Zoonotic Diseases

Last week I talked about Canine Influenza virus as a relatively recent development in canine health. The concept of ‘jumping germs’ isn’t a new one — various diseases throughout history have jumped from species to species. Some of the most vicious plagues known to man have been shared by animals as well. I’d like to talk a little about a few of these diseases that still have relevance in our current daily lives.

We should define the proper term for diseases that can be shared among species. Officially, “a zoonosis is any infectious disease that can be transmitted (in some instances, by a vector) from non-human animals to humans or from humans to non-human animals… In a study of 1415 pathogens known to affect humans, 61% were zoonotic.”

The most dangerous zoonotic disease out there is Rabies, in my opinion. We don’t hear a lot about it in Michigan, but it’s still a very real and very prevalent problem. Rabies is a virus. Any mammal can get rabies, but rodents (except for woodchucks) are less likely to have or transmit the disease. The virus is transmitted in saliva, and it infects the nervous system. No matter where the bite is, the virus makes its way toward the brain. The damage done to the brain is generally fatal. A recent case was treated by putting the brain into a medical coma, which allowed the patient to survive. This report didn’t say what degree of damage was done. Rabies is generally regarded as a uniformly fatal disease. Vaccination is available and highly effective. Vaccination is required by law in Michigan. Bats and skunks are the most common carriers in Michigan.
Bat rabies

I’ve spoken and soapboxed about Leptospirosis many times already on the blog and in the hospital. It’s a prevalent disease in Michigan. Leptospira is a group of bacteria with a spiral shape. There are over 200 varieties worldwide. Four to six are the major cause of disease in Michigan. The bacteria is carried by wild animals such as raccoons, opossum, rats, and large domestic animals. It survives well in warm, wet conditions — soil and standing water both prolong lepto’s presence in the environment. If animals or people come into contact with lepto, liver and/or kidney damage can result. We have a vaccine against the 4 most common strains of lepto encountered by dogs. The blog post about lepto is here.

West Nile Virus makes a lot of headlines. This virus mainly infects birds. However, it can also infect humans, horses, dogs, cats, bats, chipmunks, skunks, squirrels, domestic rabbits, crows, robins, crocodiles and alligators. This virus is transmitted by mosquitos and birds (crows and robins). The virus can cause an infection with no signs. It can also cause a high fever, or inflammation in the brain and spinal cord. This disease can be fatal, but some people recover after a long period of time. Horses have a vaccination, but we don’t have one for dogs/cats or people.

Lyme disease is a bacterial infection passed to pets and people by a bite from a specific kind of tick. Ixodes scapularis (the Deer Tick) will attach to an animal or person and drink blood. During that attachment/bite time, the lyme bacteria migrate into the dog or person. These bites usually create a very obvious and characteristic lesion called a Target Lesion (Erythema migrans). Lyme disease is treatable, but it’s not always easy to diagnose. The best way to avoid Lyme disease is to have your dog vaccinated and to wear protective clothing or tick repellant. Dogs and cats have topical tick prevention products that are also safe and effective.

Lastly, I want to mention intestinal parasites as a zoonotic disease. Hookworm and roundworm can cause infections in people. The eggs of these intestinal worms are passed in the feces of dogs and cats. Once in the environment, these eggs can contaminate the soil or even the interior of a house. Ingesting the eggs can infect a person. Hookworm can also burrow through the skin if a person comes into contact with contaminated soil. Bare feet in the yard is a common way exposure occurs. Hookworm larvae burrow through the skin, causing a nasty inflamed lesion on the skin surface. Roundworms get lost in the body and can migrate into the internal organs or the eye. Irreversible organ damage can occur. The best way to prevent these worms is to keep your pets clear of infections. Monthly heartworm prevention stops intestinal parasite infections. Fecal checks at least twice a year help verify that pets are not carrying parasites that could infect their families.

That’s a small selection of the more common zoonotic diseases. There’s a ton more information at the links below. Read on if you’re not looking to sleep for a night or two. There’s a lot of scary stuff out there!




Filed under infectious diseases, zoonotic

2 responses to “Zoonotic Diseases

  1. Chris

    All the more reason to keep vaccines current! Will there be a dog vaccine for West Nile eventually? My horse started getting it as soon as the equine
    version was invented. It’s the only way to protect against mosquitos.

  2. Thankfully, dogs and cats seem to suffer minimal to no problems from WNV infections. It’s not something we routinely look for in small animals. Their seeming resistance makes a vaccine unnecessary, which is a blessing. I strongly believe in vaccination but adding another to the already long list is a very unattractive option.

    The CDC has more info here:


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