Chicago has once again claimed the unwelcome title of the “rattiest” city in the United States, earning this distinction for the 10th consecutive year, according to Orkin Pest Control. Rodents like rats and mice aren’t just a nuisance—they’re proven vectors of disease. There are many dangers of rodents. And you might not know about some of them. These pests can transmit infectious parasites and pathogens directly to humans, posing serious health risks.
Dangers of Rodents
Globally, rodents are linked to over 35 illnesses that threaten human health. Beyond spreading disease, they can cause structural damage to homes and negatively impact mental well-being. In this blog, we’ll explore the hidden dangers of mice, focusing on their parasites, the telltale signs of an infestation, their role as a public health threat, and the history of diseases they’ve helped spread.
The best strategy in preventing rodents is to make your home or business as unattractive to them as possible.
-Allison Beach, Technical Coordinator
How do Rodents Behave?
In the Midwest, the Norway rat (brown rat) and house mouse are the most common rodent pests, thriving wherever humans live. These adaptable rodents easily establish themselves in man-made structures, taking advantage of their surroundings for shelter. Their behaviors make them highly effective pests. Both are nocturnal, allowing them to remain hidden as they live alongside humans. Like all rodents, their teeth never stop growing, so they gnaw relentlessly, causing structural damage to buildings and electrical wiring. Norway rats often nest in underground burrows, which can harm landscaping, while house mice prefer indoor nests, such as within wall voids. This could create potential fire hazards.
As prey animals, rats and mice are naturally cautious, skittish, and neophobic (afraid of new things), yet their curiosity drives them to explore new spaces. Remarkably, rats can squeeze through openings the size of a quarter, and mice can fit through gaps as small as a dime. Rodents communicate primarily through pheromones in their waste, often leaving urine trails to mark safe areas. To them, the scent of urine signals security—a detail that underscores their resilience and adaptability in human environments.
Identifying a Rodent Infestation:
Signs of mice and rats are quite clear when they’ve made themselves at home in or around your property. Common signs of a rodent infestation include:
- Droppings: Rodents usually leave their pellet droppings near food sources or along baseboards. Rat droppings are about ¾ of an inch in size, while mouse droppings are up to ¼ inch in size.
- Nesting material: House mice use materials like paper products, packing supplies, insulation, or fabric to make their nests. Seeing little pieces of these materials might mean there are nests nearby.
- Gnaw marks: Rodents leave little teeth marks when they chew on things like pipes and wires. Seeing physical bite marks serves as evidence that rodents were there at some point.
- Rub marks: Rats tend to leave rub marks on walls due to their oily/dirty fur. If you notice dark marks or discoloration, this could be a sign of a well-used rodent trail. Also look for little rodent tracks outside!
- Noises: If you hear unfamiliar noises at night coming from inside the walls, it could mean that rodents are actively living in the wall voids.
What Diseases can Rodents Spread?
Rodents can spread several dangerous pathogens to humans, leading to serious illnesses. These are the dangers of rodents that are the worst. Understanding these diseases and how rodent behavior contributes to their transmission is essential for protecting human health.
Food-Borne Illnesses
Rodent urine and droppings (poop) can contain harmful bacteria like E. coli and Salmonella, which can cause food poisoning symptoms if someone consumes contaminated food/liquids.
Leptospirosis
Leptospirosis is one of the most significant diseases spread by rodents. This flu-like illness is caused by bacteria found in the urine of infected rodents. Humans and animals risk infection by drinking contaminated water, such as from puddles, or coming into contact with tainted soil. Pets, particularly dogs and cats that spend time outdoors, are especially vulnerable in areas with heavy rodent infestations. In humans, leptospirosis can cause flu-like symptoms, muscle aches, and jaundice, while infected pets may show signs like muscle pain, limping, lethargy, and loss of appetite.
Rat Bite Fever
Rats may bite when they feel threatened or are protecting food or their nest. While rat bites are rare, they can transmit a disease called Rat Bite Fever through pathogens in their saliva. Each year, only 20,000 to 40,000 rat bites are reported in the United States, and even fewer—about 2,000 to 4,000 cases—result in symptoms of the disease. Those infected may experience headaches, fever, and skin rashes. Although the risk is low, understanding the potential dangers highlights the importance of avoiding close contact with rodents.
