Caffrey, C., S.C.R. Smith, and T.J. Weston (2005). West Nile Virus Devastates an American Crow Population. The Condor P.: 128-32.
Descriptors: West Nile virus, crows, population devastated, birds, sentinals.

Clark, L., J. Hall, R. McLean, M. Dunbar, K. Klenk, R. Bowen, and C.A. Smeraski (2006). Susceptibility of greater sage-grouse to experimental infection with West Nile virus. Journal of Wildlife Diseases 42(1): 14-22.
Abstract: Populations of greater sage-grouse (Centrocercus urophasianus) have declined 45-80% in North America since 1950. Although much of this decline has been attributed to habitat loss, recent field studies have indicated that West Nile virus (WNV) has had a significant negative impact on local populations of grouse. We confirm the susceptibility of greater sage-grouse to WNV infection in laboratory experimental studies. Grouse were challenged by subcutaneous injection of WNV (10(3.2) plaque-forming units [PFUs]). All grouse died within 6 days of infection. The Kaplan-Meier estimate for 50% survival was 4.5 days. Mean peak viremia for nonvaccinated birds was 10(6.4) PFUs/ml (+/-10(0.2) PFUs/ml, standard error of the mean [SEM]). Virus was shed cloacally and orally. Four of the five vaccinated grouse died, but survival time was increased (50% survival=9.5 days), with 1 grouse surviving to the end-point of the experiment (14 days) with no signs of illness. Mean peak viremia for the vaccinated birds was 10(2.3) PFUs/ml (+/-10(0.6) PFUs/ml, SEM). Two birds cleared the virus from their blood before death or euthanasia. These data emphasize the high susceptibility of greater sage-grouse to infection with WNV.
Descriptors: bird diseases immunology, galliformes, viral vaccines immunology, West Nile fever, West Nile virus, animals, wild immunology, wild virology, bird diseases virology, disease susceptibility, enzyme linked immunosorbent assay, injections, random allocation, reverse transcriptase polymerase chain reaction, survival rate, time factors, viremia, West Nile fever immunology, West Nile fever mortality, West Nile fever.

Coumbe, K., T. Mair, J. Samuelson, and D. Sinclair (2006). West Nile virus in horses. Veterinary Record 159(24): 823.
Descriptors: horses, West Nile virus, West Nile fever, disease, infection.

Dietrich, G., J.A. Montenieri, N.A. Panella, S. Langevin, S.E. Lasater, K. Klenk, J.C. Kile, and N. Komar (2005). Serologic evidence of West Nile virus infection in free-ranging mammals, Slidell, Louisiana, 2002. Vector Borne and Zoonotic Diseases 5(3): 288-292. ISSN: 1530-3667.
Abstract: After an outbreak of West Nile virus (WNV) infections in Slidell, Louisiana, in 2002, we detected neutralizing antibodies to WNV in 13 of 120 mammals, representing five of six species sampled. Seroprevalence was measured in opossum, Didelphis virginiana (75%, n = 8), raccoons, Procyon lotor (60%. n = 5), black rats, Rattus rattus (6%, n = 36), hispid cotton rats, Sigmodon hispidus (4%, n = 24), and eastern gray squirrels, Sciurus carolinensis (2%, n = 43).
Descriptors: Didelphis virginiana, Procyon lotor, Rattus rattus, Sciurus carolinensis, Sigmodon hispidus, viral diseases, West Nile virus, recorded and prevalence, Louisiana, Slidell.

Drummond, R. (2006). West Nile virus in horses. Veterinary Record 159(26): 895.
Descriptors: West Nile virus, horses, infection, diagnosis.

Durham, A. (2006). West Nile virus in horses. Veterinary Record 159(21): 723; Discussion 723.
Descriptors: horse diseases, West Nile fever, disease notification, Great Britain, horse diseases transmission, risk factors, travel, virus isolation and purification, West Nile virus, zoonoses.

Farfan Ale, J.A., B.J. Blitvich, N.L. Marlenee, M.A. Lorono Pino, F. Puerto Manzano, J.E. Garcia Rejon, E.P. Rosado Paredes, L.F. Flores Flores, A. Ortega Salazar, J. Chavez Medina, J.C. Cremieux Grimaldi, F. Correa Morales, G. Hernandez Gaona, J.F. Mendez Galvan, and B.J. Beaty (2006). Antibodies to West Nile virus in asymptomatic mammals, birds, and reptiles in the Yucatan Peninsula of Mexico. American Journal of Tropical Medicine and Hygiene 74(5): 908-914. ISSN: 0002-9637.
Abstract: Surveillance for evidence of West Nile virus (WNV) infection in taxonomically diverse vertebrates was conducted in the Yucatan Peninsula of Mexico in 2003 and 2004. Sera from 144 horses on Cozumel Island, Quintana Roo State, 415 vertebrates (257 birds, 52 mammals, and 106 reptiles) belonging to 61 species from the Merida Zoo, Yucatan State, and 7 farmed crocodiles in Ciudad del Carmen, Campeche State were assayed for antibodies to flaviviruses. Ninety (62%) horses on Cozumel Island had epitope-blocking enzyme-linked immunosorbent assay (ELISA) antibodies to flaviviruses, of which 75 (52%) were seropositive for WNV by plaque reduction neutralization test (PRNT). Blocking ELISA antibodies to flaviviruses also were detected in 13 (3%) animals in the Merida Zoo, including 7 birds and 2 mammals (a jaguar and coyote) seropositive for WNV by PRNT. Six (86%) crocodiles in Campeche State had PRNT-confirmed WNV infections. All animals were healthy at the time of serum collections and none had a history of WNV-like illness.
Descriptors: vertebrata, viral diseases, West Nile virus, prevalence of antibodies in asymptomatic individuals, immune response, antibodies, against viral disease, prevalence in asymptomatic individuals, Mexico, Yucatan Peninsula, prevalence of antibodies against viral disease in asymptomatic individuals.

