What was the cause of the narrator's family's death in the book, The Unnamable?

The narrator's family's death is caused by sausage-poisoning - a story that Mahood tells in order to convince the narrator that he has a personal history - signifying the deterioration and biological decay that will inevitably arises at the end of life. Considering that sausages are amalgams of various body parts, and that the whole scene is described in visceral imagery, Beckett invokes the grotesque to suggest that we are not exempt from the realm of the abject, for the narrator himself is told he lacks limbs, and is in a "state of decay" (311).