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Florida Mosquito Control Association

Arbovirus Surveillance Reports - 2005

December 2005

Total numbers of submitted sera have decreased as the winter approaches and some counties have stopped their surveillance programs until spring.

There were 8 seroconversions due to alphaviruses, all to Eastern Equine Encephalitis virus (EEE) for a 0.8% seroconversion rate. The rate for EEE activity is similar to the mean for EEE historical activity during December. Testing prior to 2004 did not distinguish between these two alphaviruses, thus making direct comparisons with rates reported prior to 2004 problematic.

There were 12 new HAI flavivirus positive sentinel (St Louis Encephalitis virus (SLE) antigen used in the HAI assay) confirmed as WN+ by IgM Elisa or Serum Neutralization during December, 2005, for a rate of 1.3%. This is not significantly different from the mean statewide rate for December.

Sera from 102 wild birds were screened by HAI. Table 1 lists submissions and results by county for EEE. Antibody to WN was detected in one crane from Hillsborough county and one bluejay from Okaloosa county.

Table 1. EEE positive wild birds

county

# birds

total EEE+

blue jay

cardinal

grackle

thrasher

sparrow

tit mouse

Black bird

finch

dove

crane

Hillsboro

0+/1

Okaloosa

10+/11

3+/12

1+/1

4+/33

0+/2

Santa Rosa

2+/2

0+/28

0+/2

1+/33

0+/1

0+/2

Walton (North)

0+/1

2+/14

0+/2

1+/1

2+/20

1+/1

Washington

0+/2

1+/13

0+/1

0+/20

totals

202

12+/16

6+/67

0+/3

2+/4

7+/106

0+/1

0+/2

1+/1

0+/1

* # + / # submitted

12 dead birds were submitted for arbovirus assay during December. Virus was not detected. Brain tissues from two equines and 2 raccoons were also submitted for arbovirus testing; no virus was detected.

Table 3.

county	birds			mammal
	submitted	EEE positive	WN positive	submitted	EEE positive	WN positive
Alachua				2
Broward				1
Dade	9
Hernando	2
Leon	1
Marion				1
Totals	12	0	2	4	0	0

During December, 81 traditional mosquito pools were assayed for arboviruses by real-time RT-PCR and cell culture inoculation (Sarasota, 63 pools; St. Johns 18 pools). One pool of Anopheles crucians collected 11/30/05 yielded a California group virus.

HAI

November 2005

There were 12 seroconversions due to alphaviruses, all to Eastern Equine
Encephalitis virus (EEE) for a 0.9% seroconversion rate. The rate for
EEE activity is similar to the mean for EEE historical activity during
November. Testing prior to 2004 did not distinguish between these two
alphaviruses, thus making direct comparisons with rates reported prior
to 2004 problematic.

There were 30 new HAI flavivirus positive sentinel (St Louis
Encephalitis virus (SLE) antigen used in the HAI assay) confirmed as WN+
by IgM Elisa or Serum Neutralization during November, 2005, for a rate
of 2.3%. This is not significantly different from the mean statewide
rate for November.

Sera from 104 wild birds were screened by HAI. Table 1 lists
submissions and results by county for EEE. Antibody to WN was not
detected in these birds.

17 dead birds were submitted for arbovirus assay during November. West
Nile virus was detected in two birds. Brain tissues from two equines
and one deer were also submitted for arbovirus testing; no virus was detected.

During November, 117 traditional mosquito pools were assayed for
arboviruses by real-time RT-PCR and cell culture inoculation. Three RAMP
test residual pools that had been positive in the mosquito control
district assay were also assayed by RT-PCR. Virus was not detected in these samples.

October 2005

There were 32 seroconversions due to alphaviruses: 23 to Eastern Equine
Encephalitis virus (EEE) for a 1.5% seroconversion rate and 9 to
Highlands J virus (0.6%). The rate for EEE activity is greater than the
mean for EEE historical activity during October. Testing prior to 2004
did not distinguish between these two alphaviruses, thus making direct
comparisons with rates reported prior to 2004 problematic. The October
total alphavirus seroconversions rate is 2.1%, which is significantly
greater than the historical mean and the highest alphavirus
seroconversion rate since 1988.

