Pathology of Fatal West Nile Virus Infections in Native and Exotic Birds during the 1999 Outbreak in New York City, New York

Abstract

Abstract. West Nile fever caused fatal disease in humans, horses, and birds in the northeastern United States during 1999. We studied birds from two wildlife facilities in New York City, New York, that died or were euthanatized and were suspected to have West Nile virus infections. Using standard histologic and ultrastructural methods, virus isolation, immunohistochemistry, in situ hybridization and reverse-transcriptase polymerase chain reaction, we identified West Nile virus as the cause of clinical disease, severe pathologic changes, and death in 27 birds representing eight orders and 14 species. Virus was detected in 23/26 brains (88%), 24/ 25 hearts (96%), 15/18 spleens (83%), 14/20 livers (70%), 20/20 kidneys (100%), 10/13 adrenals (77%), 13/ 14 intestines (93%), 10/12 pancreata (83%), 5/12 lungs (42%), and 4/8 ovaries (50%) by one or more methods. Cellular targets included neurons and glial cells in the brain, spinal cord, and peripheral ganglia; myocardial fibers; macrophages and blood monocytes; renal tubular epithelium; adrenal cortical cells; pancreatic acinar cells and islet cells; intestinal crypt epithelium; oocytes; and fibroblasts and smooth muscle cells. Purkinje cells were especially targeted, except in crows and magpies. Gross hemorrhage of the brain, splenomegaly, meningoencephalitis, and myocarditis were the most prominent lesions. Immunohistochemistry was an efficient and reliable method for identifying infected cases, but the polyclonal antibody cross-reacted with St. Louis encephalitis virus and other flaviviruses. In contrast, the in situ hybridization probe pWNV-E (WN-USAMRIID99) reacted only with West Nile virus. These methods should aid diagnosticians faced with the emergence of West Nile virus in the United States.

West Nile Virus Detection in the Organs of Naturally Infected Blue Jays (Cyanocitta Cristata)

“…A second study using TaqMan RT-PCR on tissues of naturally infected American crows found kidney, and secondarily brain, to be infected most consistently (Kramer and Bernard, 2001). Virus isolation and RT-PCR, performed on kidney and heart tissue from naturally infected birds in the New York area, were consistently positive (Steele et al, 2000). In this same study, brain was the least sensitive tissue for IHC in American crows, fish crows, and black-billed magpies (Steele et al, 2000).…”

“…Virus isolation and RT-PCR, performed on kidney and heart tissue from naturally infected birds in the New York area, were consistently positive (Steele et al, 2000). In this same study, brain was the least sensitive tissue for IHC in American crows, fish crows, and black-billed magpies (Steele et al, 2000). In experimental infection of blue jays, the highest viral titers were observed in lung at 9.2 log 10 plaque forming units/0.5 cm 3 (Komar et al, 2003).…”

“…In experimental infection of blue jays, the highest viral titers were observed in lung at 9.2 log 10 plaque forming units/0.5 cm 3 (Komar et al, 2003). Immunohistochemistry, virus isolation, and RT-PCR performed on replicate tissue samples from a variety of naturally infected avian species revealed that heart, kidney, and spleen were consistently positive by all three diagnostic tests (Steele et al, 2000).…”

“…American crows (Corvus brachyrhynchos) are particularly susceptible to WNV, with mortality rates of 100% reported from experimental infection studies Komar et al, 2003). Other corvids, such as black-billed magpies (Pica hudsonia), blue jays (Cyanocitta cristata), and fish crows (Corvus ossifragus), are also susceptible to disease caused by WNV (Komar, 2000;Steele et al, 2000). For this reason, corvids have been used extensively for mortality-based WNV surveillance in the United States (Eidson et al, 2001;Kramer et al 2001).…”

“…Various approaches to detecting WNV, including virus isolation, viral RNA detection, and immunohistochemistry (IHC), have proved effective (Steele et al, 2000). In order to maximize the likelihood of detection, however, information on tissuespecific viral titers associated with WNV infection is needed.…”