So they say u can catch hiv or aids from anilingus but how ? is it because of the feces or the person has to be infected with it.

HIV: This virus is only transmitted by direct contact of mucous membranes, tisssue, body fluids including blood from an infected individual to an uninfected person. Anilingus is an unlikely source since the anterior portion of the mouth contains saliva which usually kills the virus, and with fellatio the semen bypasses the saliva when ejaculated onto the tonsils or the back of the throat.

Any blood?: Hiv is not felt to be transmitted by feces unless an infected person has blood in the feces and the blood itself comes in contact with an open area in your body and enters your blood stream.