Characteristics and Clinical Course of Alveolar Echinococcosis in Patients with Immunosuppression-Associated Conditions: A Retrospective Cohort Study

Abstract

Objectives: Since the change in the millennium, an increase in cases of alveolar echinococcosis (AE) has been observed in endemic European countries. Previous studies indicate that a significant proportion of the new AE cases have an immunosuppression-associated condition (IAC). The aim of the current study was to determine how IACs impact the number of new AE diagnoses per year and the characteristics of AE at diagnosis and its clinical course at our center.

Methods: Retrospective analysis of 189 patients with AE diagnosed between 2000 and 2021 and participating in the Zurich Echinococcosis Cohort Study (ZECS) included clinical characteristics of AE at diagnosis and report of an IAC, as well as the clinical course during follow-up.

Results: Of 189 patients participating in this study, 38 had an IAC reported at, or shortly after, AE diagnosis. Over time, there was a steeper increase in the number of newly diagnosed AE patients without an IAC than the number of patients with IAC. Patients with an IAC were older at diagnosis, more frequently had an incidental finding of AE, smaller mean lesion size, and negative Em18 serology. All but two showed favorable outcomes on the last follow-up.

Conclusion: IACs have little impact on the increase in new AE cases, as well as on the extent of the disease at diagnosis and clinical course.

Keywords: Echinococcus multilocularis; alveolar echinococcosis; immunosuppression; immunosuppression-associated conditions.

Figure 1

After a query of the electronic hospital information system KISIM (Cistec), 227 patients with a new diagnosis of AE during the time period 2000–2021 could be identified. All met the inclusion criteria for participation in the Zurich Echinococcosis Cohort Study. In total, 189 patients consented to participation, of which 106 met the WHO case definition of “probable AE”, and 83 met the WHO case definition of “definitive AE”. In 38 of the 189 participants, an immunosuppression-associated condition was reported at or up to 1 year after AE diagnosis. The rest was considered immunocompetent.

Figure 2

New AE diagnosis by calendar year. Shown are the number of new AE diagnoses by calendar year. Patients without an IAC are represented by squares, and those with an immunosuppression-associated condition, by triangles. The fitted linear regression curves are displayed as solid lines and their 95% confidence bands by dotted lines. Linear regression shows a significant increase in patients without an IAC over the years (y = 0.3394x − 675.4, p = 0.001). On the contrary, while there is a trend of an increasing number of newly diagnosed AE patients with an IAC per year (y = 0.06663x − 132.2), the slope is not statistically nonzero (p = 0.112).