Parasite Pop Quiz: Test Your Understanding

by Flynn Magorian, BVMS

We have a little quiz for you to see how well you know your parasites! Are your horses on the best program possible? Get ready for some true/false questions and answers. Please don’t hesitate to call us if you have questions, we can help you come up with an effective worming protocol.

Large Strongyles are the most dangerous parasite for horses. True or False?

There is a single wormer that kills all equine parasites. True or False?

It is better to underdose my horse than overdose on dewormer. True or False?

Horses naturally aquire immunity to Ascarids (round worms) after 18 months of age. True or False?

The best way to manage pastures is to spread manure on them. True or False?

Hot dry weather kills parasite eggs better than freezing temperatures. True or False?

Small strongyles are becoming resistant to all available dewormers. True or False?

All horses on the same property will have the same worm burden. True or False?

A negative fecal exam means I never need to deworm my horse. True or False?

I’ve always used the same product, it works, so i don’t need to change it. True or False?

Moxidectin (Quest) should not be used on foals less than 6 months. True or False?

Answers:

1. Large Strongyles are the most dangerous parasite for horses. False

Almost all dewormers effectively kill large strongyles, therefore they are quite rare and pose little threat to regularly dewormed horses.

2. There is a single wormer that kills all equine parasites. False

Moxidectin plus praziquantel (Quest Plus) works well against encysted small strongyles, large strongyles and tapeworms. But does not work well against ascarids in foals, especailly as it should not be used on foals less than six months. It is also important to switch classes of wormer to prevent resistant worms from developing on your property.

3. It is better to underdose my horse than overdose on dewormer. False

Underdosing horses leads to resistance by only killing the most susceptible parasites and leaving the strongest ones to reproduce.

4. Horses naturally acquire immunity to Ascarids after 18 months of age. True

Young horses are very susceptible to ascarid impactions, and should be wormed regularly with fenbendazole (panacur) at a 10 mg/kg dose for 5 days in a row to kill them.

5. The best way to manage pastures is to spread manure on them. False

Spreading manure on your pastures can actually increase the parasite burden on your farm, unless the weather is hot and dry enough to effectively kill all the eggs.

6. Hot dry weather kills parasite eggs better than freezing temperatures. True

More parasite eggs are killed in hot dry weather then freezing temps.

7. Small strongyles are becoming resistant to all available dewormers. True

The adult version of small strongyles are fairly easy to kill while the encysted form are only susceptible to moxidectin, for the time being

8. All horses on the same property will have the same parasite burden. False

Younger horses often have higher worm burdens because they have less immunity, and just like people, some horses have less immunity and some have more.

9. A negative fecal exam means I never need to deworm my horse. False

Fecal egg counts can quite often have false negative results, meaning that they come back negative but testing a different fecal ball or a different pile of manure from your horse would actually have a positive result. Knowing that, all horses should be wormed a minimum of twice per year.

10. I’ve always used the same product, it works, so i don’t need to change it. False

Using the same product over and over breeds resistance in your parasite population. It also doesn’t kill all stages and types of parasite. Rotating wormers and using the appropriate one for the age of your horse is important.

11. Moxidectin (Quest) should not be used on foals less than 6 months. True

Horses less than 6 months of age have a higher incidence of adverse reactions, including ataxia, depression/lethargy and recumbency. Very old and very thin or sick horses should also avoid moxidectin.