Rift Valley Fever a potential emerging threat to wildlife, livestock,

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Rift Valley Fever a potential emerging threat to
wildlife, livestock, humans in the U.S.

• Christy Tedrow, Maj, USAF
• Doctoral Candidate, Biodefense Program

African outbreak history based on research by
Dr. Charles Bailey, GMU Committee Chair Dr. Ken
Linthicum, USDA Committee Member
Dr. Assaf Anyamba, NASA GCFC Committee
Member Dr. Seth Britch, USDA
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Rift Valley fever in AfricaA Mosquito-transmitted
hemorrhagic fever
Zoonotic disease first described in Kenya by
Daubney et al in 1931, after causing a fatal
epizootic in sheep on a farm north of Lake
Naivasha
RVF Infected Eggs
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Rift Valley Fever

• Distribution of Rift Valley Fever, 2002

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Rift Valley Fever Virus

• Family Bunyaviridae, genus Phlebovirus
• Mosquito-borne In Africa gt 40 species in
  the genera Aedes, Anopheles, Culex, Eretmapoites
  and Mansonia have been infected with the virus

• Outbreaks generally occur in otherwise dry areas
  following periods of heavy rainfall
• Zoonotic primarily affects animals (livestock)
• Affects pastoral people in the Rift Valley of
  Africa (living in close quarters with animals may
  be key)

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Rift Valley Fever VirusSusceptible Animals
Severe illness Abortion Mortality
Viremia Abortion
Infection Viremia
Refractive to infection
Mortality 100

• Lambs Sheep Monkeys
  Horses Guinea pigs
• Calves Cattle Camels
  Cats Rabbits
• Kids Goats Rats
  Dogs Pigs
• Puppies Water buffalo Gray squirrels
  Monkeys Hedgehogs
• Kittens Humans
  Tortoises

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Rift Valley Fever Wet Dambo Habitat
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Vector Population Rainfall Dynamics
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Rift Valley Fever Transmission Cycle
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Why focus on RVF virus?

• Has moved from Sub-saharan Africa
• Ecological infrastructure in place for RVF to
  thrive in the U.S.
• Could spread via mosquitoes across the U.S. at
  least as rapidly as WNV
• Competent Vectors in North America

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SPECIES
POTENTIALAedes albopictus
Ae. aegypti
Ochlerotatus
canadensis O. cantator

O. excrucians
O. sollicitans
O. taeniorhynchus
O. triseriatus

Potential for Selected North America Mosquito
Species to Transmit Rift Valley Fever
? 10 11 - 25
25 - 40 ? 40
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SPECIES
POTENTIALAnopheles bradleyi-crucians
0Culex pipiens
C. salinarius
C. tarsalis
C. territans

Potential for Selected North America Mosquito
Species to Transmit Rift Valley Fever
? 10 11 - 25
25 - 40
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Why focus on RVF virus?

• Risk of OIE trade ban, beyond potentially huge
  losses of wildlife and livestock
• USDA APHIS select agent threat to human and
  animal health
• Laterally transfer preparations for RVF to those
  for other emerging mosquito-borne diseases

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Product Risk Map

• GIS model that identifies high-risk areas for
  increased vector populations
• Regions susceptible to RVF - intersection of
  vectors, hosts, climatic conditions
• Delineate vulnerable regions requiring additional
  protection/monitoring
• Where and when to target disease
  surveillance/control team
• Enhance vaccination, vector-control, local
  quarantine
• Minimize cost of surveillance over large areas
• Reduce impacts of export embargoes /quarantines

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Input Data (2000-2006)
Using Geographic Information Systems and Remote
Sensing Technology for Rift Valley Fever Risk
Assessment in the U.S.
GIS Layers
Virginia Mosquito Surveillance Data

Elevation
Water
Land Cover
NDVI
NASS (Livestock)
Deer Abundance
Human Demographics
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Input Data (2000-2006)
GIS Layers
Virginia Mosquito Surveillance Data

Elevation
Water
Land Cover
NDVI
NASS (Livestock)
Deer Abundance
Human Demographics
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Risk Mapping based on climate ecological
dynamics
3 months of above normal NDVI risk of RVF (red)
in endemic areas (green savannah mask)
http//www.geis.fhp.osd.mil/GEIS/SurveillanceActiv
ities/RVFWeb/indexRVF.asp
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Input Data (2000-2006)
GIS Layers
Virginia Mosquito Surveillance Data

Elevation
Water
Land Cover
NDVI
NASS (Livestock)
Deer Abundance
Human Demographics
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NASS Data
Backyard beef cattle (combined cow/calf, feedlot,
and stocker operations) lt 10 animals
Map from Melius et al. 2006, Developing Livestock
Facility Type Information from USDA Agricultural
Census Data for Use in Epidemiological and
Economic Models
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Input Data (2000-2006)
GIS Layers
Virginia Mosquito Surveillance Data

Elevation
Water
Land Cover
NDVI
NASS (Livestock)
Deer Abundance
Human Demographics
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2004 Virginia Private Land Deer Relative
Population Abundance by County
6.5 Very High
4.9
6.5
5.0
4.1-5.4 High
4.4
1.5
4.6
5.4
3.7
4.4
2.8
2.8-3.9 Moderate
3.0
3.2
2.6
3.3
3.3
2.7
3.9
2.4
2.7
1.7-2.8 Low
3.4
3.8
3.3
2.6
1.9
2.3
2.9
3.3
2.8
2.4
3.2
2.4
2.0
2.0
0.7-1.5 Very Low
2.9
3.3
3.4
4.5
3.2
3.8
2.5
4.1
3.4
2.3
4.9
4.1
3.6
2.3
2.4
1.9
2.1
4.3
5.0
4.8
3.4
1.5
2.5
3.5
2.3
3.4
3.4
2.7
2.9
0.7
3.2
2.8
2.1
3.5
3.2
3.6
3.0
1.7
3.8
1.9
2.6
3.5
1.9
2.0
0.7
1.8
1.9
1.8
3.1
2.4
2.7
3.1
2.2
2.6
2.8
1.1
2.6
2.1
2.9
1.2
2.3
1.9
4.1
2.4
4.3
1.8
3.4
1.8
Index (Antlered Buck Kill / Deer Habitat in
Square Miles) 3 Year Average based on 2004 Data
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Input Data (2000-2006)
GIS Layers
Virginia Mosquito Surveillance Data

Elevation
Water
Land Cover
NDVI
NASS (Livestock)
Deer Abundance
Human Demographics
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Relational Database in MS Access
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Access Form to Query Data
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Mosquitoes Per Year
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Mosquitoes Per Collectionin 2006
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Mosquitoes By City/County
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Number of Mosquitoesin 2006
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Ae albopictus Per Epi Week in 2006
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Acknowledgements
Thanks to the people who have kindly and
generously shared their data, expertise, and time
for this research . . .
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Questions?

• Christy Tedrow
• [phone]
• christy.tedrow_at_verizon.net