Common Infectious Diseases from Wildlife Pests

Wild animals can have diseases without looking sick, so you should only watch them from a distance. Always remember that close contact with these animals or their droppings or urine can spread whatever disease they are carrying to pets and humans.

Protect yourself by washing your hands with soap and running water after playing or working outside, particularly in places with sightings of wildlife. Don’t hand-feed wildlife. Don’t come near or touch orphaned animals. Parents are often near and will come back for their young, so better leave wildlife animals alone.

These are the most common infectious diseases from wildlife pests. 


Brucellosis affects goats, cows, sheep and other livestock as well as wild ruminants like bison, deer, and elk. This bacterial infection causes stillbirth or abortion in infected animals. The animal can shed the bacteria in vaginal fluids after abortion or birthing and in milk.

The disease can spread to humans through the consumption of unpasteurized milk and dairy products from the infected animal or direct contact with the animal’s birthing fluids or placenta.


Anthrax usually occurs in domestic and wild herbivore mammals. It’s caused by spore-forming bacteria. Those who breathe in anthrax spores from an infected animal product like hide, hair, wool or leather or handle products from an infected animal may develop the disease.

B Virus

B virus is usually found in cynomolgus, stump-tailed, pig-tailed, rhesus, and Japanese macaques. Adult macaques should be considered as carriers of the virus. The B virus is found in their saliva and can be spread to people through scratches and bites. It can cause fatal encephalitis and acute neurological disease.

Animal Bite

An animal bite can lead to serious injuries and expose the victim to zoonotic diseases like rabies. Around 4.5 million people in the US are bitten by a dog every year.

Contact the local health department or health care provider when an animal bite happens. They can help ensure that the right proper rabies prevention measures are observed after a bite.


Plague is caused by Yersinia pestis. Carriers of the bacteria include wild rodents as well as their fleas. It can be transmitted through a break or cut in the skin while handling an infected animal. The bacteria can also be transmitted via respiratory droplets from infected animals or people. 


The symptoms of the cryptococcal disease include unintended weight loss, sharp chest pain, confusion, and fever headache, shortness of breath, long-lasting cough, and night sweats. It’s caused by inhaling the Cryptococcus fungus.

There are various kinds of Cryptococcus like C. neoformans and C. gattii. C. neoformans mainly affects those with poor immune systems. It can affect pets like cats and dogs. C. neoformans can be found in the droppings of birds. C. gattii can be found in the soil and on trees.

Tick-borne Relapsing Fever

This disease is caused by Borrelia hermsii. It is picked up by ticks when they feed on rodents. People who are bitten by an infected tick can develop the disease. The symptoms of tick-borne relapsing fever include relapsing periods of fever that last for two to seven days.

It disappears for about four to fourteen days and then relapses. Most people pick up the disease while residing in old cabins in mountainous areas during the summer. Keep rodents out of sleeping areas and cabins to reduce the risk of being infected. 


Blue-green algae or cyanobacteria are found in bodies of water such as ponds, lakes, and rivers. Sometimes, it produces toxins and those who come in contact with can develop skin irritation.

An animal or person who swallows cyanobacteria can experience fever, vomiting, headache, diarrhea, stomach cramps, sore throat, joint and muscle pain as well as liver and nerve damage. Avoid contact or swimming in bodies of water with algal blooms. Pets should not be allowed to swim or drink in water that has algal blooms.

Dead Animal Disposal

Bacteria that may usually be contained in the body of an animal can be released as it decomposes. This exposes people to possible disease-causing pathogens. You have to get rid of the bodies of domestic pets and animals properly.

Place the body of small animals in plastic before putting them in the garbage can for proper disposal. Get in touch with local animal control in your area if the owner of dead animals cannot be located or not known. Contact the county, local health department or city for advice about the disposal of wild animals.

E. coli

E. coli or Escherichia coli live in the guts of people and animals. The bacteria can be shed through feces. Most E. coli strains are harmless. Some strains like the E. coli O157:H7 cause serious diseases in people.

