By Barry C. Fox, M.D., University of Wisconsin
Zoonoses are diseases that get naturally transmitted from animals to humans. Infections from animals to humans can spread at zoos as well as in the wild outdoors. The pets at home can also be carriers of some unusual diseases. What are these diseases? Can these be treated?
Cat-scratch Disease
In the U.S., there are over 74 million cats, so it’s important to consider infectious disease risks. Cat-scratch disease is a bacterial disease by a germ called Bartonella henselae. Most people with cat-scratch illness have been bitten or scratched by a cat.
They usually develop a mild infection near the injury site. Lymph nodes become swollen, and fever and flu like symptoms can occur for several days. Surprisingly, up to 40 percent of cats asymptomatically carry this germ, especially kittens.
You would expect that once diagnosed, treatment with antibiotics would be successful. However, antibiotics have a limited role in modifying this illness, although fortunately the outcomes are rarely serious.
This is a transcript from the video series An Introduction to Infectious Diseases. Watch it now, Wondrium.
Toxoplasmosis
Toxoplasmosis is another zoonoses transmitted by cats. Cats can become infected after eating infected tissue of rodents, or less commonly cattle. Infectious cyst forms are shed by cats, and the humans become infected through accidental contact with feline fecal material.
Based on blood sample testing, only 9 percent of the U.S. population has been exposed to toxoplasmosis; but in other areas of the world, the rate is as high as 50 percent.
Infections in Humans
Surprisingly, most human infections, like cats, are actually asymptomatic. Other times, generalized whole body lymph node enlargement with flu-like symptoms can occur.
In pregnancy, if a mother becomes acutely infected, the parasite can be transmitted across the mother’s placenta to the fetus. Newborns can be born with blindness or mental disability. Thus, pregnant women should not be scooping litter boxes, should not get a new kitten while pregnant, and should not really be playing with stray cats.
Learn more about the human immune system.
Salmonella Bacteria: Intestinal Illness
Reptiles and amphibians like turtles, lizards, and frogs can carry harmful salmonella bacteria that can cause intestinal illness.
In 2013, there was an eight state outbreak of human salmonella linked to small turtles. As you might expect, most victims were under age five and owned a benign-looking little pet turtle.
The infections can not only come from handling turtles, but also from the water or containers where they are living. Using gloves for cleaning the environments of pets is essential, as well as hand-washing after handling them.
These pets are probably not appropriate for children under five who still put their hands frequently in their mouths. Moreover, birds, baby chicks, and ducks are also sources of infectious diseases, including salmonella.
Outbreaks of Salmonella
The Centers for Disease Control, or CDC, has issued an alert that the surge in small urban farms is providing the perfect environment for an outbreak of salmonella.
As people bring the chickens into their home, they are letting them walk on tables and countertops, and contaminating the home environment. This scenario is not necessarily mainstream America, but it’s increasingly common.
In 2012, the CDC monitored eight outbreaks of Salmonella linked to backyard poultry flocks.
Thus, choose your pets wisely, and consider the age, environment, and health of all the people who might be in contact with the pets.
The best thing that you can do is to educate yourselves and children about potential health hazards of owning pets, and implement strict hand-washing practices.
Learn more about the four different types of vaccines.
Infections at Petting Zoos
Other diseases may be transmitted from petting zoos, regular zoos, or farms. Petting zoo animals can shed a variety of germs without the animals appearing ill.
Most concerning are young children that may touch an animal, and then put their hands in their mouths, or on food.
Often pacifiers, sippy cups, and ice cream cones are in the hands or mouths of the children at the petting zoo. There have been numerous outbreaks of disease at petting zoos, including bacterial and parasitic germs that usually cause an intestinal illness.
Infections from Pet Rodents
Another potential cause of alarm for cute and furry pets relates to pet stores and rodents.
Pet rodents, such as hamsters and guinea pigs, can asymptomatically carry a virus called Lymphocytic choriomeningitis virus. This can cause inflammation around the brain and spinal cord. But fortunately, human infections from pet rodents are rare.
Hantavirus: Infection in Great Outdoors
Hantavirus is a rare, but serious disease that humans can contract through contact with infected urine, saliva, or droppings from rodents. Dried urine in dust particles carries viruses, and sweeping the dust or pitching a tent in the infected area can cause inhalation of the virus. This can lead to a life-threatening bleeding disorder of the lungs, with no available treatment.
Since this virus was first identified in the U.S. in 1993, there have been at least 60 cases in California residents and over 600 cases nationally.
Approximately 12 percent of deer mice in parts of the Southwest are thought to be asymptomatic carriers of hantavirus. The deer mouse is the primary reservoir responsible for most human cases, including those in Yosemite National Park in 2012. There were 10 confirmed cases of the Hantavirus in Yosemite, and 3 of them were fatal.
Of course, whenever you enter wilderness area, there are always some risks. You can protect yourself, however, by being mindful of where you pitch your tent, not sleeping on the ground, keeping food in containers, and being alert for evidence of mice in the area.
Common Questions about Transfer of Infections from Animals to Humans
Cat-scratch disease and Toxoplasmosis are two cat-transmittable diseases.
Reptiles and amphibians like turtles, lizards, and frogs can carry harmful salmonella bacteria that can cause intestinal illness in humans.
Hantavirus is a rare, but serious disease that humans can contract through contact with infected urine, saliva, or droppings from rodents.
