A zoonosis is any disease or infection that is naturally transmissible from vertebrate animals to humans. Animals thus play an essential role in maintaining zoonotic infections in nature. As well as being a public health problem, many of the major zoonotic diseases prevent the efficient production of food of animal origin and create obstacles to international trade in animal products. Any disease or infection that is naturally transmissible from vertebrate animals to humans and vice-versa is classified as a zoonosis according to the PAHO publication "Zoonoses and communicable diseases common to man and animals". Zoonoses have been recognised for many centuries, and over 200 have been described. They are caused by all types of pathogenic agents, including bacteria, parasites, fungi, and viruses.
Some examples of zoonoses, classified according to the type of causative agent, are given hereafter.
Rabies is a disease of carnivores and bats mainly transmissible to humans by bites. Almost all persons infected by rabid animals will die if not treated. An estimated number of 55 000
persons, mainly children, die of this disease in the world every year. Dogs are responsible for most human deaths. Other viral zoonoses are avian influenza, Crimean-Congo hemorrhagic fever, Ebola and Rift Valley fever.
Dermatophytoses are superficial mycoses that may be acquired from infected animals and affect the skin, hair and nails of humans, causing itching, redness, scaling and hair loss. Another mycotic infection that can be zoonotic is sporotrichosis.