Placing a monetary value on the human health component of zoonotic diseases: A methodological note with an application to cysticercosis in Africa

Ideally, policies aiming to tackle zoonotic diseases in animals and reduce the burden of disease in humans should be based on an assessment of the cost and benefits of alternative interventions. However, while the cost of actions targeting diseases in animals and humans and the benefits in terms of increased livestock production can be monetized, it is a challenge to monetize improvements in the quality of life or to life expectancy extensions in humans in zoonotic policy evaluations. This paper proposes a method to monetize the human health benefits derived from zoonotic disease reduction and applies it to cysticercosis in Burkina Faso, Egypt, Ethiopia, Kenya, Nigeria and Uganda. We propose a three-step approach to estimate the human health component of the monetary impact of zoonoses. First, we proxy society's willingness to pay to avoid a disability adjusted life year (DALY) using the annualized value of statistical life (VSL) estimated by of the United States Department of Health and Human Services. Second, we implement a benefit transfer methodology to transfer the US value into the context of the sampled countries, accounting for differences in income levels. Finally, we use the 2016 Global Burden of Disease (GBD, 2018) data on cysticercosis to estimate its monetary impact on human health. All results are estimated in current international dollars using purchasing power parity (USD PPP) exchange rates. In the sampled countries, willingness to pay to avoid a DALY is estimated between USD PPP 2 000 and USD PPP 12 700. In most cases, these estimates fall within the range of 1 and 3 times the GDP per capita. The estimated monetary value of the DALYs due to human infections of cysticercosis per 100 000 people ranges between USD PPP 18 000 and USD PPP 98 000 per year. The proposed methodology might represent a first step towards providing a consistent and unbiased measure of the benefits of interventions targeting prevention, detection and control of zoonotic diseases.