Gancz, A.Y., D.A. Smith, I.K. Barker, R. Lindsay, and B. Hunter (2006). Pathology and tissue distribution of West Nile virus in North American owls (family: Strigidae). Avian Pathology 35(1): 17-29. ISSN: 0307-9457 .
Abstract: This study describes the macroscopic and microscopic lesions and the viral antigen distribution in 82 owls (Family: Strigidae) of 11 North American and one Eurasian species that died following natural West Nile virus infection. The range of lesions seen was greater than that previously reported for owls, and involved more organs. Two patterns of antigen distribution were identified: one that involved the blood and all major organs; and a second where antigen was sparse, localized, and absent from the blood. The first pattern was associated with species of northern natural breeding range, while the second was seen in owls of a more southern distribution and appeared to be associated with a more prolonged course of illness. Further differences in lesion and antigen distribution appeared to be either species related or individual. The findings underline the complexity and variability of West Nile virus pathology within birds of a relatively narrow taxonomic group.
Descriptors: West Nile virus, North American owls, pathology, tissue distribution, natural infection, lesions, antigen distribution.

Gibbs, S.E., A.B. Allison, M.J. Yabsley, D.G. Mead, B.R. Wilcox, and D.E. Stallknecht (2006). West Nile virus antibodies in avian species of Georgia, USA: 2000-2004. Vector Borne and Zoonotic Diseases 6(1): 57-72. ISSN: 1530-3667.
Abstract: West Nile virus (WNV) was first isolated in the state of Georgia in the summer of 2001. As amplifying hosts of WNV, avian species play an important role in the distribution and epidemiology of the virus. The objective of this study was to identify avian species that are locally involved as potential amplifying hosts of WNV and can serve as indicators of WNV transmission over the physiographic and land use variation present in the southeastem United States. Avian serum samples (n = 14,077) from 83 species of birds captured throughout Georgia during the summers of 2000-2004 were tested by a plaque reduction neutralization test for antibodies to WNV and St. Louis encephalitis virus. Over the 5-year period, WNV-neutralizing antibodies were detected in 869 (6.2%) samples. The WNV seroprevalence increased significantly throughout the study and was species dependent. The highest antibody prevalence rates were detected in rock pigeons (Columba livia), northern cardinals (Cardinalis cardinalis), common ground doves (Columbina passerina), grey catbirds (Deumetella carolinensis), and northern mockingbirds (Mimus polyglottos). Northem cardinals, in addition to having high geometric mean antibody titers and seroprevalence rates, were commonly found in all land use types and physiographic regions. Rock pigeons, common ground doves, grey catbirds, and northern mockingbirds, although also having high seroprevalence rates and high antibody titers against WNV, were more restricted in their distribution and therefore may be of more utility when attempting to assess exposure rates in specific habitat types. Of all species tested, northern cardinals represent the best potential avian indicator species for widespread serologic-based studies of WNV throughout Georgia due to their extensive range, ease of capture, and high antibody rates and titers. Due to the large geographic area covered by this species, their utility as a WNV sentinel species may include most of the eastern United States.
Descriptors: aves, viral diseases, West Nile virus, host records and prevalence, Georgia, USA, viral disease.

Hukkanen, R.R., H.D. Liggitt, S.T. Kelley, R. Grant, D. Anderson, B.J. Beaty, N.L. Marlenee, R.A. Hall, and H. Bielefeldt Ohmann (2006). Comparison of commercially available and novel West Nile virus immunoassays for detection of seroconversion in pig-tailed macaques (Macaca nemestrina). Comparative Medicine 56(1): 46-54.
Abstract: We report the assessment and validation of an NS1 epitope-blocking enzyme-linked immunosorbent assay (ELISA) for detection of antibodies to West Nile virus (WNV) in macaques. Sera from naturally infected Macaca nemestrina were tested by ELISA and plaque reduction neutralization test (PRNT). Results were correlated with hemagglutination inhibition (HAI) data. Our results demonstrate that the blocking ELISA rapidly and specifically detects WNV infection in M. nemestrina. In addition, the diagnostic value of 7 commercially available immunoassays (PanBio immunoglobulin [Ig] M ELISA, PanBio IgG ELISA, PanBio immunofluorescence assay (IFA), InBios IgG ELISA, InBios IgM ELISA, Focus Diagnostics IgG ELISA, and Focus Diagnostics IgM ELISA) in M. nemestrina was evaluated and compared with that of the epitope-blocking ELISA. The PanBio IgG ELISA was found to effectively diagnose WNV exposure in M. nemestrina. Further, PanBio IFA slides are fast and reliable screening tools for diagnosing flaviviral exposure in M. nemestrina.
Descriptors: West Nile virus, immunoassays, detection, pig-tailed macques, NS1 epitope-blocking enzyme-linked immunosorbent assay (ELISA), antibodies, plaque reduction neutralization test (PRNT).

