Fascioloides magna and other liver parasites in cloven-hoofed game from northeastern Bavaria, Germany: occurrence and pathological findings with special emphasis on red deer (Cervus elaphus)

Abstract

The first detection of Fascioloides (F.) magna in northeastern Bavaria in 2011 was presumably correlated to natural migration movements of free ranging wild ruminants originating from the neighboring Czech Republic, where high infection rates have been reported frequently. To gain more data on the continuing spreading and current occurrence of the giant liver fluke in surrounding regions, 700 livers of cloven-hoofed game originating from eleven different northeastern Bavarian counties were investigated for the presence of F. magna and accompanying liver parasites in the hunting season 2019–2020. Macroscopically altered liver tissue was further investigated by pathohistological and parasitological examination. F. magna was detected in 5.9% (38/640) of livers from red deer (0.7% < 1 year, 9.8% > 1 year; p < 0.05) whereas none of the investigated livers of wild boar, roe, and fallow deer was infected (n=60). Mild pathological alterations of the liver tissue were documented in 15, moderate in 14, and major in 9 of all F. magna-positive cases. Histologically, the fluke-specific pigment haematin, large trematode eggs, and periportal fibrosis were detected in the liver tissue of infected animals. In 9% of all investigated livers, parasitic stages of other parasites, i.e., Dicrocoelium dendriticum (6.0%), Fasciola hepatica (0.3%), Taenia spp. (1.7%), and Echinococcus multilocularis (1.0%), were found. According to the results of this study, F. magna is not restricted to formerly known affected regions of Upper Franconia, but is also present in the military training ground Grafenwöhr, Upper Palatinate, and the Bavarian Forest National Park, Lower Bavaria, with estimated prevalences of 3.6 and 16.4%, respectively, and thus seems to spread in suitable habitats in northeastern Bavaria.

The Large American Liver Fluke (Fascioloides magna): A Survivor’s Journey through a Constantly Changing World

“…When the parasite finds a partner or giv searching, it terminates its migration. As a result of the parasite migrat hepatocyte damage causes fibroblast proliferation, thus progressive fibrog leads to the formation of thick-walled pseudocysts (Figure 6) around the The wall of the pseudocyst contains connective tissue and smooth muscle e inside the cyst, brownish-greenish detritus and 1-3 parasites can be foun topathological investigation of the remnant parenchyma demonstrates g inflammation, infiltration by macrophages and eosinophils, degeneration o and wall thickening in both blood veins and bile ducts [8,10]. In some carc ary bacterial infection of the necrotic tissue occurs, which is indicated by colour of the lesion or haematin mixed with blood [72].…”

“…The wall of the pseudocyst contains connective tissue and smooth muscle elements, while inside the cyst, brownishgreenish detritus and 1-3 parasites can be found [3,7,8]. Histopathological investigation of the remnant parenchyma demonstrates general chronic inflammation, infiltration by macrophages and eosinophils, degeneration of hepatocytes, and wall thickening in both blood veins and bile ducts [8,10]. In some carcasses, secondary bacterial infection of the necrotic tissue occurs, which is indicated by the yellowish colour of the lesion or haematin mixed with blood [72].…”

“…The authors concluded that the very low prevalence of the parasite in the examined red deer population is attributable to the high proportion of mild, thus barely noticeable cases. Based on their findings, the researchers suggested that F. magna was underdetected in its settled endemics [10].…”

“…In final hosts, by causing mild to severe lesions of the liver parenchyma, F. magna affects hepatic function, thus the metabolism of the body and the performance of the host [8][9][10]. The parasite reaches maturity and produces eggs in the body of the final host.…”

“…Metacercaria is a circular-shaped developmental stage that is glued to aquatic plants by adhesive substance coverage. In this form, they can survive for longer periods, even in In final hosts, by causing mild to severe lesions of the liver parenchyma, F. magna affects hepatic function, thus the metabolism of the body and the performance of the host [8][9][10]. The parasite reaches maturity and produces eggs in the body of the final host.…”