Guide to Diseases Spread by Animals
33 min read| Updated for March, 2019
Whether it’s a domestic pet or a wild animal, it is overwhelmingly clear that animals have a powerful and positive impact on human health and wellbeing. Regardless of the role animals play in your life, it’s important to be mindful of the fact that there are always some risk factors involved when you come into contact with them, including disease. Infectious diseases that are spread between animals and people are known as zoonotic diseases, and according to the Centers for Disease Control (CDC), tens of thousands of Americans are affected every year. They are so common, scientists estimate that more than six out of ten known infectious diseases in humans come from animals.
There is an abundance of diseases that you and your pets can contract from animals that you may encounter and many that you can get from your pets themselves. With a better understanding of how these diseases are transmitted and the threat that they present if contracted, you can be proactive about your health. Here is a guide to the most common and most dangerous diseases that you should be aware of.
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There is an abundance of diseases that you and your pets can contract from animals that you may encounter and many that you can get from your pets themselves.
Diseases Spread by Pets
The animals you come into contact with most often are the ones that live in your home and yard. You love your pets, so you do your best to keep them healthy. However, evaluating the wellbeing of the animals within your home doesn’t merely come at their benefit – it can also keep you and your family safe.
Here is a comprehensive list of diseases that are commonly transmitted by the animals that live closest to us, along with treatment and prevention methods.
Salmonella can be contracted directly from pets such as dogs, cats, birds, turtles, and fish.
Salmonellosis is contracted after exposure to the salmonella group of bacteria. They are found everywhere in the environment and can be transmitted in numerous ways, most often causing food poisoning in humans. According to the Illinois Department of Public Health, salmonella bacteria lead to an estimated 1,400,000 cases of food poisoning in the U.S. each year. Other health hazards include blood poisoning and even death. Due to the dangerous nature of this disease, medical attention is typically required.
You get salmonella by eating foods that are contaminated by animal feces. The most common foods that are contaminated with salmonella include animal products such as beef, poultry, milk, and eggs. However, any food is susceptible to contamination including fruits and vegetables.
Salmonella can be contracted directly from pets such as dogs, cats, birds, turtles, and fish. It can be spread from person to person when an infected person’s feces contaminate food through unwashed hands.
While healthy adults will often overcome the illness without experiencing severe symptoms, salmonella can contribute to vomiting, diarrhea, cramps, fever, chills, headache, and bloody stool. In severe cases, patients may experience long-term effects from the disease, such as post-infectious irritable bowel syndrome and reactive arthritis.
Fluids are essential in treating salmonellosis as diarrhea and vomiting may lead to dehydration. Pain relievers and fever reducers can help you feel more comfortable. Antibiotics are seldom used to treat the disease as they can prolong the amount of time that you are infectious to others.
It is far more common to contract salmonella at home than in a restaurant, so using proper cooking and food safety standards is the best prevention method. Rodent-proofing your home and proper sanitation are also important in decreasing your risk of exposure. Contaminated food may look, taste, and smell normal, so it is essential to cook meat and poultry thoroughly to the suggested internal temperature to kill off any existing bacteria. Avoid cross-contamination by using different utensils, cutting boards, and countertops once you have cooked the food. Once food cools to room temperature or sits too long, it is at risk, and you should reheat before eating.
Keeping your refrigerator settings below 40 degrees will prevent contamination as well. Thoroughly wash fruits, vegetables, and even raw poultry before cooking or eating and avoid consuming raw milk, eggs, and hamburger meat. The bacteria can live in the cracks and cut marks of a wooden cutting board, so it is safer to use acrylic boards that the dishwasher can sanitize. It is also wise to have a variety of cutting boards that serve different purposes to avoid using one board for meat in addition to fruits and vegetables.
Most importantly, thoroughly wash hands with warm, soapy water after a visit to the restroom and before handling food.
Since most pets don’t have visible signs of infection, most people don’t suspect their pets as the source of exposure.
Campylobacter infection, or campylobacteriosis, is a disease that is caused by the Campylobacter bacteria. It infects the human intestines and is closely associated with food poisoning, as it often originates in contaminated meat or eggs. Infants and children are at the highest risk of infection and men are at greater risk than women. The CDC estimates that 1.3 million people are infected every year.
You can contract the bacteria by eating undercooked poultry or other food that has been contaminated through contact with raw poultry. It can get into your system by reusing a cutting board that had raw chicken on it without thoroughly washing it. You can also contract the bacteria through contact with cat or dog feces. Since most pets don’t have visible signs of infection, most people don’t suspect their pets as the source of exposure. Campylobacter infection is most common in the developing world, and one in every five cases is linked to international travel.
