LA County Public Health - Environmental Health

Rodent-Borne Diseases: Risk Reduction Recommendations

Rodents in Los Angeles County can pose a risk to human health. Surveillance conducted by the Vector Management Program has shown that rodents can carry viruses and/or bacteria that cause disease in humans. These pathogens can be transmitted to people by various routes. Some are contracted by the bite of an infected rodent flea. Others can be transmitted by direct contact or inhalation of aerosols from infected rodents, their urine, feces, or nesting material. Examples of these pathogens include the causative bacteria of plague and murine (endemic) typhus, hantaviruses and arenaviruses. Additional surveillance has uncovered evidence of other organisms, which are currently under investigation, that have unknown human health implications.

To reduce the risk of exposure to these organisms, the Vector Management Program offers the following general recommendations:

PREVENTIVE MEASURES

Maintain your property in a sanitary manner, so as to reduce the potential for rodents on the premises.
Rodentproof all structures, using durable materials such as 1/4 inch mesh metal hardware cloth or sheet metal. Check foundation vents, conduit/wall junctures and door thresholds. Eliminate all gaps greater than 1/4 inch.
Reduce available food, water and harborage that can be used by rodents.
Do not leave pet food out at night, and remove fallen fruit promptly. Thin vegetation and either remove cast-off items or elevate 18 inches above the ground to reduce harborage.

These recommendations are aimed at making the premises less attractive to rodents, thus reducing the potential for rodents to invade or occupy the premises. This will reduce the likelihood that you would come into contact with rodents, or their feces, urine or ectoparasites.

RODENT CONTROL MEASURES

If an infestation does exist, take prompt and effective measures to eliminate the rodents. Since infestations can vary as to the species of rodent involved, the type, location and condition of the structure, and other factors, each situation should be evaluated separately. However, the following are some important points to consider when abating a rodent infestation.

Indoor: In most cases, snap traps are preferable within a structure. The use of poison bait may cause a rodent to die in an inaccessible area within the structure, causing odors and nuisance vectors, such as flies.
Outdoor: Properly applied approved baits can be effective in some situations, but adjacent structures should be properly rodentproofed before baiting. In a rural setting, the use of poison baits should be carefully considered, noting the potential impact on natural predators (i.e., hawks, owls, coyotes), and the limited long term efficiency of baiting large areas to reduce rodent numbers in such a setting.
Because rodent fleas will seek another host to feed on after the rodent dies, fleas should be controlled in an approved manner prior to baiting, especially if plague or murine typhus is a concern where you live. California ground squirrels, deer mice and Norway rats are examples of rodents that can transmit pathogens through their fleas.
Always read and follow the instructions on the label of all pesticide products you are using.
Keep baits, dead rodents and traps out of the reach of children and pets to prevent accidental poisoning, injury or illness.

SAFETY MEASURES

The following guidelines should always be used when cleaning rodent infested areas:

Avoid contact with live rodents.
Avoid disturbing contaminated material so as to prevent creating aerosols.
Always wear rubber gloves.
A dust mask or general purpose respirator may provide some protection against dusts and other airborne particles. However, they should not be relied upon to provide adequate protection against some airborne pathogens. (Respirators can be effective, but they must have appropriate filters and be properly fit-tested to the specific user in order to function correctly.)
Air out the structure prior to cleaning (open windows and doors).
Disinfect trapped rodents and contaminated materials/surfaces by thoroughly wetting them down.
Household or general purpose disinfectants may be used at maximum recommended concentration. Check the label on the container and follow any precautionary statements or warnings.
- NOTE: If you are using household bleach (sodium hypochlorite) as a disinfectant, care should be used with bleach-sensitive materials, such as carpet and upholstery. A strong detergent or a non-bleach based disinfectant may be viable substitutes.
Remove disinfected materials with a disinfectant dampened paper towel or cloth and dispose of in a plastic trash bag and seal.
Place disinfected materials (rodents, nests, towels) in a second plastic bag and secure. Dispose with other household wastes in a garbage can with a tight fitting lid.
Lastly, disinfect and rinse gloves prior to removing them, and then wash your hands with soap and water.

In case of a heavy rodent infestation, especially in a confined area with low ventilation, contact the Vector Management Program for additional information and recommendations.

ADDITIONAL RESOURCES
For more information about rodent-borne diseases in Los Angeles County, contact the Vector Management Program at (626) 430-5450.

Also, the Federal Centers of Disease Control and Prevention (CDC) has produced an excellent document that thoroughly covers rodentproofing, safety precautions and other information. The document can be found on the CDC website at http://www.cdc.gov/mmwr/preview/mmwrhtml/rr5109a1.htm.
Vector Management Program
Emergency Information & Advisory Bulletins

Environmental Health Programs