Abstract
West Nile virus (WNV) first entered the United States in 1999. In 2001, WNV found its way south to Louisiana. As part of a study to understand the epidemiology of WNV in Louisiana, heads from ten species of hunter-killed ducks in the 2002 and 2003 hunting season from Lacassine National Wildlife Refuge in southeastern Louisiana were submitted to the Louisiana State University School of Veterinary Medicine. Migratory ducks were selected for the study to understand the epidemiology of WNV in Louisiana because migratory birds are believed to have been responsible for introducing WNV in parts of the Middle East and are speculated to have a role in WNV transmission in the United States.1,2 From the 2002 collection, 190 ducks were submitted for testing, while 261 duck heads were submitted for testing in 2003. Duck heads were identified by sex and species prior to having brain tissue removed and sectioned into two pieces for testing. One section of brain was submitted for testing for WNV via nested RT-PCR while the other section was frozen at −70°C for virus isolation.
RNA was extracted from brain tissue submitted for WNV testing by nested RT-PCR using the Trizol extraction method. After the RNA was extracted, nested RT-PCR was performed on 187 of the 190 samples submitted in 2002 using the Qiagen 1-step RT-PCR. Eleven of the 187 samples tested were WNV positive by nested RT-PCR. The eleven samples were then submitted for virus isolation. No virus was isolated on culture or subculture for the 11 WNV nested RT-PCR positive samples. Duck brains from the 2003 hunting season are currently being processed. It is hoped that these results will provide information on the role migrating ducks may play in the spread and transmission of WNV.
Literature Cited
1. Malkinson, M., Banet, C., Weisman, Y., Pokamunski, S., King, R., Drouet, M., and Deubel, V. 2002. Introduction of West Nile virus in the Middle East by migrating white storks. Emerging Infectious Diseases. 8: 392–397.
2. Rappole, J., Derrickson, S., and Hubálek, Z. 2000. Migratory birds and spread of West Nile virus in the Western Hemisphere. Emerging Infectious Diseases. 6: 319–328.