THE COMMON TAPEWORM (Dipylidium caninum)
Adult Dipylidium. The segments are easily seen.
While all of this tapeworm segment passing business has been going on, fleas have been living on the pet, happily drinking the pet's blood and laying eggs of their own. The flea eggs drop off the pet and onto the ground where ever the pet goes, with the largest number of flea eggs accumulating in areas where the pet tends to frequent. This will also be where tapeworm segments accumulate as well. The flea eggs hatch, releasing hungry flea larvae that eagerly begin to graze on dust, dandruff, and flea dirt. The flea larvae do not pay close attention to what they eat and innocently consume tapeworm eggs.
As the larval flea progresses in its development, the tapeworm inside it is also progressing in development. By the time the flea is an adult, the tapeworm is ready to infect a dog or cat. The young tapeworm is only infectious to its mammal host at this stage of its development. The flea goes about its usual business, namely sucking its host’s blood and reproducing when, to its horror, it is licked away by the host and swallowed.
Inside the host’s stomach, the flea’s body is digested away and the young tapeworm is released. It finds a nice spot to attach and the life cycle begins again. It takes 3 weeks from the time the flea is swallowed to the time tapeworm segments appear on the pet’s rear end or stool.
This creature gets its name because its segments and body are very flat (like a piece of tape).
There is no other way for a pet to get Dipylidium caninum except from fleas.
Many people who had thought their pet could not possibly have fleas find out about the infestation this way. The tapeworm segment breaks open releasing its eggs. A larval flea consumes the egg along with the flea dirt that it normally eats. As the larval flea matures, so does the baby tapeworm. When a grooming dog or cat licks the flea and swallows it, the dead flea is digested in the dog’s stomach releasing the baby tapeworm. The tapeworm is passed to its new home in the dog or cat’s small intestine where it attaches and lives its life.
This parasite does not harm the pet in any way as there are plenty of nutrients passing by to serve both the host and its tapeworm (tapeworms require very little nutrients.) Still, high performance dogs, who need every calorie working for them, may show a decrease in performance because of a tapeworm infection.
There is another type of tapeworm that may be confused with Dipylidium caninum and that is the Taenia genus of tapeworms. This is a different type of tapeworm with a different appearing segment and a different mechanism of infection.
Because the eggs are passed by the pet in packets (segments), they often do not show up on the fecal exam; the packet must break open for the eggs to be seen under the microscope. This means that it is easy to miss a tapeworm infection if only a microscopic fecal exam is done. In most cases, it is the presence of visible segments on the pet or its stool that confirms diagnosis. Segments can be passed in small groups connected to each other leading the owner to describe a worm that sounds larger than a grain of rice. Tapeworm segments are also quite flat.
Some people will mistake maggots in the stool for tapeworms. Maggots are not seen in freshly passed stool and are not flat.
Theoretically, yes, people can get them but they must be infected the same way dogs and cats are: by swallowing an infected flea.
Tapeworms are killed by different medications (praziquantel, which is administered by injection, tablet, or topically, or epsiprantel, which is oral). Fenbendazole is effective against several types of tapeworms but not against Dipylidium caninum.
Only one treatment is needed to kill the tapeworms in the body; however, many clinics recommend a second injection in three weeks. The reason for the second injection is this: If the owner finds out at the time of their office visit that they need to control fleas to control tapeworms, they will need at least a month or so to control the fleas.
After the first treatment is given, there is no reason why the pet cannot immediately reinfect itself. It probably will reinfect itself at some point. By seeing the animal in three weeks and giving another treatment after the fleas are controlled, there is a good chance that the tapeworms will not just be back three weeks later. It takes three weeks from the time tapeworms are swallowed by the pet to the time segments can be seen by the owner.
On the other hand, who knows when the pet will swallow another infected flea? Our recommendation is that a single treatment be administered whenever segments are seen.
No, just because one pet in the household has swallowed an infected flea does not mean they all have. Our recommendation is to deworm only the pets who have obvious tapeworms.
While many people would like to blame the medication as ineffective, the truth is that there must be an on-going flea population in the pet’s environment. The key to eradicating Dipylidium caninum from the home is flea control. If this seems impossible for any number of reasons, there are regular dewormers for both dogs and cats that include praziquantel to kill any tapeworm infections. In this way, a pet can simply be de-wormed once a month for tapeworms (and other common intestinal worms).
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Page last updated: 5/26/2021