7 Serious Illnesses Carried by Rats and Mice

Deer mouse
  Kitchin and Hurst / Getty Images 

Rats and mice scurrying through the walls and floors of your home are more than just a nuisance, and the danger they pose goes beyond the damage caused if they gnaw on building materials and belongings. Rats, mice, and other rodents can pose a serious health risk to your family through the various disease-causing microbes and parasites they may carry.

The Center for Disease Control and Prevention) lists at least seven known illnesses caused by rats, mice, and other vermin.

Hantavirus Pulmonary Syndrome

The deer mouse (Peromyscus maniculatus), cotton rat (Sigmodon Hispidus), rice rat (Oryzomys palustris), and white-footed mouse (Peromyscus leucopus) all can carry and spread hantavirus pulmonary syndrome (also called HPS or simply hantavirus). This is one of the most serious illnesses that can be carried by rodents, receiving a good deal of attention in recent years, especially in Western regions of the U.S.

Hantavirus pulmonary syndrome is caused by a number of different viruses, and it most typically affects people's lungs, heart, and kidneys. The symptoms are similar to those of the flu, but they quickly grow worse and can be life-threatening if not treated. Rodents are unaffected by the viruses, but they spread them through saliva, urine, and feces.

The mice capable of carrying the bacteria are all found throughout most of North and South America and are common intruders in homes and outbuildings. Transmission of HPS-causing viruses to humans can occur through:

  • Breathing in dust contaminated with rodent urine or feces
  • Touching infected rodents or their urine and feces
  • Getting bitten by an infected mouse or rat

Diagnosis can be difficult, since the disease closely resembles the flu in its symptoms. Treatment of HPS requires intensive-care hospitalization with supplemental oxygen, and serious infections are fatal about 40 percent of the time. This is a very serious disease, for which the best prevention is to avoid all contact with the rodents known to carry the viruses causing HPS. Fortunately, the disease is relatively rare, though it receives lots of publicity due to its severity.

Leptospirosis

Leptospirosis is caused by a genus of bacteria (Leptospira spp.) passed by rodents and many other animals around the world. In addition to rodents, farm animals are especially likely to carry the bacteria. While the animals themselves are unaffected by the bacteria, it can cause serious problems to humans who become infected.

People can be infected with this disease by:

  • Eating food or drinking water contaminated with urine from infected animals, including rodents
  • Touching the skin or mucous membranes (such as inside the nose) with water or soil that has been contaminated with the urine of infected animals

Symptoms in milder cases resemble a serious case of the flu, with headache, fever, vomiting, and diarrhea. Serious cases may evolve to include meningitis, and liver and kidney failure. Treatment with antibiotics is quite successful when the disease is diagnosed early. Untreated victims usually recover, although it can take months. There is some risk of death if the disease progresses to meningitis (inflammation of the brain and spinal tissues) or kidney or liver failure.

Lymphocytic Choriomeningitis (LCM)

The lymphocytic choriomeningitis (LCM) virus is carried and transmitted by the common house mouse (Mus musculus) and may occur anywhere around the world. The virus is not normally carried by domesticated rodents, such as hamsters or guinea pigs, but these pets may become infected in a home where disease-carrying wild mice are present.

LCM is a disease that principally affects neurological function. The first symptoms are fever, lack of appetite, muscle aches, headache, nausea, and vomiting. In the second stage, the disease may cause meningitis (inflammation of tissues surrounding the brain and spinal cord) and encephalitis (inflammation of brain tissues, causing confusion and other symptoms).

You can get LCM by:

  • Breathing in dust that is contaminated with rodent urine or feces
  • Touching a diseased rat or mouse or its urine and feces

Treatment requires hospitalization and treatment with heavy doses of anti-inflammatory drugs. Prevention involves carefully avoiding contact with rodents or areas where rodents have been present.

