Cleaning a rabbit and found these: WARNING: Graphic Photos

Email a state vet the pictures, they might know.
Butchered about 200 rabbits so far, never seen that.
What did the lungs look like?

Sure looks like a polycystic kidney. Do rabbits get that?

Undoubtedly, the intermediate stage of a parasite of some kind--
I would suspect, tape worm larvae in the form of Taenia pisiformis. They are usually found attached to the liver, but can be anywhere in the peritoneal cavity, adhering to any organ or the mesentery membrane, which is a fold of tissue that supports the internal organs. They take on a dark color if attached to the liver, a clearer yellowish color if atached elsewhere in the peritoneal cavity or mesentary membrane. They are very common in wild rabbits, especially cottontails, and domesticated rabbits get them from coming in contact with grasses or hay on which dogs, coyotes, or fox have defacated or urinated. Rabbits are an intemediate host in the wild, with canines being the final host stage.

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Wild eastern cottontails have been found carrying hundreds of these cysts in nearly every part of the body, resulting in a gaunt rabbit in ragged condition before it dies. More usually, an infected rabbit carries the average number (6), but usually no more than up to 20 infective cysts. Usually the domestic rabbit manages fairly well despite the cysticerci, and it is uncommon that a diagnosis is made while the rabbit is alive.

Between 28% and 65% of all cottontails are infected with T. pisiformis, depending on species, location and age.

"Cysticercus pisiformis" - the condition of being infected with immature tapeworm cysts - is the extent of tapeworm infestation in rabbits. Tapeworms do not mature in rabbits. The immature tapeworms simply wait inside their cysts until a dog or coyote kills and consumes the rabbit, eating the cysts along with other rabbit parts.

- See more at: http://www.raising-rabbits.com/tapeworm-life-cycle.html#sthash.YqilE91Z.dpuf



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Fig. 212: Tapeworm larvae in rabbits. Cysticercus pisiformis in the mesentery of rabbit.

Cysticercus fasciolaris is the cystic stage of Taenia taeniaeformis, known as the cat tapeworm. This parasite can be recognized by the lack of a neck and the bell-shaped posterior segments. The intermediate host are the rabbit, rat, mouse and other rodents. Cysticercus fasciolaris is 2.5 cm long and develops in the liver.

Coenurus serialis is the intermediate stage of Taenia serialis, a tapeworm of the dog and fox. Coenurus serialis is almost fatal to hares, rabbits and other related rodents. It is passed into the connective tissue of the lumbar muscles, hind leg muscles and rarely into the jaw muscles. Coenurus serialis may also occur accidentally in the brain and muscle tissue of humans. The mature cyst in rabbits is ovoid or round, approximately 5 cm in diameter and has scolices the size of a rice grain. It may have as many as forty scolices. Sometimes these Coenuri behave like hydatids by budding off new cysts internally or externally. These internal cysts are frequently fertile. The external cysts are attached by stalks and are often sterile. They resemble a bunch of grapes.

Judgement: Rabbit carcases with extensive Cysticercus pisiformis infestation associated with cheesy material in older lesions and accompanied with emaciation are condemned. Slight or moderate infestation in which cysts contain straw coloured fluid, may have a favourable judgement. In Coenurus serialis infestation, the rabbit carcass is approved if only few cysts are present in the musculature. In extensive infestation the carcass is condemned.