What are some harmful insects that can cause diseases to humans in their circulatory and nervous systems?

Of coarse the most popular one for that is known as the Mosquito. These little blood suckers give a disease through blood known as malaria. It is the number one killer in Africa. There are many other insects such like Ticks, Fleas, Mites, certain species of Cockroach, certain flies can carry sicknesses. And the list goes on. If you need any other info just say so.

A way to prevent Mosquitos, there are such things as Mosquito nets, which can really keep out most flying insects. Bug spray is not an efficient way to help keep your home bug free, but it is the best route. Do a little research on different types of ways to help keep places bug free. If you have any, you could share it.