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Diseases That Can Strike Humans and Pets

How to Prevent Zoonotic Disease Transmission
  -- By Kristi Snyder, DVM
We all love our pets, but the fact of the matter is they can make us sick if we’re not careful. Virtually all animals carry diseases that can be harmful to humans. With so many potential diseases, it’s important to know which ones you need to be concerned with so you can take the proper steps to safeguard yourself and your family. Below are some of the most common conditions you can catch from your dog or cat (and a few of the ones you don’t need to worry about). By arming yourself with some key knowledge and following a few basic principles, you can live happily and healthfully alongside your pet without having to wonder, “Can I catch that?”

What is a Zoonotic Disease?
A zoonotic disease is one that can be transmitted between animals and humans. These consist of diseases spread by bacteria, viruses and parasites, to name a few. Common routes of infection include direct contact or accidental ingestion of infected feces or urine (often from a contaminated water source but this can also occur from being in close contact with your pet without practicing proper hygiene). Contact with your pet’s saliva (such as receiving a faceful of puppy kisses) or the bite of an infected animal also can lead to infection from certain diseases.

Can I Catch My Dog's or Cat’s Cold?
I often get questions from clients wondering whether they can catch their dog's or cat’s cold or flu. In short, the answer is no. Airborne infections such as kennel cough or feline upper respiratory disease, while highly contagious among dogs and cats, respectively, cannot be transmitted from your pet to you. Likewise, your dog is not susceptible to catching your cold. The same goes for the flu. To date, there have been no recorded cases of canine influenza spreading to humans nor have there been any reports of human influenza spreading to dogs. Lice infestation is another problem that is often wrongfully blamed on pets. Contrary to popular belief, lice are very host-specific, and dogs and cats do not play a role in the transmission of human lice.

9 Common Zoonotic Diseases
Here are some common zoonotic diseases you should watch out for (a comprehensive list can be found at www.cdc.gov):

Giardia: Giardia is a parasite that causes diarrhea in people and animals. People can acquire infection from giardia by consuming water that is contaminated with infected feces. People with weakened immune systems are most susceptible to infection with giardia.

Roundworm: Roundworm, also known as Toxocara, is a parasite of the small intestine that can be spread to humans through the feces of infected animals. Infection with roundworms is a common cause of visceral or ocular larva migrans in people, which are serious conditions that can irreparably affect the organs and eyes. Young children are the most susceptible.

Tapeworm and fleas. Dipylidium is a common tapeworm of dogs and cats that is spread by fleas. People can become infected by accidental ingestion of an infected flea. Children are particularly susceptible. Proper flea control is the most important means of prevention.

Toxoplasmosis. Toxoplasmosis is an infection caused by a parasite called Toxoplasma gondii. Cats carry the infection and can spread it via contaminated feces. Pregnant women are particularly at risk of passing the disease to their unborn fetus and should be cautious about cleaning out the litter box (scooping the litter box daily generally offers good prevention as it takes at least 24 hours for contaminated stool to become infective). Although cats often get a bad rap when it comes to the spread of toxoplasmosis, it’s important to remember that people who consume raw or undercooked meat or unpasteurized dairy products are also at risk.

Campylobacter: Campylobacter is an infectious bacterial organism that causes diarrhea, intestinal cramping and abdominal pain. People may become ill from coming into contact with the stool of an infected dog or cat. Eating undercooked meat or drinking unpasteurized milk can also expose people to infection from this organism.

Salmonella: Salmonella is a bacteria that can infect dogs, cats and humans causing watery diarrhea, fever and lethargy. The bacteria is spread through the stool of infected animals. An increased risk of infection exists for people who feed their pets raw meat diets.

Lyme Disease and Rocky Mountain Spotted Fever: Lyme disease and Rocky Mountain spotted fever are tickborne illnesses caused by the bacteria Borrelia burgdorferi and Rickettsia ricketsii, respectively. These bacteria are responsible for causing fatal illness in dogs and humans ranging from fever and muscle and joint pain to death. Although the bacteria are spread by ticks that feed off of infected dogs, your dog cannot transmit the disease directly to you. Therefore, prevention lies largely in proper tick control.

Ringworm: Ringworm is a dermatophyte, a type of fungus that can affect the skin, generally causing a ring-shaped rash in humans. In pets, this often shows up as a circular area of hair loss that might or might not be itchy. Dogs and cats, especially puppies and kittens, can carry ringworm, and it is spread by close contact. While not generally a serious condition, infection with ringworm can be unpleasant, nonetheless.

Cat Scratch Fever: Cat scratch fever is not just the name of a catchy tune; it is a bacterial disease that can be spread to humans through the bite or scratch of an infected cat. Most people will develop only mild signs, though in some cases they may experience swollen lymph nodes, fever or fatigue. Cats that carry the bacteria may not always show signs of disease, so people who suffer any suspicious scratch or bite should be checked out by a doctor.

How to Prevent the Spread of Zoonotic Diseases It’s true, our dogs and cats have the potential to spread some pretty serious stuff. However, by keeping your pet healthy and employing these basic principles, you can coexist with your animals with relative peace of mind. Remember, your pets aren’t the only way you can come into contact with these infectious diseases, so it’s important to educate yourself. Always avoid eating raw or undercooked meat and stay away from untreated water or unpasteurized milk.

Sources
Centers for Disease Control and Prevention, “Key Facts About Canine Influenza,” www.cdc.gov, accessed on August 26, 2013.

Centers for Disease Control and Prevention, “Diseases from Dogs,” www.cdc.gov, accessed on August 26, 2013.

Centers for Disease Control and Prevention, “Zoonotic Diseases,” www.cdc.gov, accessed on August 25, 2013.

Cote, Etienne, DVM, DACVIM. "Clinical Veterinary Advisor: Dogs and Cats." (Missouri: Mosby, Inc, 2007), 439-440, 979-980, 1093-1094.