Florida Mosquito Control Association

Arbovirus Surveillance Reports - 2004

December 2004 There were 20 seroconversions due to alphaviruses: 1 to Eastern Equine Encephalitis virus (EEE) for a 1.4% seroconversion rate and 9 to Highlands J virus (1.2%). The rate for EEE activity does not differ significantly from the mean for EEE historical activity during December.  There were 13 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 December, 2004, for a rate of 1.7%. This is not significantly different from the mean statewide rate for December, however, it is substantially lower than rates for 2003.  There were no seroconversions to SLE during December.

Sera from 15 wild birds and 1 zebra were screened by HAI.  HAI tests for antibody to flaviviruses and to alphaviruses were negative.

Five dead birds and two horse brains were submitted for arbovirus detection in tissues.  EEE virus was detected in a migratory whooping crane (Gilchrist county).

During December, 56 traditional mosquito pools were submitted for assay (Sarasota, 26; St. Johns, 30).  Arbovirus was not detected.

HAI

An annual summary of sentinel chicken data. The comprehensive arbovirus surveillance laboratory testing summary report for 2004 will soon be accessible at http://www.doh.state.fl.us/environment/community/arboviral/index.html

November 2004 There were 28 seroconversions due to alphaviruses: 19 to Eastern Equine Encephalitis virus (EEE) for a 1.5% seroconversion rate and 9 to Highlands J virus (0.7%). The rate for EEE activity does not differ significantly from the mean for EEE historical activity during November.  There were 14 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 November, 2004, for a rate of 1.1%. This is not significantly different from the mean statewide rate for November, however, it is substantially lower than rates for 2003.  There were no seroconversions to SLE during November.

Sera from 63 wild birds and 2 dogs were screened by HAI.  Detection of HAI antibody in wild birds to flavivirus are reported in Table 1. 

Table 2. Dead Bird Surveillance

Dead animals, primarily birds were submitted in low numbers for West Nile Virus detection in tissues.  During November 2004, tissues from 18 birds (Table 2) were received for arbovirus detection/isolation.  WN virus was detected in a bluejay from Orange county.
Table 3. Dead Bird Species Submissions

During November, 240 traditional mosquito pools and 5 RAMP test suspect positive samples were submitted for assay.  WN was not detected.
Table 4. Mosquito Surveillanc: submissions

HAI

October 2004 There were 9 seroconversions due to alphaviruses: 8 to Eastern Equine Encephalitis virus (EEE) for a 0.5% seroconversion rate and 4 to Highlands J virus (0.2%). The rate for EEE activity does not differ significantly from the mean for EEE historical activity during October.  There were 39 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 October, 2004, for a rate of 2.3%. This is not significantly different from the mean statewide rate for October, however, it is substantially lower than rates for 2002 and 2003.  There was 1 seroconversion to SLE during October.

Sera from 102 wild birds and 2 dogs were screened by HAI.  On dog (Volusia county) was WN antibody positive.  Detection of HAI antibody in wild birds to flavivirus are reported in Table 1.  However, only some have been confirmable by serum neutralization testing.  Thus, the validity of these positive screening assays cannot be ascertained.
Table 1.  Wild Bird serology

Dead animals, primarily birds were submitted in low numbers for West Nile Virus detection in tissues.  During October 2004, tissues from 51 birds (Table 2) and 41 mammals (equines) were received for arbovirus detection/isolation.  WN virus was not detected.
Table 2. Dead Bird Surveillance

Table 3.  Dead Bird Species Submissions

During October, 266 traditional mosquito pools, 7 RAMP test and 4 negative VecTest samples were submitted for assay.  WN was not detected by molecular screening
Table 4.  Mosquito Surveillance: submissions

HAI

September 2004 There were 7 seroconversions due to alphaviruses: 4 to Eastern Equine Encephalitis virus (EEE) for a 0.3% seroconversion rate and 3 to Highlands J virus (no historical record). The rate for EEE activity does not differ significantly from the mean for EEE historical activity during September.  There were 66 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 September, 2004, for a rate of 4.4%. This is not significantly different from the mean statewide rate for September, however, it is substantially lower than rates for 2002 and 2003.  There was 1 seroconversions to SLE during September.

