PENNSYLVANIA STATE
REPORT – 2008
Andy Kyle/Mike Hutchinson
PA Dept. of Environmental Protection
ABSTRACT
West Nile
Virus:
The Pennsylvania WNV Mosquito Control Program
continues to support county mosquito surveillance and control programs
throughout the state. Grants are
provided to participating counties that reimburse staff hours, travel and
training costs, surveillance equipment and control products as well as other
items that have been approved on a yearly WNV grant agreement with each
county. Due to program budget reductions
the 2009 county grants have been reduced accordingly as well as the elimination
of aerial larviciding and ground based ULV adulticiding contracts that support
the counties in control activities.
In response to CDC funding cuts to our state Health
laboratory, the DEP used state funds to purchase equipment and hire personnel
to perform WNV testing in-house using RT-PCR.
Our expectation is to continue testing mosquito pools at the level of
prior years, but the work will be distributed among both laboratories in
2009. All statewide mosquito collections
are submitted to the DEP laboratory for identification and pooling. We anticipate that having in-house testing
capabilities will greatly improve turnaround time on testing results for our
most critical samples.
A total of 33,422 mosquito samples were analyzed this
year with approximately 1.1 million individual mosquito specimens
identified. 26,026 pools were tested by
PCR and 589 were tested using RAMP. A total of 638 pools tested positive, 578
using PCR and 60 using RAMP. This year’s total positive number makes 2008
the third highest total since the program began in 2000.
Pennsylvania continues to use an Integrated Mosquito
Management approach to reduce WNV human transmission from mosquitoes in the
Culex group. Education is important but
Pennsylvania relies heavily on source reduction, surveillance and control
measures to reduce Culex populations associated with WNV transmission. Larviciding is always preferred but many
times Culex sp. habitats are very
difficult to locate and adulticiding becomes the only option. Adulticiding events are always based on Culex collections, whether they are
aimed at reducing the WNV amplifying Culex
populations or to control Culex
populations where positive mosquito pools are detected.
On August 26-27 the State of Pennsylvania's
Department of Environmental Protection and Department of Health conducted an
aerial application of "Scourge" over the Philadelphia metropolitan
area. The treatment specifically
targeted Culex mosquitoes during
their peak activity time and was done over 164,000 acres. West Nile Virus infection rates in the Culex genus were extremely high in this
densely populated area and posed a significant threat to the public
health.
Infection rates in the Philadelphia Metropolitan area
during 2008 were the highest recorded since the West Nile Virus was first seen
in Pennsylvania. As a comparison, 2003
saw a MLE near 10, while 2008 saw infection rates
ranging between 13-27.
During 2003, 54 human cases were recorded in the Philadelphia
Metropolitan area. In 2008, 13 cases
have been documented as of October 31. From this single application, recorded infection rates in the
application area dropped by at least 65%. The State hopes that the reduction in
infection rates has ultimately reduced the number of human infections in 2008.
Vector Disease Control Incorporated conducted the
applications over 2 evenings from 8:30 PM until 12:00 AM. Two planes, using Beecomist nozzles,
dispensed the product at an application height of 300 feet. The planes were able to treat more than 10,000
acres/hour. Slide spinners were used to
collect droplet density and live caged mosquitoes were used to assess the
results of the application. Public
comment regarding the application was frenzied and pushed the State to review
the existing public outreach in regards to vector borne disease and the use of
pesticides.
To date, 13 WNV human cases have been confirmed and
reported to CDC. The state also tested
77 dead birds for the presence of WNV with 14 positive results (12 crows, one blue
jay and one domesticated parrot). Two
positive equine cases were also reported this year.
Other
Mosquito-borne Disease
Three imported human cases (two dengue cases and one
St. Louis encephalitis case) were reported this year from Pennsylvania. A confirmed EEE horse case was also diagnosed
in the northwestern portion of the state late in the mosquito season.
Nuisance
Mosquito Control
Pennsylvania never observed a widespread nuisance
problem due to lack of heavy rains during 2008.
Isolated nuisance problems were controlled by county programs. However, the state did see a 6-fold increase
in the Aedes albopictus populations in the heaviest populated areas of southcentral and southeastern Pennsylvania.
Black Fly
Suppression
The Pennsylvania Black Fly Suppression Program
remains the largest black fly control program in the world. Over 50 streams were treated using Bacillus
thuringiensis israelensis (Bti), VectoBac 12AS from
April to August. Approximately 121,000
gallons of product were applied aerially while another 182 gallons were sprayed
using backpack sprayers. This program
benefits over 3 million citizens of the Commonwealth, providing relief from the
swarming and biting of black fly adults.