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Zoonotic Diseases: Disease Transmitted from Animals to Humans

A zoonosis (zoonotic disease or zoonoses -plural) is caused by infections that are shared between animals and people.

Every year, tens of thousands of Americans and people all over the world will get sick from diseases spread between animals and people. These are known as zoonotic diseases, which mean infectious diseases that are spread between animals and people.

These diseases can cause sickness or death in people, and major modern diseases such as Ebola virus disease and salmonellosis are zoonoses.

HIV was a zoonotic disease transmitted to humans in the early part of the 20th century, and strains of influenza that infect humans are human diseases, although many strains of swine and bird flu are zoonoses.

These viruses occasionally recombine with human strains of the flu and can cause pandemics such as the 1918 Spanish flu or the more recent 2009 swine flu.

HIV has now evolved to a separate human-only disease, but most Taenia Solium infection is one of the neglected tropical diseases with public health and veterinary concern in endemic regions.

Zoonoses can be caused by a range of disease pathogens such as viruses, bacteria, fungi etc…

Of the 1,415 pathogens known to infect humans, 61% are zoonotic, and most human diseases originated in animals. However, only diseases that routinely involve animal to human transmissions, like rabies, are considered direct zoonosis.

Animals provide many benefits to people, and many people interact with animals in their daily lives, both at home and away from home. Pets offer companionship and entertainment, and animals are an important food source and provide meat, dairy, and eggs.

However, some animals can appear healthy even when they are carrying germs that can make people sick.

Zoonotic diseases are very common, both in the United States and around the world, and scientists estimate that more than 6 out of every 10 known infectious diseases in people are spread from animals, and 3 out of every 4 new or emerging infectious diseases in people are spread from animals.

How Do Germs Spread Between Animals And People?

  • Direct contact: Coming into contact with the saliva, blood, urine, feces, or other body fluids of an infected animal. E.g petting or touching animals, and bites or scratches.
  • Indirect contact: Coming into contact with areas where animals live and roam, or objects or surfaces that have been contaminated with germs from animals. E.g aquarium tank water, pet habitats, chicken coops, plants, and soil, as well as pet food and water dishes.
  • Vector-borne: Being bitten by animals that carry pathogens in them. E.g being bitten by a tick, or an insect like a mosquito or a flea.
  • Foodborne: Eating contaminated food. E.g eating or drinking something unsafe such as unpasteurized milk, undercooked meat or eggs, or raw fruits and vegetables that are contaminated by an infected animal.