Sera from 65 wild birds and 1 Oryx were screened by HAI.  Detection of HAI antibody to flavivirus are reported in Table 1.  However, only some have been confirmable by serum neutralization testing.  Thus, the validity of these positive screening assays cannot be ascertained.

Table 1. Wild Bird serology

Dead animals, primarily birds were submitted in low numbers for West Nile Virus detection in tissues.  During September 2004, tissues from 54 birds (Table 2) and 1 mammals (horse) were received for arbovirus detection/isolation.  WN virus was detected in 2 birds submitted from Dade County

Table 2. Dead Bird Surveillance

Table 3. Dead Bird Species Submission

During September, 251 traditional mosquito pools were submitted for assay.  WN was not detected by molecular screening.  West Nile Virus was isolated from 3 pools . Isolates from 3 pools pending from August were identified as belonging to the California virus group (similar to Keystone).

Table 4. Mosquito Surveillance: submissions

Table 5. Mosquito Surveillance: positive

HAI

August 2004 There were 25 seroconversions due to alphaviruses: 21 to Eastern Equine Encephalitis virus (EEE) for a 1.4% seroconversion rate and 4 to Highlands J virus (no historical record). The rate for EEE activity does not differ significantly from the mean for EEE historical activity during August.  There were 76 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 August, 2004, for a rate of 4.9%. This is not significantly different from the mean statewide rate for August, however, it is substantially lower than rates for 2002 and 2003.  There were 2 seroconversions to SLE during August.

Sera from 115 wild birds were screened by HAI.  Detection of HAI antibody to flavivirus are reported in Table 1.  Unfortunately, these have not been confirmable by serum neutralization testing.  The volume of serum that can be collected from a wild bird is small and pre-diluted in the field.  In many cases there is insufficient serum for additional testing.  Thus, the validity of these positive screening assays cannot be ascertained.

Table 1. Wild Bird serology

Dead animals, primarily birds were submitted in low numbers for West Nile Virus detection in tissues.  During August 2004, tissues from 82 birds (Table 2) and 7 mammals (1 dog, 1 goat, 1 squirrel and 4 horses) were received for arbovirus detection/isolation.  WN virus was detected in 10 out of 57 birds (18%) submitted from Dade County (Table 3).

Table 2. Dead Bird Surveillance

Table 3. Dead Bird Species Submissions

During August, 241 traditional mosquito pools were submitted for assay.  WN was not detected by molecular screening.  Virus was isolated from 3 pools; identification is pending.  37 negative VecTest samples were confirmed negative by molecular and cell culture assays.  One positive RAMP test was found negative by molecular assay.

Table 4. Mosquito Surveillance

HAI

July 2004 There were 28 seroconversions due to alphaviruses: 23 to Eastern Equine Encephalitis virus (EEE) for a 1.4% seroconversion rate and 3 to Highlands J virus (no historical record); 2 sentinels presented with antibody cross-reactive to both viruses. The rate for EEE activity does not differ significantly from the mean for EEE historical activity during July.  There were 22 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 July, 2004, for a rate of 1.3%. This is not significantly different from the mean statewide rate for July.  It should be noted that 12 of these seroconversions occurred in Brevard and 6 in Hillsborough County in central Florida. 

Sera from 87 wild birds were screened by HAI.  Antibody to WN was detected in one mourning dove from Indian River county. 

