Zoonotic diseases are diseases that can be transmitted from an animal to a human being. We will be addressing the ways a disease can be transmitted from dogs to humans or humans to dogs. Remember when you are on your Therapy Dog visits it is your responsibility for the safety and health of the people you are visiting and your dog.

What is the risk of contracting a zoonotic dis­ease from my dog? 

If dog owners exercise basic hygiene principles, such as the most important one like hand washing, most of these potential diseases can be avoided.

Current evidence supports the fact that pet dogs pose a minimal zoonotic risk to their human companions. Your risk may be slightly higher if you have a compromised immune system from disease or medication, such as:

  • AIDS/HIV

  • People on chemotherapy or receiving radiation therapy

  • The elderly or people who have chronic diseases

  • Congenital immune deficiencies

  • People who have received organ or bone marrow transplants

  • Pregnant women (a fetus's immune system is not fully developed, and the pregnant woman's immune system is altered so that she won't reject the fetus)

If you fall into one of these categories, it doesn't mean you have to give up your pet! It simply means that you should take some basic precautions such monitoring your dog for any signs of illness, washing your hands after extensive handling of your dog, and avoiding direct contact with your dog's feces or urine.

The most common zoonotic diseases of animals.

  • Ringworm

  • Salmonellosis

  • Leptospirosis

  • Lyme disease

  • Campylobacter infection

  • Giardia infection

  • Cryptosporidium infection

  • Roundworms

  • Hookworms

  • Scabies

  • Harvest mites

  • Rabies

 

The most common infections you could contract from an animal.

 

 

Campylobacteriosis (Campylobacter spp.)

Campylobacter spreads through contaminated food (meat and eggs), water, or contact with stool of infected animals. Dogs infected with Campylobacter might show no signs of illness at all or might have diarrhea and a slight fever.

Most people who become sick with campylobacteriosis will have diarrhea, cramping, abdominal pain, and fever within 2-5 days after exposure to the organism. Campylobacter can cause serious life-threatening infections in infants, older persons, and those with weakened immune systems.

Dog Tapeworm (Dipylidium caninum)

The dog tapeworm is a parasite spread to dogs, cats, and people through the ingestion of infected fleas. This parasite is common but rarely causes illness in pets or people. Infections with Dipylidium caninum can sometimes be detected by finding rice-like segments of the tapeworm crawling near the anus or in fresh bowel movements. In severe infections, pets can lose weight and have mild diarrhea.

In people, children are more commonly infected but don’t usually show signs of disease. The best way to prevent infection in pets is to control the flea population in the environment.

 

Campylobacteriosis (Campylobacter spp.)

Campylobacter spreads through contaminated food (meat and eggs), water, or contact with stool of infected animals. Dogs infected with Campylobacter might show no signs of illness at all or might have diarrhea and a slight fever.

Most people who become sick with campylobacteriosis will have diarrhea, cramping, abdominal pain, and fever within 2-5 days after exposure to the organism. Campylobacter can cause serious life-threatening infections in infants, older persons, and those with weakened immune systems.

Dog Tapeworm (Dipylidium caninum)

The dog tapeworm is a parasite spread to dogs, cats, and people through the ingestion of infected fleas. This parasite is common but rarely causes illness in pets or people. Infections with Dipylidium caninum can sometimes be detected by finding rice-like segments of the tapeworm crawling near the anus or in fresh bowel movements. In severe infections, pets can lose weight and have mild diarrhea.

In people, children are more commonly infected but don’t usually show signs of disease. The best way to prevent infection in pets is to control the flea population in the environment.

Hookworm (Zoonotic) (Ancylostoma caninum, Ancylostoma braziliense, Uncinaria stenocephala)

Dog hookworms are tiny worms that can spread through contact with contaminated soil or sand. Dogs can also become infected with hookworms through accidentally ingesting the parasite from the environment or through their mother’s milk or colostrum. Young puppies are most often affected and might have dark, bloody stool and anemia. Severe infections in some puppies can lead to death.

People become infected with dog hookworms while walking barefoot, kneeling, or sitting on ground contaminated with stool of infected animals. Hookworm larvae enter the top layers of skin and cause an itchy reaction called cutaneous larva migrans. A red squiggly line might appear where the larvae have migrated under the skin. Symptoms usually resolve without medical treatment in 4-6 weeks.

