**Core Concept**
Autoinfection refers to the re-infection of an individual by the same pathogen that initially caused the infection. This phenomenon occurs when the pathogen is introduced into the body through a route other than direct contact with an infected person, contaminated food or water, or an arthropod vector. In the context of parasitic infections, autoinfection can occur through the fecal-oral route, where the parasite's eggs or ova are ingested from contaminated feces.

**Why the Correct Answer is Right**
Autoinfection is commonly seen with parasitic infections such as hookworm, Trichuris trichiura (whipworm), and Taenia saginata (beef tapeworm). In these cases, the parasite's eggs or ova are ingested, hatch in the small intestine, and penetrate the intestinal mucosa to establish a new infection. The parasite's life cycle is completed when the adult worm sheds eggs into the feces, which can then be ingested by another individual, allowing the cycle to repeat. This process of autoinfection perpetuates the infection, making it challenging to eliminate.

**Why Each Wrong Option is Incorrect**
**Option A:** This option is incorrect because autoinfection is not typically associated with viral infections, which often require direct contact with an infected individual to transmit.
**Option B:** This option is incorrect because while some bacterial infections can cause autoinfection, such as Clostridioides difficile (C. diff), it is not a characteristic of the infections listed in the correct answer choices.
**Option C:** This option is incorrect because fungal infections, such as dermatophytes, are not typically associated with autoinfection.

**Clinical Pearl / High-Yield Fact**
Autoinfection can occur through the fecal-oral route, highlighting the importance of proper hygiene, sanitation, and handwashing to prevent the spread of parasitic infections.

**Correct Answer: D. Taenia saginata**