Dissertations and Theses

Date of Degree

6-2-2020

Document Type

Dissertation

Degree Name

Doctor of Philosophy (Ph.D.)

Department

Environmental, Occupational, and Geospatial Health Sciences

Advisor(s)

Jean Grassman

Committee Members

Glen Johnson

Alexis Pozen

Timothy Bouley

William B. Karesh

Subject Categories

Animal Diseases | Behavioral Economics | Econometrics | Environmental Public Health | Health Economics | Health Policy | International Public Health | Public Health | Virus Diseases

Keywords

zoonotic disease, economic analysis, risk reduction, vaccination, multisectoral, South Africa

Abstract

Background: Rift Valley Fever (RVF) is a climate-sensitive emerging zoonotic disease associated with large-scale livestock production losses and human disease burden in Sub-Saharan Africa and the Middle East. While recognized as a key One Health issue based on its transmission dynamics involving human, animal and environmental determinants, there has been poor coordination between sectors to reduce the risk and impact of RVF. Efforts to counter the disease remain largely reactive, presenting an ongoing threat to local and global health security. The intent of this dissertation was to improve understanding of the burden of RVF across society and to identify entry points for practical and cost-effective interventions at global, national, and local scales.

Methods: For Aim 1, we quantified global impacts using official and unofficial reports of human and animal disease and deaths from RVF. We assessed univariate correlation between RVF reporting and broad country-level predictor variables for African nations and describe country development characteristics as well as review major capacity and implementation gaps. In Aim 2, we conducted the first national cost analysis for RVF in South Africa, utilizing a One Health approach to combine data from multiple sectors (agriculture, health, environment, tourism, and finance) and identify the type, magnitude, and distribution of expenditures and losses in outbreaks and inter-epidemic periods between 2003-2018. Aim 3 focuses on actionable policy recommendations, using a survey on RVF prevention and control practices and willingness to pay (WTP) measures to improve understanding of economic behaviors of farm owners, the primary decision-maker for RVF vaccine uptake, in South Africa’s Free State and Northern Cape provinces.

Results: In Aim 1, we find that a total of 5,228 suspected human cases and 987 deaths, and 72,960 animal cases and 17,810 deaths, were officially reported in 32 countries between 2000-2019. Of the twelve country-level predictor variables assessed, a higher number of RVF publications was significantly associated with higher odds of official reporting of RVF 2000-2019 (OR=1.5), whereas higher level of political stability and absence of violence was protective against RVF reporting (OR=.39), as was higher percentage of population with access to electricity (OR=.97) (all p<.05). On average, countries reporting RVF in Africa have high dependence on livestock, and face major economic, infrastructure, and capacity deficits, which can be expected to affect implementation and efficacy of RVF prevention, detection and response campaign. In Aim 2, we find that between 2003-2018, RVF was associated with at least US$120.6 million in expenditures and losses in South Africa. The majority of impacts were incurred during epidemic periods. The burden of disease from RVF was estimated at 680.913 Disability-Adjusted Life Years, with the majority from premature death. Productivity losses and medical and public health spending accounted for approximately 5% of total costs. Overall, costs were concentrated in the livestock sector, representing 85.5% of costs. Other affected sectors incurring losses included finance (via avoided tax revenue) and environment (wildlife products). In Aim 3, 90% of farms in our sample of 120 commercial livestock farms in South Africa’s Free State and Northern Cape provinces were willing to pay something annually to avoid RVF losses, with an overall mean of $727.23 per year. Higher mean WTP to avoid animal losses from RVF was significantly associated with higher number of domestic animals and wool farming (p<.05). There was also a significant difference in WTP to vaccinate herds against RVFbased on level of risk of RVF circulating in mosquitoes in their province or farm (p<.000). Most farms indicated they would take measures other than or in addition to vaccination if they thought risk of RVF was high in their province, including insecticide/dip (90.65%) and antibiotics (28.04%). Several barriers and enablers were identified for uptake of livestock vaccination against RVF. Among the barriers, approximately half the farms thought vaccine supply was sufficient in general, whereas less than one-fourth thought it was sufficient during an outbreak.

Discussion: Over the past two decades, RVF has affected multiple continents. The lack of a comprehensive reporting system for animal and human disease burden makes tracking official estimates challenging. A comparison to published estimates suggests wide under-reporting of RVF. In terms of prevention and control practices, affected countries face several major economic, capacity, and infrastructure barriers that may affect uptake and effectiveness of vaccination. Encouragingly, from our national- and farm-level analyses in South Africa, we find that there is some existing investment in RVF in interepidemic periods, and that there may be supply and demand-side practices that may be supported by low-cost or multi-disease interventions, such as enhanced risk communication and tracking of vaccine availability. Our findings can be paired with further willingness to pay studies of other payer groups to identify optimal resource allocation options. Future macro- and micro-costing studies can improve precision of data inputs. While the need for a One Health approach has been articulated for improved understanding of the risks of RVF, our findings demonstrate how a One Health lens also has utility in assessing impacts to identify a broader range of affected stakeholders and inform coordinated action to address both animal and human disease and wider societal impacts.

Available for download on Wednesday, May 19, 2021

Share

COinS