Pyogranulomatous enteritis and mesenteric lymphadenitis in an adult llama caused by Rhodococcus equi carrying virulence-associated protein A gene

Abstract

We report herein Rhodococcus equi infection in an 11-y-old, male llama with a history of diarrhea and endoparasitism. Postmortem examination revealed granulomatous and ulcerative enteritis, pyogranulomatous mesenteric lymphadenitis, fibrinosuppurative peritonitis, and granulomatous hepatitis. Intralesional macrophages were laden with gram-positive cocci. Bacteriology identified R. equi, and cultures tested positive for R. equi choE and vapA genes by PCR. This case expands the reported spectrum of lesions associated with R. equi infections in llamas from pyogranulomatous bronchopneumonia and peripheral lymphadenitis to pyogranulomatous mesenteric lymphadenitis and enteritis. We also link a R. equi that is carrying the virulent-associated protein gene VapA to clinical disease in New World camelids.

Keywords: PCR; VapA protein; camelid; pathology; virulence-associated protein.

Figures 1–4.

Llama with Rhodococcus equi infection. Figure 1. Locally extensive fibrinosuppurative peritonitis. Figure 2. Severely enlarged mesenteric lymph nodes with pyogranulomatous lymphadenitis. Figure 3. Small intestine (jejunum) with locally extensive necrosis and focal perforation; note multifocal-to-coalescing ulcers in the adjacent, thickened mucosa. Figure 4. Liver with disseminated foci of pyogranulomatous inflammation, necrosis, and hemorrhage.

Figures 5–9.

Granulomatous-to-necrotizing jejunitis and hepatitis in a llama. Figure 5. The jejunal submucosa is markedly expanded by an inflammatory infiltrate; note the area of necrosis (arrowheads) and thick mats of fibrin and cellular debris on the serosal surface (arrows). H&E. Bar = 500 µm. Figure 6. Inflammatory infiltrates of macrophages with basophilic stippling in macrophage cytoplasm in the jejunum. H&E. Bar = 25 µm. Figure 7. Gram-positive bacterial cocci within macrophages in the jejunum. Brown–Hopps Gram. Bar = 25 µm. Figure 8. Metazoan parasites surrounded by hemorrhage and pigment-laden macrophages in the liver, interpreted as tracts of migrating trematodes. H&E. Bar = 50 µm. Figure 9. Focal aggregate of macrophages and fewer neutrophils and lymphocytes in the liver. H&E. Bar = 25 µm.