Rift Valley Fever Monitoring Update November 27, 2006

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Rift Valley Fever Monitoring UpdateNovember 27,
2006
FEWS Science Meeting November 27, 2006
Assaf Anyamba, Jennifer Small, Kenneth J.
Linthicum , Jean-Paul Chretien , Compton J.
Tucker NASA/Goddard Space Flight Center,
Biospheric Sciences Branch, Code 614.4, GIMMS
Group, Greenbelt, MD 20771 Department of
Defense, Global emerging Infections System,
Division of Preventive Medicine, Walther Reed
Army Institute of Research, Washington, DC
20307-5100 Center for Medical, Agricultural
Veterinary Entomology, Agricultural Research
Service, United States Department of Agriculture,
Gainesville, Florida, 32608.
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Historical Perspective East Africa

• Zoonotic disease first described in Kenya by
  Daubney et al in 1931 - a fatal epizootic of
  sheep on a farm north of Lake Naivasha
• RVF activity follows periods of persistent,
  widespread and above normal rainfall flooding of
  dambos (grassland depressions) mosquito
  breeding habitats
• RVF has ability to establish itself in new
  ecological habitats Epizootic in Egypt in
  1977-78, Yemen Saudi Arabia 2000
• Frequency of outbreaks epizootics persist for
  1-3 years, and recur at 5-15 year intervals in
  dry, bushed and wooded grasslands

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Satellite Monitoring and Mapping

• systematic sampling (20 yr data record from
  NOAA-AVHRR Instrument)
• 8km spatial resolution
• 10, 15-day, monthly temporal resolution
• Long-term Time Series Data sets enables
  Retrospective analysis of diseases and provides
  basis for risk mapping
• Recent SPOT Vegetation global 1km, MODIS
  250m 1km, LANDSAT, SPOT HRV selective scenes
  10 30m

?? Scarcity of surface climate observations (both
temporal spatial)
NDVI can be used as the cumulative response
indicator of climatic parameters precip, temp
and their variability over time especially in
arid and semi-arid areas memory of climate
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Vector Dynamics and Ecology

• Emergence and population expansion of a number
  of disease vectors (mosquitoes, mice, locust)
  often tends to follow the trajectory of the green
  flush of vegetation in semi-arid lands
• NDVI data can therefore be used as a
  multi-purpose indicator of conditions associated
  with vector-borne disease outbreaks in support
  of disease surveillance activities

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Reconstruction of RVF Outbreak History

• 1982-83, Localized outbreak at Sukari Ranch -
  Ruiru, Ngong, Nairobi Forest (isolations in
  mosquito populations)
• 1986/87 Local flooding, local disease no
  epizootic
• 1989 Focal epizootic around Naivasha (on
  wealthy farms), some human cases documented
• 1992 -1995, limited, surveillance diminished, not
  known
• 1997/98 Massive epizootic in livestock and
  epidemic in human populations, regional event
• Recent associations with global scale interannual
  climate variability signals -- El Niño Southern
  Oscillation (ENSO)

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Operational Application
Surveillance Regions Based on Savanna Mask
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Operational Application 1997-1998 Outbreak

• Convergence of Pacific El Nino event and WIO
  Warming
• Wide spread, persistent and rainfall in semi arid
  lands
• Flooded dambos hatching of infected mosquito
  eggs, supports several generations of mosquito
  populations
• Vegetation green-up micro-ecological habitats
  conducive to mosquito survival and propagation
• First human cases identified late December 1997,
  declared Epizootic late January 1998
• Impact on Livestock Trade Ban on livestock
  imports from GHA loss of income 100
  million in 1998
• Reported losses of 70 sheep and goats and
  20-30 cattle and camels
• estimated 89,000 humans in this region could have
  been infected (North Eastern Kenya and central
  Somalia)

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Operational Application
http//www.geis.ha.osd.mil/RVFWeb/index.htm
Persistence mapping of above normal vegetation
conditions
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Situation September 2006 -- Climate

• Temporal evolution of WIO SSTs similar to
  1982-83 / 1986-87 so far
• Warming in WIO region 0.5oC
• Most of the rain has been over the Ocean in
  September 2006 (see OLR)
• Increase in the size of warm pool of WIO will
  lead to more land falling rainfall in East Africa

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Situation September 2006 -- Rainfall, NDVI

• Most of the rain has been over the Ocean in
  September 2006, except for coastal parts of Kenya
  and Eastern Somalia
• Vegetation green-up central and northern
  Somalia ( 40 above normal), coastal Kenya
• No RVF risk for East Africa for the period July
  September 2006

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Situation October 2006 -- Climate
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Situation October 2006 -- Rainfall
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Situation October 2006 -- Vegetation
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Situation November 2006 -- Climate
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Situation November 2006 -- Rainfall
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Current Situation November 2006 - Vegetation
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Daily Rainfall at RVF Monitoring Sites
Current rainfall at selected RVF monitoring sites
almost same as 1997/98, continued rainfall will
maintain flood waters and elevate risk of RVF
activity and other vector-borne diseases.
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Forecast Products
https//iri.columbia.edu/

• IRI SST Forecast for NDJ(06/07) WIO region
  0.5oC, this is close to 1997/98 SST anomaly
  correlated with widespread rainfall in East
  Africa
• Rainfall forecast DJF 40-60 probability of
  above normal rainfall during DJF(06/07).

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Summary

• It's time to watch December 2006 January 2007
  Current Forecast for November 2006 - January
  2007 continued rainfall ? risk is growing.
• Prolonged drought during the last several years -
  current livestock populations are already weak
  and highly susceptible to infection
• WHO FAO, MOA, MOH to provide advisory and
  guidance on prevention vaccination of livestock
  and pretreatment of mosquito habitats adjacent to
  pastoral settlements, livestock herds grazing
  areas with highly effective sustained release
  insecticides that can be released during current
  flooding.

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Contributors

• Kenneth J. Linthicum, Center for Medical,
  Agricultural Veterinary Entomology,
  Agricultural Research Service, United States
  Department of Agriculture, Gainesville, Florida.
• Assaf, Jennifer Small Compton J. Tucker,
  NASA/Goddard Space Flight Center, Biospheric
  Sciences Branch, Code 614.4, GIMMS Group,
  Greenbelt, Maryland.
• Jean-Paul Chretien - Department of Defense,
  Global emerging Infections System, Division of
  Preventive Medicine, Walther Reed Army Institute
  of Research, Washington, DC.
• International Research Institute for Climate
  Prediction (IRI), Columbia University, New York
• NOAA Climate Prediction Center, Camp Springs,
  Maryland.
• USDA Foreign Agricultural Service (FAS),
  Washington D.C.

Collaborators

• Department of Defense, Global Emerging Infections
  Surveillance Response System (DoD-GEIS),
  Division of Preventive Medicine, Walther Reed
  Army Institute of Research, Washington, DC
  20307-5100
• World Health Organization Pandemic Alert and
  Response Department, Geneva
• Food and Agricultural Organization (FAO), Rome.