What Does Zoonoses Mean?
Some animals, even those that look perfectly healthy, can carry harmful organisms that can make people sick. Those organisms that originate in animals can cause diseases in humans. (Sometimes this process works the other way, and organisms from humans can cause diseases in animals). Those diseases are called zoonotic diseases, or zoonoses. Zoonoses are common in the United States and around the world. In fact, as many as 60% of all communicable diseases and 75% of emerging infectious diseases of people originated with animals. Zoonoses can be caused by bacteria, fungi, mycobacteria, parasites, viruses, and prions.
How are Zoonotic Disease Agents Transmitted to Humans?
Direct contact: Contact with an animal’s body fluids, such as saliva, blood, urine, mucus, or feces, that can occur when petting or touching animals or being bitten or scratched.
Foodborne: Eating or drinking something unsafe (such as unpasteurized milk, undercooked meat or eggs, or raw fruits and vegetables) that are contaminated with feces from an infected animal.
Indirect contact: Contact with items in areas where animals live and roam or with objects or surfaces contaminated with germs. Examples include aquarium tank water; pet living areas, food bowls, and water dishes; chicken coops; plants, and soil.
Inhalation: Breathing in airborne organisms or spores.
Vectorborne: Being bitten by an infected tick or an insect (such as a mosquito or flea).
Examples of Zoonoses
Myriad zoonoses are known to exist. Here a few examples.
• Rabies, which you can get from the bite of a rabid infected animal, often a raccoon, skunk, bat, or fox.
• Anthrax, which you can get from contact with an infected animal or animal products (e.g., hides); sources include domestic and wild animals such as cattle, sheep, goats, antelope, and deer.
• Dengue, malaria, Zika virus infection, and Lyme disease, which you can get from the bite of an infected mosquito in areas where those diseases are common.
• Salmonella infection, which you can get after handling an infected baby chick, chicken, duck, turtle, or snake, or by eating contaminated food.
• Escherichia coli infection, which you can catch by touching surfaces in areas such as petting zoos or dairy farms where some of the animals may be infected, or by eating contaminated food.
Why Are Zoonoses a Public Health Concern?
Zoonoses are a threat to public health for a number of reasons.
• The number and types of zoonotic diseases are increasing as people, animals, and vectors can travel the globe in less time than it takes for disease symptoms to develop after exposure (incubation period).
• Human manipulation of the environment (e.g., climate change) is helping some zoonotic disease vectors thrive.
• Overuse of antibiotics has made some of these diseases harder to treat (antibiotic resistance).
• Some organisms that cause zoonoses could be used for bioterrorism.
• Vaccines are not available to protect humans against many zoonoses.
• Treatments may not exist or be readily available for people infected with some zoonoses.
• Some zoonoses may take a different, or more deadly, form in people than in animals.
EID Articles about Zoonoses
Learn more about high-consequence pathogens from these articles from the February issue of Emerging Infectious Diseases. For a quick overview, read the abstracts for the articles. Use the journal’s Advanced Article Search to find more articles.
• Scrub Typhus Outbreak in Chonburi Province, Central Thailand, 2013 describes an outbreak and a program for assessing potential health risks to soldiers in high-risk areas.
• Fly Reservoir Associated with Wohlfahrtiimonas Bacteremia in a Human describes how green bottle fly larvae can introduce these bacteria into human tissue.
• Cysticercosis in Shandong Province, Eastern China describes increasing risk for this human infection caused by unintentional ingestion of a tapeworm in pork.
• Macacine Herpesvirus 1 Antibody Prevalence and DNA Shedding among Invasive Rhesus Macaques, Silver Springs State Park, Florida, USA describes how monkeys in this popular state park could put humans at risk for exposure to this potentially fatal virus.
• Lethal Respiratory Disease Associated with Human Rhinovirus C in Wild Chimpanzees, Uganda, 2013 reports transmission of the virus from humans to the chimpanzees (reverse zoonosis).
Sources and Additional Information
Centers for Disease Control and Prevention. Zoonotic Diseases.
Centers for Disease Control and Prevention. What Zoonotic Diseases Are Dangerous.
Centers for Disease Control and Prevention. National Center for Emerging and Zoonotic Infectious Diseases. Our Work, Our Stories 2011–2012. Investigating how diseases from animals are spread to people.
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