Abstract
Cystic echinococcosis (CE) is a zoonotic neglected tropical disease (zNTD) which imposes
considerable financial burden to endemic countries. The World Health Organisation’s
2021–2030 roadmap on NTDs aims to achieve intensified control in hyperendemic areas
across 17 countries by 2030. Effective disease control interventions and the successful
scale-up of such programmes depend on a thorough understanding of disease transmission
dynamics, as well as the associated costs and return on investment for these interventions.
The objective of this thesis is to enhance our epidemiological understanding of CE in South
America through the integration of mathematical modelling and economic evaluation
methods.
Chapter 2 presents a Scoping Review of the cost and cost-effectiveness of CE control
interventions targeting zoonotic hosts. The review highlights the scarcity of published
data on the cost of CE control measures, with much of the available data being incomplete
or aggregated. This chapter underscores the need for greater transparency by programme
managers and for more detailed cost information to be made available. This work was
published in PLoS Neglected Tropical Diseases (Widdicombe et al., 2022).
In Chapter 3, I evaluated a pilot surveillance and control programme for CE in Peru (2015
to 2019). This chapter provides a descriptive analysis of the data collected during the
pilot study and establishes base line prevalence values of canine CE in the different regions
included in the pilot. It also details the costs of the various control strategies and the
intervention preferences of the veterinarians implementing these measures. The results
indicated that control interventions were deliverable to remote locations, and that a
largescale CE control programme is feasible in Peru. However, the pilot study also highlighted
the challenges of implementing and coordinating a control programme in remote locations,
and the necessary infrastructure required for success.
In Chapter 4, I explored preferences for equity in health resource allocation by One Health
professionals. This research examined how decisions on distributing health gains within
a population reflect a trade-off between maximising efficiency (maximum health across a
population) and reducing disparities in health based on need (equity). Through a
questionnaire, the study aimed to elucidate inequity aversion among One Health professionals.
The results showed that respondents were willing to sacrifice a considerable fraction of
total health to achieve a more equal distribution. However, achieving equitable health
outcomes for vulnerable populations requires policymakers to commit to equitable decisions,
necessitating increased resource prioritisation and financial investment.
Chapter 5 introduces the CEST model, a stochastic disease transmission model for Cystic
Echinococcosis, designed to capture the lifecycle and disease dynamics of CE in both its
definitive (dogs) and intermediate (sheep) hosts. The model is calibrated with data from
Río Negro, Argentina, and accounts for seasonal fluctuations in livestock husbandry. It
includes a retrospective analysis of historical interventions employed in the Río Negro
control programme since its onset in 1980, as well as a prospective analysis modelling
different intervention scenarios for 2025-2035. Deworming with praziquantel, and sheep
vaccination with EG95 are simulated at different frequencies and coverage levels. CE
prevalence in both dogs and sheep, as well as the predicted change in risk to humans
with each intervention, are presented annually. The model demonstrates that current
interventions can reduce disease prevalence in dogs and sheep, however even when dog
deworming was modelled at increased frequencies and the coverage of sheep vaccination
was enhanced, sporadic transmission was predicted to continue.
Chapter 6 estimates the cost of implementing a new regional control programme for CE
in South America comparing the costs of three different control programmes with
different frequencies of dog deworming against the status quo of taking no action. Using the
CEST model to simulate transmission dynamics, the cost-effectiveness of each
intervention was assessed. All control programmes were cost-effective when considered in a cost
per case avoided analysis. However, the programme with the least frequent treatment,
every 6 months, was the most cost-effective. The majority of CE programme costs were
associated with delivery logistics including the costs of vehicles, fuel, and wages, rather
than drug costs. The financial burden in CE-affected areas was overwhelmingly due to
livestock losses (99%), with human healthcare costs contributing less than 1% of the total
burden. A limitation of this research is the lack of published economic data on CE control
interventions and the under-reporting of human CE cases, which complicates traditional
cost-effectiveness analysis.
Chapter 7 provides a general discussion on the control of Cystic Echinococcosis in South
America, addressing the limitations of current data and suggesting avenues for further
research. This chapter reflects on the findings from earlier chapters, emphasising the
challenges posed by incomplete economic data, under-reporting of human cases, and the
logistical complexities of implementing control programmes. It also highlights the
importance of more detailed and transparent reporting in future studies to improve the accuracy
of cost-effectiveness analyses. The chapter concludes by identifying key areas where
further research is needed, particularly the need to better understand the production losses
associated with CE and to address the under-reporting and lack of specificity in CE case
reporting in the region.