Humans who have been affected by Campylobacter often experience abdominal pain, fever, cramping, and diarrhea. Though not serious in most adults, those with a compromised immune system, such as seniors, may have life-threatening complications as a result of the illness.
Most people recover without receiving any treatment for the infection. Drink plenty of fluids to stay hydrated and expect to recover within a week. If symptoms become severe or if you have an already weakened immune system from AIDS or cancer treatment, then you should seek medical attention.
Cook meat, especially poultry, thoroughly and to a safe minimum internal temperature. Keep raw chicken and poultry separate from other foods and avoid consuming raw milk.
Rabies is nearly always fatal once symptoms have started, which can be anywhere from a few days to months after exposure has occurred.
Rabies is likely the first disease people think of when they consider infections transmitted by animals. It is a neurologic disease that is caused by a virus and is almost always fatal if not treated immediately. However, Rabies in humans is rare. According to the CDC, only 1 to 3 cases are reported annually in the U.S. Due to the prevalence of vaccinations, reported cases of rabid cats and dogs are also uncommon in the U.S. Because of the serious nature of the disease, and it’s important to know what to look for.
Rabies is transmitted through the saliva of an infected animal, usually during a bite. It is also possible to be infected accidentally if an open cut or wound is exposed to the saliva or tissue of an infected animal. Rabies most commonly spreads to humans from dogs. The Internet Center for Wildlife Damage Management (ICWDM) states that 75% of Americans who suffer from rabies contract the disease while abroad.
Rabies is nearly always fatal once symptoms have started, which can be anywhere from a few days to months after exposure has occurred. The virus proliferates at the site of the bite and spreads slowly through the nervous system to the brain. Initial symptoms may include weakness, headache, and fever which progress to confusion, behavioral change, and delirium.
If an animal bites you that you suspect may be infected, wash the wound with warm soapy water, apply an antiseptic, and seek medical care immediately. The World Health Organization (WHO) states that receiving effective treatment soon after exposure can prevent the onset of symptoms and save your life.
You can prevent rabies through vaccination. It is also important to avoid contact with any animal, wild or domestic, that is behaving aggressively or acting unusual in any way.
The parasite can also infect through contact with surfaces, like changing tables and bathroom counters, that are contaminated.
Giardiasis is a diarrheal disease caused by a microscopic parasite called giardia, which is found everywhere in the U.S. It is often thought of as a camping or backpacking disease because it is usually contracted through the consumption of contaminated water from lakes and streams. The most significant risk associated with giardiasis is dehydration, making it more dangerous for infants, seniors, or women who are pregnant.
In giardia infected animal and people, the parasite lives in the intestines and transmits through the feces. Dogs and cats can become infected with the parasite after drinking contaminated water and may then pass the parasite on to you. The parasite can also infect through contact with surfaces, like changing tables and bathroom counters, that are contaminated. You can ingest the parasite through consumption of ice or water that comes from a contaminated source or by swallowing water from ponds, streams, lakes, or rivers that contain the parasite. It can also be passed through person-to-person contact and by eating undercooked food that contains the parasite. It is often contracted overseas in countries where it is common due to poorly treated water.
Common symptoms include diarrhea, nausea, upset stomach, and flatulence. Dehydration can result from diarrhea. Some giardiasis infected people have no symptoms at all.
Giardiasis can be treated with prescription medications when symptoms persist. You should consult a medical provider if you have symptoms and feel exposure has been possible. Dehydration, which can be especially dangerous for infants and pregnant women, should be treated with plenty of fluids.
Avoid water and food that may be contaminated. Practice good hygiene, especially making sure to wash hands thoroughly after being in contact with bathroom surfaces. Try to avoid contact with contaminated feces during sex.
Both dogs and cats can be carriers of ringworm, but cats are the more common transmitters of the fungus to humans.
Contrary to its name, a worm does not cause ringworm, but rather a fungus. The fungus tends to grow in warm, moist areas of the body like the scalp, feet, and groin and causes a skin condition commonly known as tinea. Ringworm is a common condition and does not typically pose a high level of threat to humans or pets.
While not always the case, humans can contract ringworm through contact with infected animals. Both dogs and cats can be carriers of ringworm, but cats are the more common transmitters of the fungus to humans. Kittens are more likely to be affected by ringworm than adult cats. The fungus spreads through direct contact.
