Screening for alveolar echinococcosis in household members of affected patients: A cross-sectional study with a pooled comparison to endemic population screenings.

Background: Alveolar echinococcosis (AE) is an emerging and potentially fatal zoonosis caused by accidental ingestion of infective eggs of the cestode Methods: We conducted a cross-sectional study at the University Hospital of Ulm, Germany. Unrelated household members of AE patients who shared the same household for ≥5 years prior to the patient's diagnosis were invited for screening with serological testing and abdominal ultrasound. The primary endpoint was the prevalence of possible or probable AE. Results: A total of 100 household members from 100 AE patients were recruited. Six participants showed positive or borderline results in one of the two serological tests, but none showed positivity in both and all had negative western blot results. Of the 88 participants with available imaging, only one participant had a calcified, inactive AE lesion, classified as possible AE. No participant met the criteria for probable AE. Conclusion: We observed a higher seroprevalence (6.0%) among household members than pooled estimates from population-based screenings in high-endemic areas (1.9%; 95% CI 1.6-2.1%). The prevalence of inactive AE (1136 per 100,000) also exceeded that reported in these studies (51 per 100,000; 95% CI 22-101); however, the sample size and a different screening approach limit the comparability of the findings. Importantly, AE remained rare in this group, and no clinically relevant active cases were detected. Although exposure to infective EM eggs may be increased among household members, host-related factors may influence whether infection becomes clinically manifest. Based on these results, routine screening of unrelated household members cannot be recommended at this time.