Infection can occur via direct contact with infected animals or items that an infected animal has contaminated. It can also happen when people consume contaminated food. People who are infected with E. coli O157:H7 or E. coli that produces Shiga-toxin can experience diarrhea.

A severe complication known as the hemolytic uremic syndrome may occur in some cases. The elderly and young children have increased risk for this disease.

Fish Tank Granuloma

Mycobacterium marinum, the bacteria found in an aquatic environment, causes fish tank granuloma. It often occurs in food fish or aquarium fish raised under jam-packed conditions. The disease can spread through direct contact with water sources that are contaminated.

Mycobacterium marinum enters through breaks or cuts in the skin. An infected person may experience skin lesions on the hands or fingers. Skin lesions may persist for or heal in months.

People who have poor immune systems may experience bone and joint infections. Avoid contact with contaminated water by wearing gloves when you clean aquariums. Wash your hands properly afterwards to avoid infection.


Psittacosis or parrot fever can occur through direct contact with an infected bird. It’s caused by the bacteria Chlamydophila psittaci. Breathing in contaminated dust from bird droppings and feathers can affect humans.

Bites can spread the disease as well. Common carriers of Chlamydophila psittaci include psittacine birds like parakeets, cockatiels, and parrots. Other bird species can be infected as well. Some birds that are infected don’t show any signs of disease.

However, they can shed Chlamydophila psittaci when they are stressed from nutritional deficiencies, migrating, overcrowding, or illness.


Giardia is a small parasite that can infect the guts of animals and people. Infection can occur via ingestion of contaminated water or food or contact with an infected animal or person. An infected person may not show any signs of disease.

They may also experience mild or severe symptoms such as gas, headache, fever, stomach cramps, nausea, and vomiting. Infected beavers may contaminate stream water or lakes. Giardia parasites can be found in ruminants such as cows and goats, wild animals, dogs and cats.


This is a severe respiratory disease that is caused by breathing in dust which has been contaminated with the urine, saliva, or droppings of infected deer mice. Hantavirus pulmonary syndrome starts with flu-like symptoms.

As the disease worsens, the affected individual may experience shortness of breath. However, this happens when the lungs are filled with fluid. Almost 1/3rd of all cases of hantavirus pulmonary syndrome are deadly. Don’t stir up rodent urine, droppings, or nests into the air. Prevent infectious diseases from spreading by following proper rodent control measures and cleaning up.


It’s caused by Histoplasma capsulatum, a fungus found in bird or bat droppings and soil. When droppings and soil are stirred up, the fungal spores are spread in the air. Breathing in the spores can cause infection. The disease mostly affects the lungs.

Importation of Animals

Importing animals increases the risk of spreading diseases. African rodents that were infected with monkeypox were brought into the United States in 2003. Several people became ill after coming in contact with contaminated pet prairie dogs.

Soldiers overseas have imported and adopted dogs that later were discovered to have rabies. Local, federal, and state laws about animal importation help control this problem.


Leptospirosis infects animals and humans. It’s a bacterial disease that is more common in tropical and temperate areas. Some people who are infected become severely sick. Other people don’t show any symptoms.

Some domestic and wild animals like rodents, pigs, cattle, dogs and raccoons are carriers of the bacteria and spread it through their urine. People can develop the disease through exposure to contaminated water, soil or food or direct contact with tissues or urine from an infected animal.


Listeriosis is usually transmitted through drinking or consumption of food contaminated with Listeria monocytogenes. It’s a serious disease that is particularly dangerous to people with poor immune systems, pregnant women, the elderly, and newborns.

Dairy products such as unpasteurized cheese, cold cuts, and hot dogs are most likely to spread listeriosis. Infection in goats and cattle can cause abortion. When this happens, the placental remains are contaminated with the bacteria. People may develop the disease through contact with the placental remains.

Lyme Disease

This is a bacterial disease that is transmitted through the bite of an infected tick. It’s caused by the bacteria Borrelia burgdorferi. Ticks that feed on infected rodents become infected.

Lyme disease is the most common disease caused by ticks in the US, but it’s quite rare in Washington. The most obvious symptom of this disease is an expanding bull’s eye or a target-shaped rash that begins at the bite site.