Illnesses Associated with Animal Contact

Lists of diseases

Disease Animals involved Mode of transmission
African sleeping sickness range of wild animals and domestic livestock transmitted by the bite of the tsetse fly
Angiostrongyliasis rats, cotton rats consuming raw and/or undercooked snails, slugs, other mollusks, crustaceans, monitor lizards, frogs and unwashed vegetables contaminated with larvae
Anisakiasis whales, dolphins, seals, sea lions, other marine animals eating raw and/or undercooked fish and squid contaminated with eggs
Anthrax commonly – grazing herbivores such as cattle, sheep, goats, camels, horses, and pigs by ingestion, inhalation or skin contact of spores
Baylisascariasis raccoons, badgers, skunks, bears, pandas, fishers, martens, kinkajous, marmots ingestion of eggs in feces
Bird flu wild birds, domesticated birds such as chickens close contact
Bovine spongiform encephalopathy cattle eating infected meat
Brucellosis cattle, goats infected milk or meat
Bubonic plague, Pneumonic plague, Septicemic plague rabbits, hares, rodents, ferrets, goats, sheep, camels flea bite
Cat-scratch disease cats bites or scratches from infected cats
Chagas disease armadillos, Triatominae (kissing bug) bite
Clamydiosis / Enzootic abortion domestic livestock, particularly sheep close contact with postpartum ewes
Variant Creutzfeldt–Jakob disease cattle eating meat from animals with bovine spongiform encephalopathy (BSE)
Cryptococcosis commonly – birds like pigeons inhaling fungi
Cryptosporidiosis cattle, dogs, cats, mice, pigs, horses, deer, sheep, goats, rabbits, leopard geckos, birds ingesting cysts from water contaminated with feces
Cysticercosis and taeniasis commonly – pigs and cattle consuming water, soil or food contaminated with the tapeworm eggs (cysticercosis) or raw or undercooked pork contaminated with the cysticerci(taeniasis)
Dirofilariasis dogs, wolves, coyotes, foxes, jackals, cats, monkeys, raccoons, bears, muskrats, rabbits, leopards, seals, sea lions, beavers, ferrets, reptiles mosquito bite
Eastern equine encephalitis, Venezuelan equine encephalitis, and Western equine encephalitis horses, donkeys, zebras, birds mosquito bite
Ebola virus disease (a haemorrhagic fever) chimpanzees, gorillas, fruit bats, monkeys, shrews, forest antelope and porcupines through body fluids, organs and ticks
Other haemorrhagic fevers (Marburg viral haemorrhagic fever, Lassa fever, Crimean-Congo haemorrhagic fever, Rift Valley fever) varies (sometimes unknown) – commonly camels, rabbits, hares, hedgehogs, cattle, sheep, goats, horses and swine infection usually occurs through direct contact with infected animals
Echinococcosis commonly – dogs, foxes, jackals, wolves, coyotes, sheep, pigs, rodents ingestion of infective eggs from contaminated food or water with feces of an infected, definitive host and/or fur
Food borne illnesses (commonly diarrheal diseases) animals domesticated for food production (cattle, poultry) raw and/or undercooked food made from animals and unwashed vegetables contaminated with feces
Gnathostomiasis dogs, minks, opossums, cats, lions, tigers, leopards, raccoons, poultry, other birds, frogs raw and/or undercooked fish or meat
Giardiasis beavers, other rodents, raccoons, deer, cattle, goats, sheep, dogs, cats ingesting spores and cysts in food and water contaminated with feces
Glanders horses, donkeys direct contact
Hantavirus deer mice, cotton rats and other rodents exposure to feces, urine, saliva or bodily fluids
Histoplasmosis birds, bats inhaling fungi in guano
Influenza horses, pigs, domestic and wild birds, wild aquatic mammals such as seals and whales, minks and farmed carnivores droplets transmitted through air
Japanese encephalitis pigs, water birds mosquito bite
Leprosy armadillos, monkeys, rabbits, mice Direct contact, including meat consumption. However, scientists believe most infections are spread human to human.
Leptospirosis rats, mice, pigs, horses, goats, sheep, cattle, buffaloes, opossums, raccoons, mongooses, foxes, dogs direct or indirect contact with urine of infected animals
Lyme disease deer, wolves, dogs, birds, rodents, rabbits, hares, reptiles tick bite
Orf goats, sheep close contact
Psittacosis macaws, cockatiels, budgerigars, pigeons, sparrows, ducks, hens, gulls and many other bird species contact with bird droplets
Q fever livestock and other domestic animals such as dogs and cats inhalation of spores, contact with bodily fluid or faeces
Rabies commonly – dogs, bats, monkeys, raccoons, foxes, skunks, cattle, goats, sheep, wolves, coyotes, groundhogs, horses, opossums, mongooses and cats through saliva by biting, or through scratches from an infected animal
Rat-bite fever rats, mice bites of rats but also urine and mucus secretions
Rocky Mountain spotted fever dogs, rodents tick bite
Rift Valley fever livestock, buffaloes, camels mosquito bite, contact with bodily fluids, blood, tissues, breathing around butchered animals and/or raw milk
Saint Louis encephalitis birds mosquito bite
Swine influenza pigs close contact
Taenia crassiceps infection wolves, coyotes, jackals, foxes contact with soil contaminated with feces
Toxocariasis dogs, foxes, cats ingestion of eggs in soil, fresh or unwashed vegetables and/or undercooked meat
Toxoplasmosis cats, livestock, poultry exposure to cat feces, organ transplantation, blood transfusion, contaminated soil, water, grass, unwashed vegetables, unpasteurized dairy products and undercooked meat
Trichinosis rodents, pigs, horses, bears, walruses, foxes, crocodiles, birds eating undercooked meat
Tuberculosis infected cattle, deer, llamas, pigs, domestic cats, wild carnivores (foxes, coyotes) and omnivores (possums, mustelids and rodents) milk, exhaled air, sputum, urine, faeces and pus from infected animals
Tularemia lagomorphs (type A), rodents (type B), birds ticks, deer flies, and other insects including mosquitoes
West Nile fever birds, horses mosquito bite
Zika fever chimpanzees, monkeys, apes, baboons mosquito bite, sexual intercourse, blood transfusion and sometimes bites of monkeys

Who Is At A Higher Risk Of Serious Illness From Zoonotic Diseases?

Anyone can become sick from a zoonotic disease (including healthy people), but some people may be more at risk than others. These people are more likely than others to get really sick, and even die, from infection with certain diseases, and such groups of people include:

  • Children younger than 5 years
  • Adults older than 65 years
  • People with compromised immune systems

Protect Yourself And Your Family From Zoonotic Diseases

Fortunately, there are things you can do to protect yourself and your family from zoonotic diseases;

  • Keep hands clean, and wash your hands right after being around animals, even if you didn’t touch any animals. Many germs are spread by not washing hands with soap and clean water.
  • Alternatively, use an alcohol-based hand sanitizer that contains at least 60% alcohol to clean hands.
  • Stay safe around your pets.
  • Prevent bites from parasites like mosquitoes, ticks, and fleas.
  • Learn more about ways to handle food safely
  • Be aware of zoonotic diseases, and avoid bites and scratches from animals.



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