Plague

Once a fearsome scourge that wiped out a large percentage of the population of medieval Europe, plague is caused by the bacterium Yersinia pestis. It is now easily treated with antibiotics when diagnosed promptly, but it is still a serious illness. The bacteria that causes plague is carried by fleas found on many wild rodents found in the Western U.S. and other parts of the world, including rock squirrels, prairie dogs, wood rats, fox squirrels, ground squirrels, and chipmunks. Plague is now relatively rare, affecting only about 1,000 to 2,000 people annually worldwide, most of them in undeveloped areas.

The disease bacteria is contracted through:

  • Touching an infected animal
  • Being bitten by an infected flea

The most common early symptoms of plague include abdominal pain, diarrhea, nausea and vomiting, fever and chills, and extreme weakness. Precise diagnosis is made from blood tests. Treatment of plague involves the use of powerful antibiotics and care to alleviate symptoms. There are vaccinations available for people who are at ongoing risk of contracting plague.

Rat-Bite Fever (RBF)

Rats and mice can both carry and spread the bacteria causing rat-bite fever. While it can occur worldwide, the strain most commonly found in North America and Europe is Streptobacillus moniliformis. (An Asian form of the disease is caused by Spirrilum minus.)

Symptoms of rat-bite fever include fever, vomiting, headache, and muscle pain. Soon after the fever begins, a rash may develop on hands and feet. Untreated, the disease may progress into lung, liver, and kidney infection; brain and heart infections may also occur.

You can get the rat-bite fever from:

  • Being bitten or scratched by an infected rodent
  • touching a dead rodent that is infected
  • Eating or drinking food or water that is contaminated by rat feces

Treatment for RBF consists of heavy antibiotics, which is generally effective. But untreated RBF may cause very serious problems and can sometimes be fatal.

Salmonellosis

Salmonellosis is a very common foodborne illness in the U.S. and around the world. It can be transmitted in many different ways, including rats and mice contaminating food and water with feces containing salmonella bacteria. Direct contact with infected rodents can also cause the disease.

Symptoms of salmonellis are sometimes mild, since the bacteria is commonly found in the intestinal systems of most animals, including humans. However, an extreme infection can cause nausea, vomiting, abdominal cramps, diarrhea, fever, chills, headache, and blood in the stool.

Salmonellosis can be contracted by:

  • Eating food or drinking water containing salmonella bacteria from rodent feces and other sources
  • Direct contact with rodents or other animals carrying the bacteria
  • Poor person-to-person hygiene
  • Consuming uncooked or undercooked meats, or fruits and vegetables containing the bacteria
  • Contact with pet birds and reptiles that carry the Salmonella bacteria

Treatment for salmonellosis is often unnecessary, since the illness typically resolves on its own after a short time. In cases of serious infection, treatment with anti-diarrheal medications is sometimes prescribed. If it's suspected that the bacteria has caused blood infection, treatment with antibiotics may be prescribed.

Prevention involves avoiding uncooked or undercooked foods and practicing good personal hygiene, and avoiding contact with animals (including rodents) known to carry the bacteria.

Tularemia (Rabbit Fever)

Tularemia is a disease that is caused by a bacteria (Francisella tularensis), carried and spread by wild rodents around the world, including muskrats, ground squirrels, and beavers. When caused by an insect bite, the disease often causes an ulcer at the site of the bite. When contracted through eating and drinking, the disease may cause glandular swelling, cough, or lung infection. The symptoms can range from very mild to life-threatening. Definitive diagnosis can be difficult, requiring blood tests.

The disease can be contracted if you:

  • Handle infected animal carcasses
  • Are bitten by an infected insect, such as a tick or deerfly
  • Eat or drink contaminated food or water
  • Breathe in the airborne bacteria from landscape dust

Once diagnosed, tularemia is treated by heavy doses of antibiotics. Symptoms can last for many weeks, but victims usually recover fully with treatment. Prevention involves avoiding insect bites through the use of repellants, avoiding direct handling of rodents, and wearing breathing protection to avoid inhaling landscape dust during gardening and agricultural work.