Much like it does in cats and dogs, ringworm causes itchy, scaly patches on the skin. Though it can affect many parts of the human body, ringworm of the scalp can cause hair to fall out.
Ringworm is easily treatable with topical ointments applied directly to the area. In cases where the rash is not responding to topical treatments, you can take oral antifungal medication.
Seek treatment for infected pets and avoid direct contact with them. Keep your own body cool and dry, especially in susceptible areas to discourage the growth of the fungus. If a pet has ringworm, it is essential to disinfect the home to ensure that no spores are still present.
You can also contract it by ingesting contaminated food and water – lamb, pork, and venison are common hosts for the parasite.
An infection from Toxoplasma gondii parasite causes this disease, which is incredibly common and is found throughout the world. The CDC estimates that 40 million infected people in the U.S. with the parasite, which can live undetected in your body for years. Few people experience symptoms because those with a healthy immune system can prevent illness caused by the parasite. However, it can be very threatening to pregnant women and those with a weakened immune system, including those taking chemotherapy or those who are on immunosuppressant drugs.
The parasite can be introduced into your system if you come into contact with cat feces that are infected. You can also contract it by ingesting contaminated food and water – lamb, pork, and venison are common hosts for the parasite. Eating unwashed fruits and vegetables can lead to exposure. In rare instances, it can transfer through a blood transfusion.
If you have a healthy immune system, it is likely that you may never experience symptoms. Some may experience flu-like symptoms that last for over a month. In more severe cases, damage can occur in the brain, eyes, and other organs. Toxoplasmosis may affect the eyes and lead to infections, blurred vision, and even blindness. Infants and those with weakened immune systems are at greatest risk and may experience serious symptoms like seizures and encephalitis, which can be fatal.
For most, treatment for toxoplasmosis is not necessary. For those who are at higher risk due to a compromised immune system, medications are available to treat the disease.
Wear gloves when working in the garden or handling soil that could be contaminated. Wash fruits and vegetables thoroughly before eating and avoid consuming undercooked and raw meat. Cover children’s sandboxes to prevent contamination from cat feces.
If you are pregnant and love cats, additional precautions need to be taken to prevent infection. Keep your cat indoors and never feed it raw meat. Avoid stray cats and let someone else clean your litter box if possible. If you are going to clean it, wear protective gloves and a mask when doing so.
Within two weeks you may start to experience more flu-like symptoms that include a low-grade fever, headache, fatigue, and loss of appetite.
Cat-scratch disease (CSD) affects about 40% of cats in their lifetimes, according to the CDC. The disease is a bacterial infection caused by a bacterium called Bartonella henselae. It is found more commonly in kittens than it is in older cats and humans can catch it. Though it does not typically pose a serious threat, it can lead to serious issues if untreated, especially for small children or those with weakened immune systems.
Cats become infected through flea bites or when flea droppings come into contact with open wounds. Cats may also be exposed to the bacteria when fighting with other infected cats. The bacteria are spread to humans when an infected cat licks an open wound or bites you hard enough to break the skin.
Symptoms usually occur several days after exposure to the bacteria and begin with a red bump or blister at the site of the bite. Within two weeks you may start to experience more flu-like symptoms that include a low-grade fever, headache, fatigue, and loss of appetite. You may also experience swollen lymph nodes near the infection site. For people at higher risk, especially small children, the disease may affect your eyes, bones, heart, joints, and other organs.
If you are healthy, CSD typically clears up on its own without treatment. Over-the-counter anti-inflammatory medications can be taken to reduce swelling and pain. Hot compresses can also be used to relieve swollen glands. In some cases, a doctor may drain the fluid in a swollen gland to alleviate pain and pressure. If symptoms have not diminished after two months, you can take antibiotics.
Exercise caution when you encounter a stray cat, as they are more likely to be infected. Avoid playing with your cat in ways that encourage them to scratch or bite – most cats don’t show symptoms of CSD if infected so always use caution. Take care of your cat, providing routine veterinary care and flea prevention. If you have a weakened immune system, adopt older cats as they are less likely to be infected.
Diseases Spread by Wild Animals
The most common form of transmission occurs when you breathe in air that has been contaminated with mouse droppings.
This virus can be found in the urine, saliva, and feces of infected rodents, specifically the deer mouse. It is most common in rural areas of the western U.S. and is especially prevalent in warmer months. People at greatest risk are those who live or spend time in areas where there are a lot of rodents. Having a job that includes cleaning, pest control, and construction can put you at higher risk as well. In humans, the virus can lead to a more severe condition called hantavirus pulmonary syndrome (HPS), which is a lung infection.
