Front of hookworm with teeth
The life cycle of a hookworm starts with the worm who is living inside a human's small intestine and hatches eggs. These eggs will leave the body through the feces and when left alone on soil for example, the eggs will develop into larvae which penetrate the human barefoot with their hooks, get carried through the bloodstream until they reach the lungs where they wait for the coughing fits to become violent enough to be coughed up. This is not to leave the body, but to be able to enter the stomach where they take up residency in the small intestine. There, hooked to the wall, they feed on the blood and produce eggs, which then are able to infect more people.
While the hookworm seems like a horrible thing to have in your body, it is rarely fatal in healthy adults (http://sickontheroad.com/2012/04/20/whats-the-deal-with-hookworm/) and might even prove to be a cure for allergies like asthma and the likes (http://www.theguardian.com/science/2006/feb/05/medicineandhealth.research).
Hookworm after entering the skin
Hookworms are common in tropical countries and can be prevented by not walking barefoot where other people did their business. However, they are fairly common in cats and dogs and by touching feces that contains hatched larvae, the human can be infected, so should always be mindful of contamination and practice good hygiene.
My idea is to create a black and white world with possible one other colour present and the hookworm being in the center by doings lots of quick, shocking bitey movements with great emphasis on the hooks, for example the larvae waiting for a foot to walk onto them and then they latch on, or swimming through the bloodstream and hooking onto the wall, swimming through the stomach and hooking on to feed... It's not very matured yet but I will start on some thumbnails to explore the possibilities!