Florida Mosquito Control Association

 

Arbovirus Surveillance Reports - 2006

November 2006

2006 Annual Totals

Annual by Region

In November there were two seroconversions due to alphaviruses, both due to Eastern Equine Encephalitis virus (EEE), resulting in seroconversion rate of 0.2%.  This level of activity is below the historical mean for November and is the lowest rate since 1991.  In December there were five seroconversions to EEE, all late in the month.

There were eight HAI flavivirus positive sentinels (St Louis Encephalitis virus (SLE) antigen used in the HAI assay) during November.  Three were confirmed as due to WN virus for a seroconversion rate of 0.3%, the lowest rate since the virus appeared in peninsular Florida.  There were five seroconversions confirmed as SLE, by IgM Elisa or Serum Neutralization for a seroconversion rate of 0.5%.  This is similar to the median seroconversion rate for SLE and is the highest November SLE activity since WN appeared in Florida. 

During December there were ten flavivirus seroconversions, all due to SLE, for a seroconversion rate of 1.1%.  This is the highest rate of SLE activity since 1999.

Sera from 84 live wild birds were screened by HAI in November and during December 149 bird sera were assayed.  Table 1 lists submissions and results by county for EEE.  Table 2 lists submissions and results by county for WN.

Table 1.  EEE positive live wild birds


November

# birds

total EEE+

blue jay

black-bird

cardinal

finch

grackle

mocking-bird

sparrow

thrasher

tit-mouse

Okaloosa

23

3

2+/3

0+/1

1+/7

0+/1

 

 

0+/10

 

0+/1

Santa Rosa

18

2

1+/4

 

1+/8

 

 

0+/1

0+/4

0+/1

 

Walton (North)

35

1

0+/1

0+/1

1+/25

 

0+/1

 

0+/7

 

 

Washington

8

0

0+/1

 

0+/1

 

 

 

0+/6

 

 

totals

84

6

3+/9

0+/2

3+/41

0+/1

0+/1

0+/1

0+/27

0+/1

0+/1

 

December

# birds

total EEE+

blue jay

black-bird

cardinal

Finch

grackle

mocking-bird

sparrow

thrasher

tit-mouse

Okaloosa

68

4

1+/3

0+/3

3+/14

 

 

0+/1

0+/45

0+/1

0+/1

Santa Rosa

33

2

2+/4

 

0+/6

 

 

 

0+/22

0+/1

 

Walton (North)

48

0

 

 

0+/24

 

 

 

0+/24

 

 

Washington

53

2

0+/3

0+/3

2+/24

 

0+/2

 

0+/21

 

 

totals

149

8

3+/10

0+/3

5+/68

0+/0

0+/2

0+/1

0+/112

0+/2

0+/1

* # + / # submitted
Table 2.  WN positive live wild birds


November

# birds

total EEE+

blue jay

black-bird

cardinal

finch

grackle

mocking-bird

sparrow

thrasher

tit-mouse

Okaloosa

23

1

1+/3

0+/1

0+/7

0+/1

 

 

0+/10

 

0+/1

Santa Rosa

18

0

0+/4

 

0+/8

 

 

0+/1

0+/4

0+/1

 

Walton (North)

35

0

0+/1

0+/1

0+/25

 

0+/1

 

0+/7

 

 

Washington

8

0

0+/1

 

0+/1

 

 

 

0+/6

 

 

totals

84

1

1+/9

0+/2

0+/41

0+/1

0+/1

0+/1

0+/27

0+/1

0+/1

 

December

# birds

total EEE+

blue jay

black-bird

cardinal

Finch

grackle

mocking-bird

sparrow

thrasher

tit-mouse

Okaloosa

68

0

0+/3

0+/3

0+/14

 

 

0+/1

0+/45

0+/1

0+/1

Santa Rosa

33

0

0+/4

 

0+/6

 

 

 

0+/22

0+/1

 

Walton (North)

48

1

 

 

0+/24

 

 

 

1+/24

 

 

Washington

53

0

0+/3

0+/3

0+/24

 

0+/2

 

0+/21

 

 

totals

149

1

0+/10

0+/3

0+/68

0+/0

0+/2

0+/1

1+/112

0+/1

0+/1

* # + / # submitted

There were 5 dead birds were submitted for arbovirus assay during November.    Brain tissues from four horses were submitted for arbovirus testing.  Cloacal swabs were submitted from 14 birds being treated by Wildlife rehabilitators.  Virus was not detected in any of these specimens.  During December, nine dead birds, seven mammals and two swabs were assayed.

