Is There A Difference Between Zoonotic, Non-Zoonotic And Reverse Zoonotic Diseases

We have all, by now, know that while 2024 was a year disease, but 2025 awaits even more. At the starting of the year only we saw a rise in the cases of bird flu, and saw the virus spread among people too. Then there was trichomoniasis in birds in the UK, and FMD in Germany, and many more. While the source of it all might be animal, not all of these are zoonotic diseases. Not all animal diseases are zoonotic diseases, some are zoonotic, some are non-zoonotic, and some are reverse zoonotic diseases. But, what are the difference?

What Are Zoonotic Diseases?

Zoonotic diseases or zoonoses are infectious diseases that can be spread between animals and humans. It originated with the domestication of animals, animal products or animal derivatives. The word also stems from the Greek word zoion, which means animal, and nosis, which means diseases.

The term was first used in 1885 by Rudolph Virchow in his Handbook of Communicable Diseases. It spreads between vertebrates and humans, which means animals with a backbone, and birds. The way their bodies work is similar enough to ours that pathogens can sometimes adjust to live in both.

While some zoonotic diseases spread only from animals to humans and do not spread from person to person. There are other diseases like Ebola, Mpox, COVID-19, and many more which come from animals, but continue to spread in humans, through humans, and cause outbreaks. Some of them also spread in humans and then mutate to infect only humans, like HIV

Many pathogens are limited to infecting a single type of host—humans, specific animals, plants, or even other microorganisms. However, zoonotic diseases are unique because they can infect both humans and other vertebrates. In some cases, these diseases originally affected only animals, but genetic mutations enabled them to "jump" to humans and cause infections.

Zoonotic illnesses are typically caused by bacteria, parasites, or viruses. However, they can also stem from other sources, such as fungal infections like ringworm or prion diseases like variant Creutzfeldt-Jakob disease (vCJD), often referred to as “mad cow disease.” Animals that carry zoonotic diseases:

• Bats
• Birds
• Cats
• Deer
• Dogs
• Livestock
• Non-human primates, monkeys, apes and chimpanzees
• Rodents

What Are Non-Zoonotic Diseases?

Not all animal diseases are zoonotic. Zoonoses are infectious diseases that can transfer between animals and humans such as rabies, anthrax, influenza, Nipah, COVID-19, brucellosis, and tuberculosis. However, not all animal diseases are zoonotic. Many diseases affect livestock without posing a risk to human health. These non-zoonotic diseases are species-specific and cannot infect humans. Examples include Foot & Mouth Disease (FDM), PPR, Lumpy Skin Disease, Classical Swine Fever, and trichomoniasis in birds and animals.

What Are Reverse Zoonotic Diseases?

It is the case where a disease transmits from humans to animals. This also poses threats to animals health as well as public health, due to the potential for animal disease reservoirs to form.

In 2020, several mink farms in the Netherlands experienced a severe respiratory disease outbreaks, upon investigation, it was revealed that minks had been infected with SARS-CoV-2, the same virus responsible for COVID-19. The minks came in contact with infected farmworkers.

There have been cases when domesticated dogs, cats and ferrets have developed flu-like symptoms caused by influenza A virus, passed on by their owners. Human-derived pathogens also pose significant risks to endangered wildlife. For example, in Tanzania, an outbreak of human metapneumovirus resulted in fatalities among a population of wild chimpanzees. The virus was believed to have been transmitted by researchers and visitors to the national park where the chimpanzees lived, highlighting the potential consequences of human-wildlife interactions.