Populations at Risk for Alveolar Echinococcosis, France

Martine Piarroux, Renaud Piarroux, Jenny Knapp, Karine Bardonnet, Jérôme Dumortier, Jérôme Watelet, Alain Gerard, Jean Beytout, Armand Abergel, Solange Bresson-Hadni, Jean Gaudart

, and for the FrancEchino Surveillance Network

Author affiliations: Aix-Marseille University, Marseille, France (M. Piarroux, R. Piarroux, J. Gaudart); University College London, London, UK (J. Gaudart); Franche-Comté University–University Hospital, Besançon, France (K. Bardonnet, J. Knapp, S. Bresson-Hadni); University Hospital, Clermont-Ferrand, France (A, Abergel, J. Beytout); Hospices Civils de Lyon, Lyon, France (J. Dumortier); University Hospital Nancy, Nancy, France (A. Gerard, J. Watelet)

Abstract

During 1982–2007, alveolar echinococcosis (AE) was diagnosed in 407 patients in France, a country previously known to register half of all European patients. To better define high-risk groups in France, we conducted a national registry-based study to identify areas where persons were at risk and spatial clusters of cases. We interviewed 180 AE patients about their way of life and compared responses to those of 517 controls. We found that almost all AE patients lived in 22 départements in eastern and central France (relative risk 78.63, 95% CI 52.84–117.02). Classification and regression tree analysis showed that the main risk factor was living in AE-endemic areas. There, most at-risk populations lived in rural settings (odds ratio [OR] 66.67, 95% CI 6.21–464.51 for farmers and OR 6.98, 95% CI 2.88–18.25 for other persons) or gardened in nonrural settings (OR 4.30, 95% CI 1.82–10.91). These findings can help sensitization campaigns focus on specific groups.

Alveolar echinococcosis (AE) is caused by the larval stage of the fox tapeworm Echinococcus multilocularis. In human infections, after a person ingests eggs, the metacestode cells of E. multilocularis proliferate in the liver, inducing a hepatic disorder mimicking liver cancer (1). Complete resection of liver lesions is possible in only one third of the cases, and parasitostatic and sometimes parasiticidal (2) treatment is available with benzimidazole compounds (albendazole or mebendazole). AE, observed only in the Northern Hemisphere, is linked to environmental features, such as land use for cattle breeding (pastures), which promotes high densities of rodents (main reservoir for the parasite) and thus a high prevalence of infection in foxes, which increases the environmental reservoir of the parasite (3,4). That the intermediate and final hosts of the parasite are members of wildlife species, largely explains why AE is an occupational disease of farmers and especially of cattle breeders (4). Individual risk factors vary greatly, however, depending on the country (1).
In Europe, the main AE-endemic areas are north of the Alps, primarily in Switzerland, France, Germany, and Austria, but recent studies showed that AE has spread during the past 20 years (5,6). Human AE cases have been diagnosed in countries previously considered free of the infection, such as Poland, Slovakia, Lithuania, Slovenia, Belgium, and Hungary (7,8). Molecular typing of E. multilocularis specimens collected in Europe showed that the European AE focus can be drawn as a core located in central Europe, flanked by neighboring regions where the parasite is less genetically diverse (6,9). In addition to the centrifugal spread of the disease, some epidemiologic studies also showed a significant trend of an increase in human AE incidence in some previously known foci, for example, in Switzerland (10). Schweiger et al. hypothesized that in Switzerland the increase in the fox population in rural and urban areas and high prevalence of E. multilocularis in foxes led to an increase in the infection risk for humans and the emergence of AE 10–15 years after infection increased in foxes (10).
France represents the western border of the European focus of AE and accounted for 235 (42%) of the 559 patients recorded in Europe during 1982–2000 (7). Hegglin et al. (11) have pointed out that AE is poorly known in France (only 88 [17.6%] of 500 interviewed persons were aware of it). This study reinforced the conclusion that better information is needed to identify at-risk populations. In particular, to avoid alarming the general population, we need to accurately define areas where persons are at risk for AE, identify exposed populations, and clarify behavior associated with AE contamination. Since the EurEchinoReg project (7), the FrancEchino Network has maintained a registry in France of AE cases, with the support of the French National Institute of Public Health Surveillance (Institut de Veille Sanitaire) (12). From 1982 through 2007, this registry helped identify 407 new patients in France (13). We present the results of a registry-based study in which we aimed to better define high-risk target groups for prevention campaigns.