Parasites

 is a condition in Fallout 4, Fallout 76, and Fallout: The Roleplaying Game.

Fallout 4
result in all food consumed sates just 50% of hunger, and can be cured with Herbal antimicrobial.

Fallout 76
can be inflicted by a diseased tick or bloodbug, swimming in water, eating raw mutfruit, drinking cream, and results in periodic food loss.

Fallout: The Roleplaying Game
can be inflicted by any of the random causes of disease denoted in the Core Rulebook, and results in the time taken on each step of hunger to be halved.

Appearances
appears in Fallout 4, Fallout 76, and Fallout: The Roleplaying Game.