Mouse exposure poses a small health risk to humans. Prevention of the risks occurs through appropriate protective clothing when cleaning or handling mice, and immediate treatment of any bite wounds. Even though risk is minimal it is important to be informed about potential zoonotic diseases that rodents might carry and might affect humans and animals. The zoonotic bacterial and viral diseases that may affect mice and humans include but are not limited to the diseases described below:
Bacterial Diseases:
Leptospirosis
Leptospirosis is caused by bacteria of the genus Leptospira. There are a wide variety of clinical symptoms in humans that range from a rash to a high fever and might be confused with symptoms from other diseases. The disease can be transmitted by eating food or drinking water contaminated with urine from infected animals. Additionally, it might be transmitted through contact through the skin or mucous membranes (such as inside the nose, especially if the skin is broken from a cut or scratch) with water or soil that is contaminated with the urine from infected animals. Person to person transmission is rare.
Rat bite fever (RBF)
RBF is an infectious disease caused by two bacteria, Streptobacilus moniliformis and Spirillum minus. This disease is typically carried by rats, but mice may also carry it. Mice who have these bacteria are asymptomatic. In humans the bacteria cause acute febrile illness. Clinical signs include inflammation at the wound site and lymphadenopathy. Other symptoms can include headache, malaise, myalgia, chills, joint pain, and arthritis. A person can also get infected through bites or scratches from mice that carry the bacteria. The bacteria can enter the body directly through a bite wound, open skin, or mucous membranes such as in the eyes, nose, or mouth. Another route of exposure is consumption of food or water contaminated with the urine and droppings of rodents carrying the bacteria. RBF is not spread from person to person.
Salmonellosis
Salmonellosis is a bacterial infection caused by salmonella and is relatively rare in well managed rodent facilities. Clinical signs in the mouse include anorexia, decreased activity, rough hair coat, and occasional death loss. Animals can be convalescent carriers, active disease shedders, or act as fomites. In humans, clinical signs include abdominal pain, diarrhea, fever, and vomiting. Transmission of the bacteria is often through fecal contamination of hands and food.
Viral Diseases:
Hantavirus pulmonary syndrome
Hantavirus is not a problem at all in commercially bred laboratory mice in the United States, and all the mice in the psychology department are commercially bred laboratory mice. Still, the virus has been transmitted to humans from laboratory mice or mouse tissue in North America and South America. Typically, mice with this virus show a persistent subclinical infection. Clinical signs in humans vary with the strain of virus and can include fever and pulmonary syndrome. The transmission is by inhalation of aerosol or direct contact of infected urine, feces, or saliva. Bites are a minor mode of spread, but humans do not need direct animal contact to become infected.
Lymphocytic choriomeningitis (LCM)
LCM is a viral disease caused by the lymphocytic choriomeningitis virus. The most common clinical symptoms include infection without symptoms or mild febrile illnesses. The disease can be transmitted by exposure to fresh urine, saliva, or nesting materials from infected rodents. Also, it can be transmitted though broken skin, the nose, eyes or the mouth, and a bite from an infected rodent. Person to person transmission has not been reported yet except for transmission from the infected mother to the fetus.
Other Potential Sources of Disease:
Bite or scratch wounds
Other than rat bite fever, bites or scratches from mice can become infected with a variety of bacteria and perhaps a virus if the wound is not thoroughly cleaned. Deep puncture wounds may provide entry for tetanus organisms, and tetanus immunization is required to work with rats in Psychology.
Hymenolepsis nana
This tapeworm occurs in several rodent species, and in mice, it can be asymptomatic. In humans clinical signs include enteritis, anorexia, pruritis, and headache. Transmission is fecal-oral via ingestion of feces from infected animals.
Dermatophytosis (Ringworm)
Dermatophytosis is a superficial fungal infection involving the keratinized layers of the skin and its appendages. The most common form in rodents is Trichophyton mentagrophytes, characterized by skin lesions, broken hairs, erythema, or crusts. Lesions in humans are scaly red elevated skin areas, dry, with a red ring (erythema), and can affect any part of the body. Transmission is through physical contact.
Allergies
Hypersensitivity reactions in humans to mouse allergens in urine and dander are relatively common. Symptoms vary from hay fever-like conditions to asthma, skin wheals, and eczema. Allergic sensitivity usually develops within 2 years of working with the animals. Individuals with a previous history of allergies may develop more serious manifestations to animal allergens (e.g., asthma). Protection against the development of allergic reactions to animal allergens includes the use of masks or fitted respirators, gloves, and other protective clothing; and showering after the workday.