Rabies

Rabies, a fatal neurologic disease in animals and people, is caused by a virus. Animals and people are most commonly infected through bites from rabid animals. Infected dogs might have a variety of signs, but most often have a sudden behavioral change and progressive paralysis. Rabies is prevented by vaccination.

The first symptoms in people can start days to months after exposure and include generalized weakness, fever, and headache. Within a few days symptoms will progress to confusion, anxiety, behavioral changes, and delirium. If you have been bitten by a dog or other animal and feel that there is a risk for rabies, contact your health care provider right away. Once symptoms appear, it is almost always too late for treatment.

Roundworm (Toxocara spp.)

Toxocara roundworms cause a parasitic disease known as toxocariasis. Dogs and people can become infected by accidentally swallowing roundworm eggs from the environment. In addition, larval worms can cross through the placenta, milk, or colostrum of a mother dog, passing the infection to her puppies. Infected puppies usually do not develop and grow well and might have a pot-bellied appearance.

In people, children are most often affected with roundworm. There are two forms of the disease in people. Ocular larva migrans happens when the larvae invade the retina and cause inflammation, scarring, and possibly blindness. Visceral larva migrans occurs when the larvae invade parts of the body, such as the liver, lung, or central nervous system.

 

Less common diseases associated with dogs that can cause human illness are:

 

Brucellosis (Brucella spp.)

Brucellosis is a bacterial disease that affects the ability of animals to reproduce. The disease can be transmitted to humans through contact with recently aborted tissue from infected animals or consumption of unpasteurized (raw) milk. Dogs that are infected might have decreased appetite, weight loss, behavioral changes, and lack of energy, but most dogs infected with brucellosis show no signs of illness. Brucellosis affects the reproductive organs and can cause early-term deaths of developing puppies.

People who are infected with brucellosis will usually become sick within 6-8 weeks of exposure. Sick people will have flu-like symptoms that last 2-4 weeks. Sometimes brucellosis can become a chronic illness that can be difficult to treat.

Capnocytophaga spp.

Many species of Capnocytophaga bacteria live in the mouths of dogs and cats. These bacteria do not make dogs or cats sick.

Rarely, Capnocytophaga can spread to people through bites, scratches, or close contact from a dog or cat and cause illness. Most people who have contact with a dog or cat do not become sick. People with weakened immune systems who have difficulty fighting off infections (for example, people with cancer or those taking certain medications such as steroids) are at greater risk of becoming ill.

Giardiasis (Giardia spp.)

Giardia is a parasite that causes diarrhea in animals and people. Giardia is transmitted to animals and people through food or water contaminated with stool.

Symptoms in animals and people include diarrhea, greasy stools, and dehydration. People can also have abdominal cramps, nausea, and vomiting. Symptoms can last 1-2 weeks.

Leptospirosis (Leptospira spp.)

Leptospirosis is a bacterial disease of people and animals that is transmitted through contaminated water and urine or other body fluids from an infected animal. It is difficult to detect early stages of leptospirosis in animals, but the disease can lead to kidney and liver failure if left untreated.

People who become infected with leptospirosis might not have any signs of the disease. Others will have nonspecific flu-like signs within 2-7 days after exposure. These symptoms usually resolve without medical treatment, but can reappear and lead to more severe disease.

MRSA (Methicillin-Resistant Staphylococcus aureus)

Staphylococcus aureus is a common type of bacteria that is normally found on the skin of people and animals. Methicillin-resistant Staphylococcus aureus (MRSA) is the same bacterium that has become resistant to some antibiotics. Dogs and other animals often can carry MRSA without being sick, but MRSA can cause a variety of infections, including of the skin, respiratory tract, and urinary tract.

MRSA can be transmitted back and forth between people and animals through direct contact. In people, MRSA most often causes skin infections that can range from mild to severe. If left untreated, MRSA can spread to the bloodstream or lungs and cause life-threatening infections.

ExternalPasteurellosis (Pasteurella spp.)

Pasteurellosis is a bacterial disease associated with animal bites and scratches. Pasteurella is a normal bacterium that lives in the mouths of healthy dogs. The bacteria do not typically make dogs sick; however, dogs can develop abscesses or skin infections in places where they were scratched or bitten by another animal.