There were 105 new HAI flavivirus positive sentinel (St Louis
Encephalitis virus (SLE) antigen used in the HAI assay); 104 were
confirmed as WN+ by IgM Elisa or Serum Neutralization during October,
2005, for a rate of 7.0%. This is not significantly different from the
mean statewide rate for October. There was 1 seroconversion to SLE
during October in Indian River county. WN activity was intense in
Alachua, Duval, Jefferson, Manatee, Putnam and St. Johns counties (>20%
seroconversion rate).

Sera from 94 wild birds were screened by HAI. Table 1 lists submissions
and results by county for EEE.

32 dead birds were submitted for arbovirus assay during October. No
virus was detected in these birds. Brain tissues from four equines were
also submitted for arbovirus testing; no virus was detected. West Nile
Virus was detected in tissues from two Lake county alligators.

During October, 65 traditional mosquito pools were assayed for
arboviruses by real-time RT-PCR and cell culture inoculation. Three RAMP
test residual pools that had been positive in the mosquito control
district assay were also assayed by RT-PCR; one was confirmed positive.

September 2005

There were 38 seroconversions due to alphaviruses: 36 to Eastern Equine
Encephalitis virus (EEE) for a 2.3% seroconversion rate and 2 to
Highlands J virus (0.1%). The rate for EEE activity is significantly
greater than the mean for EEE historical activity during September.
Testing prior to 2004 did not distinguish between these two
alphaviruses, thus making direct comparisons with rates reported prior
to 2004 problematic. The September total alphavirus seroconversions
rate is 2.5%.

There were 134 new HAI flavivirus positive sentinel (St Louis
Encephalitis virus (SLE) antigen used in the HAI assay); 131 were
confirmed as WN+ by IgM Elisa or Serum Neutralization during September,
2005, for a rate of 8.5%. This is not significantly different from the
mean statewide rate for September. There were 3 seroconversions to SLE
during September (Sarasota, 2; Indian River, 1). WN activity was
intense in Duval, Glades, Hillsborough, Leon, Nassau, Putnam and St.
Johns counties (>15% seroconversion rate).

Sera from 141 wild birds were screened by HAI. Table 1 lists
submissions and results by county for EEE. Table 2 lists submissions
and results by county for WN

13 dead birds were submitted for arbovirus assay during September. No
virus was detected in these birds. Brain tissues from four equines were
also submitted for arbovirus testing; EEE virus was detected in two and
WN virus in one.

During September, 353 traditional mosquito pools were assayed for
arboviruses by real-time RT-PCR and cell culture inoculation.

August 2005

There were 58 seroconversions due to alphaviruses: 40 to Eastern Equine
Encephalitis virus (EEE) for a 2.6% seroconversion rate and 18 to
Highlands J virus (0.8%). The rate for EEE activity is greater than the
mean for EEE historical activity during August. Testing prior to 2004
did not distinguish between these two alphaviruses, thus making direct
comparisons with rates reported prior to 2004 problematic. The August
total alphavirus seroconversions rate is 3.8%.

There were 53 new HAI flavivirus positive sentinel (St Louis
Encephalitis virus (SLE) antigen used in the HAI assay); 52 were
confirmed as WN+ by IgM Elisa or Serum Neutralization during August,
2005, for a rate of 3.4%. This is not significantly different from the
mean statewide rate for August. There were no seroconversions to SLE
during August. Activity was intense in Pinellas County (18.3%
seroconversion rate), the site of all human cases recognized to date,
but this was lower than the July rate. Hillsborough County, adjacent to
Pinellas, had the highest rate of sentinel seroconversion to WN (19.6%).
One chicken in Manatee County seroconverted to SLE.

Sera from 87 wild birds were screened by HAI. Table 1 lists submissions
and results by county for EEE. Table 2 lists submissions and results by
county for WN

23 dead birds were submitted for arbovirus assay during August. WN
virus was detected in three bluejays from Pinellas County. EEE virus
was detected in a crane from Alachua County. Brain tissues from ten
equines were also submitted for arbovirus testing; EEE virus was
detected in three horses.

During August, 577 traditional mosquito pools were assayed for arboviruses by real-time RT-PCR and cell culture inoculation.

July 2005

There were 94 seroconversions due to alphaviruses: 61 to Eastern Equine Encephalitis virus (EEE) for a 4.0% seroconversion rate and 33 to Highlands J virus (2.1%). The rate for EEE activity is greater than the mean for EEE historical activity during July. Testing prior to 2004 did not distinguish between these two alphaviruses, thus making direct comparisons with rates reported prior to 2004 problematic. The July total alphavirus seroconversions rate is 6.1%.

