Zoonoses are diseases that can transfer from non-human animals to humans.
There are many diseases -- whether caused by bacteria, viruses, or parasites
-- that are quite content to live in a variety of mammalian species. Some
diseases are even transferable from reptiles or birds to humans. Others are
very specific to their particular host. Still others pass part of their
life cycle in one animal host and another part in another. Mosquitoes pass
malaria from one infected animal to another. The animal can be a human, or
any one of a number of other animals. The mosquito is not bothered by the
malarial parasite, which is a protozoan, for those of you who care. The
malarial parasites spend part of their life cycle in the mosquitoes
intestinal tract, eventually migrating to its salivary glands, which is how
it get injected into a warm-blooded animal when the mosquito bites it. It
then spends part of its life cycle inside the red blood cells of humans, and
part in the sera. Malarial parasites can also encyst in the human liver and
live there for years if not treated, emerging periodically to make the
person sick. Malarial parasites do not spend any of their life cycle in the
mild ducts, and malarial is not transmissable from mother to child via
breastfeeding. My understanding of rabies is that any mammal can be a
carrier. Around here, skunks are the most common hosts. Sleeping sickness,
transmitted by the tsetse fly, can affect humans as well as domestic animals
such as cows. That's why, in Africa, wherever you have tsetse, you don't
have domestic livestock.
Pet iguanas can pass diseases on to people, so can cats (from cat poop,
cleaning cat boxes, and other diseases through scratches), and birds
(psittacosis -- through breathing). Cows can pass tuberculosis on to people
through infected milk. People have gotten leprosy from armadilloes.
And I could go on and on. But I'll spare you all!
Katherine A. Dettwyler, Ph.D.
Associate Professor of Anthropology and Nutrition
Texas A&M University
mailto:[log in to unmask]
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