Hantavirus
Rodent urine and droppings can spread dangerous viruses known as Hantaviruses. Norway rats, in particular, are known to transmit Seoul virus and Hantavirus Pulmonary Syndrome. These viruses spread when microscopic particles from rodent waste or nest materials become airborne and are inhaled. This often occurs when waste or nesting debris is disturbed. Symptoms of Hantavirus infection include fatigue, nausea, muscle aches, coughing, and shortness of breath. Understanding these risks emphasizes the importance of safely managing rodent infestations.
Lymphocytic Choriomeningitis
Lymphocytic Choriomeningitis (LCM) is caused by a virus commonly found in the urine, droppings, saliva, and even mucus of house mice. Humans can contract the virus by consuming contaminated food or water or inhaling particles from house mouse waste in the air. People infected with LCM often experience flu-like symptoms.
Rodents Spreading Disease Through Parasites
Rodents often carry parasites that can spread diseases affecting humans. These diseases don’t directly transfer from rodent to human; instead, rodents serve as vessels for these parasites, which then spread through indirect contact. Understanding which parasites are hitching a ride and the specific diseases and symptoms they cause is crucial for protecting the health of you and your pets.
Plague
Fleas and rodents were responsible for one of the most devastating pandemics in human history—the Black Plague of the 14th century. Most of us learned in history class how this deadly disease spread through flea bites from rats. When we think dangers of rodents and disease, the Plague is often the first example that comes to mind. So why mention an eradicated medieval disease in this blog? The truth is, the Plague never really disappeared. It has resurfaced sporadically since the 14th century, even in the United States. However, the good news is that common rodents like the Norway rat or house mouse are unlikely to spread the Plague in urban areas today, thanks to advancements in hygiene and medicine since medieval times.
Lyme Disease
Both rodents and humans can serve as common hosts for ticks carrying diseases. This means that pest rodents may carry infected ticks, indirectly transmitting tick-borne diseases to people. The white-footed mouse, similar to the house mouse, can carry the bacteria that cause Lyme disease in humans. Ticks can pick up this bacteria by feeding on a white-footed mouse and later transfer it to their next host, which could be a human. Symptoms of Lyme disease include a rash (often a “bull’s-eye” pattern around the bite site), fever, chills, and fatigue.
Toxoplasmosis
Toxoplasmosis is a microscopic parasite (protozoan) that affects the brains of mice, making them more attracted to their natural predators—cats. Infected mice essentially give themselves up as prey, and when a cat eats an infected mouse, it can also become infected. Humans can contract toxoplasmosis by handling contaminated cat waste, such as when cleaning a litter box. While the infection is usually not dangerous for healthy individuals, it poses significant risks for pregnant women, as it can cause birth defects and other fetal health problems.
If you experience any of these symptoms after exposure to rodents, consult a healthcare professional.
How do I Prevent Rodents from Entering my Home?
Taking proactive steps to prevent rodents from entering your home and making your property less attractive to them can save you from dealing with an infestation. The most important step is to seal off any potential entry points around your home. These gaps are often much smaller than you might think—rats can squeeze through openings the size of a quarter, and mice can fit through spaces as small as a dime. Seal these areas with foam, steel wool, or caulk to keep rodents out.
Some common rodent entry points include:
- Gaps between windows and doors both inside and outside
- Spaces where pipes and electrical lines enter/exit a structure
- Between the foundation of a building and the ground
- Behind cabinets and appliances in the kitchen
- Between floor and wall junctures
- Around floor drains or where appliance pipes enter the ground
- Pay extra attention to attics, basements and crawlspaces! These unfinished spaces may be more likely to have entry points.
Maintaining good sanitation practices—such as properly disposing of food, taking out the trash regularly, sealing garbage cans tightly, and storing food in sealed containers—will make your home much less inviting to rodents. Without a food source, they’ll have little reason to stay. By staying vigilant with these steps, you can protect your home and health from the hidden dangers of rodents!
