Rat-bite fever is an infectious disease caused primarily by bacteria transmitted through contact with rats. The two main bacteria responsible for rat-bite fever are *Streptobacillus moniliformis* and *Spirillum minus*. These bacteria live in the mouths, urine, and feces of rats and can infect humans through bites, scratches, or even close contact with rat secretions.
The most common cause, *Streptobacillus moniliformis*, is a type of bacteria that naturally inhabits rats without harming them. When a rat bites or scratches a person, the bacteria can enter the skin and cause infection. However, infection can also occur without a bite, such as through handling rats or contact with surfaces contaminated by rat urine or feces. This means that even touching rat droppings or urine and then touching broken skin or mucous membranes can lead to the disease.
The bacteria multiply in the human body after entry, leading to symptoms such as fever, rash, joint pain, and muscle aches. The infection can spread through the bloodstream, causing systemic illness. If untreated, rat-bite fever can lead to serious complications affecting the heart, brain, or other organs.
The other bacterium, *Spirillum minus*, is more common in Asia and causes a form of rat-bite fever called sodoku. It is transmitted similarly through rat bites or scratches but tends to cause a more localized infection with swelling and ulceration at the bite site, followed by fever and rash.
Rats themselves do not usually show signs of illness from these bacteria, making it difficult to identify infected animals. The bacteria live harmlessly in their mouths and excretions, which is why rat bites or contact with rat waste are the main routes of transmission to humans.
In addition to bites and scratches, rat-bite fever can also be contracted by exposure to environments heavily contaminated with rat urine or feces. This can happen in places with poor sanitation or where rats are common, such as urban areas, warehouses, or homes with rodent infestations.
Overall, rat-bite fever is caused by bacterial infection transmitted from rats to humans primarily through bites, scratches, or contact with rat urine and feces. The bacteria involved are adapted to live in rats but can cause serious illness in people when introduced into the body. Preventing rat-bite fever involves avoiding contact with rats and their waste, practicing good hygiene, and seeking medical care promptly if bitten or scratched by a rat.
