Title: Rift Valley Fever Monitoring Update November 27, 2006
1Rift 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.
2Historical 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
3(No Transcript)
4Satellite 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
5Vector 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
6Reconstruction 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 NiƱo Southern
Oscillation (ENSO)
7Operational Application
Surveillance Regions Based on Savanna Mask
8Operational 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)
9Operational Application
http//www.geis.ha.osd.mil/RVFWeb/index.htm
Persistence mapping of above normal vegetation
conditions
10Situation 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
11Situation 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
12Situation October 2006 -- Climate
13Situation October 2006 -- Rainfall
14Situation October 2006 -- Vegetation
15Situation November 2006 -- Climate
16Situation November 2006 -- Rainfall
17Current Situation November 2006 - Vegetation
18Daily 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.
19Forecast 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).
20Summary
- 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.
21Contributors
- 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.