Pasteurella is found in 50% of patients with infected dog bite wounds. Pasteurella can cause painful wound and skin infections. In more severe cases, it can cause widespread infection and might even affect the nervous system.

Ringworm (Microsporum canis)

Ringworm is a condition caused by a fungus that can infect skin, hair, and nails of both people and animals. Ringworm is transmitted from animals to people through direct contact with an infected animal’s skin or hair. Puppies are most commonly affected and can have circular areas of hair loss anywhere on the body.

Ringworm infections in people can appear on almost any area of the body. These infections are usually itchy. Redness, scaling, cracking of the skin, or a ring-shaped rash may occur. If the infection involves the scalp or beard, hair may fall out. Infected nails become discolored or thick and may possibly crumble.

Salmonellosis (Salmonella spp.)

Salmonella spreads to people through contaminated food (eggs and meat) or contact with stool of certain animals including dogs. Salmonella infections have been linked to some brands of dry dog food, treats, and chew toys like pig ears and to “raw food” diets for dogs. While it usually doesn’t make the dogs sick, Salmonella can cause serious illness when it is passed to people.

People exposed to Salmonella might have diarrhea, vomiting, fever, or abdominal cramps. Infants, elderly persons, and those with weakened immune systems are more likely than others to develop severe illness.

Sarcoptic Mange (Sarcoptes scabeii), also known as Mange

Sarcoptic mange is a parasitic skin disease that is caused by a tiny mite. Mange is transmitted between animals through close contact. In dogs, the mite causes severe itching and self-inflicted wounds from scratching.

People can’t become infested with the canine version of sarcoptic mange, but they can have a minor local reaction from the mites if they come in contact with an infested dog.

 

Which of these are more likely to cause serious illness to humans?

 

Rabies, caused by a virus, is almost invariably fatal in man.

Certain infectious organisms, such as the bacteria Salmonella and Campylobacter and the protozoan disease caused by Giardia, can cause severe gastroenteritis.

Leptospirosis, known as Weil's disease in man, can cause extremely serious liver and kidney disease but the transmission from dogs to humans is very rare. Humans usually contract this disease from exposure to contaminated water.

Roundworms (Toxocara canis) and tapeworms (Echinococcus species) can cause liver problems, but illness in man from these causes is rare. Direct handling of infected dog feces can potentially cause an infection of Toxocara canis in a susceptible person. Echinococcus tapeworms are very rare in dogs, and humans cannot directly become infected from a dog (tapeworm infections require an intermediate host for transmission).

Zoonotic skin diseases including ringworm, caused by the fungus Microsporum canis and scabies, caused by the mite Sarcoptes scabieiCheyletiella, and Harvest Mites (Trombicula species) are transmitted relatively easily to people through direct physical contact.

Prevention 

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Simple hygiene and common sense will drastically reduce if not eliminate the risk of zoonotic spread of disease from dog to man. Some of the things you can do include:

  • Any sign of illness or disease in your dog is diagnosed and treated promptly by your veterinarian. If your dog is sick, make sure you wash your hands after any contact.

  • Bathe and groom your dog regularly. This will increase the chance of early detection of any skin lesions.

  • Give your dog a broad-spectrum deworming product on a regular basis. The simplest way to do this is to use a monthly heartworm product that includes a dewormer. Wear gloves when gardening or working in areas where dogs, cats or other animals may have urinated or defecated.

  • Pick up any feces on your property using rubber gloves and "stoop and scoop" when you take your dog for a walk. Dispose of all waste materials promptly and safely.

  • Do not allow your pets to contact children's feces.

  • Always ensure you wash your hands after handling any animal.

  • Provide separate food and water dishes for your dog, and wash and store them separately from your family's dishes and bowls.

  • Wash pet bedding frequently.

  • Use flea and tick control products on a routine basis.

Following these simple precautions ensures you have done everything to reduce any risk to you and your family.

 

Can I transmit disease to my dog?

Yes, transmission of disease to dog from human are sore throats, tuberculosis and fleas are common examples. Additionally, enteritis due to Campylobacter and Salmonella infections can be passed from an infected family member to the family dog.