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摘要
The American Giant Liver Fluke (Fascioloides magna) in the Danube floodplain forests east of Vienna, Austria. Occurrence and control 2000 - 2010
Introduction
The American Giant Liver Fluke (Fascioloides magna) was imported to Europe several times with wapitis and white-tailed-deer back in the 19th and 20th century. This liver fluke mainly parasitizes ruminants, particularly various cervid species (Cervidae). In America a broad spectrum of host species has been recorded, including cattle.
In Austria the parasite was first recorded in the wild in 2000 in the Danube floodplain forests east of Vienna (Fig. 1) in red deer and one year later in roe deer. Pathogenity in red deer can be expressed in body mass loss, trophy impairment and serious general health problems in the case of heavy infestation. In roe deer, even few flukes can be fatal. In Europe the lymnaeid snail Galba truncatula has proved to act as the main intermediate host.
Material and methods
In 2000 a monitoring project was started to assess the impact on hunting economy and to examine hygienic consequences for game and cattle management. Since February 2001 red deer have been treated in one hunting area on the south side of Danube. No treatments were conducted within the national park (NP) but some northern sites outside the NP were included as of 2008. The treatment involved mixing Triclabendazol into the winter feed.
The hunting area Fischamend south of Danube was monitored throughout 10 years (2001 - 2010). The livers from red deer from all individuals that had been shot or found dead were dissected. Additionally faeces of red deer were collected at regular intervals and scanned for fluke eggs. From the areas of the national park at both sides of the Danube river, only livers with diseased appearance were examined.
Results
After treatment, between 2001 and 2005, prevalence and intensity decreased markedly in the Fischamend area. Prevalence decreased from 100 % to 13 %, intensity decreased from 47 (Min. 2, Max. 107) to 2 (Min. 1; Max. 3) individuals per liver. In the northern area only single records of positive deer had been recorded until that time. In 2006, however, the prevalence in the southern area (Fischamend) increased again up to 72 %, then and decreased slowly until 2010 to 46 %. Also the number of eggs in faeces followed the pattern of fluke prevalence, decreasing considerably after 2000 but increasing in 2006 and persisting up to 2010. The focus of the infection apparently shifted to the northern areas from 2007 on, marked by increasing intensities. The latter data set allows no estimate of prevalence.
Conclusion
Clearly, the parasite has successfully settled the studied environment. Medical treatment has markedly reduced the parasite's prevalence and intensities, but was inadequate eradicate the fluke. Further monitoring will be indispensable in order to evaluate the risks of dispersion and to determine the potential success of medication and other measures to combat the pathogen.
