ABSTRACT
In November 1997, an outbreak of a neuroparalytic disease caused by West Nile (WN) virus was diagnosed in young goose flocks. Domestic geese were similarly affected in the late summer and fall of 1998, 1999, 2000 and 2001. WN viruses were also isolated from migratory and wild birds and horses in 1998-2001. A 1278 bp sequence of the envelope gene of 24 Israeli WN virus isolates was compared with those of seven isolates from Africa, Europe and New York. As a result, the Israeli isolates could then be grouped into two clusters. The 15 avian and three equine from 1997-2001 in the first cluster of viruses were shown to be identical to WN-NY99, while the second cluster comprised one goose isolate from 1998 and two goose and two pigeon isolates from 2000. These closely resembled the most recent Old World isolates, and indicate that at least two WN genotypes were co-circulating in the region during this time.
Subject(s)
Birds/virology , Horses/virology , West Nile virus/genetics , West Nile virus/isolation & purification , Amino Acid Sequence , Animals , Disease Outbreaks/veterinary , Genes, Viral , Genotype , Israel/epidemiology , Molecular Sequence Data , Phylogeny , Sequence Homology, Amino Acid , Time Factors , Viral Proteins/genetics , West Nile Fever/epidemiology , West Nile Fever/veterinary , West Nile Fever/virology , West Nile virus/classificationABSTRACT
West Nile virus (WNV) was isolated in a flock of 1,200 migrating white storks that landed in Eilat, a town in southern Israel, on August 26, 1998. Strong, hot westerly winds had forced the storks to fly under considerable physical stress before reaching the agricultural land surrounding the town. Most of the flock were fledglings, <1 year old, which had hatched in Europe. Thirteen dead or dying storks were collected 2 days after arrival and submitted to the laboratory for examination. Four WNV isolates were obtained from their brains. Out of 11 storks tested six days after arrival, three had WNV-neutralizing antibodies. Comparative analysis of full-length genomic sequences of a stork isolate and a 1999 flamingo isolate from the USA showed 28 nucleotide (nt) (0.25%) and 10 amino acid (0.3%) changes. Sequence analysis of the envelope gene of the stork isolate showed almost complete identity with isolates from Israeli domestic geese in 1998 and 1999 and from a nonmigrating, white-eyed gull in 1999. Since these storks were migrating southwards for the first time and had not flown over Israel, we assume that they had become infected with WNV at some point along their route of migration in Europe.
