The invention relates to a detachable casing which engages with a retractable lead (9) for a domestic animal, including a handle (16) and a housing (10), the casing comprising a one-piece shell (1) having two connected side walls (2a, 2b) and an opening (17) which is defined by two lateral edges (4a, 4b) each located on a different one of the edges (2a, 2b) and by an upper edge (5) and a lower edge (6) located at the ends of the end wall (3), the end wall (3) and the side walls (2a, 2b) defining an internal space for inserting the housing (10) through the opening (17), the end wall (3) being in contact with the front portion (13) of the housing (10), and the side walls (2a, 2b) each being in contact with a different lateral wall (12) of the housing (10), the side walls (2a, 2b) being elastically deformable such as to bear on the housing (10).
