La Crosse Encephalitis

1
La Crosse Encephalitis
Oc. canadensis
Oc. triseriatus
Ae. albopictus
Oc. japonicus

• Gregory Chrislip
• Public Health Entomologist
• WV Department of Health and Human Resources

2
Photograph used with the permission of Dr. James
Joy, Department of Biological Sciences Marshall
University.
3
(No Transcript)
4
2004 La Crosse Encephalitis

• 30 Human cases
• Age Range 5 months 44 years
• 1 was gt 25 years old
• 29 were lt 15 years old
• 8 Female/22 Male
• 2 Had no risk factors
• 3 Had living among hardwoods as their only risk
  factor.

5
(No Transcript)
6
3
1
2
5
11
1-3 Cases
6
4-10 Cases
5
11-20 Cases
gt20 Cases
24
7
(No Transcript)
8
La Crosse in West VirginiaJanuary 2004
December 31, 2004
La Crosse endemic to named counties
Counties in which positive human cases
have been identified in 2004. 30 total
cases
9
LaCrosse Ecology

• Primary Vector Ochlerotatus triseriatus Tree
  hole mosquito
• Non-glaciated hardwood forests
• Breeds in
• Basal holes of oaks
• leaves accumulate in standing pools of water
• Containers, including tires, troughs, planters
• Remains close to woodland breeding sites

10
(No Transcript)
11
Tree-holes and Oc.triseriatus larvae
12
LaCrosse Ecology (2)

• Amplifying host chipmunks and squirrels
• Drink from tree holes
• Achieve high levels of viremia allows virus
  transmission to previously uninfected mosquitoes
• Do not become ill they form an immune response
• Have 1-2 litters per year, assuring a steady
  supply of previously uninfected hosts

13
LaCrosse Ecology (3)

• Overwintering
• Adults are killed by a hard freeze
• Infected eggs can over-winter
• Amplification females lay many eggs
• Newly-hatched females are capable of transmission
• Venereal transmission
• Males transmit to females
• Females can retain semen to fertilize successive
  clutches of eggs

14
Eggs can over-winter with virus.
If male mates with uninfected female, she
becomes
Small mammals do not become ill. Virus multiplies
to high levels.
15
Eggs of Aedes mosquito in a glass container
16
Aedes mosquito - egg
17
siphon
Aedes mosquito larvae - wigglers
18
Aedes mosquito pupae - tumblers
trumpet
19
(Ochlerotatus triseriatus)
20

• What is the role of socioeconomic conditions?
• Does the number of cases correlate with mast
  production?
• What are the role of other vector species?
• Aedes albopictus
• Ochlerotatus japonicus
• Ochlerotatus canadensis

21
Ochlerotatus japonicus
?
Aedes albopictus (Stegomyia albopicta)
Ochlerotatus triseriatus
Ochlerotatus canadensis
22
The scutum is black with a distinguishing white
stripe down the center beginning at the dorsal
surface of the head and continuing along the
thorax
5 tarsal bands
Aedes albopictus (Stegomyia albopicta)
23
La Crosse endemic to named counties
Counties in which species
collected/identified
24
Dark scutum with lyre-shaped yellow or golden
markings...having a yellow median longitudinal
line down center and full length...also 2 more
median yellow stripes running about halfway of
scutum from anterior end. The lateral sides have
broad patches of silver-white scales.
3 tarsal bands
Ochlerotatus japonicus
25
La Crosse endemic to named counties
Counties in which species
collected/identified
26
Integument of scutum brown to black. Scutum with
wide median stripe of narrow dark-brown scales.
The stripe becomes much broader distally and
covers most of posterior half of the scutum.
Sides with white lanceolate scales
Ochlerotatus triseriatus
27
La Crosse endemic to named counties
Counties in which species
collected/identified
28
Integument of scutum reddish brown, scutum
clothed with narrow golden-brown scales.
Posterior half-stripes of pale scales are often
present and extend anteriorly to middle of
scutum.
Ochlerotatus canadensis
29
La Crosse endemic to named counties
Counties in which species
collected/identified
30
West Nile Virus
Cx. pipiens
Culex sp. laying eggs
Cx. quinquefasciatus
Cx. salinarius

• Gregory Chrislip and Humbert Zappia
• Public Health Entomologist
• WV Department of Health and Human Resources

31
Arboviral Surveillance

• Dead Birds
• Reporting
• Submission for testing
• Mosquitoes
• Collection of adults and larvae
• Species lists
• Species distribution
• Testing (adults)

