Modern headlines scream warnings about the latest animal-to-people diseases including SARS, bird flu, and most recently, a coronavirus outbreak suspected to jump species from critters, originating in China. Technically termed zoonosis, such diseases not only make animals sick but can also jump species from an animal to a human under normal conditions. In rare cases, humans can infect pets.

There are over 200 known zoonoses, but we associate only a handful with pets. Is canine coronavirus contagious to humans? What about the cat coronavirus? There are MANY kinds of coronaviruses. While the canine and feline coronaviruses (FIP is a mutated version in cats) can cause problems in your pets, there is no evidence that the canine coronavirus or feline coronavirus (that most commonly cause diarrhea) are contagious to people.

WHAT IS ZOONOSIS?

A zoonosis is an illness that originates in one species but can infect another. For instance, bird flu originated in…well, birds, but also makes people sick.

Many animals can transmit diseases to people, but cats and dogs pose a special risk because we live so closely with them. Pets are a major reservoir for zoonotic infections and can transmit several viral and bacterial diseases to humans. Zoonotic diseases can be transmitted to humans by infected saliva, aerosols, contaminated urine or feces, and direct contact. Most problems are transient and easily treated, and the incidences remain relatively low.

Most of these illnesses pose only minor risks. But for those with compromised immune systems, like older people, already ill, or very young kids, they can be devastating. Zoonoses should never be taken lightly. These diseases potentially cause humans debilitating illness or even death. Understand the risks and how to protect your pets and yourself from these most common problems.

Scratches can transmit bacteria.

CAT SCRATCH DISEASE (CSD)

A common zoonosis of cats is cat scratch disease caused by the bacteria bartonella henselae. Cats rarely get sick themselves but even a tiny wound can cause life-threatening infection in some people. The organism is transmitted between cats by the cat flea. Infected flea feces contaminate cat claws during grooming and then the bacteria are inoculated into the human when scratched.

Signs prove mild in otherwise healthy people and go away without treatment. A healed cat scratch turns red, swollen and sore, and the lymph node closest to the injury swells. Scratches on a hand or arm tend to affect lymph nodes in the armpit, while those on the ankles and legs affect lymph nodes in the groin region. Vague feelings of fatigue or even flu-like symptoms may develop and last up to three months before going away.

CSD represents a much greater risk for people with compromised immune systems, such as transplant recipients, people with HIV or AIDS, patients undergoing anticancer treatments, and others. Year-round flea control, keeping cats indoors, and trimming kitty claws help minimize the risk.

LEPTOSPIROSIS

Leptospirosis is worldwide zoonoses mostly transmitted to people contaminated soil, water, urine, or tissue of the infected animals. Rodents are the major source, but dogs also play an important role. Contact with contaminated urine is the main transmission route and may cause no symptoms at all, to fever, nonproductive cough, headache, musculoskeletal pain, diarrhea, nausea, vomiting, lung hemorrhage, and even meningitis. Several antibiotics are useful in the treatment of the disease, and dogs are routinely vaccinated to prevent contracting leptospirosis.

Cats or dogs that catch infected prairie dogs are at risk for plague.

PLAGUE

Considered a disease of antiquity that killed millions as the “black death,” even today pockets of plague continue to exist. This deadly bacterial disease caused by Yersinia pestis primarily affects rodents and is carried by rodent-specific fleas. Dog and cat fleas aren’t effective transmitters, but cats exposed to these rodent fleas are susceptible.

The incidence of the disease depends on geographic regions. Today plague affects primarily the desert southeast states such as New Mexico, Wyoming, and Colorado. Cats become infected by ingestion of infected rabbits or rodents and possibly via bites from infected fleas. Infected cats most typically develop the bubonic form of the disease, characterized by infected and draining lymph nodes that look like cat bite abscesses. Cats with plague require hospital isolation and careful handling, with caregivers using protective clothing. Treatment with antibiotics work well, and cats are no longer contagious after 72 hours of appropriate therapy.

