Question

Zoonotic diseases are transmissible 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 human immunodeficiency virus has no effect on cats, though each may be deadly to its normal host. What can be the explanation for what may prevent cross-species infection in some cases and allow it in others?

A) Each species can fight other species virus so there are no signs of the disease

B) Each species is born with the specific memory cell against the disease already present in their body

C) Viruses use specific markers to enter cells and those might be species-specific

D) All answers are correct

Answer 1

I think A and C is most correct explanations because host in both cases may have defense like mechanical barriers and chemical barriers that prevent cross species transmission. And also virus may use specific markers or endogenous molecule to enter and take over host machinery.

memory cell develop only after first contact and then species can show signs of infection . And memory cells can be present from birth but not specific. Immunity develops with contacts with pathogens.