Cytologic diagnosis ofLawsonia intracellularisproliferative ileitis in a Japanese snow macaque (Macaca fuscata)

Abstract

Diffuse ileal thickening and ileocecocolic lymphadenomegaly were observed during exploratory laparotomy in a 2-year-old male Japanese snow macaque (Macaca fuscata) that had flu-like signs and diarrhea. Cytologic examination of ileal biopsy imprints revealed many mature, mildly karyolytic neutrophils and fewer well-differentiated lymphocytes, eosinophils, macrophages, and plasma cells in a background containing amorphous, necrotic material. Tightly cohesive sheets of moderately pleomorphic epithelial cells also were seen. The cytologic diagnosis was chronic, active, mixed inflammation with atypical epithelial cells and necrosis. Histologically, the mucosal and crypt epithelium was moderately hyperplastic with a loss of goblet cells, increased mitoses, and frequent crypt abscesses. Within the lamina propria and extending into the submucosa was a marked neutrophilic infiltrate, with low numbers of lymphocytes, histiocytes, plasma cells, and eosinophils. The histologic diagnosis was chronic, diffuse, marked suppurative and lymphocytic ileitis. Warthin-Starry silver staining of the ileal biopsy and imprint specimens demonstrated numerous pleomorphic, curved bacilli consistent with Lawsonia intracellularis. Polymerase chain reaction (PCR) and immunohistochemistry confirmed the identity of the infectious agent. L intracellularis infection may be underdiagnosed because silver stain is required to visualize the organism with light microscopy and because the pathognomonic crypt hyperplasia may be complicated by secondary pathologic changes. Application of silver stain to cytologic specimens should be considered when distal intestinal lesions associated with hyperplastic epithelium, with or without inflammation, hemorrhage, or necrosis, are identified in animals with clinical signs of enteritis, especially in frequently affected species or in stressed or young animals.

Nonhuman Primates

“…as well as H. cinaedi and recently identified H. macacae have been isolated from inflamed colons of rhesus monkeys (Fox et al, 2001a,b;Fox et al, 2007). Similar lesions have been identified in Japanese macaques (M. fuscata) (Wamsley et al, 2005;Lafortune et al, 2004). Persistent infection of rhesus macaques with H. macacae associated with colonic adenocarcinoma has been described (Marini et al, 2010;Lertpiriyapong et al, 2014).…”

Suspicion of epizootic Lawsonia intracellularis disease in a group of pileated gibbons (Hylobates pileatus)

“…12 In the Japanese macaque case, the animal had been put in contact with a black‐capped capuchin ( Cebus apella ) not long before presenting symptoms, while the capuchin never showed any signs of infection (and was not tested for Lawsonia ) 5. Individual factors (age, intestinal flora, immunodeficiency, pregnancy and stress) can also strongly influence the clinical expression of the disease 14 15. Here, animals had no significant medical history, were from different age classes (no neonate/juvenile, no geriatric case); the female was not pregnant and no significant stress factors could be identified in the group before the disease onset.…”