Endoparasites Figure 2

Figure 2: Tapeworm cyst (Taenia taeniaformis)- Resulting in death of 17-month-old male rat
Case history and photos


Hairless male, 17 months old.

Clinical Signs

This rat presented with a hard abdominal mass. Generally he did not seem to be in a great deal of discomfort, although his preference was to lie on a flat surface. He showed signs of discomfort when the lump was palpated by trying to squirm away. He did not vocalize as a sign of pain.

The day of his death he showed extreme pallor, weakness, lethargy, and loss of balance.


Histopathology confirmed the diagnosis of a fibrosarcoma of the liver triggered by the tapeworm cyst. Death was from a massive internal hemorrhage where the tumor had damaged the hepatic tissue.


A necropsy showed a severe abdominal hemorrhage. The rat had a large mass attached to the liver. When bisected a feline tapeworm cyst (Taenia taeniaformis) was found inside of the mass.


Typically, the tapeworm cyst is nothing more than an incidental finding during necropsy. However, there are occurrences of both fibrosarcomas and fibrohistiosarcomas being induced by the presence of taenia taeniaformis cysts (which have been shown to possess a carcinogenic agent). These cancers tend to be locally aggressive and can metastasize.


Tape worm cyst liver mass

The above photo is of the bisected mass. The arrow points to the cystic area inside of the mass where the tapeworm was located.

Tape worm cyst liver mass

The tapeworm after it’s removal from the mass.

Case history by J. Bella Hodges
Necropsy and photos by M. Zieten
Histopathology by IDEXX RADIL


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