Which of the following correctly describes a parasitic infestation?

A parasitic infestation refers to a situation where an organism, known as a parasite, lives on or within a host organism and benefits at the host's expense. Pediculosis, which is the correct answer, specifically relates to a condition caused by parasitic insects, such as lice, that infest the human body, particularly the scalp, body, or pubic area. This type of infestation can lead to itching, discomfort, and potential secondary infections.

The other terms listed do not pertain to parasitic infestations. Conjunctivitis is an inflammation of the conjunctiva, often caused by infections or allergens, but it does not involve a parasitic organism. Strabismus refers to a condition where the eyes do not properly align with each other, often due to muscular or neurological issues. Nystagmus involves involuntary eye movements, typically caused by neurological conditions or other eye-related issues. None of these conditions are characterized by a parasitic presence, which is why they do not fit the definition of a parasitic infestation.