Historical data is presented in a graphical format in the attached file. A graph illustrating the relationship of 2005 EEE and 2005 alphavirus seroconversion rates to the monthly average serovonversion rate (MASR) is also included. The MASR is based on historical data from 1988 and is computed from total alphavirus seroconversions, including both EEE and HJ. A rate greater than two standard deviations above the mean is significant.

There were 43 new HAI Flavivirus positive sentinel (St Louis Encephalitis virus (SLE) antigen used in the HAI assay) confirmed as WN+ by IgM Elisa or Serum Neutralization during July, 2005, for a rate of 2.8%. This is not significantly different from the mean statewide rate for July. There were no seroconversions to SLE during July. Activity was most intense in Pinellas County (33.3% seroconversion rate); the next highest rate, 13.3%, was in Indian River County.

Sera from 139 wild birds were screened by HAI. Table 1 lists submissions and results by county for EEE. Table 2 lists submissions and results by county for WN

Table 1. EEE positive wild birds

county	# birds	total EEE+	blue jay*	cardinal	grackle	thrasher	black bird	sparrow	dove	cowbird	other
Hillsborough	4	0									0+/4
Okaloosa	49	14	8+/18	4+/18	0+/2	1+/4	0+/5			1+/1	0+/1
Santa Rosa	18	7	3+/7	2+/4	1+/6	1+/1
Walton(North)	22	2	0+/2	1+/11				1+/8	0+/1
Washington	50	14	2+/4	5+/21	7+/20			0+/1		0+/2	0+/2
totals	143	37	13+/31	12+/54	8+/28	2+/5	0+/5	1+/9	0+/1	1+/3	0+/5

* # + / # submitted

Table 2. WN seropositive wild birds

county	# birds	total WN+	blue jay*	cardinal	grackle	thrasher	black bird	sparrow	dove	cowbird	other
Hillsborough	4	1									1+**/4
Okaloosa	49	0	0+/18	0+/18	0+/2	0+/4	0+/5			0+/1	0+/1
Santa Rosa	18	1	1+/7	0+/4	0+/6	0+/1
Walton(North)	22	0	0+/2	0+/11				0+/8	0+/1
Washington	50	1	1+/4	0+/21	0+/20			0+/1		0+/2	0+/2
totals	143	3	2+/31	0+/54	0+/28	0+/5	0+/5	0+/9	0+/1	0+/3	1+/5

*:# + / # submitted **: WN positive vulture

26 dead birds were submitted for arbovirus assay during July. WN virus was detected in six out of seven bluejays from Pinellas County. Brain tissues from ten equines and one llama were also submitted for arbovirus testing; EEE virus was detected in five horses (71%).

Table 3.

county	birds		mammal
	submitted	WN+	submitted	EEE positive
Alachua			1	1
Bradford			1	1
Collier	1
Dade	9
Desoto			1
Gilchrist	1
Hendry			1	1
Hernando	1
Hillsborough	1		1*
Lafayette			1	1
Levy	3
Marion			2
Monroe	2
Orange	1
Palm Beach			1
Pinellas	7	6
Sarasota			1	1
Seminole			1
totals	26	6	11	5

* llama

During July, 108 traditional mosquito pools (Table 4)

Table 4. Mosquito test results

county	# pools	EEE +	specias (#/pool)
Escambia	23	3	Cs. melanura (50, 50, 32)
Sarasota	19	3	Oc. atlanticus (50, 50, 50)
St. Johns	36	1	Oc. infirmatus (12)
Volusia	30	0
totals	108	7

A RAMP test residual from a pool of 50 of Oc. taeniorhynchus was submitted by Monroe county. EEE virus was detected by real-time RT-PCR.

HAI

EEE Historical Graph

June 2005

There were 117 seroconversions due to alphaviruses: 84 to Eastern Equine Encephalitis virus (EEE) for a 5.6% seroconversion rate and 33 to Highlands J virus (2.2%). The rate for EEE activity is significantly greater than the mean for EEE historical activity during June. Testing prior to 2004 did not distinguish between these two alphaviruses. The June total alphavirus seroconversions rate (7.9%) is higher then for any month since data collection had begun in 1988. Historical data is presented in a graphical format in the attached file.