Joint pain, headache, fever, and muscle aches may occur as well. If not treated immediately, the affected person may experience nervous system disorders, recurring joint pain, and heart disease. Horses, dogs and other animals can develop Lyme disease as well.

Lymphocytic Choriomeningitis

The common house mouse is the most common carrier of the lymphocytic choriomeningitis virus. A pet rodent can become infected after it comes in contact with a wild house mouse infesting homes or pet stores.

People can also become infected after exposure to rodent saliva, nesting material, urine, or droppings. Those who have lymphocytic choriomeningitis may experience flu-like symptoms. The disease may also cause meningitis or swelling of the lining of the spinal cord and the brain.


MRSA or Methicillin-resistant Staphylococcus Aureus can cause skin infections. This kind of bacteria is resistant to some antibiotics. MRSA can be transmitted by animals and people through direct contact. Carriers of the bacteria may not show any symptoms. 

Animal Exhibits and Petting Zoos

Some venues allow or encourage people to be in contact with or pet animals. Such settings include state or county fairs, pet stores, petting zoos, zoologic institutions, carnivals, animal swap meets, livestock-birthing exhibits, circuses, wildlife photo opportunities, educational farms, child-care facilities and educational school exhibits.

Human-animal contact may have a lot of benefits, but injuries and infectious disease outbreaks have been linked to these settings. Wash your hands after coming in contact with animals in a public setting.

Q Fever

This disease mostly affects goats, cattle and sheep, but other pets and livestock can become hosts of the bacteria Coxiella burnetii. Q fever may cause abortion in goats and sheep. Most animals, however, don’t show any symptoms.

Coxiella burnetii be shed in the feces, urine and birth products of infected animals. Breathing in or direct contact with barnyard dust infected with urine, birth fluids, dried placental material or feces from infected animals can spread the disease.

The disease in humans ranges from no signs to chronic or severe illness. People may also develop the disease by ingesting an unpasteurized dairy product made from an infected animal.

Raccoon Roundworm

Animals and people can become infected when they accidentally consume Baylisascaris eggs from objects, soil, or water that have infected with raccoon feces. Baylisascaris is a roundworm found in the intestines of raccoons.

The eggs hatch into larvae and travel throughout the animal’s body, affecting its muscles and organs. Developmentally disabled individuals and children are vulnerable to infection when they stay outdoors as they’re more likely to put contaminated objects, fingers, or soil into their mouths.

Those who spend time in habitats of raccoons or work with these animals have a higher risk as well.

Rat Bite Fever

This is a bacterial disease that’s transmitted to people through scratches or bites from rats. Other animals like cats, dogs, mice, squirrels and gerbils can get infected as well. Although they may not get sick, they can spread the disease.

Symptoms of rat-bite fever include joint and back pain, abrupt fever, muscle, vomiting, and headache. The disease is rare in the US. Those who own pet rats may be at risk for rat-bite fever.

Those who live in a house infested with wild rats or handle these rodents as part of their job have a higher risk of developing this disease. 


Ringworm or dermatophytosis grows on the skin of the infected animal or person. A lot of animals can get this fungus, including cattle, dogs, rabbits, cats, birds, goats, sheep, pigs, goats, and rodents. People can develop diseased through direct contact with infected persons or animals.

Ringworm that grows on the head of a person appears as a bald patch of crusty skin. It can cause an itchy red rash that is ring-shaped on other parts of the body. Ringworm spores can survive on other surfaces such as carpets and furniture for a long time and cause an infection.


Roundworm or toxocariasis is caused by parasites that are usually found in the guts of cats and dogs. Infected cat and dog feces contain roundworm eggs that can survive for a period of time. The disease can spread via ingestion of roundworm eggs or direct contact with feces that is contaminated with roundworm.

Children have a higher risk of infection as they play in spots where the soil may be contaminated with the feces of infected cats and dogs. Most people who have roundworm infections don’t show any symptoms at all.

Wild animals may carry diseases without looking sick at all. Stay away from them to avoid wildlife disease. Watching them from a distance is the safest way to enjoy their company.