Dead animals, primarily birds were submitted in low numbers for West Nile Virus detection in tissues.  During July 2004, tissues from 53 birds and 6 mammals were received for arbovirus detection/isolation.  WN virus was detected in a bluejay from Hillsborough county and in 15 out of 24 birds (63%) submitted from Dade county. EEE was detected in a horse from Marion county.
Table 1. Dead Bird Surveillance

During July, 129 mosquito pools were submitted for assay. One pool (St. Johns county, Oc. atlanticus, 50, collected 7/1/04) yielded an isolate identified as a California group virus, probably Keystone (not a human pathogen).  The isolate made in June (Sarasota county, Oc. atlanticus, 50, collected July, 2003) has also been identified as a California virus.

Table 2.  Mosquito Surveillance

HAI

June 2004 There were 20 seroconversions due to alphaviruses: 12 to Eastern Equine Encephalitis virus (EEE) for a 0.8% seroconversion rate and 8 to Highlands J virus (no historical record). The rate for EEE activity does not differ significantly from the mean for EEE historical activity during June.  There were 14 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 June, 2004, for a rate of 0.9%. This is not significantly greater than the mean statewide rate for June, nevertheless, it must be noted that 13 of the 14 seroconversions occurred in Hillsborough County in central Florida.  Activity in this county has been earlier than in previous years (table 1). 

Table 1 Seroconversions to WN in Hillsborough County

Sera from 77 wild birds were screened by HAI.  Antibody to EEE was detected in 2 bluejays from Okaloosa county. 

Dead animals, primarily birds were submitted in low numbers for West Nile Virus detection in tissues.  During June 2004, tissues from 18birds and 5 mammals were received for arbovirus detection/isolation.  WN virus was detected in a crow from Hillsborough County and EEE was detected in 2 horses (Osceola and Polk counties)

Table 2. Dead Bird Surveillance

During June, 100 mosquito pools were submitted for assay. One virus isolate was made.  Virus identification is pending, however the isolate is not WN, SLE, EEE, or HJ virus; it is most probably a California virus group agent that is not a human pathogen.  An additional 5 RAMP test WN positive pools were submitted for confirmation; they were, however, negative by molecular assay. 
Table 3.  Mosquito Surveillance

HAI

May 2004   There were 6 seroconversions to Eastern Equine Encephalitis virus (EEE) for a 0.4% seroconversion rate. This rate is similar to the mean for EEE historical activity for May.  There were 18 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 May, 2004, for a rate of 1.2%. This is not significantly greater than the mean rate for May.  The rate of seroconversion (% of birds seroconverting to positive antibody statue for each virus) has been computed, so that comparisons with years past when there were fewer total submissions may be made. 

Sera from 88 wild birds were screened by HAI.  Antibody to WN was detected in 7 wild birds from Walton (2 bluejays,1 cardinal, 1 robin, 1 grosbeak) and Okaloosa (2 bluejays) counties.  Cross-reacting flavivirus antibody (WN/SLE) was detected in a bluejay in Washington and an ostrich in Hillsborough counties.

Dead animals, primarily birds were submitted in low numbers for West Nile Virus detection in tissues.  During May 2004, tissues from 23 birds and 2 mammals were received for arbovirus detection/isolation.  In addition, virus detection/isolation attempts were made on 79 bird bloods from Indian River county.  No virus was detected.

During May, 188 mosquito pools were submitted for assay; none were positive for virus.  An additional 5 RAMP test WN positive pools were submitted for confirmation; they were, however, negative by molecular assay.

HAI

April 2004 There were 2 seroconversions to Eastern Equine Encephalitis virus (EEE) for a 0.2% seroconversion rate. This rate is not significantly below the mean for EEE historical activity for April.  There was 1 alphavirus HAI seroconversions due to Highlands J virus. There were 8 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 April, 2004, for a rate of 0.7%. This is not significantly greater than the mean rate for April.  The rate of seroconversion (% of birds seroconverting to positive antibody statue for each virus) has been computed, so that comparisons with years past when there were fewer total submissions may be made. 

