A Study of the Histological Effects of Hypoderma lineatum (De Vill.) on Gullet Tissue Taken from Systemically Treated and Untreated Cattle

Abstract

An evaluation was made of the histopathological effects of the systemic insecticide, O -(3-chloro-4 methylumbelliferone) O,O -diethyl phosphorothioate (Co-Ral®; Bayer 21/199), on the gullet tissues of cattle sprayed with a 0.5% concentration and cattle drenched at the rate of 10 mg./kg. body weight for control of the common cattle grub (Hypoderma lineatum (De Vill.)). Good control of grubs with the spray and none with the drench resulted. A study of the prepared sections revealed no difference in the actual tissue of the grubs, except in case of the dead grubs. An examination of the gullet connective tissue surrounding the grubs revealed the following: Tissue from Sprayed Animal: Tissue and cells appear to be normal, i.e. normal numbers of macrophages, lymphocytes, plasma cells, and fiberblasts, and collagen ous fibers, The spray apparently had no effect on the connective tissue around the parasites or on the walls of the esophagus. The esophagi from the sprayed animals were normal. Tissue from Drenched Animal: Very heavy infiltration of lymphocytes, macrophages, and plasma cells, and fiberblasts, with active inflammation was observed. In the submucosa, loose and reticular connective tissue fibers were normal. Quite a number of plasma cells and macrophages were present. Many polymorphoneuclearcytes were present, indicating active inflammation probably owing to drench. Also noticeable was a mild to acute inflammation of the connective tissue fibers and cells of the lamina propriety of the esophagus. The inflammation was doubtless caused by the reaction of the host to one or two foreign agents, namely, the larval stages of H. lineatum , and the administration of the systemic insecticide. This probably indicates that the use of Co-Ral as a drench not only failed to give grub control, but was detrimental as well.