Jacobson, E.R., P.E. Ginn, J.M. Troutman, L. Farina, L. Stark, K. Klenk, K.L. Burkhalter, and N. Komar (2005). West Nile virus infection in farmed American alligators (Alligator mississippiensis) in Florida. Journal of Wildlife Diseases 41(1): 96-106.
Abstract: In September and October 2002, an epizootic of neurologic disease occurred at an alligator farm in Florida (USA). Three affected American alligators (Alligator mississippiensis) were euthanatized and necropsied, and results confirmed infection with West Nile virus (WNV). The most significant microscopic lesions were a moderate heterophilic to lymphoplasmacytic meningoencephalomyelitis, necrotizing hepatitis and splenitis, pancreatic necrosis, myocardial degeneration with necrosis, mild interstitial pneumonia, heterophilic necrotizing stomatitis, and glossitis. Immunohistochemistry identified WNV antigen, with the most intense staining in liver, pancreas, spleen, and brain. Virus isolation and RNA detection by reverse transcription-polymerase chain reaction confirmed WNV infection in plasma and tissue samples. Of the tissues, liver had the highest viral loads (maximum 10(8.9) plaque-forming units [PFU]/0.5 cm3), whereas brain and spinal cord had the lowest viral loads (maximum 10(6.6) PFU/0.5 cm3 each). Virus titers in plasma ranged from 10(3.6) to 10(6.5) PFU/ml, exceeding the threshold needed to infect Culex quinquefasciatus mosquitoes (10(5) PFU/ml). Thus, alligators may serve as a vertebrate amplifying host for WNV.
Descriptors: alligators and crocodiles, neurologic disease, Florida, USA, alligator farms, West Nile fever, West Nile virus isolation and purification, amplifying host for WNV.

Joyner, P.H., S. Kelly, A.A. Shreve, S.E. Snead, J.M. Sleeman, and D.A. Pettit (2006). West Nile virus in raptors from Virginia during 2003: clinical, diagnostic, and epidemiologic findings. Journal of Wildlife Diseases 42(2): 335-344. ISSN: 0090-3558.
Abstract: Sixty-one birds of prey admitted to The wildlife Center of Virginia (WCV; Waynesboro, Virginia, USA) from June to November 2003 were tested for West Nile 'Arus (WNV) infection. Choanal and/or cloacal swabs were obtained and submitted to Virginia's Division of Consolidated Laboratory Services (Richmond, Virginia, USA) for analysis with real-time reverse transcriptase polymerase chain reaction (RT-PCR). Forty birds of prey were positive for WNV by RT-PCR. Five avian families and nine species of raptors were represented, with great horned owls (Bubo virginianus) and red-tailed hawks (Buteo jamaicensis) most frequently affected. Presenting clinical signs were consistent with previous reports of WNV infection in raptors; however, these differed between species. Of WNV positive birds, nonspecific signs of illness were the most common clinical findings, particularly in red-tailed hawks; signs included dehydration (n=20), emaciation (n =18), and depression (n =15). Neurologic abnormalities were frequently identified, especially in great horned owls, and included head tremors (n=17), ataxia (n=13), head incoordination (n=7), torticollis (n=3), nystagmus (n=3), and bead tilt (n=3). Great horned owls exhibited aNemia and leukocytosis with heterophilia, eosinophilia, and monocytosis consistent with chronic inflammation. Red-tailed hawks were aNemic with a heterophilic leukocytosis and regenerative left shift. The majority of WNV cases occurred during August and September; there was a marked increase in the number of raptors admitted to WCV during these months followed by a marked decrease during October, November, and December. This pattern differed from mean monthly admissions during the previous 10 years and suggests a negative impact on local raptor populations. The effects of WNV on avian populations are largely unknown; however, because of their ecological importance, further investigation of the effects of WNV on raptor populations is warranted.
Descriptors: falconiformes, strigiformes, viral diseases, West Nile virus, clinical, diagnostic and epidemiologic findings, transmission of viruses, Virginia.

Miller, D.L., Z.A. Radi, C. Baldwin, and D. Ingram (2005). Fatal West Nile virus infection in a white-tailed deer (Odocoileus virginianus). Journal of Wildlife Diseases 41(1): 246-249.
Abstract: A 3-yr-old male white-tailed deer (Odocoileus virginianus) with a history of ataxia and tremors was submitted to the Tifton Veterinary Diagnostic and Investigational Laboratory (The University of Georgia, Tifton, Georgia, USA) for necropsy. Gross findings were unremarkable. Histologically, the brain had multifocal lymphoplasmacytic perivascular inflammation, scattered gliosis, and rare satellitosis. Mild hemorrhage and congestion in the retropharyngeal lymph nodes and mild lymphoid depletion in the tonsil were present. A reverse transcription-polymerase chain reaction test performed on brain yielded a positive result for West Nile virus. This represents the first report of fatal West Nile virus infection in a white-tailed deer.
Descriptors: white-tailed deer, Odocoileus virginianus, West Nile fever, West Nile virus isolation and purification, brain stem, fatal outcome, viral RNA analysis, reverse transcriptase polymerase chain reaction methods.