32
Arboviral Surveillance (continued)

• Equines
• Testing
• Humans
• Testing

33
Arbovirus Testing

• Testing is done by the OLS
• Samples are processed using
• Birds and mosquitoes
• Molecular (NASBA)
• Humans and Equines
• Serological (antigen/antibody)

34
Arbovirus Testing (continued)

• Birds
• West Nile Virus (EEE, SLE)
• Mosquitoes
• West Nile Virus (EEE, SLE, LAC)
• Species Dependent
• Equines
• West Nile Virus (SLE, EEE)

35
Arbovirus Testing (continued)

• Humans
• West Nile Virus
• Eastern Equine Encephalitis
• La Crosse Encephalitis
• Saint Louis Encephalitis

36
Arbovirus Surveillance Results WNV Bird Testing
2004
Positive WNV Bird Negative WNV Bird Sample
Not Received No Birds Submitted
Map date 10 May 2005
37
Arbovirus Surveillance Results WNV Bird Testing
(continued)

• Comparison 2002-2004
• In 2004
• 5 of 34 counties testing with positive birds
  (14.7)
• In 2003
• 30 out of 55 counties testing (54.5)
• In 2002
• 9 out of 55 counties testing (16.4)

38
Arbovirus Surveillance Results WNV Bird Testing
(continued)
2003
2004
Map date 05/10/2005
2002
Positive West Nile Bird Negative West Nile
Bird Sample Not Received No Birds Submitted
39
Arbovirus Surveillance Results WNV Mosquito
Testing 2004

• Total of 227 Mosquito pools
• At least 5 genera and 10 species
• 16 positive pools 6 species positive

40
Arbovirus Surveillance Results WNV Mosquito
Testing 2004

• Pools from 9 counties/27 localities
• Positive pools from Kanawha, Boone and Berkeley
  counties
• Part of epidemiological response, response to
  complaints, and methods comparison

41
Arbovirus Surveillance Results WNV Location of
Mosquito Pools
2004
4(1)
6
13
2
187(16)
1
4(1)
WNV Positive Pools Counties Where Pools Were
Collected No Pools Collected 1 Number of
samples (1) Number of samples testing Positive
for WNV
2
8
42
Arbovirus Surveillance Results WNV Equine Testing

• Samples submitted from 15 horses
• Horse were from 12 Counties
• Total of 4 horses testing positive (26.6)
• From 3 counties (25 )

43
Arbovirus Surveillance Results WNV Equine
Testing (continued)
WNV Positive Equine WNV Negative Equine
No Sample Submitted
44
Arbovirus Surveillance Results WNV Equine
Testing (continued)

• Comparison 2002-2004
• In 2004
• 4 WNV positive horses
• From 3 Counties
• In 2003
• 14 WNV positive horses
• From 4 Counties
• In 2002
• 3 WNV positive horse
• From 3 Counties

45
Arbovirus Surveillance Results WNV Equine
Testing (continued)
2003
2004
2002
Map date 05/12/2005
46
Arbovirus Surveillance Results WNV Human Testing

• Samples submitted from 98 patients
• Samples submitted from 23 counties
• No positive results

47
Arbovirus Surveillance Results WNV Human Testing
(continued)
2004
48
Arbovirus Surveillance Results WNV Human Testing
(continued)

• Comparison 2002-2004
• In 2004
• 0 WNV cases
• In 2003
• 2 WNV positive cases
• From 2 counties
• In 2002
• 3 WNV positive cases
• From 2 counties

49
Arbovirus Surveillance Results WNV Human Testing
(continued)
2004
2003
2002
Map date 9/20/2004
Positive WNV sample
Negative WNV sample
No samples submitted (2004)
1 Number of samples submitted
(1) Number of samples testing positive
for WNV
50

• Here are three ways you can reduce your risk
• Avoid Mosquito Bites
• (DEET, Picaridin and
• Oil of Lemon Eucalyptus)
• Mosquito-Proof Your Home
• Help Your Community

51
Contact Information

• Greg Chrislip
• Public Health Entomologist
• Phone [phone]
• Email gregchrislip_at_wvdhhr.org
• Humbert Zappia
• Public Health Entomologist
• Phone [phone]
• District phone [phone]
• Email humbertzappia_at_wvdhhr.org

HZ 10/13/2004
52
Additional Contacts

• Stan Mills (Cabell- Huntington)
• Elizabeth Green (Mid-Ohio Valley)
• Patty Rodgers (Nicholas)
• Doris Irwin (Mercer)
• Anita Ray (Kanawha)