Mice and voles will spread diseases to people through direct contact (breathing in contaminated air, touching contaminated materials, being bitten or scratched by an infected rodent, or eating food contaminated by a rodent). They will also spread diseases through indirect contact when people are bitten by ticks, mites, fleas and mosquitos that have fed on infected rodents. Diseases can also spread to people through an intermediate host, such as beetles or cockroaches.^[1]https://www.cdc.gov/rodents/diseases/index.html In this article we will examine the most common diseases spread directly by mice in Alberta.

Hantavirus

Hantaviruses are a family of viruses primarily spread by rodents that can cause varied disease syndromes in humans. The most common hantaviruses in North America are known as “New World” hantaviruses and may cause hantavirus pulmonary syndrome (HPS).^[2]https://www.cdc.gov/hantavirus/index.html

Hantavirus Pulmonary Syndrome (HPS) is a severe, sometimes fatal, respiratory disease in humans caused by infection with hantaviruses. Anytime you come into contact with rodents that carry hantavirus you are at risk of HPS. Rodent infestation in and around the home remains the primary risk for hantavirus exposure.^[3]https://www.cdc.gov/hantavirus/hps/index.html

The rodents shed the virus in their urine, droppings, and saliva. The virus is mainly transmitted to people when they breathe in contaminated air. When fresh rodent urine, droppins, or nesting materials are stirred up, tiny droplets containing the virus get into the air. This process is known as airborne transmission. This is the most common method of transmission, however people can also get the virus through eating contaminated food, touching droppings, urine and saliva, as well as by being bitten by an infected rodent.^[4]https://www.cdc.gov/hantavirus/hps/transmission.html

Hantavirus is one of the deadliest diseases spread by rodents, with a mortality rate of 38%.^[5]https://www.cdc.gov/hantavirus/hps/symptoms.html

 Leptospirosis

Leptospirosis is a bacterial disease that affects humans and animals. The bacteria that cause leptospirosis are spread through the urine of infected animals, which can get into water or soil and can survive there for weeks to months. Humans can become infected through contact with urine from infected rodents, as well as contact with water, soil, or food contaminated with the urine of infected rodents. The bacteria can enter the body through the skin or mucous membranes (eyes, nose or mouth). Drinking contaminated water can also cause infection.^[6]https://www.cdc.gov/leptospirosis/infection/index.html Leptospirosis has also been diagnosed more frequently in pets in the last few years.^[7]https://www.cdc.gov/leptospirosis/pets/index.html

Without treatment, Leptospirosis can lead to kidney damage, meningitis (inflammation of the membrane around the brain and spinal cord), liver failure, respiratory distress, and even death.^[8]https://www.cdc.gov/leptospirosis/index.html The illness lasts from a few days to 3 weeks or longer. Without treatment, recovery may take several months.^[9]https://www.cdc.gov/leptospirosis/symptoms/index.html

Lymphocytic Choriomeningitis (LCM)

Lymphocytic choriomeningitis (LCM) is a rodent-borne viral infection caused by lymphocytic choriomeningitis virus (LCMV). The primary host of LCMV is the common house mouse. It is estimated that 5% of house mice throughout the United States carry LCMV. 

LCMV infections can occur after exposure to fresh urine, droppings, saliva, or nesting materials from infected rodents. Transmission may also occur when these materials are directly introduced into broken skin, the nose, the eyes, or the mouth, or presumably, via the bite of an infected rodent.Person-to-person transmission has not been reported, with the exception of vertical transmission from infected mother to foetus.^[10]https://www.cdc.gov/vhf/lcm/transmission/index.html

Acquired LCMV infection in immunocompetent adults is usually non-fatal, with a mortality rate of less than 1%, and recovery from even severe disease occurs without sequelae in most cases. However, congenital LCM can produce a wide spectrum of pathologic effects, from minimal to severe, depending on the developmental stage of the foetus at the time of infection. In some cases, infection may result in abortion, hydrocephalus, chorioretinitis, and/or mental retardation of the infant. The mortality rate of infants diagnosed with congenital LCMV is approximately 35%. Among survivors of congenital LCMV infection, two thirds have long-term neurologic abnormalities, including microcephaly, mental retardation, cerebral palsy, seizures, and visual impairment.^[11]https://www.canada.ca/en/public-health/services/laboratory-biosafety-biosecurity/pathogen-safety-data-sheets-risk-assessment/lymphocytic-choriomeningitis-virus.html

Rat-Bite Fever 

Rat-bite fever (RBF) is an infectious disease caused by two different bacteria: streptobacillus moniliformis (North America) and spirillum minus (Asia).^[12]https://www.cdc.gov/rat-bite-fever/index.html

Rat-bite fever can be spread through rodent bits or scratches, when handling rodents or through contact with their saliva, urine, or droppings, through contact with surfaces that are contaminated with the bacteria, or through consumption of food or drinks that have been contaminated with droppings or urine from a rodent carrying the bacteria.^[13]https://www.cdc.gov/rat-bite-fever/transmission/index.html

Without early diagnosis and appropriate treatment, RBF can cause severe disease and death. About 1 in 10 people who have streptobacillary RBF infection die.^[14]https://www.cdc.gov/rat-bite-fever/symptoms/index.html

Salmonellosis

The CDC estimates salmonella bacteria to cause about 1.35 million infections, 26,500 hospitalizations, and 420 deaths in the United States every year.^[15]https://www.cdc.gov/salmonella/ The risk of getting salmonellosis is highest if you eat certain raw or undercooked foods contaminated with salmonella, especially eggs, poultry and meat.^[16]https://www.canada.ca/en/public-health/services/diseases/salmonellosis-salmonella/risks.html The disease can also be spread by rodents by fecal-oral transmission. Food, water, and bedding may be contaminated by infected feces from wild mice or rats.^[17]http://dora.missouri.edu/rats/salmonellosis/