page_title: Fascioloides magna
section_title: (1) Definitive hosts
hierarchical_section_title: Fascioloides magna / Definitive hosts / (1) Definitive hosts
caption_attribution_description: The fibrous capsule in the liver parenchyma of red deer infected with Fascioloides magna. Five adult flukes were recovered from this capsule.
context_page_description: Fascioloides magna, also known as giant liver fluke, large American liver fluke or deer fluke, is trematode parasite that occurs in wild and domestic ruminants in North America and Europe. Adult flukes occur in the liver of the definitive host and feed on blood. Mature flukes measure 4 to 10 cm in length × 2 to 3.5 cm in width, and have an oval dorso-ventrally flattened body with oral and ventral sucker. The flukes are reddish-brown in colour and are covered by tegument. As with other digenean trematodes, the life cycle includes intramolluscan phase in snails. The parasite is currently distributed in wild ruminants in North America and Europe, including Austria, Canada, the Czech Republic, Croatia, Germany, Hungary, Italy, Poland, Serbia, Slovakia, and the United States.
context_section_description: Definitive hosts are primarily New World and some Old World cervids. In definitive hosts, flukes are encapsulated in thin-walled fibrous capsules communicating to the bile system. The eggs are passed through the bile system, enter the small intestine, and leave the host with faeces. Therefore, the infection is patent. The capsules are a result of the defence response of the host to the parasite and are pathognomonic for F. magna infection. They contain two to five flukes, greyish-black fluid with eggs and cell detritus.
  F. magna infections in definitive hosts are usually subclinical. However, massive deaths caused by the fluke in red-, fallow- and roe deer were reported. Lethargy, depression, weight loss and decreased quality of antlers can occur sporadically. In addition, nervous symptoms were observed very rarely. In the first case, urging motion followed by apathy was reported in one experimentally infected fallow deer. Authors suggested that these symptoms were associated with hepatocerebral syndrome. Other author has observed partial paralysis in naturally infected wapiti caused by migrating juvenile flukes in the spinal cord.
  Biochemical and haematological profiles are little investigated in definitive hosts. A decrease of haemoglobin, elevation of γ-globulins, and increase of eosinophils in serum was observed in experimentally infected white-tailed deer.
caption: The fibrous capsule in the liver parenchyma of red deer infected with F. magna
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