Dogs May Be Good For Your Health…Except When They’re Not

While having a dog may be good for the heart, as my colleague Alice Walton just wrote, and is certainly good for the soul, you might want to read the “terms and conditions” in the fine print.

Heather Stone

Leo and Laila, my granddogs, as irresistible puppies

I’ve seen some impressive and life-threatening infections from dogs. None of them, until Lyme, gave me any hesitation about having a dog as an integrally important family member in our homes. Here are some of the highlights of other infections from dogs you should be aware of.

Pasteurella multocida is a small bacteria commonly associated with rip-roaring infections following cat or dog bites. Usually those from cats are worse, as their sharp fangs deposit the bacteria more deeply. About 10% of bites require medical attention and account for 1% (300,000) emergency room visits each year, at an estimated cost of  $30 million per year. 1-2% of bites are serious enough to require hospitalization.

Two of the worst cases of Pasteurella I’ve seen weren’t from bites. Both were from the owners petting their dog, whose fur was apparently still wet with dog saliva, and then touching an open wound without having washed their hands. Both patients became septic; one died.

While we know that dogs and cats lick their wounds and keep them clean like that (yes, there are some antibacterial compounds in saliva), don’t let your pet lick your wound.

Mili Duggal

Leo kissing Aunt Mili

Animal bite infections are commonly treated with a penicillin type of antibiotic (often Augmentin (amoxicillin-clavulanate). Patients who are allergic to penicillin might receive doxycycline, a quinolone, or TMP-SMX (Bactrim or Septra) instead. Keflex (cephalexin) and Clindamycin are not effective substitutes for treating Pasteurella, though often used in other types of skin infections.

Capnocytophaga is a particular risk for immunosuppressed people, including those with cancer, HIV, who are taking certain medications, those who have lost their spleen, and rarely, during pregnancy. Fulminant sepsis can develop and carries a 30% risk of death. Ampicillin-clavulanate (Augmentin) is again the drug of choice for mild infections or a similar combination for severe ones; the bacteria were resistant to quinolones (Cipro/Levaquin) in half the isolates tested.

Pasteurella and Capnocytophaga are the most rapidly progressive and immediately life-threatening infections from pets. If you get systemic symptoms (fever, chills, progressive pain/swelling/redness moving up from the bite site, flu-like aching, or occasionally vomiting or diarrhea) after a bite or contact with animal saliva on a wound, you should seek medical care immediately.

Last month there was an outbreak of Campylobacter linked to puppies. Diarrheal cases ranged across 15 states and involved 67 people, with more than a quarter requiring hospitalization. Most cases were linked to Petland stores, confirmed by history and by whole genome sequencing.

Disturbingly, these Campylobacter isolates were resistant to the most commonly recommended treatment, azithromycin or quinolones. Per the CDC, the 10 isolates tested by standard methods were resistant to almost all antibiotics tested except carbapenems, now recommended for seriously ill patients. Fortunately, most people with an uncomplicated diarrhea will recover without treatment.

Leptospirosis has been one of the scourges in Puerto Rico in the aftermath of Hurricane Maria, as I wrote about here. The infection is usually transmitted by contact with water contaminated by urine from rodents or wild animals. There have been several deaths and an estimated 76 infections on the island since the hurricane. Exact numbers, as with other deaths, are unknown and likely underestimated since the infrastructure remains in shambles.

A new problem is that some of the rescue dogs saved after the hurricane and brought to New Hampshire became ill with leptospirosis, likely from the contaminated water on the island. No people are yet ill from that exposure.

For families with recurrent strep throats in kids, dogs were thought to perhaps be the culprit, secretly carrying the bacteria. This seems to be a rarity, however and the strep was likely misidentified in older studies and was a canine strain, not the Group A strep that is so common in kids.

Dried pet food was linked to an outbreak of Salmonella infecting 49 people. Most people get diarrhea from this bacteria, a common cause of “food poisoning.” Again, the Salmonella infection is usually self-limited. The CDC stresses the importance of using dedicated scoops or spoons for dishing out the dry food and washing your hands after feeding your pet.

Worms such as toxocara (round worm) commonly infect people, though most often don’t cause symptoms. Occasionally, however, Toxocara causes blindness. Most often, kids acquire the infection by eating dirt contaminated with puppy (or cat) poo. Toxocariasis is more common in the South, where the eggs persist longer in the soil, and is more commonly a disease of poverty. It’s considered one of the neglected infectious diseases, receiving little attention. Tapeworms such as Echinococcus can also be acquired from dog contact, but aren’t common in the U.S.

Rabies should be mentioned, but should not be a risk from your pet—just be sure to keep up on vaccinations. Rabies from dog bites is a problem in Latin America, Africa, Asia, and especially in India. If you are bitten while traveling you must clean the wound thoroughly and be treated immediately—and I was advised to get back to the U.S. for rabies immune globulin and post-exposure treatment given concerns about the availability and quality of some products overseas.

There are other bugs that you can get from your dogs as well, including skin and GI parasites.

There’s only one infection that would give me pause now about having a dog now—Lyme.

We did not have Lyme in western Maryland until about ten years ago. That’s part of why I didn’t recognize my own infection. Even now, at Thanksgiving, ticks are abundant in my yard. The granddogs just came for a visit. Despite tick collars, after each short walk, we found 6-10 ticks on them. Even with checking each time, it is easy to miss one and have it later attach to you, rather than your pet. They are only the size of a poppy seed when not engorged.

Judy Stone

Recent ticks I have known…Upper left, on my arm, was sent for testing and was + for Lyme. Others were picked off my granddogs.

Should you find an attached tick, please take a photo and submit it to Tick Encounter for identification and epidemiologic surveys. They can give you some idea of how engorged it is and whether you should consider having it tested for Lyme and other parasites. I submitted the tick from my most recent bite to Tick Report…and they soon confirmed it was carrying Lyme. I was lucky and was promptly treated. (Bay Area Lyme does free tick testing for citizen science but their backlog precludes using it for treatment decisions). Many people will neither be aware they were bitten nor develop a characteristic rash. The continued sorry state of Lyme diagnosis and treatment will be discussed in an upcoming post. Given where I live, Lyme is a major reason I will not have a dog again, as much as I would like to. Consider your environment and, if you opt for a dog, at least don’t let it sleep in your bed.

I have no doubt that dogs are otherwise wonderful for your health and happiness. However if you have a dog, it makes sense to take the minimal precautions that will help you to avoid the infectious risks dogs can pose.