Three zoonotic diseases you should be aware of

27/11/2023

In our last article, we discussed the concept and usefulness of the One Health concept. We also introduced the idea of zoonoses, which are pathogens that can be transmitted between animals and humans. These pathogens can be parasitic, bacterial, or viral in origin and can be transmitted via inhalation, ingestion, or direct exposure to the causative agent. Often, we think of diseases of animal origin to be contracted when we have directly encountered an infected animal—but this is not always the case. Humans can be exposed to these diseases through intermediate vectors (objects or organisms that carry and transmit the pathogen), contaminated food or water, or contact with infectious animal material. Let’s have a look at a few zoonoses and their routes of infection.

COVID-19 (also called SARS-COV-2)

COVID-19 may still be fresh in your memory, and for good reason! SARS-CoV-2, a coronavirus, is one of many coronavirus strains present in a plethora of animal species. The strain causing the recent human outbreak was from , and humans became an infectious source not only for other humans, but for animals such as cats and minks. While spread from diseased animals to humans is rare, it is still possible. This virus can result in respiratory and cardiac pathologies in both humans and animals and can progress to death in humans, but there is supportive treatment available for COVID-19 which can aid infected individuals.

Lyme disease (Borrelia burgdorferi)

Lyme disease, Borrelia burgdorferi, is another important zoonotic pathogen of concern. The disease is named after the place in the USA where it was first identified. This bacterium is passed to humans through the bite of an infected tick, which itself has become so through contact with infected wildlife (rodents and birds). Prevention of this bacterial infection relies heavily on the timely and effective removal of ticks, as the ticks need to be burrowed into the skin for at least 24 hours to transmit the bacteria. Lyme disease can also be transmitted to companion animals. The condition is characterised in both humans and animals by skin rashes, joint pain, and general malaise on a short or long-term basis. In many cases Lyme disease can be treated with antibiotics.

Trichinella spiralis (sometimes called Pork Worm)

Trichinella spiralis is a parasite that can be found in pigs but can be transmitted to humans through the consumption of undercooked and/or untested pork products. Other species of animals consumed by humans may be infected with this parasite as well—bears and horses included. While there are testing systems in place to minimise human infection and to be able to participate in international food trade, this parasite is still a concern to human health. Trichinella spiralis infection can cause the illness in humans known as trichinosis and can cause general malaise, muscle pain, and facial swelling. This parasite can be treated in humans with antiparasitic agents.

These are just three examples of zoonotic pathogens that demonstrate the potential of spread from inhalation, haematological (blood) exposure, or consumption of infected material. There are plenty more zoonotic pathogens in existence—Escherichia coli infection, campylobacteriosis, salmonellosis (these first three cause gastrointestinal illnesses in humans), leishmaniasis, rabies, toxoplasmosis, and more—with ever more emerging. Having a knowledge of transmission routes is the first step to prevention of both known and unknown zoonotic disease. We will come back to describe some other zoonoses in the future.

In our next article we will be discussing antimicrobial resistance and its role in One Health. Stay tuned.

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