The most common form of transmission occurs when you breathe in air that has been contaminated with mouse droppings. When droppings dry out, they are inhaled easily when kicked up into clouds of dust. The North American strain of hantavirus is not contagious and cannot be spread to others.
In its early stages, hantavirus is characterized by flu-like symptoms such as fever, headache, chills, vomiting, and diarrhea. The virus progresses quickly, and within a week, symptoms worsen and include a wet cough, fluid in the lungs, difficulty breathing, low blood pressure, and decreased heart function. It can rapidly become life-threatening. According to the Mayo Clinic, the mortality rate for the North American variety of HPS can be more than 30%.
There is no treatment or cure for HPS. However, if you experience flu-like symptoms after exposure to rodents, you should see a physician immediately. Getting care at a hospital during the early stages of the virus will help immensely, especially receiving oxygen to help you through pulmonary distress caused by the illness.
The best prevention is to reduce exposure to rodents by keeping them out of your home and workplace. Block all access points, set traps, and practice proper food storage habits in order to keep them away.
Humans become infected when enough of the virus gets into their eyes, nose, or mouth through direct contact or inhalation.
Humans can be infected with avian influenza, also known as “bird flu,” although transmission is rare. Many strains of the virus can spread to humans from birds, and the severity and risk depend on which variety you contract. But in almost all cases, the virus manifests in the form of respiratory symptoms. According to the American Veterinary Medical Foundation (AVMF), the risk of a cat contracting the virus in the U.S. is very low, limits to very few strains and the threat posed to humans from infected cats is also very low. While research is limited, existing studies indicate that dogs are not typically susceptible to the virus.
You can find the virus in the saliva, mucus, and feces of infected birds. Humans become infected when enough of the virus gets into their eyes, nose, or mouth through direct contact or inhalation.
Ranging from mild to severe, symptoms can include conjunctivitis (pink eye) and flu-like symptoms such as fever, cough, sore throat, and achy muscles. Additionally, some people may experience nausea, diarrhea, vomiting, and respiratory problems.
Most strains of avian influenza are susceptible to antiviral medications used to treat the disease.
The best form of prevention is to avoid contact with potential sources of exposure. Aquatic birds are the most widespread carriers of the disease; however, most humans contract it through direct contact with infected poultry.
While not common, tularemia is highly contagious and possibly fatal.
Tularemia, also referred to as rabbit fever, is a bacterial disease that infects both animals and humans. While rodents and rabbits are the most susceptible and die in large numbers after exposure, it can also infect domestic pets like cats, dogs, and hamsters. While not common, tularemia is highly contagious and possibly fatal. Anyone can develop tularemia, but you are at higher risk of exposure in the U.S. in south-central states, the Pacific Northwest, and parts of Massachusetts. You are also at higher risk if you engage in work or hobbies such as hunting, gardening, wildlife management, or veterinary medicine.
Unlike most zoonotic diseases, tularemia transfers in a variety of ways including deer tick and deer fly bites, skin contact with infected animals, drinking contaminated water, inhaling contaminated dust while landscaping, and laboratory exposure.
There are many strains of tularemia, and each one presents its own set of symptoms. If you know you have been bitten by a tick or have developed a fever, skin ulcers, or swollen glands after handling animals in areas where you can find the disease, seek medical attention as soon as possible.
Antibiotics are used to treat tularemia, and while symptoms may last for weeks, most people will make a full recovery.
There is no vaccine to protect against tularemia. If you live in an area where the bacteria are present or work in an occupation that puts you at higher risk, you need to take precautions to protect yourself. Wear protective clothing and insect repellent when outdoors to prevent tick bites, which is how most people in the U.S. contract the disease. Wear a face mask when gardening and mowing to avoid inhaling contaminated dust. If you hunt, wear gloves and goggles when handling dead animals and wash hands thoroughly. Prevent tick bites in your pets by providing flea and tick protection and keeping them away from dead animals.
You can contract the disease through contact with the infected animal’s urine and bodily fluids or if you come in contact with contaminated soil, water, or food.
Leptospirosis is a bacterial illness that affects humans and animals. It is most common in temperate and tropical climates and can be a hazard for people with outdoor jobs or who handle animals frequently. In more recent years, it is becoming more common among children in urban areas as well. A large variety of wild and domestic animals carry the bacteria.
