by David F. Kramer
Some of the best things about pet ownership involve sharing. We share our love and affection, prime real estate on the bed or couch, and even our meals. Unfortunately, another thing we share with our pets can be unwanted visitors in the form of germs and infection. Animals can pass a multitude of diseases to humans in a process called zoonosis.
In recent years, the advance of swine flu, bird flu and other animal-borne diseases have revealed just how serious this problem can be. What’s lesser known, and even lesser studied, is the prospect of reverse zoonosis, which involves the passing of disease from humans to animals.
While less prevalent than disease transmission in the other direction, we can indeed make our dogs sick. Here are some diseases you can give your dog, and a few you can’t.
Mumps is a highly contagious viral disease in people. Initial physical symptoms of the disease include lethargy, muscle pain, headache, and fever, and are usually followed by a painful swelling of the parotid salivary glands, located on the sides of the face. While often associated with children, mumps can strike at any age. The good news is that most cases of the disease can be prevented through vaccination. People who do come down with mumps typically recover over the course of a week or two, but in some cases the virus can cause serious complications such as hearing loss and inflammation of the pancreas, testicles, ovaries, and the brain and the membranes that cover it.
“Though rare, dogs can become sick after exposure to the mumps virus from an infected person,” says Dr. Jennifer Coates, veterinary advisor with petMD. She says that symptoms can include fever, lack of appetite, and a swelling of the salivary glands below the ears. After palpating your dog’s salivary glands, your vet will most likely order tests to rule out other, more common conditions that also cause the salivary glands to swell. He or she may also aspirate a sample of the infected gland by use of a small needle so that it can be analyzed.
Most dogs recover from a mumps infection in five to ten days, according to Coates. While no specific remedy for the disease is available, your vet may recommend symptomatic treatment to keep your dog comfortable during recovery. While the risk of human to dog infection from mumps is low, it is obviously best to keep your pets away from any infected family members.
Ringworm, or dermatophytosis, is an infection of the skin that affects humans as well as animals. Despite its name, ringworm is not caused by any type of parasite or worm but by a fungus. The primary symptom of ringworm in people is an itchy, round rash. In dogs, ringworm typically causes roughly round patches of hair loss that may or may not be itchy. Ringworm can be transmitted through direct contact with an infected individual (human or animal) as well as through contaminated objects (brushes, towels, etc.).
“We treat that topically with antifungal medications, and treat it systemically with an antifungal suspension or oral pill, if necessary. We also use shampoos or dips to minimize the spread of spores to avoid further infection,” says Dr. Adam Denish of Rhawnhurst Animal Hospital in Pennsylvania. “As vets, our main responsibility is to make sure that animal diseases don’t get passed to people. We may educate owners about human diseases and make sure that if they have them, they can’t be passed to their animals.”
If you have been diagnosed with ringworm, keep the affected area of skin covered to avoid transmitting the condition to your dog.
While Salmonella is often associated with food poisoning, it can also be passed to humans through contact with infected animals, and vice versa. In both humans and dogs, Salmonella can cause nausea, vomiting, diarrhea, fever, headaches, and abdominal cramps. Young children and the elderly are more at risk for complications from Salmonella infection. Coates says that, “dogs are more resistant to Salmonella than are people, so the chances of you making your dog sick are slim. That said, taking common sense precautions only makes sense.”
Avoiding passing Salmonella to your dog is simply a matter of good hygiene. For example, if your dog is prone to drinking from the toilet, then it’s certainly prudent to keep him or her from this activity while an infected person might be using it, and people with Salmonella should be extra vigilant about washing their hands after using the restroom. Also, if the disease is food-borne, you should obviously keep infected foods away from dogs, and even out of the trash if they’re prone to going through it.
Giardia infection, or giardiasis, is one of the most common waterborne infections in the U.S.
According to Denish, “Giardia is a protozoa that appears in dogs, and can be seen in cats and even in exotic animals. It is spread through contact with feces and contaminated water. Symptoms include diarrhea and weight loss; we see it in a lot of pet store and breeder dogs coming from the south with hotter weather conditions.”
A person can get Giardia from a dog’s feces, and this disease can be passed from human to dogs, though a dog is far more likely to get it from another animal, especially in a pet store or puppy mill setting where many animals are kept in close quarters. According to the Centers for Disease Control (CDC), the most common mode of Giardia transmission is water, which can include drinking water, well water, lake and stream water, and swimming pool and spa water.
