Toxoplasma gondii: the parasite with a penchant for felids

If you hadn't already realised, dear readers, I'm a huge nerd. Wipe that look of shock off your faces. Anyway, I've been extremely busy with Pokemon Alpha Sapphire, revision and Fullmetal Alchemist. I'm only human ok! I've also been working tirelessly on my Extended Project, a 5,000 word dissertation of the topic of feline intelligence. Most people chose sensible topics like stem cell research, the UK's involvement in the EU, or the parallels between historical leaders, but I, in an attempt to make my life that little bit more difficult, decided to pick a topic that has very little debate, and even fewer people who are interested in the answer. Whilst I was researching the controversial topic of the intelligence of the domestic cat, I stumbled upon a parasite known as Toxoplasma gondii (T. gondii), as T. gondii's primary host is the domestic cat. T. gondii is a unicellular eukaryotic organism, a protozoan, that causes a disease called Toxoplasmosis in human host cells. Toxoplasmosis is the root of the term 'crazy cat lady' syndrome, as there is a definite link between the disease and mental health issues like schizophrenia, although most hosts are just symptomless carriers. Great. That's what I've got to look forward to.  It is one of the most common parasites found in the human body, and it is estimated that 1/3 of the global population is infected. The parasite can reproduce asexually within virtually all exothermic mammals, however it can only reproduce sexually in the intestines of Felids. This basically means it can only adapt and change its structure to evade our immune systems within cats, making them its definitive host. In order to optimise its chances of infecting cats, T. gondii can alter the behaviour of intermediate hosts like mice, to make them attracted to the scent of cat urine, so they are more likely to be preyed on by a passing feline. To do this the parasite hijacks white blood cells, which seem to be the target for pathogenic attack quite frequently (even parasites have a sense of humour). The WBCs are converted into chemical factories, synthesising neurotransmitters like serotonin, to reduce response of fear and anxiety that usually occurs in the amygdala of the mouse, as soon as it smells a feline nearby. The parasite resides within a membrane known as an oocyst until it passes through the stomach and the membrane is hydrolysed. It then infects epithelial cells, in which it is converted to Tachyzoite cells, speeding up the rate of proliferation, then they are converted to slow dividing Bradyzoites, which form tissue cysts in the host, completing the parasite's lifecycle. It's a feat of biological adaptation that a parasite can become so ultra-specialised to one particular host, but like a lot of evolution and natural selection, this mechanism is kept because it works. It worked during the evolution of the parasite, and so that's what it does to this day, and what it will continue to do until domestic cats develop a resistance to it. T. gondii stubbornly resists change, and that's why I like it...