Host Manipulation Chapter 5

I personally found Chapter 5 to be very fascianitng; I love learning about host manipulation. Organisms, regardless of size or other classifcations, aim to survive and reproduce. Organisms that cause diseases are no exception. These organisms will manipualte their host so that the disease spreads to new victims, helping the disease-causing organisms survive and reproduce. An example of host manipualtion is the interaction between humans and the Guine worm. Intially, a human drinks water contaminated with water fleas, which have eaten the Guinea worm larvae. The human digestive system destroys the fleas, but the Guinea worm larvae survive. A year after infection, the larvae are fully grown and females make their way to the surface of the skin.

The last example is T. gondii is a parasite that is only able to sexually reproduce in cats. When the parasite reproduces, it creates oocysts, which are removed from the cat when it passes feces. Animals, such as rodents and birds, will in time eat the oocysts and become infected. The parasite can also infect humans when we eat undercooked meat and unclean vegetables or do work with cat litter. This is why pregnant women should not empty a cat litter box. Although the infection is mostly benign in humans (those with weak immune systems can face complications), if a pregnant women becomes infected with the parasite, then the fetus is at a risk for severe complications. However, if a women is infected before fertilization, then the risk is nonexistent. Despite its lackluster effect in humans, the parasite greatly affects mice and rats. Once infected, rodents become heavy, lazy, and lose the concept of fear of predators. Furthermore, the rodents are attracted to the smell of cat urine. Clearly, the rodents are now slow, appetizing, and in the presence of a cat, which leads to a nice and tasty meal for the cat. Once in the cat, the parasite is able to sexually reproduce, ensuring its survival.

Ultimately, host manipulation is a very interesting topic. Although the organism causing the disease does not take full control of the host, it does cause the host to act in certain ways that will benefit the organism survive and reproduce--the goals for all living