Nonenzymic histochemistry of bovine abomasal tissue infected with Ostertagia ostertagi.

Abomasa from calves infected with 0. ostertagi and 0. radiatum, 0. radiatum only, and an uninfected calf were studied histochemically at 2, 5, 7, 14, and 22 days after infection (DAI). Collagen, accompanied by fibroblasts, was deposited in the tissue about the dilated gastric glands beginning at 7 DAI. Structural fibers staining with reticulum stains were abundant about the necks of the infected gastric glands. Compared to uninfected tissue and tissue adjacent to the dilated gastric glands, fewer chief cell granules stained for tryptophan, SS bonds, and SH groups immediately about the dilated gastric glands from 2 through 22 DAI. The cytoplasm of chief cells, agranular leukocytes, and fibroblasts stained intensely for RNA in uninfected and adjacent tissue, whereas degenerating chief cells immediately about the dilated gastric glands stained less intensely beginning at 7 DAI. Hemoand lipofuchsin methods stained a PAS-positive iron-negative pigment in macrophages and degenerating cells in infected abomasa. Frandsen (1965) studied the nonenzymic histochemistry of oesophagostomiasis at 8 and 10 days and ostertagiasis at 8 days postinoculation. He observed no significant changes in the histochemistry of abomasal tissue infected with 0. ostertagi probably because of an absence of intimacy between the larvae of 0. ostertagi and abomasal tissue. Because intimacy of the parasite with host tissues might influence the time and degree of host response, it became pertinent to extend the period of infection and reinvestigate the nonenzymic histochemistry of bovine ostertagiasis emphasizing ground substance, structural proteins, and fibers. The histochemical data were interpreted relative to the observed pathology which was similar to that described by Ritchie etal. (1966). MATERIALS AND METHODS Abomasa from 5 calves, infected with 350, 350, 150, 75, and 150 thousand larvae of 0. ostertagi, were removed at 2, 5, 7, 14, and 22 days after inoculation (DAI), respectively. All calves were 7 months old, except the third calf which was 9 months old. At necropsy, tissues were excised from proximal and distal parts of the abomasum and fixed in (1) neutral buffered formalin, (2) formol-calcium, (3) Bouin's, (4) Carnoy's, and (5) Zenker's fixatives. Hereafter, the histochemical method will be followed by a number designating the kind of fixation used. Additional tissues were quenched at -70 C in isopentane, cooled with dry ice, and stored in screw-cap vials on dry ice. Received for publication 17 May 1973. *Animal Parasitology Institute, ARS, Beltsville, Maryland 20705. Because these calves were also infected with Oesophagostomum radiatum for other studies, control tissues consisted of abomasal tissue from a calf infected with 20,000 0. radiatum larvae only and from an uninfected calf. Where appropriate, calf tissue positive controls were processed and studied concurrently. To verify the appropriate larval stage in tissue, whole mounts of 0. ostertagi were cleared in dimethylsulfoxide (DMSO) and compared with stages described and illustrated by Douvres (1956).