Naugle, D., C. Aldridge, B. Walker, K. Doherty, M. Matchett, J. McIntosh, T. Cornish, and M. Boyce (2005). West Nile virus and sage-grouse: What more have we learned? Wildlife Society Bulletin. 33(2): 616-623. ISSN: 0091-7648.
Descriptors: Centrocercus urophasianus, grouse, West Nile virus, mortality, surveys, Wyoming, Montana, Alberta, Colorado, California.

Nemeth, N., D. Gould, R. Bowen, and N. Komar (2006). Natural and experimental West Nile virus infection in five raptor species. Journal of Wildlife Diseases 42(1): 1-13.
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.
Descriptors: bird diseases, raptors, West Nile fever, West Nile virus, animals, wild virology, species specificity, mosquito vectors, histopathology, species response to WNV infection, mode of exposure, oral and cloacal shedding.

Nemeth, N., D. Hahn, D. Gould, and R. Bowen (2006). Experimental West Nile Virus Infection in Eastern Screech Owls (Megascops asio). Avian Diseases. 50(2): 252-258. ISSN: 0005-2086.
Abstract: Eastern Screech Owls (EASOs) were experimentally infected with the pathogenic New York 1999 strain of West Nile virus (WNV) by subcutaneous injection or per os. Two of nine subcutaneously inoculated birds died or were euthanatized on 8 or 9 days postinfection (DPI) after <24 hr of lethargy and recumbency. All subcutaneously inoculated birds developed levels of viremia that are likely infectious to mosquitoes, with peak viremia levels ranging from 105.0 to 109.6 plaque-forming units/ml. Despite the viremia, the remaining seven birds did not display signs of illness. All birds alive beyond 5 DPI seroconverted, although the morbid birds demonstrated significantly lower antibody titers than the clinically normal birds. Cagemates of infected birds did not become infected. One of five orally exposed EASOs became viremic and seroconverted, whereas WNV infection in the remaining four birds was not evident. All infected birds shed virus via the oral and cloacal route. Early during infection, WNV targeted skin, spleen, esophagus, and skeletal muscle. The two morbid owls had myocardial and skeletal muscle necrosis and mild encephalitis and nephritis, whereas some of the clinically healthy birds that were sacrificed on 14 DPI had myocardial arteritis and renal phlebitis. WNV is a significant pathogen of EASOs, causing pathologic lesions with varying clinical outcomes.
Descriptors: Strigiformes, wild birds, West Nile virus, pathogenicity, vertebrate viruses, subcutaneous injection, drug delivery systems, viremia, disease transmission, insect vectors, symptoms, seroconversion, morbidity, oral administration, disease course, disease severity, hosts, new host records, pathogen-shedding, Internet-resource.
Language of Text: Summary in Spanish.

Nevarez, J.G., M.A. Mitchell, Dae Young Kim, R. Poston, and H.M. Lampinen (2005). West Nile virus in alligator, Alligator mississippiensis, ranches from Louisiana. Journal of Herpetological Medicine and Surgery 15(3): 4-9. ISSN: 1529-9651.
Abstract: West Nile virus (WNV) has been reported to affect various crocodilian species including the American alligator, Alligator mississippiensis, the Nile crocodile, Crocodylus niloticus, and the Morelet's crocodile, Crocodylus moreletii. In the Fall of 2003 an increased number of mortalities were observed at various alligator ranches in Louisiana. Affected animals were reported to have neurologic signs followed by death. At the time West Nile virus (WNV) had already been diagnosed in alligators from Georgia and Florida, but not Louisiana. This report outlines the findings of physical exam, necropsy, histopathology and diagnostic tests of affected animals. Viral isolation, real time RT-PCR and immunohistochemistry have proven to be useful tests for diagnosing WNV in alligators. One interesting aspect of these cases is that only one of the four affected facilities had alligators hatched in Louisiana. The other three had imported hatchlings from Florida and Texas.
Descriptors: Alligator mississippiensis, viral diseases, West Nile virus, occurrence at ranches, symptoms and disease origins, transmission of viruses, Louisiana.

Ollis, G., L. Morin, and A. Visser (2005). Laboratory confirmed positive cases of equine West Nile virus in Alberta in 2003. Canadian Veterinary Journal 46(2): 131-133. ISSN: 0008-5286.
Descriptors: horse diseases, West Nile virus, disease incidence, geographical distribution, symptoms, horses, risk factors, disease surveillance, disease detection, diagnostic techniques, blood serum, immunoglobulin M, enzyme linked immunosorbent assay, disease diagnosis, Alberta.

