La Niña spells trouble for mosquito season in WA

Mosquitoes are proving to be particularly troublesome in parts of Western Australia.

Mosquito management was significantly more intense in the 2019/20 season than previous years, a local Mandurah government report has revealed.

Frequent tidal surges and the continual hatching of mosquito larvae throughout the season proved havoc for the management effort with 21 aerial larviciding treatments completed.

The report revealed that early 2020 brought an unexpected change in environmental conditions and the escalation in tidal inundation required a significant increase in field surveillance and helicopter operations.

This required the program to respond with six consecutive aerial treatments on a weekly basis during February and March.

Mosquito populations were effectively restricted despite tricky environmental conditions through this period.

Season 2019/20 recorded slightly higher numbers of reported cases of Ross River virus and Barmah Forest virus in Mandurah with 71 people contracting the viruses compared to 52 last season.

Thoughts now turn to a return to La Nina conditions this season.

La Nina occurs when equatorial trade winds become stronger, changing ocean surface currents and drawing cooler deep water up from below. This results in a cooling of the central and eastern tropical Pacific Ocean.

Those significant rises in tidal inundation events and intensity lead to greater hatching events, which means more intervention by the mosquito management program is necessary.

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