Rodents and infectious disease

Definition

Rodent-transmitted diseases are responsible for severe and deadly illnesses in human populations. These diseases include hantavirus pulmonary syndrome, murine typhus, rat-bite fever, leptospirosis, and eosinophilic meningitis.

Diseases

Hantavirus pulmonary syndrome (HPS). Humans contract hantavirus pulmonary syndrome (HPS) by inhaling dried rat or mouse excrement. The most common risk factor for hantavirus exposure is rodent infestation in the home. Though rare, HPS is a public concern because its effect on the human body is severe and can be fatal. HPS manifests in two stages of symptoms, which first appear about one to five weeks following exposure to the hantavirus. In the first stage, an infected person experiences fever, fatigue, body ache, headache, lung congestion, nausea, diarrhea, and abdominal pain. In the second stage, known as the cardiopulmonary stage, the congestion in the lungs progresses to a cough, shortness of breath, a worsening buildup of fluid in the lungs, low blood pressure (hypotension), rapid heartbeat, multiple organ failure, and respiratory distress. HPS can be diagnosed with a blood test. Persons with HPS are treated with assisted respiration, often in a hospital’s intensive care unit.

Murine typhus. Humans contract murine typhus (also known as endemic typhus), a rickettsial infection caused by the Rickettsia typhi bacteria, by being bitten by lice or fleas that are often carried by rats. Domestic cats may also carry these infected fleas. Active in warm climates, murine typhus infection may last as long as two weeks. However, if left untreated, the disease can be fatal in severe cases. Following an incubation period of six to fourteen days, symptoms include headache, myalgia, and rash. A bacterial disease, murine typhus is treated with antibiotics.

Rat-bite fever. Rat-bite fever is transmitted to humans through a bite, scratch, or ingestion of food or water contaminated with infected rat feces or other secretions. It is a bacterial illness caused by Streptobacillus moniliformis and Spirillum minus. Symptoms include fever, body ache, nausea, and rash, and they may progress to arthralgia, pneumonia, or meningitis. Rat-bite fever is diagnosed by testing for the presence of the infectious bacteria on the skin or in the blood or the lymph nodes. It is treated with antibiotics.

Leptospirosis. The bacterium Leptospira is found in the urine of infected wild and domestic rodents. Humans can contract leptospirosis by handling infected rodents or by ingesting water that is contaminated with infected rodent urine. An infected person will show signs of illness two to four days after exposure. Symptoms include headache, fever, abdominal pain, diarrhea, and rash. In severe cases, infected persons may have kidney or liver damage, meningitis, or breathing difficulty. Leptospirosis is diagnosed by testing a person’s blood or urine, and the infection is treated with antibiotics.

Eosinophilic meningitis. Humans can get eosinophilic meningitis, an invasion of the central nervous system by parasites, from ingesting the larvae of the rat lungworm (Angiostrongylus cantonensis), which can be hosted by snails and slugs. Eating infected snails or vegetables will make a person vulnerable to contracting eosinophilic meningitis. Symptoms, including headache, fever, and nausea, may last several weeks or months. Treatment includes headache-control measures and antifungal therapy.

These diseases only represent a small portion of the thirty-five known illnesses rodents carry and transmit. Other diseases, including salmonella and hepatitis B, can also be transmitted from rodents to humans or from parasites carried by rodents to humans. The spread of these diseases can occur through direct and indirect contact.

Prevention

The best prevention of rodent-transmitted infectious diseases is indoor and outdoor rodent control. Indoor rodent-control measures include maintaining a clean kitchen, storing food and garbage in rodent-proof containers, throwing away uneaten pet food daily, setting rodent traps, and sealing entry holes larger than one-quarter-inch in diameter. Outdoor rodent-control measures include clearing brush and stored items from a building’s foundation and removing woodpiles and other potential nesting sites.

Flea control is another preventive measure against rodent-transmitted infectious disease. Flea-control medicine should be administered to pets. To avoid contact with feral, and potentially infective, animals, one should not provide food for birds or wild animals. Fallen fruit from trees should be picked up and discarded. One should use a flea-killer spray around sites that are vulnerable to rodent nesting.

Other measures include not swimming in water that may be contaminated with rodent urine. Also, for walking through shallow water or on ground inhabited by rodents, one should wear protective footwear and clothing.

Response

Rodent infestation in the home, marked by droppings (feces), nests, or gnawed food packaging, requires disinfection of the suspected areas of infestation. Because dried rodent urine and feces will aerosolize during removal, a mask or respirator should be worn while cleaning an area known or suspected to have rodent infestation. One should wear rubber gloves when cleaning, and instead of sweeping or vacuuming droppings and nests, one should wipe the contaminated areas with detergent or a hypochlorite solution. After wiping up the droppings or nesting materials, the area should be disinfected. Dead rodents should be sprayed with disinfectant, bagged with cleaning materials, and discarded in a waste disposal system recommended by a local or state health department.

Impact

Rodents are the cause of many bacterial, rickettsial, and viral infections impacting humans. The control of rodent populations is critical to public health and health management.

Bibliography

Committee on Infectious Diseases of Mice and Rats. Companion Guide to Infectious Diseases of Mice and Rats. National Academies Press, 1991.

"Controlling Wild Rodent Populations." Centers for Disease Control, 8 Apr. 2024, www.cdc.gov/healthy-pets/rodent-control/index.html. Accessed 4 Feb. 2025.

Gratz, Norman. Vector- and Rodent-Borne Diseases in Europe and North America: Distribution, Public Health Burden, and Control. Cambridge UP, 2006.

Meek, Frank. “Rodent Infestations and the Spread of Infectious Diseases.” Infection Control Today, 2 Feb. 2023, www.infectioncontroltoday.com/view/rodent-infestations-spread-infectious-diseases. Accessed 4 Feb. 2025.

Padovan, Dennis. Infectious Diseases of Wild Rodents. Corvus, 2006.

"Typhus." Medline Plus, US National Library of Medicine, 7 Dec. 2014, medlineplus.gov/ency/article/001363.htm. Accessed 17 Nov. 2016.