<prompt> A 6-year old child who presented with perianal pruritus, excoriation of skin and nocturnal enuresis was found to be infected with a parasite causing autoinfection. The causative agent is diagnosed by the -NIH swab methodString testHetrazan testEncysted larvae on muscle biopsy  <response>: The causative agent is Enterobius vermiculais is diagnosed by NIH swab or perianal swab moistened with saline ie by applying the adhesive surface of cellophane tape to perianal skin in the morning then this is examined on a glass slide inder microscope. Reference: Harrison20th edition pg 1102 