The Scoop on Poop, Part 3

Intestinal Parasites 101, Tapeworms

The common tapeworm of dogs & cats, Dipylidium caninum, is ubiquitous in all the places that have fleas. Although very different biologically from the other intestinal parasites we've reviewed in the earlier blogs, it too has a fascinating lifecycle. The adult tapeworm lives in the small intestine and actually hooks onto the wall of the intestine. It absorbs nutrition through it's surface as the food material passes by. This causes no great hardship for the average well-fed American dog or cat. The tapeworm's body is essentially a head, neck and several tail segments and is typically 6 or more inches long. As new segments are produced, the older segments  move down the tail. By the time they fall off, they are little but a sac of tapeworm eggs. This egg sac or segment passes out of the body and is whitish and about the size of a grain of rice, just flatter. It is still moving at this point and is often in the stool or attached to the hair around the animal's anus.

As it dries out, it shrinks and looks more like a sesame seed. When the sac breaks open, the eggs fall into the environment. At this point, they are still not infective to a mammal. Flea larvae are present in the environment and they feed upon the microscopic organic debris and flea dirt in the pet's environment and accidentally ingest the tapeworm eggs while feeding. As the flea larvae develops into to an adult flea, the tapeworm inside it is also maturing to a stage in which they are infective to dogs & cats. The pet then accidentally ingests the flea containing the tapeworm while grooming. The tapeworm is released form the flea's body during digestion and so the pet becomes infected with a tapeworm.

So, the flea is an essential part of the tapeworm lifecycle and pet's cannot become infected without ingesting the flea. Since the segments are passed intermittently, the animal can have tapeworms and yet no eggs or segments may be seen in a specific fecal sample. However, this is the one intestinal parasite that a pet owner may spot themselves. The single segment looks like a flat grain of rice, but they occasionally pass several segments at a time & so my appears longer.

Theoretically, humans can acquire tapeworm infestations, but the infection would have to occur by the same mechanism… swallowing a flea infected with a tapeworm larvae. The CDC has an article about this topic although the human infection rate is extremely low.

Tapeworms are quite easy to eliminate from the pet with medication and only one treatment is required. If tapeworm segments are seen subsequent to treatment, the pet has ingested more infected fleas from the environment. The essential key to tapeworm eradication is the removal of all fleas in all life stages, including eggs and larvae.

The other tapeworm is much less common in suburban and urban areas. There are many species, but they all belong to the genus Taenia. Their lifecycle is completely different from the common tapeworm. They start out in much the same way in the dog or cat host although they are much longer & can reach fifteen feet! They too drop segments that are essentially sacs of eggs.  Instead of a flea larvae acting as the intermediate host, another mammal accidentally ingests the eggs. Typically this host may be a rabbit, mouse, rat, deer or sheep. The tapeworm develops for a few months in the host, but then cannot go any further in it's development within this intermediate host. After that animal is killed or dies, the final host, the dog or cat, ingests the animal and the infective stage of the tapeworm with it.  After a few months of maturation, that tapeworm is now attached and growing and the cycle has come full circle. 

Fortunately, the Taenia species can be eliminated by the same medication used for the common tapeworm. However, prevention is completely different since these come from hunting, eating raw or undercooked meat or ingesting carrion. The segments and eggs do differ in appearance and can be distinguished from each other on a fecal evaluation.

So, this completes the three part series on the major intestinal parasites of dogs & cats. It may be more than you thought you wanted to know about "worms" and the parasites your pet's poop may harbor, but now you are armed with the knowledge to help prevent and eliminate these risks for your pets and your family.