As we expand our activities into the natural environment, we come into closer contact with different types of rodents and more rodent-borne diseases. Rodents play a significant role in the transmission of many disease-causing pathogens to humans.
Rodents can carry several parasites at the same time and are reservoirs for many diseases including those carried by ectoparasites such as fleas, ticks, lice, and mites. In fact, rodents are likely responsible for more deaths than all the wars over the last 1,000 years. That’s a stat we definitely don’t want to end up being part of!
Rodents carry a wide range of disease-causing organisms, including many species of bacteria, viruses, protozoa, and helminths (worms). Humans can end up with one of these diseases by:
- Inhaling or coming in direct contact with rodent excreta (urine, feces, saliva)
- Handling of or coming in close contact with infected rodents
- Getting bitten or scratched by a rodent
- Consuming water or food contaminated by rodent droppings or urine
Below we lay out the list of some of the most prevalent rodent-borne diseases.
Many rodent species carry hantaviruses, especially voles and mice. In the U.S., most hantavirus cases are caused by humans breathing in aerosolized particles, but there is a slight risk of catching this disease through contact with rodent excrement, the rodent itself, or contaminated food or drink. Those who contract hantavirus usually end up with flu-like symptoms.
In North America, different types of hantavirus have been identified in various rodent species. The most important of these is the Sine Nombre virus which is carried by deer mice in Canada, Mexico, and the U.S. This causes Hantavirus pulmonary syndrome, which has a high fatality rate.
Bartonellosis is caused by a number of species of Bartonella bacteria, several of which can be carried by rodents. This virus causes a wide range of symptoms including fever, headache, fatigue, poor appetite, brain fog, muscle pain, and swollen glands. It is most commonly transmitted by the bites of infected fleas. Rats are known reservoirs for Bartonella and fleas found on rats can potentially vector this bacteria to humans who come in contact with them.
In the U.S., probably one of the most common diseases associated with mice is foodborne illness. Mice have a tendency to frequent unsanitary places where they acquire bacteria, such as salmonella, and harbor it in their digestive tracts. Mice then enter homes and contaminate food and surfaces (kitchen counters, utensils etc.) with their infected droppings, which can lead to acute food-poisoning in humans.
Symptoms will show 12 to 72 hours after infection and include diarrhea, fever, vomiting, and abdominal cramps. Once a person is infected, salmonella is easily transmitted to other people through poor hand hygiene and poor sanitation.
Found worldwide, leptospirosis is an infection caused by a bacteria called Leptospira. It is found in the blood and urine of animals, which include rodents, cattle, pigs, and dogs. The bacteria live inside the animal’s kidneys and are passed out in urine. The bacteria can survive for weeks or months in soil or water. Humans can become infected through an infected rodent bite, by ingesting food or water that was contaminated by the infected rodent urine, or from skin contact with contaminated water, soil, or vegetation.
In the U.S., rodent-associated leptospirosis has been shown to be quite prevalent in some areas. The risk of contracting leptospirosis is low for most people. However, occupations or activities that involve frequent contact with freshwater sources or moist environments have a higher risk.
Symptoms of Leptospirosis show in around 7–14 days and can include mild to severe flu-like symptoms including headache, chills, muscle pain, nausea, vomiting, redness of the eyes, diarrhea, and a skin rash.
In about 10% of leptospirosis cases a more serious form develops, called Weil’s disease. This can result in organ failure, internal bleeding and death. Symptoms of Weil’s include jaundice, swollen ankles, feet, or hands, chest pain, symptoms of meningitis or encephalitis (headaches, vomiting, and seizures), and coughing up blood.
Rat-bite fever is caused by two bacteria: Streptobacillus moniliformis and Spirillum minus. In infected rodents, the bacteria are present in rat feces and urine as well as secretions from the mouth, nose, and eyes. Rat-bite fever is usually caused by a bite or scratch from an infected rat or rodent. It can also be caught by handling infected animals or ingesting food or drink contaminated by rodent feces or urine.
Symptoms of rat-bite fever differ between the two bacteria.
- Streptobacillus: symptoms appear 3-10 days after infection and can include fever, vomiting, muscle pain, headache, joint pain, and a rash.
- Spirillum: symptoms appear 7-21 days after infection and can include repeated fever, ulcer at the bite wound, swelling around the wound, swollen lymph nodes, and a rash.
In addition, more serious complications can include heart infections, meningitis (brain infection), pneumonia (lung infection), and abscesses in internal organs. Luckily, reports of rat bite fever are rare in North America. However, many experts believe that rat-bite fever is under-reported, and that numbers of actual human cases are much higher than what the literature shows.
Tularemia is present in a wide geographic band across the whole northern hemisphere. It is caused by the bacteria, Francisella tularensis, which has several strains that vary in virulence and geographical range.
A large number of mammals and arthropods can carry Tularemia. The rodent reservoirs of tularemia include voles, mice, rats, muskrats, beavers, ground squirrels, lemmings, and hamsters. Rabbits and hares are also common carriers of the disease. Outbreaks in humans correlate to peaks in populations of rodents and hares.
