Horsehair Worms in the Toilet

Horsehair worm in pool
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We recently received a question from a reader about a horsehair worm in his toilet. Or at least we think this is what the question is about, as the wording is a little unclear: “I have horse hair worm .i my toilet do i flush it?” Obviously, a horsehair worm (or “horse hair worm,” to use the reader’s understandable misspelling) is involved, and it seems to be in the toilet, and the reader’s only question is about whether or not he can flush it. So we’ll focus on the question “can you flush a horsehair worm down the toilet,” but we’ll cover a little more ground so the article has broader applicability.

Unlike most questions we receive, the reader did not ask us to identify anything, so we’ll take it for granted that he did in fact find a horsehair worm. The various horsehair worm species belong to the phylum Nematomorpha, so named because horsehair worms look like nematodes (a.k.a. roundworms). They are parasitoids because rather than simply being parasitic on a host, they actually kill it. These hosts are generally insects such as grasshoppers, crickets, and cockroaches. The eggs of horsehair worms are laid in small cysts on several different plants. When insects eat these plants, horsehair worms slowly grow inside them. Given the small environment in which they mature, it is perhaps surprising that horsehair worms commonly grow to be a foot long (and sometimes much longer). However, they are extremely skinny – they look like dental floss – and they can coil up tightly, thus allowing them to fit into the small interior of an insect. Having reached maturation after several weeks inside the host, the worm will exit the insect when it comes near water, as adult horsehair worms live in aquatic environments.

We have not received a question before about horsehair worms in toilets, as people tend to find them outside. We have written about horsehair worms in swimming pools, for instance, and people also find horsehair worms in puddles and other naturally occurring bodies of water. However, it is certainly possible that a horsehair worm could end up in your house for the simple reason that insects carrying horsehair worms can end up in your house. If one of these insects goes near standing water, like a toilet, the horsehair worm could exit the host. Perhaps the reader also found a dead insect lying around the toilet and failed to appreciate the connection between this and the worm he found.

As concerns our reader’s specific question, you could certainly flush a horsehair worm down the toilet. It is unclear how this could conceivably cause any harm, in fact. The worms are completely unobstructive, so flushing them wouldn’t cause any plumbing issues. For the record, though, horsehair worms are harmless, as they are not the parasites (or parasitoids, technically) of pets or humans. This doesn’t mean that you won’t want to still flush it down the toilet, but it is worth noting in case the reader perceived the worm as a threat.

If our reader found a horsehair worm – an assumption mandated by the reader’s question, and one that is reasonable to believe in any case – there is no danger in flushing it down the toilet. They are nothing to fear and do not necessarily need to be gotten rid of, but we suppose flushing it down the toilet is probably what most people would do, and this shouldn’t cause any problems.


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