Care and Use of Rats and Mice

This document is part of a larger Occupational Health and Safety component (in development) for the PSU Institutional Animal Care and Use Program. This sheet is designed to inform individuals who work with animals about potential zoonotic diseases (disease of animals transmissible to humans), personal hygiene and other potential hazards associated with animal exposure. This information sheet is directed toward those involved in the care and use of laboratory rats, mice, and other rodents.

Potential Zoonotic Diseases

Colony-born rodents are generally docile, but may occasionally inflict injury such as a bite or scratch. Larger laboratory rodents such as rats and guinea pigs can inflict particularly painful bites. While rodents may carry organisms that may be potentially infectious to humans, the most common health risk to individuals working with rodents is the development of an allergy. If you have an immune-compromising medical condition or you are taking medications that impair your immune system (steroids, immunosuppressive drugs, or chemotherapy) you may be at higher risk for contracting a rodent-borne disease and should consult your physician. The following is a partial list of known and potential rat or mouse zoonoses.

Lymphocytic choriomeningitis

Lymphocytic choriomeningitis (LCM) is an arenavirus commonly associated with house mice. LCM is rare in laboratory animal facilities, more common in wild. Tranmission to humans is through contact with tissues including tumor, feces, urine, or aerosolization of any one of these. Disease in humans is generally flu-like symptoms that range from mild to severe. Pregnant women are at increased risk of spontaneous abortion, particularly in their first trimester.

Leptospirosis

A bacterium found in many animals, including laboratory rodents. Leptospires are shed in the urine of infected animals. Direct contact with urine or tissues via skin abrasions or contact with mucous membranes has been reported. Transmission can also occur through inhalation of infectious droplet aerosols and by ingestion, as well as with water contaminated by urine from infected animals contacting abraded skin. Disease in humans is flu-like symptoms generally mild to severe.

Rat Bite Fever

Rate Bit Fever is caused by the bite of a rat infected with Streptobacillus moniliformis or Spirillum minus. Rats may be asymptomatic carriers of these bacteria, which are considered normal flora in the pharynx of rats. Transmission is via the bite of an infected rat, or contact with urine or mucus secretions. Symptoms of disease in humans include fever, lymphadenopathy, swelling at the site of the wound, and may cause arthritis in untreated humans. Incubation period is generally 1-3 days but may be up to 6 weeks.

Hantavirus Infection

Hantaviruses occur among wild rodent and shrew populations in certain portions of the world. Rats and mice of numerous species have been implicated in outbreaks of the disease. Numerous Hantavirus infections from rats have occurred in laboratory animal facility workers. Rodents shed the virus in their respiratory secretions, saliva, urine, and feces. Transmission to humans is via inhalation of infectious aerosols. Disease manifestations in humans from the most common Hantavirus documented from laboratory animal exposure, Seoul Virus—hosted by Rattus noryegicus--is characterized by fever, headache, myalgia and petechiae and other hemmorhagic symptoms including anemia and gastrointestinal bleeding.

Other Pathogenic Diseases

There are several other diseases that have been documented as occupationally acquired. These include bacterial pathogens Salmonella spp. from guinea pigs and Shigella spp. from mice, rats, and guinea pigs; and fungal agents Microsporum and Trichophyton spp. from mice and guinea pigs. Good hand washing technique and appropriate use of gloves are critical in reducing the risk of infection. In addition, because the clinical manifestation from the infections described above are so similar to flu, annual flu vaccinations are recommended for laboratory animal workers, such that flu may be discounted as a potential cause.

Allergic Reactions to Rats/Mice

By far the greatest occupational risk to working with rodents is allergic reaction or developing allergies. Those workers that have other allergies are at particular risk. Animal or animal products such as dander, hair, scales, fur, and saliva, and body wastes, urine in particular contain powerful allergens that can cause both respiratory and skin disorders. Allergy is most often manifested by nasal symptoms, itchy eyes, and rashes. Symptoms usually evolve over a period of exposure 1-2 years. It is estimated that 30% of individuals working with rodents will develop allergies. Occupation-related asthma, a more serious disorder, might develop in about 10% of persons with allergic disease who work with laboratory animals. The National Institute for Occupational Safety and Health (NIOSH) has developed a set of recommendations for “Preventing Asthma in Animal Handlers”. We encourage reviewing this document. The link is http://www.cdc.gov/niosh/animalrt.html.

How to Protect Yourself

  • Wash your hands. The single most effective preventative measure that can be taken is thorough, regular hand washing. Wash hands and arms after handling rats and mice. Never smoke, drink or eat in the animal rooms or before washing your hands.
  • Wear gloves. When working with rats and mice, wear gloves appropriate for the task. The use of latex gloves can cause an allergic reaction over time. EHS recommends using nitrile or other suitable alternative glove material. Sometimes wearing thin silk or cotton gloves under protective gloves is practiced to add comfort and reduce the buildup of perspiration. Please be advised that this comfort layer can become contaminated and may need replacing or appropriate laundering. Leather gloves or leather gloves with cuffs and Kevlar lining are good choices when working with Rattus or similar or large animals that may bite (Cavia, Cricetomys, etc.)
  • Wear respiratory protection. Respiratory protection can be worn when working with rodents, especially if there is a risk of aerosol transmission of a zoonotic agent or reduction of allergy symptoms. Contact EHS (725-5268) for additional information on recommendations on respirator type, training, and general information on respiratory protection.
  • Wear other protective clothing. Lab coats should be available and worn when working with the rodents. Avoid wearing street clothes while working with animals. Since lab coats are considered personal protective equipment they should not be taken home to launder. PIs or Departments are responsible for laundering soiled lab coats. Note that all lab coats worn in an animal room should stay in the animal room rather than being worn to and from labs, class, etc.

Seek Medical Attention Promptly

If you are injured on the job, promptly report the accident to your supervisor even if it seems relatively minor. If you are experiencing symptoms that you think may be related to animal handling, talk to your faculty supervisor for advice and additional guidance. Minor cuts and abrasions should be immediately cleaned with antibacterial soap and then protected from exposure to rats and mice. For more serious injuries or if there is any question, seek medical attention. As soon as practical complete the following forms: 1) SAIF 801 form, and 2) PSU Injury Report form. These forms are found on the Human Resources forms page under the heading “Workers’ Compensation” at the following link: http://www.pdx.edu/hr/policies_contracts_forms. If medical treatment is sought, the cost is covered by Workers’ Compensation Insurance managed by the PSU insurance carrier SAIF.

Tell your physician you work with laboratory animals.

Whenever you are ill, even if you are not certain that the illness is work-related, always mention to your physician that you work with laboratory animals. Many zoonotic diseases have flu-like symptoms and would not normally be suspected. Your physician needs this information for a more informed diagnosis.

Please direct any occupational health and safety questions to PSU Environmental Health and Safety 725-4312.