Mattress encasement for preventing bed bug escapement via a zipper opening

protective sleeve (100) against bedbugs for a mattress (101), said mattress six sides, said sheath comprising: i. a fabric cover (102) sized to surround the six sides of a mattress, said cover being formed of a material impenetrable to bedbugs; ii. an opening (103) formed in said cover and which is sized to receive the mattress; iii. sliding closure mechanism (111) disposed in said opening (103) and operable to close said opening once received the mattress, said mechanism comprising: (a) a zipper head (120); and (b) a pair of zipper tracks (121, 123) with a longitudinal axis; iv. a barrier (140) extending a distance along said tracks fastener (121, 123), said barrier (140) opposite said tracks fastener (121, 123) being disposed; v. stitches (160, 162) securing said barrier (140) relative to said tracks fastener (121, 123), said stitches with respect to each side of said longitudinal axis of said tracks fastener (121 , 123), said stitches being formed to prevent passage of bedbugs through said stitching (160, 162); and I saw. a channel (151) between said barrier (140) and said tracks fastener (121, 123), said channel formed by said stitching (160, 162), said barrier (140) and said tracks fastener being ( 121, 123), receiving said channel (151) slidably a portion of said head of fastener (120) and becoming said channel (151) in a channel (151) closed when said tracks fastener (121, 123) are coupled together; wherein said channel (151) has a confined space of a size to prevent displacement of bedbugs along the channel (151).