What signifies a parasitic infestation?

A parasitic infestation is characterized by the presence of organisms, such as mites, that live on or within a host organism, often causing harm. Option B describes a tiny mite or parasite burrowing into the skin, which clearly aligns with the definition of a parasitic infestation. Parasites can derive nutrients from their host while often causing discomfort or disease. In this context, the action of burrowing into the skin indicates a direct interaction with the host's body and can lead to a variety of skin issues or systemic problems.

The other options involve different types of pathogenic mechanisms. A virus entering through the mouth mucosa involves a viral infection, which is not classified as a parasitic relationship. Fungi feeding on skin waste products refers to a fungal infection rather than parasitic infestation, as fungi are distinct organisms that have their own modes of lifecycle and infection. A bacterial infection spreading through the bloodstream describes a bacterial pathogen's action, which again differs from the behavior typically associated with parasitic organisms. Thus, option B most accurately fits the criteria for a parasitic infestation.