Table 3.  Numbers of field specimens for virus isolation submitted by county

 

birds

mammal

cloacal swabs

 

Nov

Dec

Nov

Dec

Nov

Dec

Alachua

 

2

 

1

 

2

Brevard

 

 

1

1

 

 

Dade

3

4

 

 

 

 

Dixie

1

 

 

 

 

 

Hernando

 

1

 

 

 

 

Hillsborough

1

 

 

 

 

 

Holmes

 

 

1

 

 

 

Lake

 

 

 

 

1

 

Marion

 

 

1

1

 

 

Orange

 

 

 

 

6

 

Osceola

 

 

 

 

2

 

Polk

 

 

 

1

 

 

Seminole

 

 

 

 

2

 

Sumter

 

 

 

2

3

 

Volusia

 

 

 

1

 

 

Washington

 

 

1

 

 

 

 

5

9

4

7

14

2

Table 4. Numbers of submissions by species.

 

Nov

Dec

Catbird

1

 

Dove

3

1

Duck

 

1

Eagle

1

 

Flamingo

1

 

Grackle

 

1

Hawk

5

1

Loon

 

1

Owl

5

 

Sora

 

2

Unknown

 

1

Vulture

3

 

Willet

 

1

Deer

 

1

Equine

4

6

 

23

16

During November, 119 and during December, 59 traditional mosquito pools were assayed for arboviruses by real-time RT-PCR and cell culture inoculation. One RAMP test positive specimens was submitted for confirmation during November.  All were negative for virus.

Table 6.  Mosquito Pool submissions by county

 

traditional

ramp

 

Nov

Dec

Nov

Dec

Escambia

 

6

 

 

Manatee

26

 

 

 

Monroe

 

 

1

 

Palm Beach

26

 

 

 

Sarasota

67

38

 

 

Walton

 

15

 

 

 

119

59

1

0

HAI November 2006

September 2006

In September there were nine seroconversions due to alphaviruses, seven to Eastern Equine Encephalitis virus (EEE) and two to Highlands J, resulting in seroconversion rate of 0.5% and 0.1% respectively.  These levels of activity are similar to historical means for September.

There were nine HAI flavivirus positive sentinels (St Louis Encephalitis virus (SLE) antigen used in the HAI assay) during September.  Six were confirmed as due to WN virus for a seroconversion rate of 0.4%, the lowest rate since the virus appeared in peninsular Florida.  Three seroconversions were confirmed as SLE, by IgM Elisa or Serum Neutralization for a seroconversion rate of 0.2%.  This is similar to the median seroconversion rate for SLE. 

Sera from 159 live wild birds were screened by HAI in September.  Table 1 lists submissions and results by county for EEE.  Table 2 lists submissions and results by county for WN.

Table 1.  EEE positive live wild birds


September

# birds

total EEE+

blue jay

black-bird

cardinal

dove

finch

grackle

sparrow

thrasher

tit-mouse

Okaloosa

54

2

1+/17

0+/15

0+/8

 

 

0+/10

 

0+/2

1+/2

Santa Rosa

18

0

0+/7

 

0+/8

0+/2

0+/1

 

 

 

 

Walton (North)

51

4

0+/3

 

2+/31

 

 

0+/4

2+/13

 

 

Washington

36

2

0+/3

 

2+/24

 

 

0+/2

0+/7

 