Read, R.W., D.B. Rodriguez, and B.A. Summers (2005). West Nile Virus Encephalitis in a Dog. Veterinary Pathology. 42(2): 219-222. ISSN: 0300-9858.
Abstract: In November 2002, a 2-year-old, spayed Maltese Terrier in central Mississippi was presented for an acute illness characterized by uncontrolled hyperactivity that rapidly progressed to generalized tremors, ataxia, and intermittent hyperthermia. Postmortem examination after a 2-week course revealed mild, multifocal, nonsuppurative meningo encephalitis, with focal necrosis in the medulla. Reverse transcriptase-nested-polymerase chain reaction for West Nile virus (WNV) was positive on brain and negative on other tissues. Immunohistochemistry was negative on all tissues. The clinical, postmortem, and laboratory findings are consistent with acute encephalitis due to WNV infection. WNV infection should be considered in dogs showing signs of encephalitis when and where WNV and mosquito vectors occur.
Descriptors: dog diseases, case studies, disease course, Mississippi, West Nile virus, symptoms, diagnosis.

Root, J.J., P.T. Oesterle, N.M. Nemeth, K. Klenk, D.H. Gould, R.G. McLean, L. Clark, and J.S. Hall (2006). Experimental infection of fox squirrels (Sciurus niger) with West Nile virus. American Journal of Tropical Medicine and Hygiene 75(4): 697-701. ISSN: 0002-9637.
Abstract: Tree squirrels (Sciurus spp.) have exhibited high seroprevalence rates, suggesting that they are commonly exposed to West Nile virus (WNV). Many characteristics of WNV infections in tree squirrels, such as the durations and levels of viremia, remain unknown. To better understand WNV infections in fox squirrels (S. niger), we subcutaneously inoculated fourteen fox squirrels with WNV. Peak viremias ranged from 10(4.00) plaque-forming units (PFU)/mL of serum on day 2 post-infection (DPI) to 10(4.98) PFU/mL on 3 DPI, although viremias varied between individuals. Oral secretions of some fox squirrels were positive for WNV viral RNA, occasionally to moderate levels (10(3.2) PFU equivalent/swab). WNV PFU equivalents in organs were low or undetectable on 12 DPI; gross and histologic lesions were rare. The viremia profiles of fox squirrels indicate that they could serve as amplifying hosts in nature. In addition, viral RNA in the oral cavity and feces indicate that this species could contribute to alternative WNV transmission in suburban communities.
Descriptors: rodent diseases, squirrels, West Nile fever, West Nile virus, viral biosynthesis, brain pathology, kidney pathology, liver pathology, myocardium pathology, viral RNA analysis, random allocation, reverse transcriptase polymerase chain reaction, virus shedding, mortality, pathology.

Steinman, A., C. Banet Noach, L. Simanov, N. Grinfeld, Z. Aizenberg, O. Levi, D. Lahav, M. Malkinson, S. Perk, and N.Y. Shpigel (2006). Experimental Infection of Common Garter Snakes (Thamnophis sirtalis) with West Nile Virus. Vector Borne and Zoonotic Diseases 6(4): 361-368. ISSN: 1530-3667.
Abstract: The role of various reptilian species in the infectious cycle of several arboviruses is documented, but their role in that of West Nile virus (WNV) is uncertain. Common garter snakes (Thamnophis sirtalis) were infected subcutaneously with 10(5) plaque forming units (PFU) WNV-Isr 98, five of nine snakes became viremic, and five exhibited persistent low levels of neutralizing antibodies. Four of the parentally infected snakes died and high titers of virus were found in multiple organ samples. In contrast, orally infected garter snakes did not become viremic, but viral RNA was detected in cloacal swabs. Since oral infection of predator birds by WNV is known, their ingestion of infected snakes may also result in their becoming infected.
Descriptors: reptilian species, West Nile virus, garter snakes, subcutaneous infection, oral infection, viremic, RNA, predator birds.

Stout, W., A. Cassini, J. Meece, J. Papp, R. Rosenfield, and K. Reed (2005). Serologic evidence of West Nile virus infection in three wild raptor populations. Avian Diseases. 49(3): 371-375. ISSN: 0005-2086.
Abstract: We assayed for West Nile virus (WNV) antibodies to determine the presence and prevalence of WNV infection in three raptor populations in southeast Wisconsin during 2003-04. This study was conducted in the framework of ongoing population studies that started before WNV was introduced to the study area. For 354 samples, 88% of 42 adult Cooper's hawks (Accipiter cooperii), 2.1% of 96 nestling Cooper's hawks, 9.2% of 141 nestling red-tailed hawks (Buteo jamaicensis), and 12% of 73 nestling great horned owls (Bubo virginianus) tested positive for WNV antibodies by the constant virus-serum dilution neutralization test. Samples that tested positive for WNV antibodies were collected across a wide variety of habitat types, including urban habitats (both high and low density), roads, parking areas, recreational areas, croplands, pastures, grasslands, woodlands, and wetlands. Based on the increased prevalence and significantly higher WNV antibody titers in adults compared with nestlings, we suggest that nestlings with detectable antibody levels acquired these antibodies through passive transmission from the mother during egg production. Low levels of WNV antibodies in nestlings could serve as a surrogate marker of exposure in adult raptor populations. Based on breeding population densities and reproductive success over the past 15 yr, we found no apparent adverse effects of WNV infections on these wild raptor populations.
Descriptors: wild birds, hawks, Accipiter, Buteo jamaicensis, owls, Bubo virginianus, West Nile virus, immunologic techniques, viral diseases of animals and humans, disease detection, disease prevalence, wildlife habitats, biomarkers, maternal immunity, Wisconsin, Accipiter-cooperii.
Language of Text: Summary in Spanish.

