Rodents

Someone working in a facility with rodents could potentially be exposed to any zoonotic disease agent affecting wild rodents. In practice, however, these conditions are very rare. Modern laboratory animal facilities pay particular attention to vermin control, thereby reducing the likelihood of infection of laboratory mice by their wild counterparts. However, there is always the potential for outbreaks to occur.

The major health risk to individuals working with rodents is the development of an allergy. Conditioned, colony-born rodents are generally docile, but may occasionally inflict injury such as a bite or scratch. Staff assigned to rodent areas should be trained in handling techniques and protective clothing requirements prior to beginning hands-on work.

Recommended Preventative Measures

  • Training on proper rodent handling techniques is available through LACF.
  • Follow any posted personal protective equipment requirements.
  • Wash hands after handling animals or related equipment.
  • When seeking medical advice for any illness, inform your physician that you work with rodents.

Conventional rodent areas: To reduce the risk of exposure to allergens when rodents are transported to or used in laboratories, staff are advised to adhere to the following practices:

  • Dust masks should be worn at all times when working with rodents and whenever there is a risk of aerosol transmission of a zoonotic agent.
  • When recommended, approved respirator masks (e.g., Type N95 by 3M) should be worn instead of dust masks.
  • Perform procedures in a laminar flow hood whenever possible.
  • Minimize wearing protective clothing, such as lab coats, outside of animal areas.
  • Use disposable supplies whenever possible.
  • Sanitize lab work areas after animal work.

Response to Injury

For all injuries incurred when working with rodents:

  1. Wash any injured site with soap and water for at least 5 minutes.
  2. Control bleeding by applying direct pressure with a sterile gauze or bandage.
  3. Cover wound with clean bandage (do not apply an ointment or spray).
  4. Seek advice from the Research Occupational Health Program.

Infectious Diseases

Lymphocytic Choriomeningitis
LCM is an arenavirus commonly associated with hamsters, but it does infect mice. In 1965, during an outbreak in hamsters, 23 human cases were recorded. Now rare in laboratory animal facilities, LCM has been eliminated from most vendors through breeding and viral screening of their colonies.

  • Reservoir/source of infection to people: Wild mice worldwide are the reservoir of infection to laboratory and pet rodents. Mice and hamsters are the only animals known to develop latent infection; experimentally transplanted tumors are the other source of infection to mice.
  • Transmission: Contact with tissues including tumor, feces, urine, and aerosolization of all of the above.
  • Disease in people: Flu-like symptoms, mild to severe.

Leptospirosis
Leptospira spp. are bacteria found in many animals but are most commonly associated with livestock and dogs. Transmission from laboratory rodents to people has been reported.

  • Reservoir/source of infection to people: Rats, mice, voles, hedgehogs, gerbils, squirrels, rabbits, hamsters, reptiles, dogs, sheep, goats, horses, and standing water.
  • Transmission: 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.
  • Disease in people: Flu-like symptoms, mild to severe. Death has been reported.

Rat-Bite Fever
This is caused by the bite of a rat infected with Streptobacillus moniliformis or Spirillum minus.

  • Reservoir/source of infection to people: Rats are asymptomatic carriers. Bacteria are normal flora in oral pharynx of rats.
  • Transmission: Bite of infected rat.
  • Disease in people: Fever, lymphadenopathy, swelling at site of wound. Incubation period is usually 1–3 days but may be up to 6 weeks. May cause arthritis in untreated patients but is easily treated with penicillin.

Hantavirus Infection
Hantaviruses occur among wild rodent populations.

  • Reservoir/source of infection to people: Rats and mice have been implicated in outbreaks of the disease. Hantavirus infection from rats has occurred in laboratory animal facility workers. Rodents shed the virus in their respiratory secretions, saliva, urine, and feces.
  • Transmission: Via inhalation of infectious aerosols; brief exposures of even 5 minutes have resulted in human infection.
  • Disease in people: The form of the disease that has been documented after laboratory animal exposure is characterized by fever, headache, myalgia, and petechiae and other hemmorhagic symptoms, including anemia, gastrointestinal bleeding, etc.

There are several bacterial pathogens, including Salmonella spp. and Campylobacter spp., that are frequently associated with diarrhea in rodents and may also cause disease in people.

  • Reservoir/source of infection to people: Symptomatic or asymptomatic rodents.
  • Transmission: Fecal/oral.
  • Disease in people: Diarrhea, dysentery.

Allergies

All Rodent Areas

  • Conventional and barrier rodent environments have allergens present, such as dust from bedding and animal dander.
  • Specific allergy-producing exposures are associated with urine and saliva.