 

totals

159

8

1+/30

0+/15

4+/71

0+/2

0+/1

0+/16

2+/20

0+/2

1+/2

* # + / # submitted

Table 2.  WN positive live wild birds


county

# birds

total WN+

blue jay

black-bird

cardinal

dove

finch

grackle

sparrow

thrasher

tit-mouse

Okaloosa

54

0

0+/17

0+/15

0+/8

 

 

0+/10

 

0+/2

0+/2

Santa Rosa

18

1

0+/7

 

0+/8

0+/2

1+/1

 

 

 

 

Walton (North)

51

2

0+/3

 

1+/31

 

 

0+/4

1+/13

 

 

Washington

36

2

1+/3

 

1+/24

 

 

0+/2

0+/7

 

 

totals

159

5

1+/30

0+/15

2+/71

0+/2

1+/1

0+/16

1+/20

0+/2

0+/2

* # + / # submitted

In addition, one horse from Escambia County was positive for EEE antibody.  Serum from an Egyptian goose was positive for WN antibody and sera from 5 thick-billed parrots were negative for antibodies to alpha and flaviviruses (Hillsborough County)

There were 13 dead birds were submitted for arbovirus assay during September.  Cloacal swabs (20) were submitted from live wild birds being treated by wildlife rehabilitators.  Brain tissues from one horse and one alpaca were submitted for arbovirus testing.  Virus was not detected in any of these specimens. 

Table 3.  Numbers of field specimens for virus isolation submitted by county

 

# birds

# mammals

# swabs

Alachua

 

1

 

Dade

8

 

10

Duval

 

1

 

Hernando

1

 

 

Hillsborough

2

 

 

Leon

1

 

 

Manatee

 

 

10

Orange

1

 

 

 

13

2

20

Table 5. Numbers of submissions by species.


Species

#

Chicken

1

Dove

9

Duck

2

Goose

1

Grackle

4

Gull

3

Heron

2

Ibis

2

Mockingbird

1

Owl

1

Pigeon

4

Ruddy Turnstone

1

Whip-poor-will

1

Wren

1

Alpaca

1

Equine

1

Total

35

During September, 163 traditional mosquito pools were assayed for arboviruses by real-time RT-PCR and cell culture inoculation.  A California group virus was detected in one pool of 50 Anopheles crucians from Sarasota county collected 8/30/06; all others were negative for arboviruses.

Table 6.  Mosquito Pool submissions by county


July

# pools

Citrus

7

Escambia

10

Flagler

21

Sarasota

125

total

163

HAI 2006

July 2006, August 2006

In July there were 18 seroconversions due to alphaviruses, all to Eastern Equine Encephalitis virus (EEE), resulting in a seroconversion rate of 1.2%.  During August there were 7 seroconversions to EEE (0.5% seroconversion rate) and one to HJ.  These levels of activity are not significantly lower than historical means for those months.

There was one new HAI flavivirus positive sentinel (St Louis Encephalitis virus (SLE) antigen used in the HAI assay) during July.  This was confirmed as due to WN virus for a seroconversion rate of 0.1%, the lowest rate since the virus appeared in peninsular Florida.  Five seroconversions were detected in August by HAI.  Two were confirmed as WN+ and three as SLE, by IgM Elisa or Serum Neutralization for a seroconversion rate of 0.1% and 0.2% respectively.  This is not significantly different from the mean statewide rate for those months. 

At first glance, the overall seroconversion rate during 2006 has seemed extraordinarily low however, intervals with such low rates have routinely occurred in the past.  (Table 1)  It is likely that the extended period of drought statewide this spring strongly influenced the transmission cycle. 

Table 1.  Sentinel Seroconversions from June through August by year. 


