6 dangerous diseases you can get from your pets

Pets enrich our lives in so many ways. Not only is your furry (or scaly, or feathered, or hairless) friend a great source of companionship, research has found that having a pet can improve your physical fitness, lower stress, and boost overall happiness.

The benefits of pet ownership also come with some risks, specifically germs and pathogens that can be transferred to humans. In fact, companion animals are a potential source of more than 70 human diseases. “People may acquire pet-associated zoonotic infections through bites, scratches, or other direct contact of the skin or mucous membranes with animals,” wrote Jason W. Stull, a diplomate of the American College of Veterinary Preventive Medicine, in a study on the risk of pet-associated infections. 

COVID-19 is known to infect both cats and dogs alike. Although human-to-pet transmission has been confirmed, researchers are still unsure of the possibility of pet-to-human transmission. Until more is known, the CDC recommends socially distancing from your pet as you would other humans, especially if you become ill with COVID-19. 

If you’re thinking of adopting a pet or already have one, it’s important to know the types of infections you risk being exposed to. Here, we discuss several zoonoses—diseases that can be transferred from animals to people—as well as some preventive measures to reduce the risk of contracting an infection.

Zoonotic infections

Ringworm

Also known as “tinea” or “dermatophytosis,” ringworm isn’t actually a worm. It’s a highly contagious fungal infection that presents as a circular skin rash. Ringworm often spreads through skin-to-skin contact with an infected person or animal. According to the Mayo Clinic, it can be contracted when petting or grooming an animal, or by touching surfaces contaminated by infected animals, such as grooming tools (combs, brushes, etc.), blankets, pet beds, and anywhere else the animal’s infected body parts may have touched. Many different animals, including dogs, cats, cows, goats, pigs, and horses, can spread ringworm to people, who are more likely to contract it from an animal if they live in warmer climates, have frequent close contact with animals, have a compromised immune system, or wear tight or restrictive clothing. 

Ringworm presents in raised, round, red-colored, scaly patches on the skin that are usually darker around the edges. The most common treatment is antifungal cream, lotion, or powder, which usually gets rid of rashes within 2 to 4 weeks. In cases of stubborn ringworm, physicians can prescribe the oral medications terbinafine, griseofulvin, and itraconazole, though these can cause side effects like nausea, diarrhea, indigestion, and other rashes. Fungal infections like ringworm rarely spread below the surface of the skin or cause serious illness. However, in serious cases it can cause fever, result in pus or drainage, and be extremely difficult to eliminate. This risk is highest in immunocompromised people, such as those with HIV, who are more likely to experience fungal spread.

Lyme Disease

Lyme is the most common vector-borne illness in the United States, caused by the bite of blacklegged ticks (also known as deer ticks) infected with Borrelia burgdorferi that live in the northeastern, mid-Atlantic, and north-central US. Cats and dogs are known to get Lyme disease from tick bites. Although there’s no evidence that these pets can spread it directly to their owners, pets that roam in tick-infested areas (including wooded areas, tall brush/grass, beneath leaves, near woodpiles, and where woods or fields meet lawns) increase the odds that ticks will be carried into your home and infect you.

Ticks can attach to any part of the body, but are often found in nooks and crannies, like in the groin, armpits, and scalp. Typically, ticks need to be attached to the human body for about 2 days or more before they can transfer the bacteria that causes Lyme disease to their hosts. For people who get infected, symptoms include fever, headache, fatigue, muscle aches, and a bull’s eye-shaped rash. If left untreated, Lyme disease can spread to the joints, heart, and nervous system, but is an extremely rare cause of death. To prevent Lyme disease, check yourself and your pets for ticks frequently, and avoid outdoor areas that may be breeding grounds for ticks during warmer months.

Parasitic Worms

Intestinal worms that affect animals include roundworms, hookworms, whipworms, and tapeworms, among many others. Inside your pets, a single intestinal worm can produce more than 100,000 eggs per day, which are then passed into the infected animal’s roaming environment through their feces. Worms pose a risk to humans if they’re exposed to the parasitic eggs and larvae in these feces—that’s why it’s critical to clean up after pets responsibly and ensure you don’t directly touch your pet’s droppings. Roundworms, the most common intestinal parasite in pets and the worms that are most likely to be transferred to humans, can survive in many different environments after being spread in feces, including contaminated surfaces such as soil and dirt. The risk doesn’t end with feces, though.

