# Presentation: 832256

## Rift Valley Fever Monitoring UpdateNovember 27, 2006

**Rift Valley Fever Monitoring Update****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.

**FEWS Science Meeting**
**November 27, 2006**

## 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

**Historical Perspective: East Africa**

## Slide 3

## Satellite Monitoring and Mapping

**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

## 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

**Vector Dynamics and Ecology**

## Reconstruction of RVF Outbreak History

**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)

## Operational Application

**Surveillance Regions: Based on  Savanna Mask**

## 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)

**Operational Application: 1997-1998 Outbreak**

## Operational Application

- Persistence mapping of “above” normal vegetation conditions

*http://www.geis.ha.osd.mil/RVFWeb/index.htm*

## 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

## 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

**Situation: September 2006 -- Rainfall, NDVI**

## Situation: October 2006 -- Climate

## Situation: October 2006 -- Rainfall

## Situation: October 2006 -- Vegetation

**Situation: October 2006 -- Vegetation**

## Situation: November 2006 -- Climate

## Situation: November 2006 -- Rainfall

## Current Situation:  November 2006 - Vegetation

## 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.

## Forecast Products

-  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).

- https://iri.columbia.edu/

## 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.

## Contributors

- 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**

- 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.