Many animals carry diseases. Raccoons, bats, squirrels and other animals are commonly found to have parasites, viruses and bacteria in their systems. They are able to infect other animals, especially humans by biting them or through contact with their waste. In fact, much of the animal waste is where the real concern lies.
Rats are no different. In fact, they are one of the worst carriers of disease of them all. They carry a large number of parasites and illnesses including, but not limited to, the following:
Bubonic plague - some of the greatest plagues that the earth has ever seen have been caused by this disease. In fact nearly half of Europe was wiped out by the disease in the late 1500s. This is spread primarily by rats. The disease is spread by fleas getting it from the rats and then jumping on humans, biting the humans and spreading the infection. It can also be contacted by breathing in a few cells of the bacteria from waste or bodily fluids from the rat. This can kill large numbers of people rather quickly, and rats are the primary cause of this illness spreading.
Salmonella - we normally think of salmonella as associated with food poisoning, but the truth is that rats spread this disease through their droppings. This occurs primarily when the droppings have come in contact with food that humans would consume. The disease easily gets in the food and if not cooked thoroughly it can cause severe illness and even death. This is also easily spread to your pets, so you need to be really careful about rats in your home.
Rat-bite Fever - in 10 percent of the cases where a person contracts this disease the person will die. A bacterium that causes this disease is spread through a bite from a rat, but this is not the only way a person can get the disease. They can also contract it by coming in contact with the rats waste, the waste contaminating food, or through a cut in the skin that comes in contact with the rat waste.
Tapeworms - tapeworms are quite dangerous because of how they affect the overall health of the host. The tapeworms that rats spread come through eating contaminated food. This usually occurs when a person comes in contact with rat waste and then touches food that is consumed by another without washing their hands first or when a person eats food and they have not washed their own hands. This parasite grows in the intestines and is quite dangerous.
Murine Typhus - this disease is also spread through the bites of fleas, and is quite dangerous. This can easily cause death in the elderly and those who are already sick.