The Wikipedia article on Fascioloides magna (giant liver fluke) claims that the parasitic species was once consumed primarily in Wisconsin and to a lesser extent in other parts of North America:
In North America, especially in Wisconsin, flukes found inside deer livers are sometimes consumed by humans, sautéed in butter. They are served as 'liver butterflies', 'little livers' or 'little flapjacks'."
The Wikipedia passage cites a 2010 scholarly article, When parasites become prey: ecological and epidemiological significance of eating parasites.. The article has a sentence with no accompanying citation:
In Wisconsin, giant liver flukes (Fascioloides magna), which achieve a length of 8 cm inside deer, are sautéed in butter and served as ‘liver butterflies.’
However, a search on Google Books for "liver butterflies" only brings up a single passage lacking a citation in a textbook titled Parasitology: A Conceptual Approach that gives the same description of these parasitic organisms being eaten in North America. A search on Google for "eating liver fluke" does not bring up any other sources for the consumption of this parasite that does not infect humans and only brings up descriptions of unintentional exposures to other species of flukes that sicken humans and led to infections.
Are there any well-attested and historically supported sources for the intentional consumption of this parasitic organism by humans in any culture?