Sunday, August 21, 2011

Beware what lies in the sand beneath

Another month, another speech. This one was a fun one to give, as most people in the audience really hadn't heard of toxoplasmosis.

Beware what lies in the sand beneath

There is a parasite that lives amongst us.

A parasite so small that when eaten by you, it will make its way through your gut wall, and then, using your bloodstream as a vehicle it moves to the sites in your body which it will call home.

These sites being your muscles and your brain.

Once the parasite has arrived at its future home it forms cysts inside your cells, hiding in the cysts, safe from your immune system.

It is a parasite that most of us aren't aware of.

Which is odd – because at least one in five of us are infected.

That's just the humans – a whole range of other animals are also subject to attack by this parasite. From mice and rats through to humans.

Not only is it a common parasite – but once infected it is very difficult to clear the infection.

The name of the parasite I am talking about tonight is Toxoplasma Gondii

Until recently it wasn't considered a bad infection to have.

Then it was noticed that toxoplasmosis alters the behaviour of infected rats.

Infected rats started to behave in very un-rat like ways.

They begin to hang out in areas where there are cats – even at times trying to go one on one against the cats, trying to show those cats exactly who is the boss.

Which is not a very bright thing to do, because, well, cats eat rats.

So infected rats, despite their bravery, generally don't have happy endings.

But here's the thought provoking thing: Toxoplasmosis can only breed in the small intestine of a cat.

So it needs to be ingested by a cat to breed. It is critical for the survival of the parasite that it find its way to a cat's gut.

How convenient then, from the parasites point of view, that a rat infected with Toxoplasmosis would change it's behaviour in such a way as to make it more prone to be eaten by cats.

Scientists believe that convenience plays no role in this. Rather, they believe that Toxoplasmosis cruelly and deliberately plays with the brain of its rat hosts to make them go out and get eaten by cats.

Singapore zoo has a its tigers separated from us human viewers by large plate glass windows. From some angles it looks as though nothing separates you from the tigers.

I don't know about you, but in those moments, when it just me and the tiger, my stomach always instinctively tightens in an apprehensive knot.

It is almost as though my subconscious recognises that a few thousand years back, when men were far more puny, and tigers, lion, and other large cats were far more plentiful, that, well, we were the prey.

Let us all do some basic scientific research in the form of a little thought experiment.

Could it be possible that us humans are also susceptible to behavioural changes driven by something so much smaller than one of our cells?

Also, if there are behavioural changes, just what might they be?

Scientists were also intrigued by this line of thought.

Having a fairly large infected population to sample, they found it fairly easy to design experiments and tests that would reveal changes.

And they found them!

Interestingly they found that the changes were gender related

Infected men are far more likely to disregard rules and are more expedient, suspicious, jealous, and dogmatic.

Infected women are more beautiful, warm hearted, outgoing and persistent.

Common to both are impaired motor skills, and slower reactions

So much so that people with toxoplasmosis are six times more likely to have traffic accidents than people without.

Thought provoking. Are these behaviours that increase your chances of hanging out with the cats?

Regardless, the killing tigers have now been replaced by the killing cars.

More disturbingly, there is emerging evidence that some of us might become schizophrenic or neurotic when infected. And now forms of brain cancer are also being linked to infections

How do you get toxoplasmosis?


Touching or coming into contact with sand containing infected cat poo.

Eating uncooked, unwashed fruits or vegetables that have been contaminated by manure with infected cat poo.

Eating raw or undercooked meat that's contaminated.

And sometimes, very rarely, by being born with it (a woman who gets a toxoplasmosis infection while pregnant can pass the parasite on to her unborn child).

There is a belief by some that we humans are where we are today because of schizophrenia.

And because of dominant rule breaking people who have pushed the boundaries.

It is a sobering thought that our civilisation might be what it is because of a tiny parasite.

But you know what: looking at the modern world I think that perhaps we can live without this parasite

That the time has come for us to make our own way, brains unaltered, into the future.

So make sure that your children's sand pits are covered when they aren't playing in them.

Keep your cat away from the wildlife.

Do a good job of washing and preparing your food.

Wear gardening gloves.

Such simple steps to stay safe.

And remember, if you get hot under the collar while driving, and want to gun your car from one stop to the next, and those idiot cyclists who just slow you down and you get so tense at the stupidity of others...

Just remember it could be your inner parasite trying to introduce you to your modern tiger.

So take a deep breath, calm down.

Beware what lies in the sand beneath.

1 comment:

Daniel said...

Mmmm - What a lovely thought!

Now can you investigate if there a human-targeting equivalent of the Emerald cockroach wasp?

"the wasp stings precisely into specific ganglia of the roach. It delivers an initial sting to a thoracic ganglion and injects venom to mildly and reversibly paralyze the front legs of its victim. This facilitates the second venomous sting at a carefully chosen spot in the roach's head ganglia (brain), in the section that controls the escape reflex. As a result of this sting, the roach will first groom extensively, and then become sluggish and fail to show normal escape responses.

The wasp proceeds to chew off half of each of the roach's antennae. Researchers believe that the wasp chews off the antenna to replenish fluids or possibly to regulate the amount of venom because too much could kill and too little would let the victim recover before the larva has grown. The wasp, which is too small to carry the roach, then leads the victim to the wasp's burrow, by pulling one of the roach's antennae in a manner similar to a leash. Once they reach the burrow, the wasp lays a white egg, about 2 mm long, on the roach's abdomen. It then exits and proceeds to fill in the burrow entrance with pebbles, more to keep other predators out than to keep the roach in.

With its escape reflex disabled, the stung roach will simply rest in the burrow as the wasp's egg hatches after about three days. The hatched larva lives and feeds for 4–5 days on the roach, then chews its way into its abdomen and proceeds to live as an endoparasitoid. Over a period of eight days, the wasp larva consumes the roach's internal organs in an order which guarantees that the roach will stay alive, at least until the larva enters the pupal stage and forms a cocoon inside the roach's body. Eventually the fully grown wasp emerges from the roach's body to begin its adult life"