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Rift Valley Fever Monitoring Update November 27, 2006. FEWS Science Meeting November 27, 2006. Assaf Anyamba*, Jennifer Small*, Kenneth J. Linthicum § , Jean-Paul Chretien †, Compton J. Tucker*

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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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  • 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

Historical Perspective: East Africa


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Coastal Flood Plain

Riverine Flood Plain

Savanna Grassland


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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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AP

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.

  • 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.

Collaborators


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