Sera from 110 wild birds were screened by HAI.  Antibody to EEE was detected in 2 wild birds: a bluejay (Walton county) and a sparrow(Santa Rosa County). Antibody to HJ was detected in a bluejay (Santa Rosa county) and antibody to WN was detected in one sparrow (Santa Rosa county). 

Dead animals, primarily birds continue to be submitted for West Nile Virus detection in tissues.  During April 2004, tissues from 81 birds and 1 mammals were received for arbovirus detection/isolation.  No virus was detected.

During April, 35 mosquito pools were submitted for assay; none were positive for virus:

HAI

March 2004 There were 5 seroconversions to Eastern Equine Encephalitis virus (EEE) for a 0.5% seroconversion rate. This rate is below the mean for EEE historical activity for March.  There were 8 alphavirus HAI seroconversions due to Highlands J virus. There were 5 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 March, 2004, for a rate of 0.5%. This is similar to the mean rate for March.  The rate of seroconversion (% of birds seroconverting to positive antibody statue for each virus) has been computed, so that comparisons with years past when there were fewer total submissions may be made. 

Sera from 88 wild birds were screened by HAI.  Antibody to EEE was detected in 4 wild birds: a bluejay and a blackbird(Okaloosa County), a mockingbird and a cardinal (Santa Rosa county). 

Dead animals, primarily birds continue to be submitted for West Nile Virus detection in tissues.  During March 2004, tissues from 43 birds and 2 mammals were received for arbovirus detection/isolation.  No virus was detected.

During March, 149 mosquito pools were submitted for assay; none were positive for virus:

HAI

February 2004 There were 5 seroconversions to Eastern Equine Encephalitis virus (EEE) for a 0.6% seroconversion rate. This rate is similar to the mean for EEE historical activity for February.  There was one alphavirus HAI seroconversion due to Highlands J virus in Volusia county. There were 19 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, 2004, for a rate of 2.4%. This is higher than the mean rate for February, but not statistically significant.  The rate of seroconversion (% of birds seroconverting to positive antibody statue for each virus) has been computed, so that comparisons with years past when there were fewer total submissions may be made. 

Sera from 87 wild birds were screened by HAI.  Antibody to WN was detected in 2 wild birds: a bluejay (Walton County), a dove and a thrasher (Okaloosa county).  Antibody to EEE was detected in a bluejay in Okaloosa county

Dead animals, primarily birds continue to be submitted for West Nile Virus detection in tissues.  During February 2004, tissues from 40 birds and 4 mammals were received for arbovirus detection/isolation.  West Nile virus was detected in a cardinal from Marion county.

During February, Palm Beach county submitted 23 mosquito pools for assay; none were positive for WN virus:
HAI

January 2004 There were four seroconversions to Eastern Equine Encephalitis virus (EEE) for a 0.5% seroconversion rate. This rate is similar to the mean for EEE historical activity for January.  There were 25 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, 2004 for a rate of 2.9%; this is slightly above the mean rate for January.  Four sentinels developed antibody to SLE, for a rate of 0.5%, similar to the median rate for SLE for December.   The rate of seroconversion (% of birds seroconverting to positive antibody statue for each virus) has been computed, so that comparisons with years past when there were fewer total submissions may be made. 

Sera from 56 mammals, 3 reptiles and 86 wild birds were screened by HAI.  Antibody to WN was detected in 3 wild birds: a cardinal (Santa Rosa County), a dove and a thrasher (Okaloosa county).

Dead animals, primarily birds continue to be submitted for West Nile Virus detection in tissues.  During January 2004, tissues from 3 birds, 3 tortoises and 2 mammals were received for arbovirus detection/isolation.    EEE virus was detected in one horse.  West Nile virus was detected in a wolf and one bluejay.

Of the 362 mosquito pools submitted, none were positive for WN virus:

The Laboratory Arbovirus 2003 Annual Report will be available on the Bureau of Community Environmental Health Website. HAI