Dr. Greene’s Answer:
The dog tapeworm (Dipylidium caninum) is a common infestation in domestic dogs and cats. The adult worm lives in the animal’s intestines and is about 50 to 70 cm in length. The head, or scolex, consists of four cup-shaped suckers and several rows of hooks by which the worm attaches to the inside of the animal’s intestines and feeds. The body of the dog tapeworm is composed of many segments. The closer the segments are to the tail of the worm, the more ripe they become — each one containing up to 30 eggs. When segments reach the tail of the worm, they fall off and are excreted in the animal’s feces. These segments are the shape, color, and look of a cucumber seed (except that they tend to squirm around in the feces and around the anus of the dog or cat). If a dog or cat ingests some of this seed-containing stool it will not become infected — the eggs themselves are not infectious to mammals. However, the fleas that land on the stool will ingest the eggs.
Tapeworm eggs will hatch and begin to mature inside the body of a flea. When a dog or cat nips at, and swallows some of the infected fleas, it becomes infected. The larval stage tapeworm, ingested in the flea, is liberated, and attaches and grows into an adult tapeworm inside the animal.
Dog Tapeworms in Humans
Occasionally, human infants and children become infected with the dog tapeworms. This happens through ingesting larvae-containing fleas. Children will sometimes eat the fleas directly if they are playing in sand or in a spot where the fleas are abundant. Sometimes a dog that has been nipping at the fleas will still have partially digested fleas in its mouth when it licks a child, causing the larval stage tapeworm to be ingested.
The dog tapeworm has been found in infants as young as five weeks old. Children who ingest these fleas or flea parts will have tapeworms attach in their intestines and grow to maturity. Many of these children will have no symptoms at all. Some will have diarrhea, cramping, abdominal pain, and sometimes rectal or anal itching (if the cucumber shape segments squirm about near the anal opening). It was probably by seeing the moving cucumber-seed-shaped egg sacks in the child’s diaper or stool that the tapeworm infestation was diagnosed.
Passing Dog Tapeworms Around
Unfortunately, it is not uncommon in the daycare setting for stool from one child to pass to the mouth of another child, particularly in situations where hand washing is not strictly observed. If your child were to ingest stool that contains the dog tapeworm egg sacks he would not become infected (with the dog tapeworm). The infection is not passed directly from child to child. If there are infected fleas in the daycare setting, however, your child could become infected. Fleas in daycare are usually found either on animals or in a sand box.
A dog tapeworm infestation in a child is diagnosed by examining a child’s stool. It is typically easy to treat with a medicine such as niclosamide, and is not a cause for great concern (although it is, admittedly, a little gross). The associated dog or cat should also be treated, and flea control measures should be undertaken. Considering the large number of domestic dogs and cats, and the relative commonness of worms in pets, the infestation of children with dog tapeworms is, thankfully, relatively uncommon.
Thorough and frequent hand washing is the best way to prevent the spread of dog tapeworm as well as so many other infections.