Date Published: March 12, 2019
Publisher: Public Library of Science
Author(s): Susana Monge, Roan Pijnacker, Wilfrid van Pelt, Eelco Franz, Laetitia M. Kortbeek, Marie-Josée J. Mangen, Brecht Devleesschauwer.
Burden of disease (BoD) estimations are increasingly used to prioritize public health interventions. Previous Cryptosporidium BoD models accounted only for acute episodes, while there is increasing evidence of long-term manifestations. Our objective was to update Cryptosporidium BoD and cost-of-illness (COI) models and to estimate BoD and COI for the Netherlands in years 2013–2017.
We performed a scoping literature review and drew an outcome tree including long-term manifestations for which sufficient evidence was found, such as recurrent diarrhea and joint pain. We chose the Disability-Adjusted Life Year (DALY) metric to synthesize years of life lost due mortality (YLLs) and years lived with disability due to non-fatal outcomes (YLDs). For the costs, we adopted a societal perspective accounting for direct healthcare costs, patient costs and productivity losses. Uncertainty was managed using Latin Hypercube sampling (30,000 iterations).
In the Netherlands in 2017, we estimated 50,000 Cryptosporidium cases (95% uncertainty interval (UI): 15,000–102,000), 7,000 GP visits, 300 hospitalizations and 3 deaths, resulting in 137 DALYs (95%UI: 54–255) and €19.2 million COI (95%UI: €7.2 million– €36.2 million). Estimates were highest for 2016 (218 DALYs and €31.1 million in COI), and lowest in 2013 (100 DALYs and €13.8 million in COI). Most of the BoD was attributable to YLD (≈80% of DALYs). The most important cost was productivity losses (≈90% of total COI). Long-term manifestations, including recurring diarrhea and joint pain, accounted for 9% of the total DALYs and 7% of the total COI.
Current evidence supports the inclusion of long-term manifestations in Cryptosporidium models, which contribute close to 10% of the total DALYs and costs. This may be an underestimation, as we were conservative in our assumptions. Cryptosporidium should be considered a priority organism with respect to public health surveillance, even in industrialized countries with high hygiene standards.
During the last decades, there has been a growing interest in estimating the burden of disease (BoD) in order to prioritize healthcare, public health interventions and health research. Different metrics have been proposed for this, such as the Disability-Adjusted Life Year (DALY) or the Quality-Adjusted Life Year (QALY), among others . The DALY metric was developed in the 1990s by the World Health Organization, the World Bank and the Harvard School of Public Health for the Global Burden of Disease project (GBD), and has been widely used since [3–5]. DALYs were also adopted by the European Centre for Disease Prevention and Control (ECDC) for the Burden of Communicable Diseases in Europe (BCoDE) project in 2009, and an easy-to-use toolkit has been developed to help expand its application [6, 7]. In the Netherlands, DALYs are calculated annually for 14 food-borne pathogens  and for over 30 infectious diseases, including foodborne pathogens , to monitor their BoD and help decision making.
In the years between 2013 and 2017 (Table 3), Cryptosporidium caused between 100 and 218 DALYs per year, with a higher burden estimated in the years 2015 and 2016, in which a higher number of cases was reported to the surveillance system. The increase was mainly due to an increase in C. hominis (160 DALYs in 2016 vs. 12 in 2014), while the BoD of C. parvum was more stable at between 58–96 DALYs (Table 3). In the same period, the associated annual costs were between 13.8 million € (M€) and 31.1 M€ (Table 3). In the year 2017, Cryptosporidium caused a total of 137 DALYs and 19.2 M€ in COI in the Netherlands (i.e. 8 DALYs and 1.1 M€ per million inhabitants).
This is the first estimation of burden of disease and cost of illness of Cryptosporidium infection to account for long-term manifestations. Recurrent diarrhea and joint pain together accounted for 9% of the total DALYs and 8% of the total COI. Overall, Cryptosporidium produced 137 DALYs and a cost of 19.2 M€ in the Netherlands in 2017, although this varied by year. The highest burden is observed in years 2015 and 2016, where there was an increase in sporadic cases reported to surveillance, mainly of C. hominis, resulting in 218 DALYs and 31.1 M€ in COI in 2016; no single source or prominent risk factor was found to explain this increase . This protozoon should be among the priorities for public health surveillance in the Netherlands.