Sullivan, H., G. Linz, L. Clark, and M. Salman (2006). West Nile virus antibody prevalence in red-winged blackbirds (Agelaius phoeniceus) from North Dakota, USA (2003-2004). Vector Borne and Zoonotic Diseases 6(3): 305-309. ISSN: 1530-3667.
Abstract: This study was designed to explore the role that red-winged blackbirds (Agelaius phoeniceus) may have played in disseminating West Nile virus (WNV) across the United States. Using enzyme-linked immunosorbent assays designed to detect WNV antibodies in avian species we were able to determine the WNV antibody prevalence in a cohort of red-winged blackbirds in central North Dakota in 2003 and 2004. The peak WNV antibody prevalence was 22.0% in August of 2003 and 18.3% in July of 2004. The results of this study suggest that red-winged blackbird migratory populations may be an important viral dispersal mechanism with the ability to spread arboviruses such as WNV across the United States.
Descriptors: West Nile virus, red winged black birds, antibody prevalence, migratory populations, disseminating, disperal, spread.

Ternovoi, V.A., E.V. Protopopova, S.G. Surmach, M.V. Gazetdinov, S.I. Zolotykh, A.M. Shestopalov, E.V. Pavlenko, G.N. Leonova, and V.B. Loktev (2006). [The genotyping of the West Nile virus in birds in the far eastern region of Russia in 2002-2004]. Molekuliarnaia Genetika, Mikrobiologiia i Virusologiia(4): 30-35.
Abstract: Samples from 20 species of trapped and dead birds were collected in the Far Eastern Region in 2002-2004 and were analyzed by the anti-WNV MAb-modified immunoenzyme assay for antigen detection and RT-PCR for viral RNA detection. Five positive samples from cinereous vultures (Aegypius monachus) and two positive samples from cattle egret (Bubulcus ibis) were found in both tests. The sequencing of the 322 bp fragments of protein E gene showed 99-99.67% homology with the strain WNV/LEIV-VlgOO-27924 of the WNV isolated in Volgograd, Russia, 2000. Additionally, five positive samples from birds (Pica pica, Corvus macrorhynchos, Larus crossirostris, Parus minor, Emberiza spodocephala) collected in autumn 2004 were found during screening with anti-WNV MAb-modified ELISA. These results confirm that the WNV is circulating in the Far Eastern Region of Russia and outbreaks of WN fever in humans may be possible. This demonstrates that the genotype 1a of the West Nile virus could spread in the southern regions of the Far East by migrating birds and introduction of the WNV into other southern regions of the Asian part of Russia are probably.
Descriptors: birds, West Nile fever, viral genotype, immunoenzyme techniques, reverse transcriptase polymerase chain reaction, Russia, West Nile virus classification.
Language of Text: Russian.

Tesh, R.B., M. Siirin, H. Guzman, A.P. Travassos da Rosa, X. Wu, T. Duan, H. Lei, M.R. Nunes, and S.Y. Xiao (2005). Persistent West Nile virus infection in the golden hamster: studies on its mechanism and possible implications for other flavivirus infections. Journal of Infectious Diseases 192(2): 287-295.
Abstract: Golden hamsters (Mesocricetus auratus) experimentally infected with West Nile virus (WNV) developed chronic renal infection and persistent shedding of virus in urine for up to 8 months, despite initial rapid clearance of virus from blood and the timely appearance of high levels of specific neutralizing antibodies. Infectious WNV could be recovered by direct culture of their urine and by cocultivation of kidney tissue for up to 247 days after initial infection. Only moderate histopathologic changes were observed in the kidneys or brain of the chronically infected hamsters, although WNV antigen was readily detected by immunohistochemistry within epithelium, interstitial cells, and macrophages in the distal renal tubules. Comparison of WNV isolates from serial urine samples from individual hamsters over several months indicated that the virus underwent both genetic and phenotypic changes during persistent infection. These findings are similar to previous reports of persistent infection with tickborne encephalitis and Modoc viruses.
Descriptors: flavivirus infections, West Nile fever, viral blood antibodies, antibody formation, animal disease models, enzyme linked immunosorbent assay, kidney, Mesocricetus auratus, golden hamster, viremia immunology, West Nile virus.

