Abstract

Ten lions (six juvenile males, one adult male, and three adult females) from Etosha National Park, Namibia were presented for necropsy. Gross lesions included gunshot trauma and enteric cestodiasis in all individuals, and pulmonary nematodiasis in three individuals. The parasitism was not considered clinically significant.

Histologic evaluation of Steiner-stained gastric tissue revealed two of four adults and one of six juveniles had moderate numbers of gastric spiral bacteria. The gastric spiral bacteria were located extracellularly in fundic and pyloric glands, and also intracellularly within parietal cells in the fundic region. The organisms were 4–8-µm long by light microscopy, and 0.53–0.73-µm wide with a periodicity of 0.50–0.67 µm by transmission electron microscopy (TEM). The bacteria had blunted ends with multiple flagella. No periplasmic fibrils were observed. The histologic and ultrastructural characteristics of the bacteria were considered most consistent with Helicobacter-like organisms (HLO). Gastric inflammation in the infected individuals consisted of mild to moderate, diffuse lamina propria, lymphoplasmacytic and eosinophilic infiltrate with moderate to marked lymphofollicular hyperplasia in both the fundic and pyloric regions. However, gastric inflammation in uninfected animals did not differ significantly from that observed in the infected individuals. Possibly the bacteria are commensals or an opportunistic pathogen, which has been previously suggested for HLO infection in other species.⁴ HLO have been previously observed in domestic cats (Felis domesticus) and various captive felids including cheetahs (Acinonyx jubatus) and one cougar (Felis concolor), but histologic gastritis and clinical gastric disease are only variably observed in these cases.^3,5,7,8 Continued study, particularly controlled pathogenesis studies, are needed to adequately ascertain the role of these bacteria in gastric pathology. To the authors’ knowledge, this is the first report of gastric spiral bacteria in a free-ranging animal.

Histologic examination of skeletal muscle revealed all adult lions had rare to moderate numbers of sarcocysts within individual myocytes measuring 40x70 µm to 50x260 µm. Sarcocysts were not observed in juvenile lions; however, all juveniles had enteric Sarcocystis sp. oocysts within small intestinal lamina propria macrophages. Enteric Sarcocystis sp. infection was not observed in adults. TEM was performed on affected skeletal muscle. All observed cysts were mature and were contained within myocytes. The cyst wall consisted of a 44 to 66 nm, granular, electron-dense parasitophorous membrane with subjacent, 0.9–2.0-µm thick, granular and fibrillar ground substance which also extended into the cyst interior as thin septa. The parasitophorous membrane was folded into irregularly spaced, 0.8–1.3-µm tall villi centrally containing small amounts of ground substance. The membrane was continuous in the villar projections but divided into discrete aggregations of the electron-dense material between villi. Bradyzoites within the interior of the cyst were approximately 3x12 µm. The sarcocysts were determined to be consistent with Sarcocystis felis based on the characteristic ultrastructural appearance of the cyst wall.¹ The life cycle and definitive host for Sarcocystis felis has not, to date, been ascertained; however, it likely employs a scavenger species as the definitive host.^1,6 Intramuscular Sarcocystis felis sarcocysts have been previously reported in a single lion in eastern Africa.²

Acknowledgments

Partial funding for this work was obtained from the Chicago Zoological Society and the University of Illinois College of Veterinary Medicine. The authors wish to thank the histopathology and electron microscopy sections of the University of Illinois Laboratories of Veterinary Diagnostic Medicine, and the Ministry of Environment and Tourism, Republic of Namibia, for their excellent technical assistance.

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