Wildlife to Human Disease Transmission

Diseases that wildlife may transmit to humans are called zoonotic diseases or zoonoses. Everyone needs to be aware of the dangers of wildlife diseases and how to safely avoid infection and reduce the risk of spreading diseases to other people or animals. Diseases, such as rabies, may be contracted from bodily secretions such as saliva.  Ticks that vector Lyme disease or Powassan virus could transfer infections from a dead mouse or woodchuck to you.   

Awareness of how humans are infected by diseases will help you take proper precautions to prevent exposure. Disease agents, such as bacteria and viruses, can enter your body through any of the following:

  • Injection –by an insect or animal bite,

  • Ingestion -biting fingernails, eating contaminated food.

  • Inhalation -breathing contaminated dust, airborne spores, or eggs.

  • Absorption -An organism enters through mucosal membranes around the eyes and mouth; and through minor cuts or scrapes on the skin.

Reduce risks before you start working:

  1. Get a tetanus shot, and keep your vaccinations current;
  2. Have emergency telephone numbers handy for contacting your local police, animal control, county department of health, state wildlife department, and your doctor;
  3. Consider attaching to a lanyard the Medical Alert Wallet Card for Wildlife Professionals.
  4. Vaccinate your pets.
  5. Purchase protective gear and know how to use it properly. If you must work in high‐risk areas, wear protective gloves. 

If you live in an area where rabies is endemic (regularly found) and you plan on working with mammals, obtain pre‐exposure vaccinations for rabies.

Reduce risks while you are working:

  1. Wash your hands thoroughly and often, especially before eating, drinking, smoking, or using a restroom.
  2. Keep your gear clean.
  3. Record all animal contact in a daily log.
  4. Be careful when handling a sick animal or one that is behaving oddly.
  5. If you have been bitten, scratched, or are sick, go to the doctor promptly and tell them about your activities. If you are bitten or scratched by a mammal, capture the animal  and have it tested for rabies.  Use care and PPE if handling rabies-vector species such as bats, raccoons, skunks, foxes, and coyotes. Always follow State Health Department guidelines for rabies vector species.
  6. Safely dispose of dead animals and contaminated materials.

Reduce risks when the job is complete:

  1. Clean any equipment you used (disinfect all used traps or replace them).
  2. Remove work clothing and wash separately,
  3. Before removing gloves, wash your hands in disinfectant and then in soap and water. Then, remove the gloves and thoroughly wash your hands with soap and water, and
  4. Remove work clothes and wash separately. Shower before greeting family or friends.

Because many zoonoses have symptoms that mimic the flu, regularly remind your doctor that you work with wildlife and in areas laden with fecal contamination. Knowing this will help your doctor consider other possible diseases when examining you.

Summary Chart of ZOONOTIC DISEASES. (List is NOT comprehensive)

How people catch diseases Precautions

Bites or scratches

  • Rabies (mammal bites or scratches)
  • West Nile virus (mosquito bites)
  • Lyme disease (tick bites)
  • Hantavirus (can be transmitted by rodent bites or contaminated dust)

Mammal bites or scratches

  • Get rabies pre-exposure vaccination and keep it current
  • Wear suitable gloves when handling animals
  • Use a restraining device (catch-pole)
  • Capture animals in traps
  • Avoid contact with animal’s mouth and saliva
  • Shower soon after work, every day

Mosquito or tick bites

  • Wear loose-fitting, light-colored clothing (harder to bite through and easier to see small ticks)
  • Use insect repellent (DEET or Permethrin)
  • Tuck pant legs into socks (keeps ticks from crawling into pant legs)
  • Check yourself for ticks frequently; remove any you find

Inhale disease organism

  • Histoplasmosis
  • Hantavirus
  • Wear an appropriate and properly fitted respirator, disposable clothing, goggles, gloves, and hood
  • Ventilate area if possible
  • Dampen contaminated materials, wipe with a wet sponge
  • Spray contaminated area or dead animals with disinfectant (10% bleach/water mix). CAUTION: spraying bleach on bird guano may release ammonia gas; instead, use soapy water to wet down droppings.
  • Schedule job for cool, damp weather

Handle infected animal or contaminated equipment

  • Mange (caused by mites)
  • Wear gloves
  • Minimize contact with a mangy animal by using restraining devices
  • Minimize contact with contaminated clothing and equipment
    • Dry clothing with high heat to kill mites

 

Rabies

Rabies is a disease that affects the nervous system of animals and humans. It’s caused by a virus present in the saliva and brain/spinal cord of infected animals. The virus is usually transmitted to other animals or humans either by the bite or scratches from a rabid animal or by contact with infected saliva. Only mammals are susceptible to rabies. The disease is primarily found in bats and furbearers in the U.S., especially skunks, raccoons, foxes, and coyotes. Rabbits, deer, and rodents rarely are diagnosed with the disease.

Hantavirus – Hantavirus pulmonary syndrome (HPS):

Rodents, such as deer mice, shed the virus in their urine, droppings, and saliva. The virus can become airborne, and people are infected by breathing the microscopic particles. It is possible, although less common, for someone to contract the disease from the bite of an infected rodent. If you touch an object contaminated with rodent urine, droppings, or saliva, and then touch an open wound or your eyes, you could become infected. It may be possible to catch hantavirus by eating food or drinking water that has been contaminated. Hantavirus is not transmitted between people.

The most common exposure route in humans is cleaning, working, or living in rodent-infested areas.  Although Hantavirus deaths are uncommon, the disease can be fatal. The most vulnerable people are in close contact with rodents and their nesting areas, such as rodent-infested homes, agricultural workers, WCOs, and people who clean seasonal-use buildings. WCOs have a higher risk of being infected with hantavirus than many other people because they frequently enter areas infested by mice and are more likely to disturb materials that contain the virus.

Treating HPS
There is no specific treatment, cure, or vaccine for hantavirus infection. However, we know that if infected individuals are recognized early and receive medical care in an intensive care unit, they may do better. In intensive care, patients are intubated and given oxygen therapy to help them through the period of severe respiratory distress.

Links: Symptoms, Diagnosis & Treatment 

Protection on the job includes proper protective equipment and ventilation.

Ventilate areas before entering, particularly if a building has been closed for a time, such as a seasonal cabin. Wear latex/nitrile or similar protective gloves and a proper respirator while handling traps containing rodents or cleaning up their droppings, urine, or nest materials. Avoid stirring up dust because it may contain hantavirus.

Dampen contaminated materials with a 10% bleach-water solution, or household disinfectant. (Spraying bleach on bird guano may release ammonia gas; instead, use soapy water to wet down droppings.) Let the materials soak to reduce dust, and wipe them with a damp towel or sponge. Mop or sponge the area with disinfectant. Double-bag soiled materials. Furthermore, you should also spray dead rodents with disinfectant and double-bag for disposal as municipal waste. Disinfect all gear and traps following standard procedures.

Residents should wash toys, silverware, and other items that may have contacted rodent waste.  Discard contaminated foods, drinks, napkins, paper plates, or cups. There are countless reasons to exclude mice from a home. Mice spread diseases, chew on wires, and sometimes make their nests in fans or vents, leading to fires. They may destroy insulation and cause heating and cooling bills to increase. After rodents are removed, you may need to make repairs to ensure that they cannot return.

The information on this webpage is based on the contents of the Wildlife Control Operator Core Training Manual published by the National Wildlife Control Training Program.