• Share
  • Email
  • Embed
  • Like
  • Save
  • Private Content
Rift Valley fever in Africa
 

Rift Valley fever in Africa

on

  • 1,351 views

Presentation by Dr Kariuki Njenga of the Centers of Disease Control & Prevention, at the Enhancing Safe Inter-regional Livestock Trade held at Dubai, UAE, 13-16 June 2011.

Presentation by Dr Kariuki Njenga of the Centers of Disease Control & Prevention, at the Enhancing Safe Inter-regional Livestock Trade held at Dubai, UAE, 13-16 June 2011.

Statistics

Views

Total Views
1,351
Views on SlideShare
1,346
Embed Views
5

Actions

Likes
0
Downloads
21
Comments
0

2 Embeds 5

http://rvfworkshop2011.wordpress.com 4
http://paper.li 1

Accessibility

Upload Details

Uploaded via as Adobe PDF

Usage Rights

CC Attribution-NonCommercial-ShareAlike LicenseCC Attribution-NonCommercial-ShareAlike LicenseCC Attribution-NonCommercial-ShareAlike License

Report content

Flagged as inappropriate Flag as inappropriate
Flag as inappropriate

Select your reason for flagging this presentation as inappropriate.

Cancel
  • Full Name Full Name Comment goes here.
    Are you sure you want to
    Your message goes here
    Processing…
Post Comment
Edit your comment

