Question

living on or inside other animals which can spread diseases to people, animals and plants.​

Answer 1

Explanation:

Researchers have discovered that grazing animals such as deer and rabbits are actually helping to spread plant disease – quadrupling its prevalence in some cases – and encouraging an invasion of annual grasses that threaten more than 20 million acres of native grasslands in California.06-Jan-2009

Answer 2

These are called parasites. They cling onto a host and then feed off of them for nutrition.
Eg: Tapeworms, head lice, etc.