Tiawsirisup, S., K.B. Platt, B.J. Tucker, and W.A. Rowley (2005). Eastern cottontail rabbits (Sylvilagus floridanus) develop West Nile virus viremias sufficient for infecting select mosquito species. Vector Borne and Zoonotic Diseases 5(4): 342-350. ISSN: 1530-3667.
Abstract: The potential of the eastern cottontail rabbit (CTR; Sylvilagus floridanus) to contribute to an enzootic West Nile virus (WNV) cycle was demonstrated by characterizing the WNV viremia profile of 15 CTRs and demonstrating that mosquitoes could become infected by feeding on these CTRs. Eight CTRs were infected with a titer of 10(5.0) cell-infectious dose 50% endpoints (CID50s) of WNV (NY99-Crow) by needle and seven CTRs by bite of one or more WNV-infected mosquitoes. There were no marked differences between the WNV viremia profiles of CTRs infected by either method. West Nile virus was detected in serums of all CTRs by 24 h p.i. The daily mean titers of all 15 CTRs on days 1-4 p.i. were 10(4.1+/-0.4), 10(4.7+/-0.3), 10(4.1+/-0.6), and 10(3.7+/-0.6) respectively, declining to 10(1.2+/-0.1) CID50s/ml of serum by day 6 p.i. No virus was detected in the blood of any CTR on day 7 p.i. The average duration of WNV titers of >or=10(4.3) and <10(5.0) CID50s/mL for all CTRs was 2.2 +/- 0.6 and 1.0 +/- 0.1 days, respectively. The minimum estimated infection rates (MEIRs) of Culex pipiens (L.) and Culex salinarius (Coq.) that fed on CTRs with titers of >or=10(4.3) and >10(5.0) were 11.5 +/- 5.5 and 21 +/- 6.0%, respectively. These rates increased to 20.5 +/- 6.4% and 25.0 +/- 3.0% when CTR serum titers were >10(5.0) CID50s/mL. Neither Aedes aegypti (L.) nor Aedes albopictus (Skuse) were infected by feeding on CTRs with titers of <10(5.0) CID50s/mL. The MEIRs of these two species were 11.5 +/- 3.5% and 1.5 +/- 0.5% after feeding on CTRs with titers of >10(5.0) CID50s/ml. None of the CTRs infected by mosquito bite or by needle showed any symptoms of WNV disease.
Descriptors: cottontail rabbit, West Nile virus, viremia, Culex mosquitos, infection rates.

van der Meulen, K.M., M.B. Pensaert, and H.J. Nauwynck (2005). West Nile virus in the vertebrate world. Archives of Virology 150(4): 637-657. ISSN: 0304-8608.
Abstract: West Nile virus (WNV), an arthropod-borne virus belonging to the family Flaviviridae, had been recognized in Africa, Asia and the south of Europe for many decades. Only recently, it has been associated with an increasing number of outbreaks of encephalitis in humans and equines as well as an increasing number of infections in vertebrates of a wide variety of species. In this article, the data available on the incidence of WNV in vertebrates are reviewed. Moreover, the role of vertebrates in the transmission of WNV, the control of WNV infections in veterinary medicine as well as future perspectives are discussed. A wide variety of vertebrates, including more than 150 bird species and at least 30 other vertebrate species, are susceptible to WNV infection. The outcome of infection depends on the species, the age of the animal, its immune status and the pathogenicity of the WNV isolate. WNV infection of various birds, especially passeriforms, but also of young chickens and domestic geese, results in high-titred viremia that allows arthropod-borne transmission. For other vertebrate species, only lemurs, lake frogs and hamsters develop suitable viremia levels to support arthropod-borne transmission. The role of vertebrates in direct, non-arthropod-borne transmission, such as via virus-contaminated organs, tissues or excretions is less well characterized. Even though direct transmission can occur among vertebrates of several species, data are lacking on the exact amounts of infectious virus needed. Finally, the increased importance of WNV infections has led to the development of killed, live-attenuated, DNA-recombinant and chimeric veterinary vaccines.
Descriptors: animal diseases, West Nile fever, horse diseases, horses.

Wunschmann, A., J. Shivers, J. Bender, L. Carroll, S. Fuller, M. Saggese, A. Van Wettere, and P. Redig (2005). Pathologic and immunohistochemical findings in goshawks (Accipiter gentilis) and great horned owls (Bubo virginianus) naturally infected with West Nile virus. Avian Diseases. 49(2): 252-259. ISSN: 0005-2086.
Abstract: The carcasses of 25 great horned owls and 12 goshawks were investigated for West Nile virus (WNV) infection by immunohistochemistry (IHC) performed on various organs, including brain, spinal cord, heart, kidney, eye, bone marrow, spleen, liver, lungs, pancreas, intestine, and proventriculus, using a WNV-antigen-specific monoclonal antibody and by WNV-specific reverse transcriptase-polymerase chain reaction (RT-PCR), performed on fresh brain tissue only. WNV infection was diagnosed by IHC in all owls and all goshawks. WNV-specific RT-PCR amplified WNV-RNA in the brain of all goshawks but only 12 owls (48%). Cachexia was a common macroscopic finding associated with WNV infection in owls (76%). Myocarditis was occasionally macroscopically evident in goshawks (33%). Microscopically, inflammatory lesions, including lymphoplasmacytic and histiocytic encephalitis, myocarditis, endophthalmitis, and pancreatitis were present in both species but were more common and more severe in goshawks than in owls. The most characteristic brain lesion in owls was the formation of glial nodules, in particular in the molecular layer of the cerebellum, while encephalitis affecting the periventricular parenchyma of the cerebral cortex was common in the goshawks. In owls, WNV-antigen-positive cells were present usually only in very small numbers per organ. Kidney (80%), heart (39%), and cerebellum (37%) were the organs that most commonly contained WNV antigen in owls. WNV antigen was frequently widely distributed in the organs of infected goshawks, with increased amounts of WNV antigen in the heart and the cerebrum. Spleen (75%), cerebellum (66%), heart (58%), cerebrum (58%), and eye (50%) were often WNV-antigen positive in goshawks. In contrast with the goshawks, WNV antigen was not present in cerebral and retinal neurons of owls. WNV infection appears to be capable of causing fatal disease in great horned owls and goshawks. However, the distribution and severity of histologic lesions, the antigen distribution in the various organs, and the amount of antigen varied among both species. Therefore, the diagnostician may choose organs for histology and immunohistochemistry as well as RT-PCR depending on the investigated species in order to avoid false-negative results.
Descriptors: Accipiter gentilis, Bubo virginianus, wild birds, birds of prey, West Nile virus, bird diseases, pathogenesis, immunohistochemistry, immunopathology, disease incidence, animal organs, monoclonal antibodies, antigens, reverse transcriptase polymerase chain reaction, cachexia, viral diseases of animals and humans.
Language of Text: Summary in Spanish.