Symptoms of tularemia are flu-like, including fever, headache, and nausea. These symptoms are accompanied by an ulcerated lesion at the site of inoculation if the infection was acquired by a bite or through a break in the skin. Additional signs include swollen lymph nodes, pneumonia, and a rash.
The cause of this disease is the rickettsia bacterium known as Rickettsia akari, usually transmitted via the house mouse mite. Symptoms of this nonfatal disease include headaches, rash, and fever. The disease is often misdiagnosed as chicken pox.
Caused by the bacterium Rickettsia typhi, this disease is transmitted from fleas found on rats and other rodents. The Norway rat and the roof rat are the predominant rodent reservoirs. Interestingly, murine typhus is not transmitted directly through flea bites. Rather, infections occur when infected flea feces enter a flea bite wound when it’s scratched.
Symptoms of murine typhus include fever, chills, headache, and a rash. The rash usually appears about five days after symptoms start occurring and will last about a week. Although relatively rare in the United States, cities near seaports in warmer climates could see the risk increase.
Toxoplasmosis is an infection caused by the protozoan Toxoplasma gondii. In the U.S., the CDC estimates that up to 22% of the population have been infected. Cats are the main host of T. gondii, acquiring this protozoan by eating infected rodents or contaminated meat. Humans can serve as an intermediate host for T. gondii.
Although a human infection is usually mild and self-limiting, toxoplasmosis can have devastating and/or deadly effects on unborn fetuses. Humans most commonly acquire toxoplasmosis infections through contact with infected cat feces. As such, medical professionals advise pregnant women to use extreme caution around cat litter boxes during pregnancy.
Lymphocytic choriomeningitis (LCM)
An LCM infection can range from asymptomatic to severe cases that produce mild meningitis. A typical infection involves fever, headache, and muscle pains that resemble typical flu and other common viral ailments. Thus, this virus may actually affect more people as the illness is easily misdiagnosed.
Arenaviruses such as LCM and their biology are not well understood, but they are transmitted to humans by contact with food or other items contaminated by rodent excretions. They can also be transmitted through inhalation of contaminated particles in the home, factories, or agricultural areas. Some are known to be transmitted from person to person through methods such as direct contact with blood or bodily fluids of an infected person or infected objects such as medical equipment in a hospital.
Plague is the most notorious disease that is linked to rats in the human environment. In the 14th century, it killed 25 million people over a 50-year period throughout Europe, becoming known as the “Black Death.” This disease is caused by the bacteria Yersinia pestis, which cycles between rodents and fleas. Several species of rodents, including rats, ground squirrels, prairie dogs, and chipmunks are reservoirs of the plague bacteria in the wild. Humans can become infected from:
- Flea bites: rats and other rodents can carry infected fleas — as can cats.
- Contact with infected animals: handling tissue or fluid of an infected animal. Cats (and other carnivores) can also acquire plague-causing bacteria by eating infected rodents.
- Inhalation of infectious particles: when plague infection reaches the lungs, coughing produces infected airborne particles that people in close proximity may breathe in.
In the Western US, two types of plague occur — urban and sylvatic plague. Urban plague cycles between commensal rats (species that live in close association with humans) and their fleas (primarily the Oriental rat flea). Human cases of urban plague are extremely rare. More common is the sylvatic plague, primarily seen in wild rodents, rabbits, and their fleas. There are three clinical forms of the plague: Bubonic, Septicemic, and Pneumonic.
- Bubonic plague: This is the most common form, acquired through an infected flea bite. The bacteria travel through the bloodstream and concentrate within lymph glands. Symptoms include swollen and painful lymph nodes in the groin and under the armpits. This is accompanied by a sudden onset of fever and extreme weakness.
- Septicemic plague: Untreated bubonic plague will allow the bacteria to spread throughout the body, leading to this deadly form. Symptoms include fever, extreme weakness, diarrhea, delirium, abdominal pain, and shock. Bleeding occurs under the skin, turning it black. This is the reason why the plague was referred to as the “Black Death.”
- Pneumonic plague: This form is known to be the most dangerous because the bacteria is concentrated in the lungs and can spread by coughing. Symptoms include fever, difficulty breathing, chest pain, bloody mucous, pneumonia and shock.
Allergens and asthma
Aside from the diseases listed above, an infestation of mice or rats also means the introduction of allergens. A protein found within their urine may trigger asthma and closely related allergic conditions in susceptible people. The residue from rodent urine can easily spread all over a home, with the highest concentrations usually in kitchens, and can lead to asthma attacks. Mice typically urinate in micro-droplets wherever they are nesting. And since they eat and travel throughout the day, mouse urine can literally be found on thousands of surfaces throughout a home. This means residents are likely exposed to rodent allergens whether they realize it or not – yuck!
Eliminate rodents with Ehrlich
Wow! Did you know rodents could bring that many diseases into your home? Don’t give them a chance! Prevent rodents with Ehrlich and contact us today! We offer free inspections and can give you all the tips and tricks to stop rodents from making your house their home.