Atrophy of Jejunal Peyer´s Patches (JPP) as a Consequence of Experimental Infection of Goats with Mycobacterium avium subsp. paratuberculosis (MAP)

Introduction: MAP may cause granulomatous enteritis predominantly in ruminants. Initial lesions are detectable during the clinically non-apparent phase of infection in organized gut-associated lymphoid tissues (oGALT). The objective of this study was to characterize re-organization of JPP as part of oGALT during the first year after infection of goats with MAP.

Material and methods: Goat kids were orally inoculated with a total dose of about 10⁹ CFU of MAP. Six goats were necropsied at 3 mpi and ten at 12 mpi and JPP were collected. Lesions were assessed in H&E stained paraffin sections. Lymphocyte subsets and macrophages were labeled in consecutive frozen sections.   

Results: At 3 mpi, JPP (especially in the proximal jejunum) were thickened and sometimes ulcerated. Severity of lesions varied along the intestine and between individuals. Extensive granulomatous infiltrates of CD68⁺ epitheloid cells, CD4⁺ and gd T cells had replaced the oGALT. At 12 mpi, respective JPPs were thin, inconspicous and often recognized by a circumscribed serositis only. oGALT was segmentally to diffusely atrophic and replaced by a mild to moderate infiltrate of T cell subsets, plasma cells and macrophages.

Conclusions: The mycobacterial-host interaction caused marked tissue lesions even during the clinically non-apparent phase of infection. This resulted in a partial loss of oGALT.