Rise in Mosquito Population Mirrors
2003 Trends
July 15th - Mosquito activity in Boulder County traps has
increased by almost threefold since the first week of July.
Due in part to wet weather in June, followed by
the recent high temperatures, most county traps report a sharp
increase in both the total number of mosquitoes, as well as a
significant increase in the presence of Culex mosquitoes –
the species known to carry and transmit the West Nile virus (WNV).
“We are now seeing a similar rise in the
mosquito populations that were observed last year in late June,”
said Heath Harmon, Boulder County Public Health’s (BCPH)
Epidemiologist.
“This current rise is a reminder of the
importance of taking precautions to reduce exposures to mosquitoes,”
Harmon continued. “Even
though we have not yet seen significant West Nile activity in the
mosquitoes we’ve collected, the fact that there have been four human
cases throughout the county indicates that there is still risk for
infection.”
Symptoms
of WNV typically begin between 3 and 14 days after being bitten. One out of five people infected will suffer an illness that
includes fever, head and body aches, skin rashes, swollen lymph
glands, and fatigue that can greatly reduce one’s ability to perform
normal daily activities. One
out of one hundred and fifty people infected may suffer from the more
severe complications of encephalitis and meningitis.
“It is more important than ever for residents
to take precautions to protect themselves,” said Chana Goussetis,
BCPH’s Health Educator. “With
such an increase in the numbers of mosquitoes now present throughout
the county, the likelihood of getting bit is even greater. It only takes one bite from an infected mosquito to contract
the illness, and possibly become severely ill.”
BCPH will be meeting with representatives from
the county’s municipalities in the coming week to discuss current
trends and the next steps to help protect the public’s health.
“Boulder County Public Health has worked
closely with city leaders to develop a plan
for responding to this kind of situation,” said BCPH’s Director of
Clinical Services, Helen Majzler.
The plan involves the consideration of several
factors to determine the risk of WNV infection to humans and
subsequent preventive actions, including spraying for mosquitoes. These factors include an increase in the numbers of Culex
mosquitoes, an increase in the rate of infection in mosquitoes, the
number of infected birds and horses and, the occurrence of human
cases.
Only after these factors have been evaluated is
spraying considered. Chemical
application for control of adult mosquitoes makes up only six percent
of the mosquito control program, and is considered for target areas of
high mosquito activity. Ninety-four
percent of control activities include biological and physical control
of mosquito breeding and harboring areas.
People concerned about
large numbers of mosquitoes around their home can also take personal
steps to reduce these numbers. Bti (Bacillus thuringiensis sub.
Israeliensis) is a naturally occurring bacteria that is packaged in
higher concentrations called mosquito dunks, mosquito donuts, or bti
briquettes and can be added to standing water. These products work to
kill larvae in standing water and are available at most hardware
stores.
So far this year, there have been four confirmed
cases of West Nile virus in Boulder County. All of these patients had symptoms that included fever, head
and body aches and fatigue. None
were hospitalized for their illness, and all are currently recovering.
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