Zoonosis: Contagion without borders

What do you do when there is a worldwide pandemic and you have too much time on your hands? Well if you’re me, you research zoonotic diseases. A zoonosis is an infectious disease caused by bacteria, viruses, or parasites that spread from non-human animals, to humans.

Being a dog trainer by trade, I have always been acutely aware of diseases and parasites transmitted by domestic pets. However, in addition to dogs and cats, transmission can occur in any context related to: farming, ranching, hunting, butchering or consuming wild game, consuming domestic animals, researching animals or animal products.

You can catch a zoonotic disease through the air, by eating contaminated meat or produce, from close contact with an infected animal, by touching a surface touched by an infected animal or through an insect bite. So pretty much by simply living your life as we all do. In fact, the majority of all human infectious diseases, outbreaks, epidemics and pandemics alike, originated through the transmission of microorganisms from animals to humans.

Zoonotic disease transmission is very common. Pets and wild animals can transmit a number of diseases. Some examples of common and uncommon zoonotic diseases are:

Toxoplasmosis: This disease comes from a parasite found in cat feces and contaminated food. Though mild for most of us, it can cause serious issues for pregnant women and people with weakened immune systems. Cats get the parasite from eating infected rodents, birds or other small animals. It is one of the worlds most common parasites.

Rabies: This virus can be spread to humans from the saliva/bite of infected animals. Animals most likely to spread rabies include dogs, bats, coyotes, foxes, skunks, and raccoons. Rabies is present in 150 countries and all continents except for Antarctica. It is responsible for 59,000 worldwide deaths annually. Once symptoms appear, it’s nearly always fatal. A simple vaccine can prevent infection.

Hemorrhagic colitis E Coli: A type of gastroenteritis in which certain strains of the e coli bacteria infect the large intestine and produce a toxin that causes bloody diarrhea and other serious complications. The organisms that cause this disorder can come from contaminated ground beef or water or unpasteurized milk. These bacteria naturally occur in the intestines of about 1% of healthy cattle. Cooking your meat and washing your produce can prevent this disease.

Hydatid disease: A hot topic east of the mountains with the resurgence of wolves, Cystic Echinococcosis is spread by contact with animal feces, soil, water and food contaminated with tapeworm eggs. Contrary to popular belief this tapeworm is not a wolf disease and can be found in canines, sheep, cattle, goats, and pigs. It is extremely rare in the United States

An epidemic-is a rise in the number of cases of a disease beyond what is normally expected in a geographical area. These epidemics have started all over the world including China, Africa, Malaysia and the Middle East.

MERS: This disease likely came from an animal source in the Arabian Peninsula. It has been found in camels as well as humans in several countries. Some theorize that people became infected after having contact with the animals. More study is needed to figure out how camels and other animals’ figure in the transmission of this disease. Originally called a “novel coronavirus” in 2012 it has spread to 21 countries, including the US. It has sickened approximately 2500 people and killed 858 as of November 2012.

SARS: First appearing in the early 2000’s, in China the disease was eventually traced to cave-dwelling horseshoe bats in China’s Yunnan province. Many believe that the virus might have come from wild animal market, and its hosts might include civets, cats, snakes, wild boars, muntjac, rabbits, pheasants, and bats. However, no specific source for how the jump from those bats to humans has been identified. Another coronavirus, it sickened over 9000 people and killed approximately 774 before disappearing in 2004

Ebola: This virus was first discovered near the Ebola River in what is now the Democratic Republic of Congo. Another animal-born virus, scientists are not sure where it comes from, but bats or nonhuman primates are the most likely source. Bats are considered a delicacy in the region. Since its discovery in 1976, Ebola has sickened nearly 34,000 people and killed almost 14,000.

In the modern era, there have been many pandemics – a disease that has spread across many countries and affects a large number of people – all with zoonotic origins. While some of the most serious outbreaks have been traced to Chinese origins, many others have started elsewhere – including some right here in the United States.

The 1918 flu: Commonly known as the “Spanish” flu, wasn’t Spanish in origins. This pandemic started during World War I, during which time censorship was prevalent in most of Europe. News of the flu wasn’t getting out in most countries, but Spain was neutral and its King, Alfonso XII, was very ill, giving an impression that the disease was more prevalent there than other places. Speculation now is that it started in a hospital in England where pigs and poultry were brought in as a food supply (the disease jumped from birds to pigs to humans) or more likely had a North American origin from a United States military training base in Kansas, Camp Funston. An estimated 500 million people contracted this virus, killing an estimated 50 million worldwide.

HIV/AIDS: Originally known as the “Gay Cancer,” the Human Immunodeficiency Virus (HIV) causes Acquired Immunodeficiency Syndrome (AIDS). Originating in West African Chimpanzees, it mutated into HIV when humans hunted these chimpanzees for meat and came into contact with their infected blood – thus transmitting the disease. Transmission was not limited to gay men, but to anyone who came into contact with a carrier’s blood. 75 million people have been infected with the HIV virus and 32 million died by the end of 2018.

Photo by Francesco Ungaro on Unsplash

Covid-19: It will likely be a long while before researchers know for sure what started this latest pandemic, but they suggest it was a bat that transmitted the virus to another intermediate animal (possibly a pangolin) and that animal brought the virus to humans.

So, what did I learn from all this research? I learned that according to the CDC, “Scientists estimate that more than 6 out of every 10 known infectious diseases in people can be spread from animals, and 3 out of every 4 new or emerging infectious diseases in people come from animals.”


I believe this newest pandemic is not the fault of the Chinese or anyone else, it’s just what happens when we eat and coexist closely with animals.

So, what can we do to protect ourselves?

  • Wash our hands.
  • Use insect repellent or other methods to keep mosquitos, fleas, and ticks away.
  • Practice safe food handling
  • Avoid being bitten or scratched by an animal.
  • Make sure pets are vaccinated, flea and tick treated and go to the vet regularly
  • Keep areas where animals are kept clean
  • Be aware of areas where animals or insects might be when you’re out in nature, especially when you participate in activities like hunting and camping.

Be particularly aware always of at-risk individuals. These would include:

  • pregnant women
  • adults aged 60 or older
  • Young children
  • Cancer patients
  • People with weakened immune systems

Now that we are aware this can happen on such a grand scale, we can start taking steps to prevent this from happening again and keep ourselves safer from such an occurrence in the future.

At least I hope we can.

Photo by Sarah Brown on Unsplash

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