The bacteria spread through the urine of infected animals. You can contract the disease through contact with the infected animal’s urine and bodily fluids or if you come in contact with contaminated soil, water, or food. While household pets can become infected with this disease, you are not at high risk of contracting it through daily activities. However, you should avoid contact with your pet’s urine and blood while infected.
In humans, leptospirosis may cause a wide range of symptoms or no symptoms at all. Most common symptoms include fever, headache, chills, nausea, vomiting, diarrhea, jaundice, red eyes, and rash. The illness may occur in two phases. If a second phase occurs after the initial recovery, the symptoms are more severe and may include kidney and liver failure or meningitis.
To treat Leptospirosis in pets and humans with antibiotics, you should take them as soon as symptoms appear for best outcomes. Pets may require other treatment methods like dialysis and hydration therapy.
Reduce your risk by avoiding contact with water that may be contaminated with animal urine and wear protective clothing if your job may put you in contact with contaminated dust and soil. To prevent the infection in your pets, keep rodents out of your home and have your pets vaccinated.
It is extremely dangerous for a fetus or newborn baby, causing extreme illness.
Listeriosis is a severe bacterial infection that is caused by the bacteria Listeria monocytogenes. Pregnant women, elderly adults, and those with a compromised immune system are at highest risk. Most healthy people will not become ill after exposure. It is extremely dangerous for a fetus or newborn baby, causing extreme illness. According to the CDC, about 1,600 people in the U.S. contract listeriosis every year and about 260 people die as a result.
Listeriosis is caused by eating food that is contaminated with listeria. The bacteria is found in soil, water, cattle, and poultry. It is often found in raw milk and soft cheeses as well as processed meats like hot dogs and deli meats.
Pregnant women may experience flu-like symptoms like muscle aches and fatigue. The infection is far more harmful to the fetus and may result in miscarriage, stillbirth, and premature delivery. In others, symptoms can include a headache, confusion, fever, muscle aches, loss of balance, and convulsions.
Listeriosis is treatable with antibiotics.
If you fall into one of the three categories of people at the highest risk, prevent exposure by avoiding foods that are most commonly contaminated with the bacteria. In addition to the ones listed above, celery, bean sprouts, cantaloupe, and ice cream have been known to contain the bacteria.
Pets, particularly dogs, are susceptible to the disease though it cannot be passed between animals or between animals and people.
Valley Fever (Coccidioidomycosis)
Valley Fever is an infection caused by the fungus Coccidioides. It is most often found in the soil in the Southwest U.S. (Arizona, California, Nevada, New Mexico, Texas, or Utah) though recently it has also been found in south-central Washington. Anyone can get valley fever, though the following groups are at higher risk: adults 60 years and older, people with HIV/AIDS, pregnant women, people with diabetes, and people who are Black or Filipino. The disease typically resolves on its own without medical attention unless a more severe form is contracted.
You can contract the disease by breathing in airborne fungal spores from soil that has been disturbed. Pets, particularly dogs, are susceptible to the disease though it cannot be passed between animals or between animals and people.
Most people who are exposed to the fungus through aspiration do not become sick, but some do. Symptoms include shortness of breath, fatigue, cough, fever, night sweats, headache, muscle aches, and an upper body rash. Generally, dogs that become infected experience coughing, fatigue, and weight loss.
The illness resolves on its own most of the time, but should be addressed with your doctor if symptoms persist for more than a week. Treat more severe cases with antifungal medications. If you think your pet may have contracted valley fever, consult a veterinarian. There is no vaccine for valley fever.
It is difficult to avoid breathing in the fungus if you live in an area where it is prevalent. Common sense precautions can lower your chances and should be observed, especially if you are in a high-risk category. Avoid areas with a lot of dust, like construction sites, close your windows and stay inside during dust storms, get an air filtration system for your home, and avoid activities like gardening and digging. Clean cuts and wounds well to prevent infection on the skin.
Animals, whether kept as pets or enjoyed in the wild, bring an immense amount of beauty and joy into our lives. To fully appreciate them, it is important to be responsible when interacting with them by understanding all of the risks involved. This means monitoring your pet’s health, as well as being mindful of the close links between your pet’s wellness and your own.
Armed with thorough information about the zoonotic diseases that can be contracted and transmitted, you can keep your family and your pets safe from both minor illness and chronic conditions alike. With this guide as a resource, make sure to consult both a veterinarian and your primary health specialist with any concerns you may have about zoonoses. For more in-depth guides about your pet’s health, please visit WARL.org.
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