Question: how do the diseases spread

Marisol Collins answered on 7 Nov 2016:

A good question A.T.! There are lots of ways diseases spread, but I’ll give you the example of the parasite that I study, which is a little worm called Echinococcus. This parasite has an amazing way of spreading! Now this tiny worm lives in the intestines of dogs, and it lays eggs, which are passed in the dog’s poo. This could be in a field, where there are sheep grazing. A sheep may accidentally eat some of the worm eggs when it’s eating grass, and the egg hatches in the stomach of the sheep. The young worms, called larvae, find their way into the blood system and travel to the liver and lungs of the sheep, where they form large fluid-filled cysts and wait.. Eventually, the sheep might die and be eaten by dogs, especially stray or wild ones, and the worms become adults one again in the intestines of the dog, and the whole process starts again! Amazing huh? This parasite is a big problem in poorer parts of the world, where there are many stray dogs and big flocks of sheep. Worryingly, people can accidentally become infected too and it can make them very ill.