Reovirus associated with mortality of an Upland Sandpiper

60 Population dynamics of waders are shaped by a range of different environmental factors including annual variation in food availability, climatic conditions, predation pressure, and the interaction of these factors with population density (Evans & Pienkowski 1984, Yalden & Pearce-Higgins 1997, Whitfield 2003). One factor that is poorly understood in most wildlife populations is the ecological role of pathogens and parasites (Friend et al. 2001). Disease dynamics are difficult to study in free-living birds because carcasses of small animals are usually consumed by scavengers and decompose rapidly (Osborne et al. 2000), and because large die-offs are rare events (Adams et al. 2003, Woodard et al. 1977). Nevertheless, diseases of waders may be of ecological and epidemiological importance, particularly if long-distance migrants are a vector for dispersal of zoonotic pathogens, such as West Nile virus (Komar 2003), avian influenza virus (Hurt et al. 2006, Makarova et al. 1999), avian cholera (Adams et al. 2003), and avian malaria (Mendes et al. 2005). Here, we report isolation of a reovirus from the brain of a wild Upland Sandpiper Bartramia longicauda found dead in the field. Reoviruses are viruses of respiratory or enteric origin (REO), and are characterized by spherical virus particles 75 to 80 nm in size, a double-stranded RNA genome, and a double capsid protein shell (Read-Connole 2000, Ritchie & Carter 1995). Reoviruses are best known as a pathogen of domesticated or captive poultry, waterfowl and psittacines (Ritchie & Carter 1995, Robertson & Wilcox 1986), but have also been detected in wild populations of waders, waterfowl and other birds (Docherty et al. 1994, Hlinak et al. 2006, Hollmen et al. 2002). We conducted a population study of Upland Sandpipers during April to August of 2002–2007 at Konza Prairie Biological Station in northeast Kansas, USA (39°05'N, 96°34'W). In this six-year period, we radio-marked 261 adult sand pipers by attaching transmitters with either a leg-loop harness (n = 203) or adhesives (n = 58). Mortality of sandpipers during the breeding season was infrequent, and the probability of surviving the ten-week breeding period was 0.875 in females and 0.965 in males (Mong & Sandercock 2007). We recovered eight carcasses of radio-marked birds during our six-year study, and evidence at recovery sites indicated that seven of eight dead sandpipers were killed by predators or scavenged after dying of unknown causes. This case history is based on a single Upland Sandpiper (U.S. Fish & Wildlife Service band 1573-29956) that was captured and radio-marked on 19 May 2005 by BKS and AEC, and monitored for 30 days. We discovered the bird incubating a four-egg clutch on 25 May, and the clutch successfully hatched on 12 June. We relocated and observed the bird on three brood checks between 13–16 June. The bird exhibited normal behavior when approached by an observer, including flying, perching on fence posts, and giving vocalizations associated with brood attendance and defence of young. On 18 June, we recovered the intact dead bird lying on its side with the legs flexed and the head arched back over the spine. From inspection of the carcass at the recovery site, BKS and AEC discounted predation, collision and harness entanglement as possible causes of death. The six-day old young were not relocated and their fate was unknown. The carcass was frozen and shipped on dry ice to the National Wildlife Health Center (U.S. Geological Survey) at Madison, Wisconsin for diagnostic examination. Upon receipt, the sandpiper was dissected by DEG and a range of cultures and tissue analyses were completed. External examination revealed no significant abnormalities. Internally, the bird was in fair body condition and in good post-mortem condition without decomposition. Internal gross examination revealed a small, atrophied spleen (1.5 × 5.0 mm), and reddish-black pasty material in the small intestine, presumed to be blood from intraluminal hemorrhaging. The bird had been initially sexed by molecular markers based on the CHD-gene (Griffiths et al. 1998, S.M. Wisely, Kansas State University), and its sex was confirmed to be male by inspection of the gonads during necropsy. Reovirus associated with mortality of an Upland Sandpiper