West Nile Virus Infection in Farmed American Alligators (Alligator Mississippiensis) in Florida

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]/0.5cm 3 ), whereas brain and spinal cord had the lowest viral loads (maximum 10 6.6 PFU/0.5cm 3 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.

Validation and Use of an Indirect Enzyme-Linked Immunosorbent Assay for Detection of Antibodies to West Nile Virus in American Alligators (Alligator Mississippiensis) in Florida

“…Two groups of alligators from an alligator farm in Florida that had an outbreak of WNV (Jacobson et al, 2005) were used to validate an indirect ELISA to determine exposure of American alligators to WNV. Ten alligators (group 1) from a pen where alligators died during an outbreak of WNV in September to October 2002 were positive by ELISA, HAI, and PRNT.…”

“…In September and October 2002, a large commercial alligator farming operation in Florida (28Њ32ЈN, 80Њ56ЈW) had an epizootic of central nervous system disease in alligators up to 2 yr of age (Jacobson et al, 2005). Approximately 2 mo after the epizootic ended, 10 alligators from a pen where deaths occurred (group 1) and 10 from a pen where there were no deaths (group 2) were moved into separate pens.…”

“…West Nile virus (WNV) infection was recently identified in farmed American alligators (Alligator mississippiensis) in Georgia (Miller et al, 2003) and Florida (Jacobson et al, 2005), USA. During the outbreak in Florida, WNV was isolated from multiple tissues and was confirmed using TaqMan reverse transcription-polymerase chain reaction.…”

Pathogenesis of West Nile Virus Infection: a Balance between Virulence, Innate and Adaptive Immunity, and Viral Evasion

“…Certain aspects of the biology of WNV facilitate its ability to cause severe disease. WNV productively infects diverse cell populations from many animal species, suggesting usage of multiple and/or well-conserved receptors (9,53,58,79,157,178,195). The relatively diverse tropism of WNV allows viral replication in several tissues in animal and human hosts and may contribute to the wide spectrum of clinical manifestations (76,142,167,199).…”

Detection and Characterization of Naturally Acquired West Nile Virus Infection in a Female Wild Turkey

“…4,5,6 Furthermore, the findings in WNV infection of alligators and other aquatic animals suggested that contaminated environment, including food or water, may contribute to the spread of WNV. 8 Although wild and domestic turkeys are not generally recognized as susceptible to WNV, individual variation in susceptibility and immune status may alter risk for infection. Such is true with mammalian species that are generally resistant to the disease, but infections in humans, horses, squirrels, cows, and dogs have been reported.…”