When you hear the prefix “zoo,” it probably takes you back to childhood trips, eagerly watching some of your favorite four-legged creatures. You might not be familiar with the term zoonotic diseases, but you’ve likely guessed it has something to do with animals — and you’d be right!
What Are Zoonotic Diseases?
Zoonotic diseases are illnesses caused by viruses, bacteria, parasites or fungi that spread between animals and humans. A well-known example is rabies, which can be transmitted to humans through animals like raccoons or bats.
But what about diseases like West Nile Virus? It begins in wild birds, but since birds aren’t flying out of the sky to bite us, how do humans get infected? This is where insect vectors come in.
The Role of Insect Vectors in Disease Transmission
Insect vectors, like mosquitoes, ticks, flies and fleas, play a crucial role in transmitting numerous zoonotic diseases to millions of people worldwide. While they don’t cause the diseases themselves, they carry and transfer the pathogens from infected animals to new hosts.
The process starts when an insect bites an infected animal, picking up the pathogen. When the insect bites another host, it transfers the pathogen, potentially infecting the new animal or human.
One common example is West Nile Virus. Without insect vectors, the virus would likely remain confined to wild bird populations. However, mosquitoes feed on a variety of animals and can spread the virus to humans, who otherwise wouldn’t be exposed.
How Insect Vectors Transmit Zoonotic Diseases
Insects transmit pathogens through a variety of methods, including:
- Bites
When insects bite their hosts, they often introduce pathogens directly into the bloodstream. This is the most common type of transmission.
- Regurgitation
Occasionally, insects like tsetse flies regurgitate partially digested food that transfers disease-causing pathogens onto the host. If this material comes into contact with the insect’s bite or an open wound, the host may become infected.
- Defecation
If an insect defecates on or near a human or animal’s wound, it may also introduce pathogens into the host’s bloodstream, potentially leading to infection.
Types of Pathogens Transmitted by Insect Vectors
Different types of pathogens cause different types of diseases. Here are some categories of pathogens that insect vectors can transmit from host to host, along with some common zoonotic diseases associated with each.
Viral Pathogens
A virus is the smallest and simplest of all infectious agents. Composed of genetic material encased in protein, it must enter a living being to replicate. As the virus begins to take over our cells, it starts to rapidly reproduce, often outpacing the immune system’s ability to respond. As the virus multiplies, it begins to harm the body, causing symptoms specific to the type of virus the host has contracted.
Common viruses that are often transmitted by different types of mosquitoes include:
- Dengue virus
- West Nile virus
- Zika virus
Bacterial Pathogens
There are healthy bacteria, like the microbiome in your gut that help with digestion. Then, there are the harmful kinds that cause conditions like food poisoning and urinary tract infections. Larger and more complex than viruses, bacteria infiltrate their hosts by multiplying quickly, damaging nearby tissue and occasionally creating toxins that block normal cell function.
Bacterial zoonotic diseases that insect vectors spread from host to host include:
- Lyme disease
Caused by black-legged tick bites, the CDC estimates that 476,000 people are diagnosed and treated for Lyme disease each year in the United States.
- Typhus
This rare bacterial disease is spread by lice, fleas and chiggers. Although it is not commonly seen today, outbreaks can occur in areas with overcrowding, where it can be transmitted easily from person to person.
- Plague
The bubonic plague may evoke images of the fearsome bird-faced doctor masks worn during the 17th century, but it still exists today, albeit on a smaller scale. Surprisingly, the plague is primarily spread by fleas (not birds) that have bitten infected rodents and other small animals.
How to Prevent the Spread of Zoonotic Diseases
While it’s challenging to eradicate vector-spread zoonotic diseases, we can work to slow their spread by implementing the following prevention strategies:
- Reducing insect habitats
Remove any standing water around your home, such as water in buckets, birdbaths or plant saucers. This can help eliminate potential breeding grounds for mosquitoes.
- Using insecticides and repellents
Apply personal insect repellents when going for walks, especially during early mornings or around dusk, to protect against mosquito bites. Additionally, use insecticides around your home to manage insect vector populations.
- Vaccinating pets
Ensure that your pets, particularly those that spend time outdoors, are up to date on their rabies vaccinations and any other vaccines recommended for your area.
Play Your Part in Slowing the Spread of Zoonotic Diseases
At the University of Florida, we offer four unique specializations that allow you to earn an entomology master’s degree or graduate certificate in the field of your choice:
- Medical Entomology
- Landscape Pest Management
- Urban Pest Management
- Beekeeping
If you’re interested in playing a larger role in slowing the spread of zoonotic diseases, a career in entomology might be right for you. Our online specialization in Medical Entomology focuses on topics like mosquito biology and advanced medical and veterinary entomology while allowing you to choose from a diverse array of electives that can be tailored to your specific interests and future ambitions.
To learn more about our entirely online graduate programs, explore our program pages or contact our Student Outreach and Engagement specialist with questions. We look forward to helping you choose the program that’s right for you!
Sources:
https://onlineentomology.ifas.ufl.edu/vector-borne-disease-preparedness-in-the-united-states/
https://www.sciencedirect.com/topics/medicine-and-dentistry/insect-vector
https://www.cedars-sinai.org/blog/germs-viruses-bacteria-fungi.html
https://www.cdc.gov/lyme/data-research/facts-stats/index.html#
https://www.nationalgeographic.com/history/article/plague-doctors-beaked-masks-coronavirus
