A ProMED-mail post
ProMED-mail is a program of the
International Society for Infectious Diseases
Date: Mon 28 Feb 2011
Source: Nola.com (Times-Picayune online) [edited]
A case [sic] of West Nile virus has been found in a mosquito sample
tested in January [2011], providing significant information about how
the virus outlasts the winter, a recent St. Tammany Parish Mosquito
Abatement District report stated. [Detection or isolation of a virus
from a mosquito or mosquito pool is not referred to as a case. Case
refers to disease in humans or animals. The mosquitoes are infected,
but not "diseased." - Mod.TY]
A test sample returned positive for West Nile [virus], giving new
evidence that the virus cycles as normal during the winter months. The
virus was found in the mosquito _Culiseta inornata_, a species
normally active in the winter and early spring. This is the 1st time
the species has tested positive for West Nile [virus], the report
said. A total of 96 mosquito samples [pools] were tested for the virus
in January [2011], with one _Culiseta inornata_ pool returning
positive, the report said. A mosquito sample [pool] typically consists
of up to 50 mosquitoes that are tested as one unit.
According to Charles Palmisano, director of the mosquito abatement
district, the new evidence backs suspicions the virus actively cycles
[is transmitted] via infections between mosquitoes and birds instead
of lying dormant during the winter when cold temperatures slow
mosquito activity and development. "It's just another piece of the
puzzle to the question of what happens to the virus in the winter,"
Palmisano said. "While this indicates the (infection) cycle could be
continuing during the winter, we aren't sure what effect this could
have in late spring, early summer."
No human cases of West Nile have been reported this year [2011], and
once weather permits and adult mosquitoes become more active, the
district will begin spraying ditches in the parish to control the
mosquito population, Palmisano said. "The spring is a very important
time of year to hopefully have an impact on West Nile virus activity
for the entire year," Palmisano said. "Our thinking is that if we can
reduce the viral activity in the early spring, perhaps this will also
reduce its impact during the summer when human transmission is most
likely."
Through 21 Feb 2011, there have been no other positive findings for
West Nile [virus], Palmisano said.
About 90 percent of the people who contract West Nile will never
experience any symptoms and likely will never know they have the
disease, officials have said. Nearly all the rest will suffer from
West Nile fever, which has symptoms similar to the flu and is not
typically diagnosed as West Nile.
Only about one percent of patients who contract West Nile will
develop the neuro-invasive form of the disease, which can result in
brain or spinal swelling leading to permanent damage or death. People
who are at least 65 years old are the most likely to suffer
complications.
When a mosquito feeds on a bird infected with West Nile, the mosquito
can carry the virus and infect a person through a bite. It is not
transmitted from person to person.
--
Communicated by:
HealthMap Alerts via ProMED-mail
[West Nile virus (WNV) was isolated from _Culiseta inornata_ in the
USA from 2002 at least to 2008 as reported to the US CDC by the states
_Culiseta inornata_ has been shown in the laboratory to be infected by
and to transmit WNV. It primarily feeds on mammals and may be a
"bridge" vector transmitting the virus to humans and equine animals.
Reference:
Laura B. Goddard,* Amy E. Roth,* William K. Reisen,* and Thomas W.
Scott*. 2002. Vector competence of California mosquitoes for West Nile
virus. Emerg Infect Dis. 2002 December; 8(12): 1385-1391.
A HealthMap/ProMED-mail interactive map showing the location of
Louisiana in the southeastern USA can be accessed at
[see also:
2008
----
West Nile virus update 2008 - Western Hemisphere (15) 20080814.2516]
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