While some diseases show host species specificity, meaning that they can only occur in one animal species, many other diseases can be spread between different animal species, including humans and animals. These diseases are collectively known as zoonotic diseases. The term zoonoses is derived from Greek zoon (animals) and noses (diseases) with a literal translation of “disease from animals”.
Zoonotic diseases can be transmitted by a variety of routes. Some documented means of transmission include direct and indirect contact with infected animals, airborne exposure to infective agents shed by animals, consumption of animal products, consumption of water that has been contaminated by animal fecal material, or exposure to insect vectors such as fleas or ticks.
Previously, the primary mode of transmission of zoonotic diseases at agricultural fairs, petting zoos, and farm visits was thought to be fecal-oral, that is, by ingestion of bacteria-laden feces via contaminated food or water, or transfer by hand to mouth following contact with contaminated surfaces or animals. Conclusions reached by investigators in several recent fair-associated outbreaks of E. coli O157:H7 suggest that ingestion or perhaps even inhalation of contaminated dust particles may be another way people can be infected with the bacterium.
Infants and children under the age of five are more likely than most people to get diseases from animals. This could be due to high hand-to-mouth activity combined with lessened cleanliness habits. The Centers for Disease Control and Prevention (CDC) recommends that infants and children under the age of five avoid contact with reptiles, amphibians, baby chicks, and ducklings. In addition, children under age five should be extra cautious when visiting farms and having direct contact with farm animals, including animals at petting zoos and fairs.
CDC provides advice on its website (CDC Healthy Pets Healthy People) regarding contact between infants or young children and animals. Specific similar advice is also given for Salmonella and for E. coli).