From hookworm to heartworm, our pets can shelter no shortage of creepy crawly horrors. But few are as renowned as the tapeworm. The mere mention conjures images of people wasting away as the parasite secretly steals their lunch. Indeed, some have even tried harnessing tapeworm in a desperate (and dangerous!) bid to lose weight.
There are a variety of species of tapeworm. The most common to infect dogs and cats is a critter called Dipylidium caninum. Contrary to its reputation, this particular tapeworm usually causes no symptoms at all. Pets can harbor these slithering stowaways for months or years, and you’d never know it. Not, at least, until the day you happen to see something crawling around your pet’s rear end. It’s not a tapeworm. But it’s part of one.
The head of an adult tapeworm is adorned with grappling hooks and suction cups which it uses to latch onto the wall of the intestine. Trailing from the head is a long chain of tiny segments. Each of these segments contains a complete digestive and reproductive system, allowing it to siphon nutrition from intestinal contents and generate tapeworm eggs. As the head produces new segments, the older ones move toward the tail like a kind of vile conveyor belt. And by the time those segments reach the end of the line, they are basically bags full of eggs. They then detach from the parent worm and drift toward the exit.
This is what owners ultimately notice. When fresh, these segments pulse and writhe like little grubs. You might spot them in an animal’s poop, or stuck to the fur under their tail. Eventually they dry out, appearing like grains of rice in your pet’s bed. Observing these segments is pretty much the only way to diagnose tapeworm, and it’s a matter of chance.
Gross as they are, these segments pose no hazard on their own. If an animal (say another pet in the house) were to consume them, absolutely nothing would happen. They aren’t infectious. Tapeworm can’t spread without an accomplice. Unfortunately, it finds a convenient one in another common pest—the flea.
When flea larvae encounter these tapeworm eggs, they happily dig in. Inside the flea—and only inside the flea—the tapeworm hatches and develops into its infectious form. Some time later, a dog or cat finds itself infested with that flea, and licks it off its own fur. The flea doesn’t survive getting swallowed and digested, but the tapeworm inside it does. And it was delivered straight to a cozy new intestine to call home.
This can’t be emphasized enough. The common tapeworm depends on fleas to infect new hosts. While it is easy enough to cure tapeworm with a single dose of deworming medication, it will keep coming back until fleas are completely eradicated from that pet’s home.
On the bright side, this means that tapeworm is easy to both treat and prevent. Sure, it’s not the worst parasite out there. Its primary symptom is usually disgust. But, for most pet owners, that’s more than enough.
Dr. Mike Fietz is a small-animal veterinarian at Georgetown Veterinary Hospital. He received his veterinary degree from Cornell University in 2003 and has lived in Charlottesville since.