Pittwater Life December 2020 Issue

La Nina threatens mozzi
es en masse
MONITORING:
NSW Health will check
traps at Warriewood
Wetlands and Narrabeen
Lagoon on a weekly basis.
News
Northern Beaches Council
has adopted a key NSW
Health recommendation
that it sign up to a regular
seasonal Mosquito Surveillance
and Monitoring Program
across Pittwater.
It follows the alarming first
ever detection of Ross River
Virus and Barmah Forest Virus
in mosquitoes on the beaches
earlier this year, as well as
cases of debilitating Ross River
Fever in Peninsula residents.
The recommendation is
contained in a comprehensive
report to Council on last
season’s mosquito monitoring
compiled by NSW Health
Pathology expert Associate
Professor Cameron Webb.
The report was released in
early November after several
months of internal assessment.
Council announced that
commencing November
30, traps will be set at Warriewood
Wetlands and Deep
Creek – where the viruses were
detected during NSW Health
monitoring from December
2019 through May 2020.
The latest surveillance will
continue through April 2021,
with traps collected each week
for assessment and health
alerts issued immediately
should any detections be made.
Council is warning residents
that an anticipated ‘La Nina’
weather pattern
in coming
months will
bring aboveaverage
rainfall
and provide
ideal breeding
environments
for mosquitoes.
Meanwhile,
Associate Professor Webb told
Pittwater Life it remained a
mystery how Ross River Virus
has landed in our midst.
“There is some uncertainty
about this, not just on the
Northern Beaches but elsewhere
in Sydney where the
virus is found to be active
when not previously known or
suspected to be present,” he
said.
“It almost certainly wasn’t
an infected mosquito flying
into the area. It is also highly
unlikely that an infected person
introduced the virus.”
Associate Professor Webb
said it may be that the viruses
have always been in Pittwater,
circulating
between
mosquitoes
and wildlife
at such low
levels that
people were
rarely exposed
to infected
mosquitoes.
“On the other hand, perhaps
the virus was introduced by an
infected animal – a bird, bat, or
a wallaby.”
He stressed there was still a
lot to learn about how activity
of these viruses changed from
year to year and from place to
place – adding it was possible
last season’s detections could
prove one-offs.
“There is a lot we don’t know
about Ross River Virus and
other Australian mosquitoborne
viruses,” he said. “What
we do know is that it can be
very difficult to predict when
we are likely to see spikes in
activity.”
Surveillance and research
elsewhere in Sydney indicated
that the activity of mosquitoborne
viruses could fluctuate
dramatically between seasons,
he said.
He added the unpredictability
of Ross River Virus activity
meant that ongoing mosquito
control may not necessarily be
the best course of action, as
much effort could be put into
managing mosquito populations
and their habitats when
the risk was generally low.
“Surveillance is a much better
course of action as it can
provide a clearer picture of the
ongoing pest and public health
risks associated with local
mosquitoes and how those
risks change with local conditions,”
Associate Professor
Webb said.
He agreed the quantity and
pattern of rainfall would be
the most important factor in
future years.
“Even if similar quantities of
rainfall are recorded in coming
years, if that rainfall occurs in
spring or late autumn, when
weather is cooler, we may not
see as substantial a rise in
mosquito populations nor an
elevated pest or public health
threat,” he said.
“For example, there has
been a lot of rain in spring but,
elsewhere in Sydney where
surveillance was already underway
in November, mosquito
populations remained low due
to relatively cooler weather.”
Associate Professor Webb
said any ‘La Nina’ weather pattern
would provide an interesting
situation.
“In theory we may see more
mosquitoes due to forecast
increased rainfall but I’m reluctant
to predict whether we’ll
see such a large increase in
mosquitoes,” he said.
“It really depends on just
how much rainfall occurs and
over what period. The same
amount of rain that falls as
steady rainfall over the summer,
versus a week of exceptional
rainfall, can have very
different impacts.
“I think it is reasonable to
conclude though that we’ll
have average to above average
mosquito activity with the
expected rainfall.”
Associate Professor Webb
said he and colleagues at the
University of Sydney were looking
for clues in the genetics of
the viruses “to see if that may
identify pathways of introduction
or insights to their history
in the local area”.
Mayor Michael Regan said
Council is undertaking a
public education program that
will include an information
hub on its website, advice and
education to the community
via social media and on-site
signage.
NSW Health advice on simple
steps to avoid being bitten by
mosquitoes include:
Avoid being outside unprotected
at dusk, when mosquitoes
are commonly active and
cover up as much as possible
with light-coloured, loosefitting
clothing and covered
footwear.
Apply mosquito repellent
regularly to exposed areas.
Don’t use repellents on the
skin of children under the age
of three months. Instead use
physical barriers such as netting
on prams, cots and play
areas.
Eradicate mosquito breeding
sites around the home, including
containers and that hold
water.
Use flyscreens on windows
and doors of houses and keep
them in good order.
– Nigel Wall
News
8 DECEMBER 2020
The Local Voice Since 1991
The Local Voice Since 1991
DECEMBER 2020 9