Unexpected Increase of Alveolar Echincoccosis, Austria, 2011

The Study

Conclusions

Acknowledgment

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Suggested Citation

Renate Schneider, Horst Aspöck, and Herbert Auer

Author affiliations: Author affiliation: Medical University Vienna, Vienna, Austria

Abstract

Austria is part of the classical area of central Europe to which alveolar echinococcosis (AE) is endemic. Annual incidences in Austria were 2.4 and 2.8 cases/100,000 population during 1991–2000 and 2001–2010, respectively. Hence, the registration of 13 new AE patients in 2011 was unexpected. Increasing fox populations and past AE underreporting might have caused this increase.

Alveolar echinococcosis (AE) is one of the most serious helminthic diseases of humans. It is caused by the larval stages (metacestodes) of the fox tapeworm, Echinococcus multilocularis. Final hosts are foxes and, rarely, dogs and cats; intermediate hosts are rodents (voles). Humans are aberrant hosts and acquire the infection by oral ingestion of parasite eggs released in the feces of infected foxes or other carnivores. The metacestodes proliferate in the human liver and induce a hepatic disorder mimicking liver cancer (1) that becomes clinically apparent after an incubation period of 5–15 years. The prognosis for untreated AE is poor, and early diagnosis is essential for curative treatment (2).
AE has been known to be endemic to Austria, southern Germany, Switzerland, and eastern France since the second half of the nineteenth century. From the Austrian echinococcosis researcher, Adolf Posselt, who documented all reported human AE cases during 1867–1936, we know that the annual incidence of AE in Austria was 1.4 cases at the beginning of the twentieth century and that most patients resided in Austria´s western provinces, Vorarlberg and Tyrol (3).
Meanwhile, the parasite and the disease have spread from its classical distribution area in central Europe to at least 11 other European countries (2,4). Furthermore, several reports from Austria, Germany, and Switzerland document increasing fox populations during the 1990s and 2000s, presumably caused by successful antirabies vaccination (2,5), which was established in Austria in 1992. In addition, a suspected increase in and/or underreporting of human AE has been discussed within the past few years (6,7).
The goal of our study was to determine the annual incidence of AE during the past 20 years. We also aimed to discuss possible reasons for the unexpected increase of human AE during 2011.

The Study

Our institute is Austria`s national reference center for echinococcosis (8). The study comprised 65 patients in whom AE was diagnosed and registered during 1991–2011; the patients derived from all 9 of Austria’s provinces. Inclusion criteria were as follows: 1) AE characteristic imaging findings and 2) E. multilocularis–positive species-specific serology and/or 3) AE characteristic histopathologic findings and species-specific molecular analysis. All available details about sex, age, province of origin, results of serologic and molecular biologic investigations, histopathologic findings, and clinical status of AE patients before AE diagnosis were logged into an Excel spreadsheet (Microsoft, Redmond, WA, USA) and analyzed.