Coates says that the main symptom of Giardia in dogs is diarrhea. Your vet can often confirm this diagnosis through fecal analysis. “Once diagnosed, Giardia is usually treated with fenbendazole and/or metronidazole,” she says.
MRSA is caused by Staphylococcus aureus bacteria that have developed resistance to several types of antibiotics. The condition is especially prevalent in health care settings where a patient’s immune system may already be compromised by other illnesses, but it can be contracted in the general community as well. MRSA usually causes skin infections, but pneumonia, surgical site infections, sepsis (infection of the bloodstream), and other conditions are also possible.
As for the treatment of MRSA, Dr. Katie Grzyb says, “MRSA treatment is dependent on culture and sensitivity. A culture is taken by the human physician and many antibiotics are tested against this pathogen to see which resolves the infection best. Once determined, the patient is then put on this antibiotic usually for upwards of 6-8 weeks and then recultured after finishing the antibiotics to ensure the MRSA has cleared.”
According to Denish, pet owners who work in a health care setting have a very low chance of passing this infection to their dogs and would most likely need to be actively infected to pose a risk to their animals.
Lyme disease, or Lyme borreliosis, is a bacterial disease spread through the bite of infected blacklegged ticks (Ixodes scapularis and Ixodes pacificus). The initial symptoms in people include a growing patch of redness on the skin, lethargy, swollen lymph nodes, and fever, though 20-25% of those affected will not develop a rash. A diagnosis can be confirmed through blood tests to detect antibodies against the bacteria, but these are not always reliable and can have false positive results.
Lyme disease can lead to very serious complications, including partial facial paralysis, joint pain, severe headaches, memory loss, and heart palpitations. Even with medical treatment, those affected with Lyme disease may experience these debilitating symptoms for six months or more.
Lyme disease can also be serious in dogs, and can lead to swollen lymph nodes, fever, lack of appetite, kidney issues, and potential lameness due to inflammation of the joints, according to Coates. The treatment for both humans and dogs often includes the antibiotic doxycycline, although other medications may be used depending on the specifics of the case. As with humans, there is always the possibility that several courses of antibiotics and medication may be needed, and that symptoms may return despite appropriate treatment.
Luckily for both pets and their owners, the tick itself is the conduit for Lyme disease. The disease can’t be passed from person to person or from person to dog.
While humans and animals are both capable of developing symptoms that are typically associated with the common cold, the good news is that the likelihood of a person transmitting the illness to a dog is extremely low. Coates says, “in almost every case, the viruses that cause cold-like symptoms in people and dogs are species-specific.” Colds in both dogs and people generally resolve on their own, but if symptoms worsen or fail to improve, it’s best to see your doctor (or vet).
As far as transmission goes, the same can’t necessarily be said for the flu. While most of the medical community has long believed that the flu cannot be passed from human to animal, recent cases have shown that the adaptable nature of the flu may very well mean that some strains can indeed be passed from humans to other animals, including dogs. In truth though, the risk of this occurring is still extremely small (though who’s to say what the future holds!). While some pet owners might swear that their dog came down with the sniffles shortly after they did, this is most likely a coincidence.
The good news is that while your family should keep their distance from you while you’re suffering with the latest cold or flu bug, you can still curl up with your dog for comfort and emotional support—and the same goes for when your dog is feeling under the weather.
Keeping your pets safe from illnesses is no different than keeping yourself and your family healthy.
“You should always practice cleanliness when it comes to your pet,” says Denish. Even if the likelihood of passing a disease between you and your dog is low, take simple precautions like washing hands and avoiding being licked around the face. Denish adds “be educated, and don’t strictly rely on the internet for information. Talk with your physician as well as your veterinarian whenever you’re sick about the potential risks to others in your family, as well as your pets.”
The risk for infection both from owners to their pets, as well as in the other direction, is always increased for humans and animals with compromised immune systems. For owners and pets afflicted with immune disorders caused by infections, chemotherapy, steroid use, diabetes, etc., every care needs to be taken to avoid cross-infection. Developing a good rapport with both your veterinarian and your family doctor will help maintain your health and that of your pets.