There were 6 new HAI Flavivirus positive sentinel (St Louis Encephalitis virus (SLE) antigen used in the HAI assay) confirmed as WN+ by IgM Elisa or Serum Neutralization during June, 2005, for a rate of 0.4%. This is not significantly different from the mean statewide rate for June. There were no seroconversions to SLE during June.

Sera from 150 wild birds were screened by HAI. Table 1 lists submissions and results by county for EEE. Table 2 lists submissions and results by county for WN

Table 1. EEE positive wild bird

county	# birds	total EEE+	blue jay*	cardinal	grackle	thrasher	black bird	sparrow	dove	cowbird	other
Hillsborough	4	0									0+/4
Okaloosa	49	14	8+/18	4+/18	0+/2	1+/4	0+/5			1+/1	0+/1
Santa Rosa	18	7	3+/7	2+/4	1+/6	1+/1
Walton(North)	22	2	0+/2	1+/11				1+/8	0+/1
Washington	50	14	2+/4	5+/21	7+/20			0+/1		0+/2	0+/2
totals	143	37	13+/31	12+/54	8+/28	2+/5	0+/5	1+/9	0+/1	1+/3	0+/5

* # + / # submitted

Table 2. WN seropositive wild birds

county	# birds	total # WN+	blue jay*	cardinal	grackle
Okaloosa	44	1	1+/20
Santa Rosa	32	2	2+/13
Walton (North)	29	0
Washington	45	3		2+/21	1+/8
total	150	6	2+/54	1+/18

Eleven dead birds were submitted for arbovirus assay during June. EEE virus was detected in one dove from Alachua County. Brain tissues from seven equines and one Impala were also submitted for arbovirus testing; EEE virus was detected in five horses (71%).

EEE

Table 3. county, birds, mammal

county	submitted	positive
Alachua	2
Dade	3
Hernando	2
Hillsborough	1	1*
Leon	1	1
Levy	1	1
Madison	1
Marion	2	2
Orange	1
Osceola	1	1
Sarasota	1
totals	11	6
*Impala

During June, 94 traditional mosquito pools (Table 4) and 26 RAMP test pool residuals (Monroe county, 24; Sarasota county,2) were submitted for assay. Arbovirus was not detected in the RAMP test samples.

Table 4. Mosquito test results

county	# pools EEE+	CAL+	species (#/pools)
Palm Beach	20
Sarasota	16	1	An crucians
St. Johns	14
Volusia	35	2	Cq perturbans, Cx nigrapalpus
Walton	9
totals	94

HAI

April 2005

Table 1. Submissions have increased from March.

	March	April
# Counties	18	24
# sites	145	199
# birds	850	1259
# sera	2703	3611

There were 23 seroconversions due to alphaviruses: 21 to Eastern Equine Encephalitis virus (EEE) for a 1.7% seroconversion rate and 2 to Highlands J virus (0.2%). The rate for EEE activity is significantly greater than the mean for EEE historical activity during April.

There were 8 new HAI Flavivirus positive sentinel (St Louis Encephalitis virus (SLE) antigen used in the HAI assay) confirmed as WN+ by IgM Elisa or Serum Neutralization during April, 2005, for a rate of 0.5%. This is not significantly different from the mean statewide rate for April. There were no seroconversions to SLE during April.

Sera from 107 wild birds were screened by HAI. They were all negative for antibody to flaviviruses. Table 2 lists submissions and results by county.

Table 2. Dead Bird Surveillance

County	# birds	# EEE pos	species
Okaloosa	23	6	bluejay (3)cardinal (3)
Santa Rosa	22	3	bluejay (3)
St. Johns	2
Walton (North)	35	5	bluejay(2)sparrow(3)
Washington	25	0
totals 107	14	8	bluejay(3)cardinal(3)

Thirteen dead birds (Alachua, Dade, Gilchrist, Hillsborough, Jackson, Leon and St. Johns counties) were submitted for arbovirus assay. No virus was detected. Brain tissues from seven equines were also submitted for arbovirus testing (Duval, Lee, Manatee, Pasco, Putnam, Sumter and Washington counties). No virus was detected.

