Introduction to Zoonotic Diseases

Bat with shapes

※ What’s a zoonotic disease?

A zoonotic infection is a disease caused by a microorganism, such as a virus, bacterium, or parasitic worm, that is transmitted to humans from other animals like bats, cats, or rats. Together, we call these infectious diseases “zoonoses.”

※ Okay, what are viruses, bacteria, parasites, etc.?

Viruses, bacteria, helminths (parasitic worms), protozoa, fungi, and prions (misfolded proteins) are the main categories of microorganisms that elicit disease. Microorganisms are also called “microbes.” Microbes that cause disease are often referred to as “pathogens” or “infectious agents.”

※ How do they cause disease in people?

A zoonotic infection is a disease caused by a microorganism, such as a virus, bacterium, or parasitic worm, that is transmitted to humans from other animals like bats, cats, or rats. Together, we call these infectious diseases “zoonoses.”

L

Bats are reservoirs for zoonotic diseases, including Ebola, Nipah, and coronaviruses.

L

Rodents are reservoirs for zoonotic diseases, such as Lyme, plague, and hantavirus. They can also carry disease-spreading ticks and fleas.

L

Pigs are reservoirs for zoonotic diseases, such as swine flu, taeniasis, and Nipah.

L

Mosquitoes are vectors and reservoirs for vector-borne diseases, including West Nile, malaria, and Zika.

L

Monkeys are reservoirs for zoonotic and vector-borne diseases, including malaria, Zika fever, and monkeypox.

L

Ticks are vectors and reservoirs for vector-borne diseases, including Lyme, anaplasmosis, and spotted fevers.

※ What’s a spillover event?

A zoonotic infection is a disease caused by a microorganism, such as a virus, bacterium, or parasitic worm, that is transmitted to humans from other animals like bats, cats, or rats. Together, we call these infectious diseases “zoonoses.”

※ What drives spillovers?

A zoonotic infection is a disease caused by a microorganism, such as a virus, bacterium, or parasitic worm, that is transmitted to humans from other animals like bats, cats, or rats. Together, we call these infectious diseases “zoonoses.”

Climate change

Deforestation, biodiversity loss, and environmental degradation.

※ Where do we go from here?

Something something

The CDC’s 8 Most Concerning Zoonotic Diseases in the USA

Zooonotic influenza

Pathogen(s)

Influenza A viruses (e.g., H1N1 or H5N1)

Involved Animals

Pigs, wild birds, or poultry (e.g., chickens)

Transmission

Close contact with infected animals or subsequently infected people

Signs & Symptoms

Fever, Sore throat, cough, runny or stuffy nose, aches, or fatigue

Salmonellosis

Pathogen(s)

Salmonella bacteria

Involved Animals

Livestock (e.g., cattle or poultry)

Transmission

Consumption of undercooked or unwashed eggs, meat, vegetables, or other foods contaminated with feces

Signs & Symptoms

Diarrhea, stomach cramps, fever, or nausea

West Nile fever

Pathogen(s)

West Nile virus

Involved Animals

Wild birds or horses

Transmission

Mosquito bite

Signs & Symptoms

Febrile form: Fever with aches, joint pain, or vomiting
Severe form: High fever, brain inflammation, meningitis, disorientation, weakness, or tremors

Plague

Pathogen(s)

Yersinia pestis bacterium

Involved Animals

Wild rodents or cats

Transmission

Flea bite

Signs & Symptoms

Bubonic form: Fever, headache, chills, weakness, and swollen lymph nodes
Septicemic Form: Fever, weakness, chills abdominal pain, shock, bleeding, or skin necrosis
Pneumonic plague: Lung infection, fever, headache, weakness, shortness of breath, chest pain, cough, or bloody mucus

Emerging coronaviruses

Pathogen(s)

Coronaviruses (e.g., SARS-CoV-2 or MERS-CoV)

Involved Animals

Bats, camels, or civets

Transmission

Close contact with infected animals or subsequently infected people

Signs & Symptoms

COVID-19: Fever, cough, shortness of breath, sore throat, loss of taste or smell, aches, or fatigue

Rabies

Pathogen(s)

Rabies lyssavirus

Involved Animals

Dogs, cats, bats, cattle, horses, raccoons, or skunks

Transmission

Animal bites or scratches

Signs & Symptoms

Flu-like symptoms, brain inflammation, meningitis, paralysis, confusion, paranoia, delirium, coma, or death

Brucellosis

Pathogen(s)

Brucella bacteria

Involved Animals

Cattle, bison, elk, or wild swine

Transmission

Consumption of infected milk products or direct contact with infected animals

Signs & Symptoms

Fever, chills, sweats, weakness, loss of appetite, fatigue, aches, or arthritis

Lyme disease

Pathogen(s)

Borrelia burgdorferi bacterium

Involved Animals

Mice, deer, birds, lizards, or dogs

Transmission

Tick bite

Signs & Symptoms

Early: Fever, chills, fatigue, aches, or rash
Untreated: Neck stiffness, headaches, facial palsy, joint swelling or pain, central nervous system inflammation, or arthritis

Sources

Bauerfeind, R., Von Graevenitz, A., Kimmig, P., Schiefer, H. G., Schwarz, T., Slenczka, W., & Zahner, H. (Eds.). (2016). Zoonoses: Infectious Diseases Transmissible Between Animals and Humans. ASM Press. (Original work published 2013)

Centers for Disease Control and Prevention. (2021). Symptoms of COVID-19. U.S. Department of Health and Human Services. https://www.cdc.gov/coronavirus/2019-ncov/symptoms-testing/symptoms.html

Salyer, S. J., Silver, R., Simone, K., & Barton Behravesh, C. (2017). Prioritizing Zoonoses for Global Health Capacity Building—Themes from One Health Zoonotic Disease Workshops in 7 Countries, 2014–2016. Emerging Infectious Diseases, 23(13). https://doi.org/10.3201/eid2313.170418

U.S. Department of Health and Human Services, U.S. Department of Agriculture, & U.S. Department of the Interior. (2019). Prioritizing Zoonotic Diseases for Multisectoral, One Health Collaboration in the United States: Workshop Summary. https://www.cdc.gov/onehealth/pdfs/us-ohzdp-report-508.pdf

Skip to content