Year

avg# birds

EEE

HJ

SLE

WN

total +

total %+

1988

603

17

0

0

0

17

2.8%

1989

558

19

0

0

0

19

3.4%

1990

550

2

0

202

0

204

37.1%

1991

866

90

0

14

0

104

12.0%

1992

980

56

0

3

0

59

6.0%

1993

913

56

0

13

0

69

7.6%

1994

919

68

0

5

0

73

7.9%

1995

969

65

0

2

0

67

6.9%

1996

1104

64

0

0

0

64

5.8%

1997

830

58

0

111

0

169

20.4%

1998

1036

10

0

14

0

24

2.3%

1999

894

16

0

10

0

26

2.9%

2000

924

3

0

11

0

14

1.5%

2001

1125

34

0

6

9

49

4.4%

2002

1218

18

0

0

252

270

22.2%

2003

1739

205

0

0

454

659

37.9%

2004

1570

57

19

2

118

196

12.5%

2005

1524

185

84

1

101

371

24.3%

2006

1487

29

1

3

4

37

2.5%

Avg # birds= average number of birds exposed per month during June through August

Sera from 147 live wild birds were screened by HAI in July and 133 birds were screened in August.  Table 2 lists submissions and results by county for EEE.  Table 3 lists submissions and results by county for WN.

Table 2.  EEE positive live wild birds


July

# birds

total EEE+

blue jay

black bird

cardinal

dove

grackle

mocking bird

sparrow

thrasher

tit mouse

Okaloosa

44

8

5+/22

1+/2

2+/15

 

0+/1

 

 

0+/2

 

Santa Rosa

32

4

4+/10

 

0+/16

0+/1

0+/1

0+/1

0+/3

 

0+/1

Walton (North)

30

0

0+/3

 

0+/16

 

 

 

0+/11

 

 

Washington

41

0

0+/6

 

0+/18

 

0+/8

 

0+/9

 

 

totals

147

12

9+/41

1+/2

2+/65

0+/1

0+/10

0+/1

0+/23

0+/2

0+/1

August

# birds

total EEE+

blue jay

black bird

cardinal

dove

grackle

mocking bird

sparrow

thrasher

Okaloosa

37

4

4+/18

0+/4

0+/6

0+/1

0+/7

0+/1

 

 

Santa Rosa

23

3

3+/7

 

0+/10

0+/1

 

 

0+/4

0+/1

Walton (North)

36

0

0+/2

 

0+/22

0+/1

 

 

0+/11

 

Washington

37

1

0+/3

 

0+/22

0+/1

0+/3

 

1+/8

 

totals

133

8

7+/30

0+/4

0+/60

0+/4

0+/10

0+/1

1+/23

0+/1

* # + / # submitted

Table 3.  WN positive live wild birds


July

# birds

total WN+

blue jay

black bird

cardinal

dove

grackle

mocking bird

sparrow

thrasher

tit mouse

Okaloosa

44

0

0+/22

1+/2

0+/15

 

0+/1

 

 

0+/2

 

Santa Rosa

32

0

0+/10

 

0+/16

0+/1

0+/1

0+/1

0+/3

 

0+/1

Walton (North)

30

0

0+/3

 

0+/16

 

 

 

0+/11

 

 

Washington

41

2

0+/6

 

2+/18

 

0+/8

 

0+/9

 

 

totals

147

2

0+/41

0+/2

2+/65

0+/1

0+/10

0+/1

0+/23

0+/2

0+/1

county

# birds

total WN+

blue jay

black bird

cardinal

dove

grackle

mocking bird

sparrow

thrasher

Okaloosa

37

0

2+/18

0+/4

0+/6

0+/1

0+/7

 

 

 

Santa Rosa

23

0

1+/7

 

0+/10

0+/1

0+/1

 

0+/4

0+/1

Walton (North)

36

0

0+/2

 

0+/22

0+/1

 

 

0+/11

 

Washington

37

0

1+/3

 

0+/22

0+/1

0+/3

 

1+/8

 

totals

133

0

4+/30

0+/4

0+/60

0+/4

0+/10

0+/1

1+/23

0+/1

* # + / # submitted

There were 28 dead birds were submitted for arbovirus assay during July and 24 during August.  Cloacal swabs (53) were submitted from live wild birds being treated by wildlife rehabilitators.  Brain tissues from two equines in July and from three equines and 1 rabbit in August were submitted for arbovirus testing.  Virus was not detected in any of these specimens. 

