The World Health Organization defines Zoonoses (Zoonosis, sing.) as "Those diseases and infections which are naturally transmitted between vertebrate animals and man".

A variety of domestic animals are capable of transmitting disease to people including: cats, cattle, dogs, horses, poultry, sheep and swine. People also contact zoonoses from pests such as bats, birds, insects, opossums and rodents to name a few.

For example, in 1997 it was confirmed that Mad Cow Disease was related to certain outbreaks of a variant of Creutzfeldt-Jakob disease (CJD) and caused by eating contaminated beef. Since first recognized in 1985, Mad Cow Disease has prompted the destruction of over a million cows in Britain. Incinerators had to be constructed to properly dispose of all the infected dairy cattle.

Many people in the United Kingdom and France contracted the new CJD variant. Most of them are now dead. There is no known treatment for the disease.

More than 250 different diseases have been linked to contaminated food or drink in the United States. Tainted food causes an estimated 6.5 million to 33 million illnesses and 9,000 deaths annually in the United States. Many food borne illnesses are traced to poor animal husbandry and diseased animals.

In California, over 45% of human diseases reportable to the California Department of Health Services are zoonoses.

The most obvious sources of infection from bird and animal pests are the other pests and parasites that live on their bodies as well as the fecal matter they all produce. Birds alone are hosts to dozens of types of parasites and infectious diseases which can be caused by bacterial (such as E. Coli), fungal, protozoal, or viral (including Influenza) agents.

A few of the diseases Associated with Pest Birds are American Trypansomiasis, Blastomycosis, Candidiasis, Cryptococcosis, Encephalitis, Histoplasmosis, Listeriosis, Meningitis, Newcastle Disease, Paratyphoid, Pasteurellosis, Psittacosis (Ornithosis), Salmonellosis, Sarcosporidiosias, St. Louis Encephalitis, Toxoplasmosis, Vibriosis, Trichomoniasis, and "Pigeon Breeders' Hypersensitivity Pneumonitis" or "Pigeon Fanciers' Allergic Alveolitis", (also known as "Pigeon Breeders' Lung").

Some of the other diseases and conditions associated with pests and the parasites that they host are Anthrax, Brucellosis, Campylobacter, Encephalomyelitis, Erysipelas, Hantavirus, Lyme disease, Mad Cow disease, Malaria, Plague, Rabies, Ringworm, Scabies, Tosocariasis, Trichinosis, Tuberculosis, Viral Hemorrhagic Fevers (e.g., Crimean-Congo, Ebola, Lassa and Marburg viruses), West Nile Virus, Yellow Fever, and water-associated diseases.