Nematodes are the parasitic equivalent of the Addams family, but without the funny side. Most of your deworming campaign will focus on keeping nematodes under control.
The main nematodes that affect horses are large strongyles, small strongyles, large roundworms, threadworms and pinworms.
We’ll be dealing with each of these nematodes in greater detail later, but essentially nematodes follow similar life cycles.
The eggs laid by adult nematodes generally pass out of the horse in dung. Several larval stages will generally follow either in the dung or the soil, or both.
Their last moulting in the environment will produce an infective larvae with the aim of being eaten by a passing horse as it browses its paddock or snuffles in its bedding.
With some kinds of nematodes, infection can occur by licking a contaminated coat and some can even be passed to foals through contaminated mare’s milk.
In the case of large roundworms or pinworms, the parasite relies on the ingestion of the eggs directly, not larvae.
Each kind of nematode will have a different effect on a horse’s health, with much depending upon the level of infection.
Suffice to say that nematodes are public enemy number one – top of the equine “Ten most unwanted” list.
If you deworming programme manages to knock nematodes out of the park, there’s a very good chance you’ll have the other key parasites under control, too, except, perhaps, tapeworms.
Let’s now look at each of these parasites in detail.
First published on Horsetalk.co.nz in February, 2009