By Barry C. Fox, M.D., University of Wisconsin
Zoonoses are diseases that get transferred from both exotic and pet animals to humans. While most of the infectious diseases originate from wildlife, pets at home can also transfer infections. Let us find out about these infectious diseases— their causes, treatments, and preventive measures.
Zoonosis: Monkeypox
Zoonosis is defined as any disease or infection that is naturally transmittable from animals with a backbone to humans.
In 2003, there was a multi-state outbreak of an unusual and rare illness known as monkeypox in six Midwestern states, with 71 cases reported. Monkeypox is a virus related to the smallpox virus, but normally is only seen in Africa.
An extensive epidemiological investigation eventually revealed that it was brought to the United States in a shipment of 800 prairie dogs from Africa. During boat shipment, the prairie dogs were contaminated with the monkeypox virus by being in contact with giant Gambian rats from Ghana which harbored the virus but were not ill. The prairie dogs had asymptomatic viral infection, but in turn, passed the monkeypox virus on to vulnerable humans.
Since the monkeypox skin lesions resemble smallpox, this created a chaotic and scary scenario for the health departments. While no one died from the monkeypox outbreak, a ban was put in force immediately which prohibits the importation of African rodents.
This is a transcript from the video series An Introduction to Infectious Diseases. Watch it now, Wondrium.
Exotic Animals and Infectious Diseases
Importation of exotic animals and wild animals harvested for the commercial pet trade—many of them illegal—have been associated with a wide array of outbreaks of infectious diseases in humans.
Human health around the world today includes more and more exotic disease names like MERS and SARS, as well as flu viruses with names like bird and swine flu. Diseases are jumping from animals to humans at a faster pace than before.
Why are new diseases so prevalent and how are these exotic diseases being transmitted to us from animals?
The phenomenon has been around for centuries, and over 200 diseases have been identified as zoonotic. In fact, up to 70 percent of all infectious diseases originate from wildlife.
It is important to know that infectious diseases are not always spread just by exotic animals, but at times by our pets at home and other common animals.
Learn more about the anatomy of a bacterium cell.
Pet Animals and Infectious Diseases
When we talk about companion animals, we think mostly of dogs and cats, but we should also include other caged animals in the home. Dogs and cats can also become the vectors of disease if they have contact with wild animals, potentially spreading germs to humans.
For example, one day while playing with our two Samoyed dogs in the yard, we noticed one had disappeared from sight. We looked anxiously around and within a few minutes, the dog happily trotted back into the yard with a very large woodchuck in its mouth.
Fortunately, he obeyed the drop it command and the woodchuck scurried back to the woods leaving both of them unharmed. This happened again a few days later with our other dog, who proudly carried over a baby opossum that was infringing on its territory.
Which diseases do these two scenarios have in common for transmitting illness from wildlife to humans? Well, we might be at risk of contracting the rabies virus from the woodchuck or the opossum, or another zoonotic bacterial infection known as tularemia from handling a woodchuck.
Rabies: Cause and Spread of Virus
The rabies virus has a bullet-shaped configuration. After a bite, or even a scratch by an infected animal, the virus can enter the body through the skin. If the wound goes unnoticed, which might occur with scratches, the virus next establishes itself in the local nerves where the injury occurred.
Over the course of the next weeks or months, the virus is able to travel insidiously from the skin nerves to deeper nerves in the body.
Once local neurological symptoms develop, such as burning pain at the site and tingling of the nerves, the disease is almost uniformly fatal. As the virus spreads deeper into the body to the central nervous system, fatal inflammation of the brain and spinal cord develops. There are no reliable treatments available.
Rabies Vaccination
An unvaccinated dog or cat bitten by a woodchuck or opossum could contract rabies, and then could bite, scratch, or even lick a cut on my arm, making me vulnerable to rabies as well.
Fortunately, the strict adherence to rabies vaccination in the United States has made transmission of rabies from domestic animals extremely rare.
Nevertheless, today in several third world countries that you might visit, rabies may be transmitted from domestic animals since they are often unvaccinated. In the U.S., more than 90 percent of rabies comes from wildlife, but especially bats. Other animals that harbor rabies include raccoons, skunks, and foxes.
Around 40,000 people in the U.S. every year get rabies shots after exposure to wild animals. The estimated cost of receiving these vaccinations is more than $300 million dollars. So, you should avoid the temptation to feed or handle wild animals.
Learn more about the life cycle of a virus.
Treatment of Rabies
If you are bitten or scratched by a susceptible animal, wash the wound with soap and water and get healthcare attention quickly for post-exposure prevention. Immediate disinfection of the wound and rabies immune-globulin injected into the wound confers passive immunity—and they’re crucial measures for protection. There is also a six-week rabies vaccination program that you must follow.
Also try to have the domestic or wild animal captured by appropriately trained personnel. Then notify the county health department, so the animal can either be sacrificed and tested for rabies or observed for rabies symptoms.
Animals that have rabies usually exhibit strange, bizarre behavior patterns, especially a fear of water. If the animal is quarantined for 10 days without symptoms, additional rabies vaccinations can be avoided.
Rabies is a preventable disease with the use of vaccines. For wild animals, one of the means of vaccination is by using oral rabies baits, with a marshmallow-flavor. The Wildlife Service program targets raccoons, coyotes, and foxes, and is being used throughout the United States, Canada, and Europe.
Common Questions about Zoonosis and the Spread of Infections
Zoonosis is defined as any disease or infection that is naturally transmittable from animals with a backbone to humans.
Rabies may be transmitted from domestic animals if they are unvaccinated. In the U.S., more than 90 percent of rabies comes from wildlife, but especially bats. Other animals that harbor rabies include raccoons, skunks, and foxes.
If you are bitten or scratched by a susceptible animal, wash the wound with soap and water and get healthcare attention quickly for post-exposure prevention. Immediate disinfection of the wound and rabies immune-globulin injected into the wound confers passive immunity—and they’re crucial measures for protection. There is also a six-week rabies vaccination program that you must follow.
