Abstract:
Since the discovery of West Nile (WN) virus in the Western Hemisphere many surveillance
programs have been implemented to monitor the epidemiology and genetic variation of WN
virus in North America. This project was based on the WN virus Adult Mosquito
Identification and Diagnostic Program conducted at Brock University for Ontario, Canada,
during the 2002 and 2003 transmission seasons. There are three sections to this thesis. The
first section investigated which mosquito species carry WN virus in Ontario, Canada
throughout the 2002-2003 transmission seasons. It was found that from the 2002 data, eight
mosquito species were detected with WN virus (Aedes vexans, Anopheles punctipennis,
Coquilleltidia perlurbans, Culex salinarius, Cx. pipiens, Cx. resluans, Ochlerolalus Irivillalus
and Och. Iriserialus) and 7.19% of the total mosquito pools tested were found to be WN virus
positive (129 positive poolsll, 793 total pools tested). In 2003, WN virus was detected in only
five mosquito species (Ae. vexans, Cx. salinarius, Och. Iriserialus, Cx. pipiens and Cx.
resluans) and 1.42% of the total mosquito pools tested were WN virus positive (101 positive
poolsl7,1 01 total pools tested). WN virus positive mosquito pools were detected 3-4 weeks
earlier in 2002 compared to 2003 data. The second section investigated the actual infection
rate (IR) of clearly identified Cx. pipiens and Cx. resluans from the 2002 outbreak. It was
found that significantly more ex. resluans were infected with WN virus compared to ex.
pipiens. The third section investigated the degree of variability of the WN virus genome. A
879 nucleotide section of the WN virus genome was amplified from 21 American Crows and
20 adult female mosquitoes from Ontario, Canada, and compared to the homologous region of
the original New York 1999 Chilean Flamingo sequence (NY99FL). Seventy-two nucleotides
from Ontario WN virus sequences showed variability compared to NY99FL with 10
synapotypic changes. Phylogenetic analysis revealed a close relationship between Ontario
and US WN virus sequences.
