Appearance
''T. pisiformis'' typically infect dogs and other carnivores such as coyotes and foxes. In rabbits, ''T. pisiformis'' larvae attach themselves to the liver and intestines, forming cysts 6–18 mm in diameter. This is referred to as cysticercosis.In adult ''T. pisiformis'', the long hooks of the scolex are on average 239.9 μm and the short hooks are 140.1 μm . The dimensions of the suckers are 322.3 μm × 288.1 μm . They can have from 34 to 38 hooks, which can be up to 234 μm in length. Adult ''T. pisiformis'' can grow between 0.5 to 2 m .
The intermediate host is represented by hares and rabbits, in which are found the mesacestoide known as cysticercus pisiformis. This is found in the peritoneum of the intermediate host and can be ingested by the definite host when the dog or cat feeds on the viscera of such an infected intermediate.The adult stage consists of a scolex with four suckers and an armed rostellum, a short neck region, a series of immature proglottids with undeveloped reproductive organs, a series of mature proglottids with fully developed male and female reproductive organs, and a series of gravid proglottids with an expanded uterus filled with eggs.
Behavior
Eggs are introduced into the environment through infected canine feces. In the feces are the gravid proglottids that house the ''T. pisiformis'' eggs that will eventually be released from the proglottid onto nearby vegetation. The eggs are then ingested by a rabbit or from any member of the ''Leporidae'' family. Once inside the rabbit's gut the larva or oncosphere phase will then penetrate into the intestinal wall until they reach the blood stream. When the worm reaches the liver the larva transforms into a cysticercus form. This cysticercus will stay in the liver for about two to four weeks, then move to the peritoneal cavity where it will wait for the definitive host to eat the rabbit. The definitive hosts are ether dogs or other members of the ''Canidae'' family. Once ingested the cysticercus finds its way into the intestine and attaches to the intestinal wall with hooks and suckers. After the worm has time to develop and grow in size, the gravid proglottids is released from the distal end of the parasite and passed in the feces to start a new cycle.References:
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