When they bite you they inject a type of saliva into you to thin your blood. This saliva is filled with the germs from the animal that was previously bitten. These insects are the culprits that are responsible for spreading most of the deadly diseases in the world. The plague, responsible for killing so many people in Europe was spread from the rat to people via the flea. Malaria, now responsible for killing one person in the world every 15 seconds is spread by mosquitoes.
Limes disease is always in the headlines and is spread by ticks.
Mites that are parasitic on wild animals and birds occasionally bother us along with the hair follicle mites and the scabies mite. Outbreaks of rickettsialpox, a disease similar to chicken pox have been traced to the mouse mite in some parts of the country. Flies sponge up the liquids from animal feces and then try to crawl onto our food and spread many diseases. The first thing you must do is to make your landscape unfriendly to rodents. You should also use beneficial nematodes on your grounds every year.