Five young adult and two adult cheetahs presented with lethargy, anorexia, watery diarrhea, and regurgitation over an 11-day period. Fecal samples were submitted for electron microscopy and culture. Electron microscopy results revealed all animals to be positive for an astrovirus, and no significant bacterial pathogens were identified on fecal cultures. All animals were monitored and treated with bismuth subsalicylate tablets (524 mg PO BID for 5 days) and recovered without additional intervention.
The astrovirus was confirmed and sequenced using consensus astroviral PCR. Phylogenetic analysis was performed on both the RNA-dependent RNA polymerase (RdRp) and the capsid protein.
Astroviruses are small RNA viruses that are difficult to distinguish by electron microscopy from picornaviruses and caliciviruses. In mammals, they typically cause diarrhea. Astroviral diarrhea differs from other viral diarrheas in that the capsid interacts with apical enterocyte membranes, causing a secretory diarrhea without leaving much of a histologic lesion.1,2 This is the first report we are aware of documenting an astrovirus outbreak in cheetah.
1. Koci, M.D., L.A. Moser, L.A. Kelly, D. Larsen, C.C. Brown, S. Schultz-Cherry. 2003. Astrovirus induces diarrhea in the absence of inflammation and cell death. J. Virol. 77: 11798–11808.
2. Moser L.A., M. Carter, S. Schultz-Cherry. 2007. Astrovirus increases epithelial barrier permeability independently of viral replication. J. Virol. 81: 11937–11945.