I have always been fascinated in the Natural World and often find myself reading articles on the more obscure and unusual aspects of the subject. One such article that I read a few months ago detailed the life of a parasitic fluke named dicrocoelium dendriticum. A fluke is a term used Trematoda, a large species group of parasitic flatworms (of around 18-24,000 species). This particular fluke has a very specific life cycle which is both intriguing and highly disturbing.

First of all, you do not need to worry about becoming infected by D. dentriticum; cases of human infection are very rare and they are usually found in grazing animals such as sheep and, more commonly, cattle. Let us take the example of a cow; an adult parasite spends its life in the cow’s liver where it eventually reproduces whereupon the offspring are excreted in the cow’s faeces. From this point, the larvae of the fluke are eaten by snails who are feeding on the cow’s faeces, the snail acts as the first of three hosts in which the parasite will live its life. The parasite then works its way into the snail’s digestive system and is secreted through small balls of slime in the snail’s trail.

This is when the second host approaches; an ant. Ants drink from the slime balls which contain the parasite and consequentially ingest them. This is where the story of D. dentriticum becomes almost unbelievable: upon being ingested by the ant, the parasite works its way towards a cluster of nerve cells which control the ant’s movements. The parasite now commands total control over the ant’s motor skills. That’s right; the parasite essentially controls the ant’s mind. I think the fact that things like this actually exist in nature gives us a bit of an insight into the inspiration of a few science fiction novels, don’t you?

Now that the parasite has control over the ant’s movement, it acts in the same way as any other ant would, for the time being. Before you get ahead of yourselves, no, the parasite does not infiltrate the ant’s nest and take it over from within, the parasite's focus is entering a host in which it can reproduce. The parasite waits until nightfall, at which point it makes the ant climb to the top of a blade of grass and cling there with its jaws. The parasite is very sensible; it knows that if it did this during the day the head would cause the ant to dry up, killing them both. The parasite repeats this process every night until the blade of grass (along with the ant) is eaten by a cow. From this point the parasite works its way into the cow’s liver, just as every other adult parasite has done before it, and there it finds other flatworms that have done the exact same thing. Now the parasite reproduces within the liver and the entire process stars all over again.

As I have said, you don’t need to be particularly scared unless you ever eat any ants or blades of grass with ants on them… However there was one case in which a man drank a bottle of water which had been contaminated by infected ants, so it’s still possible. Have a nice lunch.