Natural and Experimental West Nile Virus Infection in Five Raptor Species

Abstract

ABSTRACT:We studied the effects of natural and/or experimental infections of West Nile virus (WNV) in five raptor species from July 2002 to March 2004, including American kestrels (Falco sparverius), golden eagles (Aquila chrysaetos), red-tailed hawks (Buteo jamaicensis), barn owls (Tyto alba), and great horned owls (Bubo virginianus). Birds were infected per mosquito bite, per os, or percutaneously by needle. Many experimentally infected birds developed mosquito-infectious levels of viremia (.10 5 WNV plaque forming units per ml serum) within 5 days postinoculation (DPI), and/ or shed virus per os or per cloaca. Infection of organs 15-27 days postinoculation was infrequently detected by virus isolation from spleen, kidney, skin, heart, brain, and eye in convalescent birds. Histopathologic findings varied among species and by method of infection. The most common histopathologic lesions were subacute myocarditis and encephalitis. Several birds had a more acute, severe disease condition represented by arteritis and associated with tissue degeneration and necrosis. This study demonstrates that raptor species vary in their response to WNV infection and that several modes of exposure (e.g., oral) may result in infection. Wildlife managers should recognize that, although many WNV infections are sublethal to raptors, subacute lesions could potentially reduce viability of populations. We recommend that raptor handlers consider raptors as a potential source of WNV contamination due to oral and cloacal shedding.

West Nile Virus Vector Competency of Culex quinquefasciatus Mosquitoes in the Galápagos Islands

“…Thus, some species encountered in Galápagos, for example Tyto alba (peak viremia 3.6 log 10 PFU/ mL when tested in the United States), would have a limited role in WNV amplification by being unlikely to develop titers high enough to infect mosquitoes. 54 However, passerine birds have viremic profiles with the highest magnitude of titers; certain species peak at 11 log 10 PFU/mL. 43 A study to determine the host susceptibility and likely morbidity of Galápagos native vertebrates is required.…”

Experimental Infection of Cliff Swallows (Petrochelidon pyrrhonota) with Varying Doses of West Nile Virus

“…Infectious WNV persisted in the kidneys of several apparently healthy swallows for up to 17 DPI, consistent with several other experimental studies in birds from which WNV was isolated from tissues (i.e., spleen, kidney, skin, heart, brain, and eye) at 15-43 DPI and 8-14 days post-viremia. 2,35,36 Given that cliff swallows are likely WNV reservoir competent and appear to have relatively low associated mortality, the role of this species in transmission should be further explored. Cliff swallows have ample opportunities for exposure to WNV because large numbers of birds, including many young birds, congregate in areas of abundant mosquito vectors during the breeding season, a scenario that could greatly amplify local transmission.…”

Ecology of West Nile Virus Transmission and Its Impact on Birds in the Western Hemisphere

“…Laboratory infection studies to estimate host competence have been published for 44 species of nondomesticated birds in 23 families and 11 orders Reisen et al 2005aReisen et al , b, 2006Reisen et al , 2007aClark et al 2006;Nemeth et al 2006;Owen et al 2006;Reisen and Hahn 2007;Platt et al 2008), 3 species of wild mammals (Tiawsirisup et al 2005b, Root et al 2006, Platt et al 2007, and 5 species of reptiles and one amphibian Komar 2003, Klenk et al 2004). In these experiments, animals are infected by either allowing infectious mosquitoes to feed on them or by an intramuscular or subcutaneous injection of virus.…”