During April, 32 traditional mosquito pools from St. Johns, county and 11 RAMP test residual samples (Monroe, 9; St. Johns, 2) were submitted for assay. Arbovirus was not detected.
HAI

March 2005

There were 11 seroconversions due to alphaviruses: 10 to Eastern Equine Encephalitis virus (EEE) for a 1.2% seroconversion rate and 1 to Highlands J virus (0.1%). The rate for EEE activity does not differ significantly from the mean for EEE historical activity during March.

There was 1 new HAI Flavivirus positive sentinel (St Louis Encephalitis virus (SLE) antigen used in the HAI assay) confirmed as WN+ by IgM Elisa or Serum Neutralization during March, 2005, for a rate of 0.1%. This is not significantly different from the mean statewide rate for March. There were no seroconversions to SLE during March.

Sera from 43 wild birds were screened by HAI. They were all negative for antibody to flaviviruses. Eight birds were confirmed positive for antibody to EEE from

Walton (2 sparrows) and Washington (6 cardinals) counties.

Eight dead birds (Alachua, Dade, Dade, Hernando, Hillsborough, Hillsborough, Jefferson and Pinellas counties) were submitted for arbovirus assay. No virus was detected. Brain tissues from five equines were also submitted for arbovirus testing (Alachua, Escambia, Orange, Pasco and Hillsborough counties). No virus was detected.

During March, 50 traditional mosquito pools (Escambia, 29; St. Johns, 21) and 19 RAMP test residual samples (Monroe, 18; St. Johns, 1) were submitted for assay. Arbovirus was not detected.

HAI

February 2005

There were 10 seroconversions due to alphaviruses: 9 to Eastern Equine Encephalitis virus (EEE) for a 1.1% seroconversion rate and 1 to Highlands J virus (0.1%). The rate for EEE activity does not differ significantly from the mean for EEE historical activity during February.

There were 3 new HAI Flavivirus positive sentinels (St Louis Encephalitis virus (SLE) antigen used in the HAI assay) confirmed as WN+ by IgM Elisa or Serum Neutralization during February, 2005, for a rate of 0.4%. This is not significantly different from the mean statewide rate for February. There were no seroconversions to SLE during February.

Sera from 47 wild birds were screened by HAI. They were all negative for antibody to flaviviruses. Nine birds were confirmed positive for antibody to EEE from Okaloosa (3 bluejays, 1 cardinal), Santa Rosa (1 sparrow), Walton (1 sparrow) and Washington (2 sparrows, 1 cardinal) counties.

Three dead birds (Hernando, Hillsborough and Orange counties) were submitted for arbovirus assay. No virus was detected.

During February, 44 traditional mosquito pools (Escambia, 14; Walton, 30) were submitted for assay. Arbovirus was not detected.

HAI

January 2005 Also attached is a poster ("Coordinated-laboratory based surveillance for Arboviruses is effective in moderating risk of WNV disease in humans") that will be presented at the Association of Public Health Laboratories (APHL)Infectious Disease conference in Orlando on March 3, 2005.
APHL

There were 6 seroconversions due to alphaviruses: 4 to Eastern Equine Encephalitis virus (EEE) for a 0.4% seroconversion rate and 2 to Highlands J virus (0.2%). The rate for EEE activity does not differ significantly from the mean for EEE historical activity during January. There were 11 new HAI Flavivirus positive sentinels (St Louis Encephalitis virus (SLE) antigen used in the HAI assay) confirmed as WN+ by IgM Elisa or Serum Neutralization during January, 2005, for a rate of 1.4%. This is not significantly different from the mean statewide rate for January. There were no seroconversions to SLE during January. Of the 17 total seroconversions to arbovirus antibody positive, 10 occurred in Walton County in the Florida panhandle.

Sera from 23 wild birds were screened by HAI. They were all for antibody to flaviviruses. Three from Volusia County (2 bluejays, 1 cardinal) and 0ne sparrow from Washington county were confirmed with antibody to EEE.

Nine dead birds (Columbia, Dade, Hernando, Madison, Orange counties) and tissue from 5 mammals (2 horses, 1 cow, 2 rhinoceroses) were submitted for arbovirus assay. No virus was detected.

During January, 18 traditional mosquito pools (Escambia, 13; St. Johns, 5) were submitted for assay. Arbovirus was not detected. Two RAMP Assay residual samples were submitted by Bay County for confirmation; WN virus was not detected.

HAI