34 Bridge -7 Enzootic –21 # of HU -17

35 Bridge -2 Enzootic –23 # of HU -18

36 Bridge -0 Enzootic –7 # of HU -19

36 Bridge -0 Enzootic –2 # of HU -19

36 Bridge -0 Enzootic –3 # of HU -19

Seasonality of infection in enzootic (top) and bridging vectors at Halton, Peel and Toronto

Larval surveillance in 2002 Some health units: Established inventory (mapping) of standing water sites (larval breeding sites) Conducted surveys of these larval breeding sites to determine mosquito species (habitat preferences), relative abundance & seasonal activity patterns Skills gained: developed protocols for establishing inventories and conducting larval surveys, obtained training on identification of mosquito larvae (to genus and/or species level) & trained students to perform these tasks

Mosquito surveillance in 2002 Conclusions: WN virus infection in enzootic vectors peaked in late July & remained high during August and September WN virus detected in mosquitoes from all 12 health units with activity in 2001and 7 where WN virus not previously detected Infection in bridging species detected less frequently, sporadic early in season, peaked in August and September

Mosquito surveillance in 2002 Conclusions cont’d: Mosquito infection data (abundance & seasonality info) used by some HU to inform local decisions about need for mosquito control (e.g., Peel) Six mosquito species identified in 2002 have potential to act bridging species. Though specific contribution of each species to human infections unclear, Culex salinarius suspected to play major role in transmission Capacity to provide timely results too limited

Mosquito surveillance in 2003 Options for 2003: Mosquito surveillance should be done to better define epidemiology of WN virus and to continue to evaluate risk to public health Any proposed surveillance program will need to consider: probability and geographic extent of future epidemics, proposed abatement activities or lack thereof, local resources & overall capacity

Mosquito surveillance in 2003 Options for 2003 cont’d: To maximize utility of mosquito-specific data requires increased capacity (identification, sorting & testing), timeliness, & a system for reporting results back to health units (preferably with interpretation of results)

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