The Brief Transport plans disrupted: Sunnyside Street Dogs says 16 dogs that were vaccinated, fixed and cleared with health certificates can no longer be transferred to out-of-state adopters because of new screwworm-related restrictions. Growing concern over screwworm cases: Texas has confirmed five cases of New World screwworm, including four livestock animals and one dog. The parasite is the larva of a fly that feeds on the living tissue of warm-blooded animals.