Watch Tower: Who are you?

Imagine a cat readying itself to pounce on a mouse. The mouse notes the feline but does not budge. It grooms itself and looks away. Soon, it is cat food.
The parasite Toxoplasma gondii was looking for a definitive host (primary host where a parasite matures and in many cases reproduces sexually). Lodged inside the rodent's brain, the microbe manipulated the mouse to release dopamine, a mood regulator that gives rise to extreme emotions: euphoria, depression. Its central nervous system doped on dopamine, the mouse's survival instincts were lulled. Thereafter, life seemed pleasant, the cat friendly. T gondii survived.
Now imagine further. The cat's owner is a pregnant woman. It is possible that her unborn child would become a schizophrenic. The pregnant woman takes out the cat litter, wanders into the kitchen and bites into an apple-without washing her hands. The parasites reach her brain via the bloodstream. The dopamine spell follows, changing the woman's personality. It makes her feel guilty and duty-conscious. The microbe then makes its way to the foetus through the placenta, leaving it vulnerable to a mental disorder someday.
Most schizophrenics are known to have high levels of antibodies against T gondii in their blood. At the same time, some studies noted that individuals infected by T gondii were bound to exhibit psychiatric symptoms such as depression, anxiety and disorientation, characteristic of schizophrenia.
EF Torrey studies schizophrenia at the Stanley Medical Research Institute in Bethesda, USA. He decided to investigate a possible connection. He and his team treated infected and oddly behaving rats with anti-psychotic drugs used to suppress schizophrenia. The drugs blocked the tachyzoite formation (an asexual stage where the microbe divides and increases its number). As the microbes died, their influence on the rat brain also decreased. Dopamine levels went down subsequently and the rats were not as foolhardy.
Life on earth began with microbes. As multicellular organisms evolved, their relationship with the unicellular ones became complex. Natural selection forced them to co-evolve. Several microbes made houses inside multicellular organisms. To colonize humans, the microbes made some lifestyle changes. They had to match the host's way of life, which was not going to be easy. They were up against one of the most complex and evolved life forms.
Early humans were nomadic-they hunted prey, gathered nuts and fruits, and collected seafood. To understand the nature of the human-microbe relationship at this stage, scientists studied a handful of such tribes left in the world, such as the Bushmen of Africa's Kalahari desert . People in these tribes wander in small, isolated groups; their contact with people from other groups is rare.
If the microbes wanted to survive off such people, they, too, would have had to follow suit, inferred anthropologists. Since the microbes were isolated along with the people, it made no sense to overcome the host's immune system, turn virulent (the relative ability of a pathogen to cause disease) and kill the host that provided it with very few chances of moving on to another one.
There were the impatient ones that did turn virulent, leading to unfavourable consequences for them. After rapidly infecting and killing the entire group, they ran out of hosts, and disappeared themselves. The solution was harmonious co-existence. They engaged in low-intensity warfare, causing mild infections that kept coming back. Those days, killing the host was not wise.
The revolution in food security for people, agriculture, changed drastically the equation with microbes. Farming brought human groups closer. Captive food production meant people had free time on their hands. Communities grew bigger, populations denser.
A 2007 DNA study at the University of Utah , USA , confirmed the pace of human evolution increased after agriculture became widespread. It was time the microbes changed their lifestyle; they became more infectious. As the interactions between people increased, so did the degree of microbial virulence.
Every community also attracted its own set of migrants. The migrants brought new microbes with them and the community, in turn, gave its own to them. It was a unique barter system-one in which the microorganisms got to travel the globe and diversify.
Agriculture increased the demand for two things: land for farming and livestock for draught, meat and by-products like milk and leather.
The Human Immuno Deficiency Virus (HIV) is believed to have made the jump from wild monkeys to humans. The monkeys were carrying the Simian Immuno Virus that mutated into the HIV, say some researchers.
Domestication of animals into livestock expanded the microbial horizon further. Of the 1,415 pathogens infecting humans, about 863-more than 60 per cent-were originally animal pathogens. Some of the common diseases contracted by humans from animals (zoonotic) are hitting headlines every year now. This year it was the swine flu-declared a global pandemic of the highest level by who. The virus from pig farms in Mexico travelled the globe. Mad cow disease, avian influenza and SARS (severe acute respiratory syndrome, caused by the coronavirus, an important pathogen of mammals and birds) haven't quite been forgotten yet.
-Down to earth feature