Keeping cats indoors and preventing fleas keeps you and your pets safe. Cats that have been exposed can be given a week-long course of the antibiotic tetracycline to prevent infection.

Raccoons in some parts of the country serve as a rabies reservoir and can infect cats and dogs–which then put humans at risk.

RABIES

Rabies virus belongs to the family Rhabdoviridae, which is found throughout the world and continues to be a presence in wild animal populations. Different strains affect specific kinds of animals—from raccoons and skunks to bats, foxes and coyotes—but all strains attack the brain, and kill the victim. Virtually all mammals including cats, dogs, and humans are at risk. There is no cure or effective treatment once symptoms develop.

The disease spreads via direct contact with an infected animal, usually through a bite that introduces virus-laden saliva into the wound. The time it takes from the bite to symptoms varies from days to years, but most times illness develops within three to eight weeks of the bite. Stricken dogs may appear to have something caught in their throat. Cats afflicted with rabies tend to vocalize much more with lots of meows and cries.

Preventive vaccination offers the very best protection for you and your pet, and most states require vaccination by law.

Bald places usually on the head and ears can be a sign of ringworm in cats.

RINGWORM

This fungal infection usually caused by Microsporum canis grows on keratin, the substance that makes up the hair shaft, and causes skin disease. People with depressed or immature immune systems are at the highest risk. In people, ringworm infections spread outward from a central spot. As the inside central sore heals, the “ring” of reddened skin surrounding the area gives it a characteristic look and name.

But ringworm infection in pets looks like a variety of other pet skin diseases. Often the infected hairs break off and leave a stubby patchwork fur pattern, and mild to severe crusty sores also can develop. Some pets become itchy, others do not. Some cats become “typhoid Mary” carriers and show no signs but spread the infection. Once a pet becomes infected, spores contaminate the environment and can remain infective for months. The disease usually is self-limiting in pets, but they can become reinfected time and again. Read more about ringworm here.

Many of the pet food recalls are due to ingredients or the food itself becoming contaminated with salmonella. Safe food handling keeps your pet–and you!–safe.

SALMONELLA

Salmonella colonizes the large intestine of a variety of mammals, and people can also get infected by eating contaminated food. Infection can cause a variety of signs, but the most common are gastrointestinal diseases in both people and dogs. You may see your dog vomit or have diarrhea. However, a majority of infected dogs never show signs, but can still transmit the pathogen to other animals and people. Proper food handling—your own and your pet’s food—prevents most risk.

Cat feces may spread toxoplasmosis.

TOXOPLASMOSIS

Caused by the single-cell organism Toxoplasma gondii, this parasitic protozoan has evolved to infect people and animals without making them sick. The most common sign in both people and pets is transient swelling of the lymph glands. In otherwise healthy people, treatment may not be needed. However, the disease can cause life-threatening illness in immune-suppressed people, and deadly to a woman’s unborn baby.

People become infected most commonly by eating undercooked meat, especially pork. Cats become infected either by swallowing the infective stage of the protozoan from the environment, by eating infected animals, or by eating raw meat. Infected cats are the only animals that pass on these immature forms of the organism, which are shed in the cat’s stool for two to three weeks. Once this stage is passed it’s rare for the cat to ever again shed the eggs.

Pregnant women or those with compromised immune systems should have someone else perform litter box duty. Wash your hands after handling raw meat, and cook it thoroughly before eating. Prevent the cat from hunting. Wear gloves while working in the garden to prevent contracting the disease from the soil.

Preventing Zoonosis

Without exception, these zoonotic diseases can be avoided. Basic hygiene, preventive vaccines and parasite products protect both you and your pet from illness. Always check with your veterinarian for the best preventive and treatment options for your pets.

I am not a veterinarian, nor am I a physician. Your family doctor should be your first call when addressing human family members’ health.

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Amy Shojai, CABC is a certified cat & dog behavior consultant, a consultant to the pet industry, and the award-winning author of 35+ pet-centric books and Thrillers with Bite! Oh, and she loves bling!