Humans can accidentally ingest roundworm eggs when they touch animal feces and then touch their mucous membranes. The eggs transferred from the feces to the inside of the body can hatch in the human’s intestinal tract and the immature worms then travel to different tissues throughout the body, including eye and even brain tissue, causing serious infections that result in wheezing, severe abdominal pain, vomiting, anemia, bloody stools, and more. Tapeworm can even be spread by accidentally swallowing an infected flea carried by your pet. The key to reducing the risk of parasitic infection is to practice proper hygiene. Additional measures include restricting access to high-risk contamination areas, such as sandboxes or litterboxes, and cleaning up feces regularly. 

Cat-scratch disease

An infection spread by cats, cat-scratch disease (CSD) is caused by a bacterium called Bartonella henselae, which is carried by 40% of cats at some point in their lives, despite many showing no signs of illness. Cats can get infected from flea bites or by interacting with other infected cats. CSD spreads to humans when an infected cat licks a person’s open wound, or bites or scratches a person hard enough to break skin. Typically, the infected area swells and populates with raised lesions. In more severe cases, someone with CSD may develop a fever, headaches, and enlarged and painful lymph nodes. To prevent CSD, wash cat bites and scratches with soap and water immediately and do not let cats lick open wounds.

Toxoplasmosis

Contracted through exposure to a microscopic parasite found in animal feces, toxoplasmosis is common in pets, especially cats. Transmission occurs when you accidentally ingest the parasites in animal feces if you touch your mouth after gardening, cleaning a litter box, or touching anything that has come in contact with infected cat feces. Outdoor cats that hunt and those that are fed raw meat are more likely to carry this disease.

Most healthy people show no symptoms, but when symptoms do occur, they include swollen glands, tiredness, fever, and sore throat. In pregnant women, toxoplasmosis can be very serious, causing miscarriage, premature birth, and severe illness in newborns. For prevention, clean up cat litter using gloves and avoid direct contact with animal feces in general. Pregnant women should avoid litter cleanup altogether.

Leptospirosis

Commonly spread through animal urine, leptospirosis is a bacterial disease that can be carried by cattle, pigs, horses, dogs, rodents, and wild animals. People become infected through direct contact with the urine or other fluids of infected animals. For example, if someone accidentally touches an infected animal’s urine, the bacteria can enter the body through open wounds or mucous membranes. Some people might also become infected by accidentally drinking infected water sources. Without treatment, Leptospirosis can have very serious consequences. The disease can lead to kidney damage, meningitis, liver failure, respiratory distress, and even death. Infected animals may show no symptoms. You can reduce your risk of infection by avoiding swimming in bodies of water that may be contaminated with animal urine.

How to prevent infection

Because our pets often feel like family, it’s important to keep them healthy and free from parasites and other infections. While veterinarians can diagnose and treat health problems that affect pets, it’s up to pet owners to practice protocols that reduce transmission of zoonotic pathogens. In an interview with the New York Times, Scarlett Magda, MD, president of Veterinarians International, said that taking precaution against animal-borne illnesses comes down to a vital practice: “Just wash your hands.”

A study published in the Canadian Medical Association Journal lists several precautionary measures one can take to reduce the risk of disease transmission:

• Protect skin from contact with animal feces by wearing gloves and using a plastic bag when cleaning up after a pet.

• Wash pet bedding regularly.

• Do not allow pets to lick open wounds or cuts.

• Keep litter boxes away from kitchens or other areas where food contamination is possible.

• When visiting other households with pets, take the same precautions.

Strict hand hygiene is critical, as is disinfecting bites and scratches inflicted by animals, and cleaning high-contact surfaces such as countertops and tables. Pet owners should be made aware of the possible risk of infection from animals, especially from newly acquired pets. During consultations, physicians should obtain a history of contact with pets and inform patients of the use of zoonotic disease prevention measures. For many people, simply being aware of these risks can help them protect themselves, their friends, and families.