Wunschmann, A. and A. Ziegler (2006). West Nile virus-associated mortality events in domestic Chukar partridges (Alectoris chukar) and domestic Impeyan pheasants (Lophophorus impeyanus). Avian Diseases 50(3): 456-459. ISSN: 0005-2086.
Abstract: West Nile virus (WNV) infection was diagnosed in captive juvenile chukars (Alectoris chukar), and captive juvenile Impeyan pheasants (Lophophorus impeyanus) on the basis of necropsy, histopathology, polymerase chain reaction, and immunohistochemistry. The chukars were kept in a game bird farm that experienced two outbreaks with approximately 25% mortality in hundreds of chukars between September and October 2002 and during the same months in 2003. The submitted pheasants were part of a group of 15 juvenile Impeyan pheasants that all died within approximately 2 wk at the end of August 2002. The macroscopic lesions in the pheasants were dominated by mucosal hemorrhage at the proventricular to ventricular junction and cecal ulcers, whereas the gross lesions in the chukar partridges were nonspecific. The predominant microscopic lesion in the chukar partridges was myocardial necrosis, whereas fibrinous and necrotizing splenitis was prominent in the pheasants. Viral antigen was usually widespread in animals of both species. Spontaneously occurring WNV infection should be considered a differential diagnosis in cases of mortality among select species of galliform birds.
Descriptors: bird diseases, mortality, West Nile fever, necrotizing enterocolitis, heart virology, myocardium pathology, juvenile chukars, juvenile Impeyan pheasants.

Yaremych, S.A., R.E. Warner, P.C. Mankin, J.D. Brawn, A. Raim and R. Novak (2005). West Nile virus and high death rate in American crows. S.K. Majumdar, J.E. Huffman, F.J. Brenner and A.I.E. Panah Wildlife Diseases: Landscape Epidemiology, Spatial Distribution and Utilization of Remote Sensing Technology., Pennsylvania Academy of Science, Easton., p. Chapter pagination: 200-204, i-ix. ISBN: 0945809190.
Descriptors: Corvus brachyrhynchos, dipteran parasites, culicidae, viral diseases, West Nile virus, viral prevalence, epidemiology and associated mortality rate, satellite tracking study, transmission of viruses, mortality, mortality rate, USA.

Zhang, Z., F. Wilson, R. Read, L. Pace, and S. Zhang (2006). Detection and characterization of naturally acquired West Nile virus infection in a female wild turkey. Journal of Veterinary Diagnostic Investigation 18(2): 204-208.
Abstract: An adult female wild turkey exhibiting disorientation and failure to flee when approached was submitted to the Mississippi Veterinary Research and Diagnostic Laboratory. Gross pathologic examination revealed evidence of dehydration and the presence of modest numbers of adult nematodes in the small intestine. Histologic examination revealed extensive multifocal perivascular lymphocytic infiltration in brain, marked heterophilic hyperplasia in bone marrow, and multifocal interstitial lymphocytic infiltration in heart, pancreas, ventriculus, and skeletal muscles. West Nile virus (WNV) was isolated from the brain, lung, and kidney tissues using cultured Vero cells. Higher copies of viral RNA were detected from brain, lung, and kidney than from heart, liver, or spleen by quantitative real-time reverse transcription-polymerase chain reaction (RRT-PCR) analysis. Immunohistochemical (IHC) analysis detected WNV antigen in various tissues including neurons, kidney, respiratory tract epithelium, heart, and bone marrow. On the basis of the data from this investigation, it is concluded that WNV caused encephalitis along with many other pathologic changes in the affected wild turkey.
Descriptors: poultry diseases, turkeys, West Nile fever, West Nile virus isolation and purification, wild animals, Cercopithecus aethiops, histocytochemistry, kidney, lung pathology, pathology of adult female wild turkey.