Causes of Tapeworm Infection
Dogs become infected with tapeworms by eating an intermediate host that contains tapeworm eggs, larvae or cysts. Intermediate hosts are organisms that other organisms, usually parasites, live inside of while they are going through some transitional stage of development. For example, the parasite may hatch from an egg into its larval form inside of its intermediate host. The intermediate host may or may not also act as the carrier, or vector, that transmits the parasite to its ultimate victim.
Dogs pick up Taenia, Echinococcus and Mesocestoides tapeworms by eating raw or undercooked flesh of a bird, reptile, sheep, cow, goat, deer, elk, horse, pig, rabbit, rat or other intermediate host that is carrying some form of the parasite. Diphyllobothrium tapeworms are found encysted in the organs of fish, primarily in the northern United States and parts of Canada. Dogs become infected with those parasites by eating fish that are infected with the cyst form of the worm. Dogs get the fairly common Dipylidium caninum tapeworms when they eat infected adult fleas or lice. Fleas and lice become infected when they ingest the eggs of the parasite when feeding on the blood of an infected mammal.
Regardless of how they initially get inside of a dog, tapeworms eventually end up in the dog’s small intestine. The parasites bury their heads into the lining the dog’s small intestine and attach themselves to that sensitive tissue. There, they feed on the dog’s blood, depleting the animal of essential nutrients and, in cases of serious parasite loads, draining it of essential blood, as well. Tapeworms grow, mature and eventually reproduce inside the dog’s small intestine. Adult tapeworms typically remain there indefinitely. Adults produce and carry eggs in separate segments of their increasingly long bodies; these segments are also referred to as “egg packets.” Those body segments eventually break off and are passed out in the infected dog’s feces. Many times, tapeworm egg packets are motile, meaning that they can move independently (on their own) in the outside environment.
The best way to prevent or eliminate tapeworm infection in companion dogs is to follow a regular de-worming program using products recommended by the dog’s veterinarian. Flea control is also extremely important. People can become infected with tapeworms if they come into contact with and accidentally ingest a bit of feces from an infected dog, or if they swallow an infected flea or louse. Good hygiene is essential to prevent both canine and human infection by tapeworms. People should avoid eating raw or undercooked meat that comes from animals that are known to be potential intermediate hosts of the larval stage of these parasites, such as sheep, cattle and rabbits. Dogs should not be permitted to eat dead animals or other raw or undercooked wild game.
Because of their indiscriminate oral experimentation, young children have an increased risk of “getting tapeworms”, either by inadvertently consuming adult fleas or lice or by swallowing a bit of feces from an infected animal. This can happen, for example, when a dog licks a child’s face, or when a child playing outside touches infected fecal material and then puts its fingers into its mouth. Because humans are not their definitive hosts, adult tapeworms usually don’t mature inside of people. Instead, in people, tapeworm larvae tend to form large cysts, called “hydatids,” mostly in the liver, lungs and brain. Hydatid cysts in humans can cause extremely serious disease. They can even be fatal.