    Rift Valley fever in Africa Rift Valley fever in Africa Presentation Transcript

    • Rift Valley Fever in Africa Kariuki Njenga, DVM, PhDCenters for Disease Control & Prevention, Nairobi, Kenya
    • Density map of human and animal cases onsolonchak soil Legend: • Livestock confirmed cases + Sublocations with confirmed human cases Solonchak soils L. Baringo L. Bogoria Munyua et al., Amer J Trop Med Hyg 83 (Supp2), 58-64,2010
    • RVF Disease: Transmission in Livestock Transmitted by infected mosquito bites – Various species of mosquito – other biting insects can transmit Affects sheep, cattle, camel, goats – Abortions – bleeding
    • RVF Disease: Transmission in humans o Direct contact with blood, meat, milk and other body fluids of infected animals o Can occur during slaughtering, skinning o Bite of infected mosquitoAerosol transmission? – Generated during slaughter of infected livestock
    • What are risk factors of acute RVF in humans?• Touching an aborted fetus [OR = 3.83]• Consuming or handling products from sick animals [OR = 2.53]• Being a herdsman [OR = 1.77]• Exposure to mosquitoes was not an independent risk factor Amwayi et al., Amer J Trop Med, 83 (supp2), 14-21, 2010
    • 1940 1950 1960 1970RVF activity in East Africa* Egypt 1980 RVF Epidemics (1932 – 2011) Mauritania 1990 Egypt Mauritania 2000 KSA/Yemen Egypt Sudan RSA/Comoros Madagascar 2010 RSA RSA
    • Recent Severe Human RVF OutbreaksYear Countries Estimated Reported Deaths Cases Cases1977 Egypt 200,000 18,000 5981987 Mauritania 1500 300 2241993 Egypt 1500 ? 201997-98 Kenya, Somalia, 89,000 ? 4581 Tanzania1998 Mauritania 300 150 71999 Mauritania ? ? 22000 KSA, Yemen 1500 516 87 2000 1087 1212003 Egypt 300 148 272006-07 Kenya, Tanzania, ? 700 158 Somalia 309 144 107 542007 Sudan ? 125+ 60+2008, 2009 Madagascar, RSA, ? ? ? Comoros2010,2011 RSA ? 255 261Data available from Kenya only
    • RVF Risk Mapping: Set upRVF – epizootics occur under favorable andpersistent eco-climatic conditionsCan be mapped – either as rainfall orvegetation – NDVI integrates all the required conditionsAlgorithm: – Mapping of potential epizootic areas – based on literature survey and climate variable thresholding= potential epizootic area mask (PEAM) – (C. J. Peters & K.J. Linthicum in Handbook of Zoonoses) – NDVI anomaly calculation -- + anomalies > 0.025 threshold (desert calibration) over 3 month period – Persistently + anomalies must have three month mean > 0.1 – All “pixels” that meet this criteria and are within the PEAM are mapped to have conditions necessary for the occurrence of RVF activity
    • Epidemic prediction: Relies on field dataTeamworkCapacity Building
    • Kenya: RVF Spread Over 52Last 2 epizootics affected 6 of 8 provinces, 38 of 69 districts 1951-1955 1997-2007 10 12 21 22 19 19 2 20 7 20 7 14 16 14 16 1 11 18 11 13 4 18 15 13 8 17 3 9 5 6 - 6 Murithi et al., Epi Infect 18, 1-9, 2010
    • Prediction vs. Outbreak Timing: Epi-Curves: 2006 - 2008Anyamba et al (In Review AJTMH)
    • What is the inter-epizootic period (IEP)? Based on Kenya Dept Vet Svs Data – 1910 - 2007 Mean IEP = 3.6 years IEP IEP IEP IEP Murithi et al., Epi Infect 18, 1-9, 2010
    • Where is RVF virus maintained ?1. Transovarially in Aedes mosquito spp2. Endemicity. Cycling between wildlife, livestock and possibly humans within a permissive ecosystem, mediated by the appropriate vectors.In wildlife Cummulative percent of positive samples at each titer level 9 of 17 species tested 100.00 were positive % of positive samples of 80.00 60.00 - Buffalos, Black rhinos, - Thompson gazelles, species Buffalo 40.00 Black rhino - Impalas, Elands, Kudus Other 20.00 0.00 80 0 0 0 80 40 20 10 64 32 16 -20.00 12 1: 1: 1: 1: 1: 1: 1: 1: Titer level Evans et al, Epid Inf 8, 1-92007 Negative: Lions, giraffes, common zebras
    • Where is RVF virus maintained ?In livestock : Kenya during the 1999 – 2006 IEP Sheep Goats Year Percentage Percentage of No. tested No. tested positive positive birth 1999 12 25 5 0 2000 27 11 7 14 2001 17 29 7 0 2002 19 11 10 0 2003 17 18 17 0 2004 29 24 10 10 2005 63 17 15 0 2006 4 0 4 0 Total 188 18* 2/75 3 Rostal et al, Amer J Vet Res 71, 522-6, 2010
    • Northeastern Province of KenyaDecember, 1997 December, 2006
    • Sequential Epidemics in Kenya, Somalia, and Tanzania [1997-8; 2006-7]
    • Reported Human RVF Cases (Deaths) in Kenya NEP 333 of 700 (45%) Wajir 26(12) cases ISIOLO Baringo 13(0) 174(13) Garissa Baringo Nakuru 176(59) 1(1) 174 of 700 (24.8%) Ijara Cases Kirinyaga 131(27) 5(2) Kajiado Tana-River Maragua 10(6) 21(8) 4(0) Taita-Taveta Malindi 15(4) Kilifi Thika 15(1) 73 of 700 (10.4%) 2(0) Kilifi Nairobi 73(20) cases 5(2)
    • Cases 0 2 4 6 8 10 12 14 16 18 20 21/11/2006 28/11/2006 05/12/2006 12/12/2006 19/12/2006 NEP 26/12/2006 02/01/2007 09/01/2007 16/01/2007 Kilifi 23/01/2007 30/01/2007Date of Onset 06/02/2007 13/02/2007 Kenya 2006/07(N=340) 20/02/2007 Baringo 27/02/2007 06/03/2007 13/03/2007 Alive Dead 20/03/2007 Confirmed and Probable Rift Valley Fever Cases , 27/03/2007
    • RVF Outbreaks in SomaliaFirst case confirmed 20th January, 2007Total:107 cases, 54(50.5%) deaths
    • RVF Outbreak in TanzaniaFirst case confirmed Feb 1st, 2007Total: 309 cases, 144 deaths
    • Sequential Epidemics: How does the virus spread? 2006-2007 Epidemic Region 1: Nov 26, 2006 Region 2: Dec 26, 2006 Regions 3,4: Jan 7, 2007 Region 5: Feb 5, 2007 Region 6: Jan 27, 2007 Region 7: Feb 1, 2007 Nderitu et al., J Inf Dis 203, 2011
    • How do epizootics spread?Multiple lineages of RVF virus during one epidemic indicate spontaneousactivation of resident virus Kenya 2 Kenya 1b Kenya 1a Tanzania 1 Nderitu et al., J Inf Dis 203, 2011; Bird et al, 2008
    • Number of confirmed RVF cases and deaths byprovince, South Africa, 2010- 2011 (latest April 10, 2011)All cases occurred mid-February – May each yearProvince Cases Deaths 2010 2011 2010 2011Eastern Cape 17 13 1 0Free State 123 3 11 0Gauteng 0 0 0 0KwaZulu-Natal 0 0 0 0Limpopo 0 0 0 0Mpumalanga 0 0 0 0Northern Cape 74 2 11 0North West 9 0 2 0Western Cape 4 9 1 0Total 228 27 26 0 Source: NICD, South Africa
    • South Africa: RVF Infection Map, April 2011Source: NICD, South Africa
    • RVF in Madagascar 1st Epizootic / Epidemic 1990 -few cases Antananarivo Another in 1991 #Perinet ForestEpizootic / Epidemic 1990Epizootic / Epidemic 1991 26
    • RVF in Madagascar Last cases in March 2009 AntananarivoPrimary Forest of Perinet #Epizootic / Epidemic 1990Epizootic / Epidemic 1991Epizootic / Epidemic 2008Epizootic / Epidemic 2008-2009Last cases in 2009 27
    • Major Interventions (Eastern Africa) Social mobilization Slaughtering ban – Major religious holiday (Idd festival) Livestock quarantine Livestock vaccination Vector control (minimal)
    • RVF Outbreak Response 2006 – A Step BehindLivestock vaccination Public Education
    • ChallengesPoor accessibility: FloodingTiming: Occurred in peak holiday seasonLimited health services in the regionCoordinating surveillance betweenlivestock and human health