5 Dangerous Diseases Spread by Animals and Insects


There are so many ways to contract a pathogen that there isn’t an actual solid number. You can get sick from eating raw food, drinking unsanitary water, even just swimming. It would be foolish to think you can’t catch disease and sickness from animals. The transmission of pathogens or germs, from animal to human is called zoonotic transfer. The diseases that are transmitted are called zoonoses. One instance where this is theorized to apply today is COVID-19, caused by SARS-CoV-2, which allegedly came from bats.

Here are some other dangerous diseases spread from animals to humans:

Malaria & Dengue Fever

If mosquitoes are good for anything, it’s transmitting disease. While many zoonotic diseases are transferred via a bite, mosquitoes lead the way. One parasite that infects mosquitoes, and in turn is transmitted to humans, is malaria. There were 228 million estimated cases in 2018 alone according to the Center for Disease Control (CDC). Deaths related to malaria, which were mostly children in Africa, was around 405,000 in 2018.

400 million people are infected annually with mosquito-borne dengue fever. About a quarter of those infected become sick, and 22,000 die. Back in 2002, a virus caused the largest neuroinvasive arboviral illness in the Western Hemisphere. The virus, known as the West Nile Virus (WNV), first appeared in the US just in time to party, the year of 1999. While not nearly as largely present as before, there were still 917 cases as of January 7th, 2020. Unfortunately, there is no vaccine or cure at this time.

On the bright side, many infected people don’t get sick, with 1 in 5 developing fever and other symptoms. That ratio is even lower when talking about serious illness, and fatalities. About 1 out of 150 people develop serious conditions or die. The best way to prevent WNV is long sleeved-shirts, long pants, and insect repellent, and avoiding mosquitoes the best you can. They’re more than just annoying.


Another example of animal-to-human transfer is tularemia, a bacterial zoonotic disease. Even dogs and cats can catch this one, in the same way we do. Rabbits are the leading cause of human infection in regard to tularemia. Ticks, specifically ones that have fed on an infected rabbit, are also a source of transmission to humans (ticks can also spread Lyme disease).

In places like Canada, Russia, and Europe there is another strain that is more commonly carried among rodents. The fatality rate for tularemia is much lower when transmitted by rodents, with rabbit transmission fatalities ranging from 30-60% without antibiotics. Another terrifying trait of the disease is its ability to act as a stable, highly infective aerosol. During the Cold War both the US and Soviet Russia allegedly weaponized tularemia.

However, this disease typically kills 100% of its natural hosts in the US. This reduces the likelihood of infection. That doesn’t mean it won’t happen though; there’s always a chance. Most cases are the result of cleaning a rabbit in the early stages of the infection. Tip: If you see white spots on the spleen or liver it’s best to not proceed.

How do you know if you have it? One expert says an unexplained fever when in or just coming from an area with an abundance of rabbits may be a sign. Other symptoms include:

  • Chills
  • Aches
  • Cough
  • Respiratory Pain
  • Weakness
  • Weight Loss
  • Nausea
  • Vomiting
  • Diarrhea

If the pathogen came through the skin via a tick bite or scratch that came into contact with infected blood, local lymph nodes will become tender and swollen. This occurs a few days after the fever sets in. An ulcer may even form in the area of the bite.

Inhaling the bacteria-laden debris results in the symptoms above along with:

  • Chest Pain
  • Sore Throat
  • Drowsiness
  • Profuse Sweating

Another indication is no increase in pulse as the fever increases. Typically when you have a fever the more your body temperature rises, your pulse will also increase. 10-14 days of antibiotics is the best way to combat it when infected. Perhaps the best method in the overall combat of tularemia is to protect yourself and your pets from tick bites. Special care when cleaning rabbits is good practice as well.

Black Death

When comparing global impact and the ability to bring civilization to its breaking point through a single outbreak, the 14th-century Black Death has no competition. Also known as the Bubonic Plague, this disease wrote the book on being a pandemic. With a death toll of 75 million people worldwide, about 21% of the global population was wiped out. Once infected, you only had days to live, and often they were very painful.

Caused by a bacterial disease known as Yersinia pestis, it was carried largely by rodents, even cats. The disease’s transmission to humans came from infected flea bites, commonly rat fleas. The disease however reaches its deadliest potential when being transmitted from person to person. Symptoms include; fever, chills, weakness, and swollen painful lymph nodes. Even in today’s age, if not treated properly, Bubonic Plague proves to be deadly.

Swine Flu

Within months, an influenza pandemic killed around 50 million people in 1918. Taking the title of most deaths from any illness in relation to the short-lived pandemic. One-third of the globe was infected with H1N1, and was of avian origin. The virus first identified by military personnel in the US spring of 1918 killed an estimated 675,000 Americans. One characteristic trait of this virus was that it hit the young adult population the hardest. Perhaps the older generations had an immunity built up from prior H1N1 viruses.

In the spring of 2009, another H1N1 virus infected an estimated 60.8 million cases and 12,469 deaths in the US, according to the CDC. Globally, the virus killed between 151,700 and 575,400 people. The virus appeared to have originated in pig herds, earning it the name “Swine Flu”.

Humans Are Guilty Too

Zoonotic diseases only come from animals, but humans are scientifically classified as animals, too. We can just as easily spread disease to our animal counterparts as well. Chimps at the Gombe Stream National Park in Tanzania are speculated to have contracted polio from humans. Anthrax outbreaks that may have originated in cattle herds created by humans killed gorillas and chimpanzees alike in West Africa. In 2009, a 9-year-old male chimp named Kipper died from a disease known as human metapneumovirus. The disease affects the respiratory system, and an outbreak in the Lincoln Park Zoo located in Chicago, Illinois may be the result of human exposure.

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