This week I’m going to talk about a fairly boring but very important topic — zoonotic diseases. Long name, but a pretty simple definition. A zoonotic disease is a disease that can be spread between humans and animals. The truth is that a very wide variety of diseases can be zoonotic. In fact, one of my colleagues from vet school studies and follows these trends as her entire job.
I am only going to talk about some pertinent zoonotic diseases that we need to focus on with our pets; though everything from Ebola, plague, mad cow disease and some of our flu issues are a result of zoonotic diseases. I will start with those we vaccinate against.
Thankfully rabies is still rare, though each year there seem to be more and more cases. Most of the cases of human exposure come from unvaccinated pets who were exposed to wildlife with rabies. Rabies is transmitted directly from saliva. However, it is so dangerous and fatal that if you have been exposed to any animal that tested positive or isn’t vaccinated you must undergo a series of injections. At this point, only one human in recent history who didn’t have a vaccine has survived a rabies infection.
Veterinarians must be vaccinated because of our high exposure risk (which my husband claims is why I have to deal with every bat), but the best thing for most people to do is make sure their pets are up to date on vaccines. The rabies vaccine is mandated by law in pets for this very reason. In Vermont in 2018, there have been over 20 cases of wildlife that tested positive for rabies, which is a small sample of the likely affected animals. We like to think rabies isn’t a clear and present danger, but, as the positive kitten last year taught us, it is still around and a threat.
Leptospirosis is a bacteria that is shed in urine. It typically starts with wildlife (commonly rats, raccoons and deer) but that urine then pools in groundwater which our dogs then drink. We see surges in lepto whenever the water table changes. For instance, we have had several affected dogs recently with the crazy rain. We also get a surge in the spring as snow melts and water pools, though typically fall is our most affected time.
Lepto affects the kidneys and liver most commonly. Dogs usually present not feeling well, not eating, and with changes in drinking and urination. Sometimes they will even be icteric, which means their gums and the whites of their eyes will look yellow. Lepto can be treated with antibiotics, but if the kidneys have undergone enough damage they may not return to normal function. While dogs have lepto they do shed it in their urine, and humans can contract the disease. Humans suffer chills, muscle pain and ultimately also kidney and liver damage.
Vaccines against leptospirosis are effective and some types can also prevent shedding of lepto. Cats do not commonly get lepto and we do not vaccinate them for it, but horses and dogs both get lepto far more commonly. This vaccine has gotten a bad reputation in the past, but actually causes very few reactions now. We often split it up from the Lyme vaccine, since both are vaccines against bacteria; however, this vaccine is safe and effective.
Those are the two that we can vaccinate against, now I will talk about two that we can NOT vaccinate against but are still a concern from our pets.
Toxoplasma is a parasite which is shed in cat poop. Typically toxo is not a big concern for humans unless they are pregnant or very immunosuppressed. It can affect the fetus, so all pregnant women are encouraged not to handle cat feces. If you live alone or your husband can’t/won’t empty the box, it doesn’t mean you can’t have a cat. We recommend cleaning the box wearing gloves and washing your hands after. Many cats do not shed toxo, and when they do it is sporadically. I was tested for toxo exposure and was negative- this is after handling cats my entire life, both at home and work. However, it is always best to take precautions (especially if it means your husband gets litter-box duty for 9 months!)
Roundworms are spread through fecal-oral contamination. Of course, you are thinking that you never would put poop in your mouth, and I would hope not. However, it isn’t always that easy. Roundworm eggs are very sticky. You may pet your dog’s back legs, and there are microscopic eggs stuck to the fur that transfer to your skin. Then you eat a cheeseburger and they are transferred into your mouth. More likely, your dog licks their behind (I hate to break it to you, but they all do) and then licks your face/mouth. This is the number-one and -two reasons that my dogs aren’t allowed to lick me.
The biggest concern is with smaller children, who put their hands everywhere and put their hands in their mouth. I recommend monthly deworming with a heartworm pill year-round for dogs with young children in their family. It is also important that you always have kids wash their hands after playing outside in dirt where worm eggs may be laid. Worms don’t always just live in the gastrointestinal tract of people, but can migrate to the skin, eyes and brain.
There are so many zoonoses that we had entire semesters learning about them in vet school, and I could go on for days. However, these are the main ones that I like people to be aware of.