Tapeworm Life Cycle: Domestic and cottontail rabbits are intermediate hosts for the canid tapeworm, Taenia pisiformis. Pictures of tapeworm cysts; how to cure.
A tapeworm infestation of Taenia pisiformis in rabbits is actually called Tapeworm Cyst Infection, or Cysticercosis Pisiformis. This is because in a rabbit, the tapeworm goes from an egg, to a larva, to an immature tapeworm that resides in a ‘cysticercus’ in the rabbit, but almost never all the way to a mature tapeworm.
Here are the different stages of their life cycle:
The tapeworm life cycle starts with an adult tapeworm (T.pisiformis), which inhabits the intestines of the dog, coyote, wolf, fox or other canid. The adult tapeworm sheds its eggs, and the infested canine excretes tapeworm eggs in their scat or feces.
Stage II of the tapeworm life cycle is the transmission of the eggs to the intermediate host, most often a rabbit, rodent or hare. This occurs through contamination of their fur with dog feces, or through contaminated food. Wild cottontails easily pick up tapeworm eggs as they run through the brush, and then meticulously groom themselves, eating the eggs.
The same mode of infection can be true of those domestic rabbits allowed to run in the same space as the family dogs. In the case of caged rabbits however, it is more likely that they ingest tapeworm eggs through contaminated hay.
Stage III of the tapeworm life cycle is the larval
stage. In the rabbit’s guts, the eggs hatch, and the larvae migrate
to the liver. It takes the larvae 15-30 days to mature to their next phase - a
'cysticercus' (plural = cysticerci) or fluid-filled cyst. During the 15-30
days, the larvae are changing and maturing, while they migrate through the
liver. Sometimes they leave scars on or within the liver.
Stage IV of the tapeworm life cycle is the formation of multiple cysticerci within the secondary host - the rabbit. Cysts measure up to 2-3 cm (1 1/4 inches).
A cysticercus looks like a small balloon filled with clear fluid. They vary in size from that of a pea, to the size of your fingertip.
(Pictured is a rabbit's liver. The dark green object is the gallbladder; the whitish balloon in the center of the picture is a cysticercus (pictures courtesy of the rabbit breeder). The head of the immature tapeworm, or scolex, is to the right within the cyst. Also see pictures below from the same rabbit.)
Normally, you might find one or a few of these cysts (on average around 6-10) attached to the surface of the liver, intestines, lining of the gut and even the lungs. Each cysticercus contains a white floating head (scolex) of an immature tapeworm. Older cysts may be pus-filled.
Depending upon the severity of the infection, the rabbit may
develop hepatitis leading to acute death or chronic wasting. It is possible for
cysticerci to form in other areas of the body, such as the brain, and if so, symptoms
such as seizures, or other signs of compromised organ function may be seen.
This, however, is far less common than finding cysts in or attached to the
liver, intestines or body cavity.
Wild eastern cottontails have occasionally 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
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.
Stage V of the tapeworm life cycle completes itself with the ingestion of the cysticercus by the primary host - a dog or other canid. The immature tapeworms finally mature into adult tapeworms. The canid begins shedding tapeworm eggs, and the cycle starts all over again....
The good news - T.pisiformis does not infect humans.
Mebendazole, 1 gm/kg of feed for 14 days (approx 50 mg/kg bodyweight per day), should kill both mature and immature tapeworm cysts of T.pisiformis. Withdrawal time is 48 hours. Please confer with your rabbit-savvy vet.
To prevent reinfection, clean living spaces of all feces, especially dog feces, and prevent recontamination. If your rabbits are caged, consider discarding all hay, and purchasing fresh.
When you recognize a tapeworm infestation:
Other Species of Tapeworms seen in Rabbits:
This Tapeworm Life Cycle page is specific to Cysticercus
pisiformis - an infestation of the common dog tapeworm Taenia pisiformis, the most common tapeworm infestation seen in rabbits.