Zoonotic diseases are transmissable from animals to humans. These include ringworm, a fungus which infects pets and people, plague, a bacterial disease resulting from a flea bite to mammals including humans, and rabies, a viral disease of the central nervous system that affects all mammals and is almost always fatal. On the other hand, the feline immunodeficiency virus has no effect on humans and

Question

human immunodeficiency virus has no effect on cats, though each may be deadly to its normal host. Speculate on what may prevent cross-species infection in some cases and allow it in others.

What will be an ideal response?

Answer 1

Some pathogens require conditions that are species specific. In the case of viral infections, it may be that some
species lack certain cell-surface markers that viruses bind to before they invade. In the case of a virus such as
rabies, the virus may bind to a cell marker that is present in all mammalian neural tissue. Some pathogens may
require specific chemical environments. The existence of zoonotic diseases underscores the common features of
humans and nonhuman animals.