You will notice in the images below that tapeworms use an "intermediate host" to accomplish transmission from one dog or cat to another. There are three common species that affect dogs and cats: Dipylidium caninum which can infect dogs, cats and people uses the flea larva as an intermediate host; Taenia pisiformis which infects dogs uses the rabbit; Taenia taeniaeformis which infects cats uses the rat or mouse. To make a long story short, if you can keep your pet from eating fleas, rabbit, mouse or rat viscera it won't get a tapeworm. The intermediate host is required.

In the images below I have labeled the scolex or head end of the tapeworm. The scolex has a little sucker and or hooks which grasp onto the wall of the small intestine of the dog or cat. Behind the scolex are individual segments joined together to form the length of the worm, much like a beaded chain. These segments are called proglottids. Each individual proglottid is a separate reproductive unit. They each contain ovaries and ducts leading to a tiny pore on their surface. Any number of proglottids can break free from the scolex and pass with the feces. We often see them mixed with feces - they appear as little white, rice grains if individual or if chained together they are flat appearing like a shoe-string. These individual units are mobile and can move around on the ground or worse yet on furniture in the house. As they move they squeeze out little packets of 6 to 12 eggs all nicely cemented together. Flea larva love eating these eggs (a delicacy). The eggs are also laid on grass or vegetation and are consumed by rabbits, mice or rats. The egg hatches within the intermediate hosts and becomes an infective stage for dogs and cats. When a dog or cat eats the flea or intestines of the rat or mouse the immature tapeworm scolex attaches to the wall of the small intestine and begins growing its' own chain of proglottids. The lifecycle then can repeat anew as the proglottids break free and pass with the feces. The images below will make the lifecycle easier to understand.

Most tapeworm infestations go totally unnoticed. We rarely ever know unless we find a segment on the couch or see them in the feces. In other cases, we can hear a "rumbly tummy syndrome" where the animal undergoes increased intestinal motility, cramping and sometimes gas. We can also see diarrhea streaked with mucous, but most of the time tapeworms don't cause problems that we are aware of.

Unlike other intestinal parasites of the dog or cat, tapeworms don't lay eggs inside the pet. For that reason, when veterinarians perform fecal floatations looking for parasite eggs, tapeworms are often overlooked. We usually have to see the segments stuck to the hairs around the anus, or in the feces or environment to diagnose tapeworms.

Most over-the-counter wormers won't affect a tapeworm. In the "old days" it was rather difficult to rid a pet of tapeworms. Purgatives were used that caused violent contractions of the intestine in attempts to physically flush the worm free. These were the wormers that caused severe diarrhea when administered; since they didn't get rid of the scolex they were very ineffective. The modern tapeworm medications work on a different principal. They cause the tapeworm to lose their protective layer and they are simply digested. We never see them pass; they just disappear. Personally we use a medication called Droncit® to deworm dogs and cats.

Sometimes it is difficult to keep tapeworms from reoccurring over and over again. First of all you need to get rid of the fleas. We use Frontline TopSpot to effectively rid the pet of flea infestations. This takes care of the Dipylidium species which uses the flea as an intermediate host. Where we have problems is with the cats that are hunters. They often get the Taenia species which use the mouse as an intermediate host. With these pets, it is often necessary to prophylactically worm two or more times a year.

Not generally. On very rare occasions, children have been infected with Dipylidium species by swallowing a flea accidentally. It generally causes tremendous cramping and discomfort. Totally unrelated to dogs and cats are the tapeworms that people are getting from eating Sushi or raw fish. There are certain species of tapeworms that use the fish as an intermediate host. If food is cooked properly there is no worry.