Mind Manipulating Parasite and Fatal Attractions

Greetings everybody, 

It's Monday which means it's not everybody's favourite day of the week but I read something recently that said reading a scientific blog post on a Monday increases individual productivity by up to 30%! 

Am I lying about that figure... yes, yes I am. Let's get to the point though shall we, today we are looking on the stranger side of nature, today we learn about how a parasite can manipulate the mind of its host. 

Introducing Toxoplasma Gondii

Image Source

This single-celled intracellular protozoan has the capability of infecting all mammals and even birds and leads to the onset of toxoplasmosis. The disease caused by this pathogen, Toxoplasmosis, is of serious medical, veterinary and economic importance. The Centre for Disease Control recognises Toxoplasma Gondii and the disease it causes to be a Neglected Parasite Infection and as such is targeted by the  CDC for public health action. 

Parasitic lifestyles are always a bit complicated... 

Image Source

Gametes (the sex cells) of the parasite meet on the inside of a predator (usually a cat) gut and fuse together to form an oocyte. 

The oocytes that carry the infectious agents are shed in the cat's faeces. Changing of the cat litter and failing to wash hands could lead to humans ingesting the parasite themselves, and in pregnant women could lead to vertical transmission from mother to baby. Alternatively, the oocytes could work their way up the food chain and contaminated drink or undercooked meat could lead to people getting infected also. 

The "Fatal Attraction Phenomenon"

The most interesting route of transmission, however, comes when a mice becomes infected with the oocyte itself. The effects of the parasite on mice are unique in that this pathogen invades the brain of the mice and removes the fear of cats. This manipulation can partly be explained by the manipulation hypothesis. It states that parasites altering the behaviour of its host for the continued existence of the parasite, often by intensifying its chances for successful transmission.  

If you're still wondering why this parasite removes the inbuilt fear of cats in mice allow me to explain further. Toxoplasma gondii is able to infect a wide range of mammals and birds. However, cats are the only mammals known to shed the parasites oocytes in their faeces, as their gut offers the perfect environment to complete their life cycle, making cats the ultimate endgame. 

Interestingly, rodents are not only absent of all fear to cats but have been shown to be drawn towards the smell of a cat's urine! How does this "fatal attraction phenomenon" work? Toxoplasma gondii may have an anxiolytic effect on rodents infected by it. It has been shown in past studies that by blocking key receptors that are usually anxiogenic it allowed rats to feel a sense of reduced anxiety in situations where predator threat was high.  This increases the chances of the parasite landing exactly where it wants to be, in the gut of a cat, by causing the mouse to be eaten! 

Are you a man, a mouse, or a mouse infected with Toxoplasma gondii....

Well, that brings us to the end of this magically parasitic post. Some would argue that manipulation of the host's mind was an evolutionary inevitability in cases such as Toxoplasma gondii. Either way, I thought it was an awesome case study of a not so classic parasitic relationship. Let's face it we all know the most common parasitic relationship, the one of a child (the parasite) and its parent's bank account (the host)! 

Have an awesome week guys, 

Biobunch

Over and out.