids around 4-5 months old. Drug choice depends on your farm, and your history, so I recommend a chat with them rather than winging it off what Dr. Google said. Dr. Google went to a really crappy vet school. Don’t trust it for anything! 

Why no egg count in the Fall?

Remember earlier when I said small strongyles live for about 8-10 months? We’re about to take advantage of that. One way to make worms more susceptible to dewormers is to hit them when they’re sick, or stressed, or…..old. We’re going to take advantage of the fact that most of them are old around late Fall, and push them into their little worm graves. Horses also need to be dewormed once yearly with an ivermectin to kill large strongyles, and praziquantel to kill tapeworms, so our Fall deworming plan does all the things we need a good deworming plan to do. 

Don’t want to remember any of this? Sign up for a Wellness Program, and my Docs will take care of it all. From fecals to deworming, done. Crossed off the list. No worrying. Seems like a no brainer to me! You can even sign up at 3 a.m. from the website. Seriously, what’s not to love about this thing? Did I mention no emergency fees? If you haven’t already, go to the menu bar, go to the Wellness page, sign up, be happy. 

Until next week,

~ Tony

P.S. If you want to advance to cat-level knowledge on deworming, you should listen to the podcast my docs did on the topic. It will give you all the information you need to convince your hard-headed friends to stop contributing to the drug resistance problem! Find it on our Podcast Page.