What is the term for the growth of a parasitic organism within the body?

The term that accurately describes the growth of a parasitic organism within the body is "infection." Infections occur when pathogens such as bacteria, viruses, fungi, or parasites invade the body, multiply, and lead to a pathological condition. This process often triggers an immune response, as the body attempts to fight off the invading organisms.

The definition of “infestation” typically refers to the presence of larger parasites, such as worms or insects, on or within the body but is associated more with external environments or localized areas rather than a systemic condition. “Inoculation” refers to the process of introducing a vaccine or pathogen into the body to elicit an immune response, and “contamination” signifies the presence of unwanted substances or organisms, but doesn’t specifically imply growth or multiplication within the body. Thus, "infection" is the most accurate term in this context.