Bett, Bernard K.

Bukachi, S.

Gachohi, John M.

Karungo, C.

Njenga, K.

Oyas, H.

Svitek, Nicholas

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Towards the development of optimal vaccination strategies for Rift Valley fever (RVF) in East AfricaBernard Bett1, John Gachohi2ǂ ,Catherine Karungo1,, Salome Bukachi3, Nicholas Svitek1, Kariuki Njenga2, Harry Oyas41. International Livestock Research Institute, P. O. Box 30709-00100, Nairobi, Kenya 2. Washington State University Global Health Program – Kenya, UNITID Complex, KNH, Nairobi3. Institute of Anthropology, Gender and African Studies, University of Nairobi, P. O. Box 30197-00100, Nairobi4. Directorate of Veterinary Services, Ministry of Agriculture, Livestock and Fisheries, Private Bag 00625, Kangemi, RVF vaccination – gaps • New vaccines being developed – not much attention on vaccination strategies • Current strategy – reactive vaccination which often fails to achieve required coverage • RVF vaccines often delivered through state financing – can value chain actors cost share? Are they willing to pay? What influences acceptance?• One Health dimension  – economic benefits of vaccination in livestock?Activities and their schedules timing workshopAntibody decay studyLivestock pop dynamicsSocio-economicsworkshopsDev. vaccination strategiesRefine decision support toolsTime Stakeholder consultations – regional workshopWORKSHOP ON DEVELOPING VACCINATION STRATEGIES FOR RIFT VALLEY FEVER IN EAST AFRICA - 4-5 OCTOBER, 2017 – NAIVASHA COUNTRY CLUB, NAIVASHA, KENYAObjectives • Review RVF status in East African region• Design RVF vaccination strategies in livestock• Identify institutional arrangements, capacities and networks required for their implementationWorkshop recommendations: vaccination strategies (i) Routine vaccination in high risk areas (annual)- This should be based on RVF risk map. However, Uganda – no formal risk map- This should target all animals of all ages - Subsequent vaccinations should target animals not vaccinated -- animal identification is an issue to follow up(ii) Vaccination ahead of predicted outbreak (During alert/ Emergency)- Issues to consider: • procurement of vaccines,• sensitivity and accuracy of predictions,  • resources are and how to mobilize them on short notice(iii) Intermittent multiyear vaccination- Once every 3 years in high risk areas- Vaccinate yearlings once every 3 years and maintain a some level of herd immunity because vaccination is a very costly exercise (iv) Use of multivalent vaccines- For each of the above strategies, analyse costs and logistics of using multivalent vaccinesLongitudinal study involving vaccinated livestockObjectives • To determine the longevity of anti-RVF virus response in cattle, sheep, goats and camels• To determine the effect of livestock population turn-over on herd immunity against RVF in cattle, sheep, goats and camels• To collect demographic and socio-economic data that can be used to estimate parameters for modelling livestock population dynamics in a pastoral production systemWhat do we know about longevity of RVF response?Vaccination study – Sampling design • Two sampling designs:– Longitudinal study using 30 cattle, 30 sheep/goats and 30 camels– Repeated cross sectional sampling of 22 herds from which these animals come from• Sample size considerationso 75% of the animals develop neutralizing Abs following vaccination and about 50% retain protective levels after 1 year o One sample comparison of proportions o Clustering in herds, assume correlation coefficient of 0.04o Level of confidence 95% and a power of 80% • Vaccinate all the animals with Smithburn vaccine at day 0Work Plan / Study DesignN = 300    7    10    14    21    28         56         84         112         140         168         196         224         252 280         308         336         364 Serum White blood cells in RNAlater SerumTime plan [days]SmithburnRVF vaccine• Collect WBC at early time-points for transcriptomics• Collect sera at all time-points– cELISA– VNTVaccination study – Data collection • Baseline sampling – all animals • Vaccination with Smithburn– all animals• Sampling – longitudinal • Population changes –entries and exits• Drug use Modelling Modelling tool is availableModel structure – explicit livestock,mosquitoes and rainfall dynamicsImprove and expand models – epi and econModelling Impacts a function of coverage, time to outbreak and perhaps the host spp ecologyImpacts – vaccination coverages vs time to outbreak Modelling Impacts – vaccination coverages at outbreak onset Modelling Impacts – biannual and annual vaccination strategiesQuantifying vaccine doses by strategy • Decision support framework – Quantifying vaccine quantities– Coordination of campaigns• Risk maps– Impacts:• 33% of East Africans  (51.5 out of 155 million in high risk areas)Rift Valley fever risk mapDistribution of the target livestock speciesCattle GoatsSheep CamelsRobinson TP, et al. Mapping the global distribution of livestock. PLoS One. 2014;9. doi:10.1371/journal.pone.0096084Crude estimates of livestock numbers by risk  Crude numbers of livestock species by risk level that can be used to guide Estimation of the number of RVF vaccine doses in East Africa Potential sources of bias:- RVF risk is underestimated in Ugandaefforts to develop the risk map in Uganda on-going - Livestock estimates for Tanzania generally poorProject will convene Workshops to obtain more accurate livestock numbers Acknowledgements • Range of stakeholders including those involved in designing the studies during the inaugural workshop• Pastoralists participating in the longitudinal study in Isiolo, Kenya• Funding from OFDA, USAID 

Towards the development of optimal vaccination strategies for Rift Valley fever in East Africa

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Towards the development of optimal vaccination strategies for Rift Valley fever in East Africa

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