Table 4.  Numbers of field specimens for virus isolation submitted by county


July

# birds

# mammals

# swabs

Citrus

3

 

 

Dade

17

 

 

Hillsborough

3

1

 

Holmes

1

 

 

Lee

1

 

 

Madison

1

 

 

Pasco

 

1

 

Seminole

2

 

 

Totals-July

28

2

 

August

 

 

 

Alachua

3

 

 

Dade

5

 

 

Franklin

1

 

 

Hernando

6

 

 

Hillsborough

3

1

 

Lake

 

 

1

Manatee

 

 

16

Monroe

 

 

11

Orange

 

 

12

Osceola

 

 

4

Pasco

2

 

 

Pinellas

3

 

 

Seminole

 

 

8

Sumter

1

1

 

Suwannee

 

1

 

Volusia

 

 

1

Washington

 

1

 

Totals-August

24

4

53

Table 5. Numbers of submissions by species.


Species

July

August

Anhinga

 

1

Blackbird

1

 

Bluejay

 

1

Chicken

4

3

Cormorant

 

5

Crane

1

1

Dove

13

5

Duck

 

2

Egret

1

2

Equine

1

3

Finch

 

1

Flamingo

 

1

Frigate

 

1

Gnatcatcher

 

1

Grebe

 

1

Gull

 

7

Hawk

1

12

Heron

 

4

Ibis

1

1

Llama

1

 

Martin

1

 

Mockingbird

1

 

Osprey

 

6

Ovenbird

 

1

Owl

 

11

Pelican

 

3

Rabbit

 

1

Rail

 

1

Sapsucker

 

2

Sparrow

1

 

Tern

 

1

Thrasher

1

 

Thrush

1

 

Turkey

 

1

Vulture

 

1

Warbler

1

 

Woodstork

 

1

total

30

81

During July, 188 traditional mosquito pools and 1 RAMP assay residual pool were assayed and during August, 254 traditional pools were assayed for arboviruses by real-time RT-PCR and cell culture inoculation.  A California group virus was isolated from one pool of 50 Oc. atlanticus from Sarasota County (collected 7/12/2006 and submitted 8/30/2006).

Table 6.  Mosquito Pool submissions by county


July

traditional

Ramp

Escambia

11

 

Flagler

43

 

Monroe

 

1

Pinellas

5

 

Sarasota

129

 

total

188

1

August

traditional

Ramp

Citrus

3

 

Flagler

26

 

Okaloosa

9

 

Palm Beach

34

 

Santa Rosa

6

 

Sarasota

172

 

total

250

0

HAI July, HAI August

June 2006

In June there were four seroconversions due to alphaviruses (Eastern Equine Encephalitis virus (EEE)for a seroconversion rate of 0.3%.  June activity has not been this low since June 2000. There was one new HAI flavivirus positive sentinel (St Louis Encephalitis virus (SLE) antigen used in the HAI assay) during June, confirmed as WN+ by Serum Neutralization for a seroconversion rate of 0.1%, which is not significantly different from the mean statewide rate for June. 

Figures 1 depicts the seroconversion rates for EEE and to WN for the January through June in 2005 and 2006.  The effect of this year’s spring drought is most noticeable for EEE seroconversions.

Figure 1.
 arboJune2006

Sera from 161 live wild birds were screened by HAI in June.  Table 1 lists submissions and results by county for EEE.  Table 2 lists submissions and results by county for WN.

Table 1.  EEE positive live wild birds


county

# birds

total EEE+

blue jay

cardinal

blackbird

grackle

mocking-bird

sparrow

thrasher

Okaloosa

30

8

6+/15

1+/7

0+/2

1+/3

 

 

0+/3

Santa Rosa

29

5

4+/10

0+/7