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Rift Valley fever outbreak response Dec 2006 – Feb 2007

Rift Valley fever outbreak response Dec 2006 – Feb 2007. Jason Richardson Entomology & Vectorborne Diseases U.S. Army Medical Research Unit-Kenya. Highlights. Ken Linthicum is omnipotent. Last RVF outbreak in Kenya was in 1997/98. 14 Dec 2006 - Vector surveillance initiated in NE Kenya.

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Rift Valley fever outbreak response Dec 2006 – Feb 2007

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  1. Rift Valley fever outbreak responseDec 2006 – Feb 2007 Jason Richardson Entomology & Vectorborne Diseases U.S. Army Medical Research Unit-Kenya

  2. Highlights • Ken Linthicum is omnipotent. • Last RVF outbreak in Kenya was in 1997/98. • 14 Dec 2006 - Vector surveillance initiated in NE Kenya. • 20 Dec 2006 - Fatalities due to an unexplained fever confirmed as RVF. • 14 Dec through today – Vector surveillance • 4 ecologically distinct areas of Kenya. • > 420 trap nights, • > 40 collection sites, • > 105,000 mosquitoes, sand flies, and biting midges, • > 2,500 pools (760 already tested for RVFV) • 30 RVFV positive pools, • Virus isolated in cell culture, • Virus sequenced • Outstanding team effort!

  3. RVFV Background • Rift Valley Fever (RVF) is a viral zoonosis. • Primarily affects livestock. • It is spread by the bite of infected mosquitoes. • The disease is caused by the RVF virus, a member of the genus Phlebovirus (family Bunyaviridae). • The disease was first reported among livestock in Kenya around 1915, but the virus was not isolated until 1931. • RVF outbreaks occur across sub-Saharan Africa, • Egypt in 1977-78, several million people were infected and thousands died during a violent epidemic. • Saudi Arabia and Yemen – 2000.

  4. RVF epidemic foci (Clements et al., , 2006)

  5. Impact • Approximately 1% of human sufferers die of the disease. • Amongst livestock the fatality level is significantly higher. • In pregnant livestock infected with RVF abortion rates approach 100%. • An epizootic of RVF is usually first indicated by a wave of unexplained abortions.

  6. Transmission Cycle Epizootics are dependant on flooding and population densities of flood water Aedes species

  7. Transmission Cycle • No known vertebrate reservoir. • Various competent vectors including Aedes, Culex, Mansonia, Ochlerotatus spp. • Sand flies, culicoides, ticks? • Efficient mechanical transmission. • Transovariol transmission in Ae. mcintoshi, Ae. vexans • Blood and milk-borne. • Aerosolized virus  lab infections. • Man is NOT a dead end host.

  8. Dambo

  9. Linthicum, K.J., A. Anyamba, C.J. Tucker, P.W. Kelley, M.F. Meyers, C. J. Peters, 1999: Science, 285, pp. 397-400

  10. A collaborative project between DoD-GEIS and NASA Goddard Space Flight Center. • The ability to map such areas of potential RVF activity 2 to 5 months before outbreaks occur.

  11. Rainfall & “Greeness” This Normalized Difference Vegetation Index (NDVI) anomaly map depicts the percent deviation or change from mean vegetation greenness

  12. El Nino and Sea Surface Temperatures

  13. Outbreak Response • Nov 06 – received an email from Dr. Anyamba (GEIS/NASA) warning of a possible RVF outbreak. • 14 Dec 06 – USAMRU-K initiated vector collections in NE Kenya. • Aedes mcintoshi populations were overwhelming. • Human hemorrhagic fever cases evident.

  14. Outbreak Response • 20 Dec 06 – First confirmed human case. • Surveillance  outbreak response planning. • Risk management • Interagency coord. • CDC • USAMRIID • NAMRU-3 • DOS • KMOH

  15. USAMRU-K, Vector-borne Disease Program KEMRI VHF Reference Lab (GEIS) USAMRIID NAMRU-3 CDC, Ft Collins

  16. Surveillance in NE Kenya

  17. Nomadic pastoralists

  18. Typical “village”

  19. Manyatta – Typical home

  20. Herder hooch

  21. Herders live on raw blood & milk

  22. Dry ice is not candy

  23. Tick collections

  24. Serosurvey

  25. Driving to the coast

  26. Driving to the coast

  27. Life at the beach

  28. Kilifi RVF Case Locations

  29. Lab Results • Tested 765 pools by real-time and conventional RT-PCR. • Detected 30 positive pools (2 species not previously implicated as vectors). • Aedes mcintoshi (11 pools), • Ae. ochraceus (11 pools), • Ae. pembaensis (1 pool), • An. squamosus (1 pool), • Culex bitaeniorhynchus (3 pools), • Cx. poicilipes(3 pools). • 12 of 21 sites tested had at least one positive pool.

  30. Lab Results • Minimal field infection rate (MIR) • MIR = (# pools pos/# of samples) * 1000 • 30 positive pools (25 per pool) • 19125 specimens tested (to date) • MIR = 1.57

  31. Lab Results • Identified ~40,000 arthropods to date. • > 40 species • > 10,000 Ae. mcintoshi

  32. Real-Time & Conventional RT-PCR KLF-014 (#4) 588F-946RC + 642 probe KLF-085 (#9) 588F-946RC + 642 probe KLF-091 (#15) 588F-946RC + 642 probe KLF-112 (#33) 588F-946RC + 642 probe neg cntl 588F-946RC + 642 probe Collected in Kilifi on 13 January 2007 Species: Ae. pembaensis (lane 5); Cx. bitaeniorhynchus (lane 10) Sample: KLF014/04; KLF 085/09 Product 551 bp, Ibrahim et al. 1997

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