Tapeworms in Dogs & Cats

Or How a Lowly Trematode Teamed up With the International Drug Cartel - Ron Hines DVM PhD 2/20/03 second.chance2@verizon.net

Tapeworms are very common in dogs and cats. All tapeworms require two different types of animals, one (the intermediate host) to be carried around by, to a new animal and a second type of animal (the final host) where the tapeworm can mature in the intestine and lay its eggs.

Tapeworms do not have a mouth. They feed through their skin (integument). Tapeworms are all segmented – like a string of pearls. Some tapeworms are many feet long, other types, only a few segments long.

Every tapeworm has an oval head (scolex) to which are attached a group of hooks – similar to fish hooks. These hooks bind the tapeworm to the lining of the small intestine.

Only the last pearls break off and leave the body with or after a bowl movement. These pearls (proglotids) are really an egg case.

They are filled with thousands of tapeworm eggs. When the egg case breaks open, these eggs are scattered about in hopes that an intermediate host will eat one by accident. In the intermediate host, the tapeworm egg hatches, forms a cyst and waits.

Eventually, the second animal eats some of these intermediate host animals in the parasite’s life cycle and a new tapeworm matures in the final host’s intestine (your dog or cat). Then the cycle can begin again and again.

Over 98% of the pets I see are infested with Dipylidium caninum, the pigmy tapeworm. When this worm passes “eggs” they appear as white or off-white grains of rice.

Depending on the size of the tapeworm, these egg segments (proglotids) can be as small as sesame seeds or as large as a housefly maggot. They tend to be seen on the stool or around the pet’s rear and move very slowly until they dry. When these segments dry on the pet’s coat they explode hundreds of eggs.

Then fleas that are present on the pet ingest (eat) these eggs. In the flea, the new tapeworm (cysticercoid) develops. Then, when the pet eats a flea while grooming a new tapeworm develops in the pet’s intestine.

A few of these tapeworms are not dangerous to an animal’s health but they are very disgusting to observe. To successfully eliminate them, every dog and cat in the household must be treated with praziquantel and, at the same time, all fleas must be eliminated.

If, for a single instant, there are no fleas and no adult tapeworms, the problem is solved. If you don’t eliminate all mature fleas, within a month or so the tapeworms return. Some pets in a contaminated household may remain free of tapeworms.

These are pets with “smushed” faces such as Persian cats or pug-like dogs, which cannot catch fleas. Occasionally, after a bout of diarrhea, long strings of segments are passed intact.

I occasionally see other tapeworms in pets. Feeding undercooked meat passes these worms or I see them in cats that hunt out of doors. These tapeworms pass segments that are more rectangular in shape. Praziquantel kills them all.

It breaks down the protective coating over the worm and the body just absorbs the parasite. This is why you do not see dead tapeworms in the pet’s stool after it has been wormed.

Praziquantel is marketed by the multinational drug firm, the Bayer Corporation, under the name, Droncit. It is an exceptionally safe medicine. The patent on Droncit was acquired a number of years ago by Bayer. At that time, a second very effective medicine, Niclosamide, was marked by a competing firm under the trade name Yomisan.

At that time both medicines were quite reasonably priced. However, a short time later, Bayer purchased the patent for Yomisan as well and quickly took it off the market. They then proceeded to raise the price of Droncit from month to month. The last time I calculated its cost in ounces of active ingredient it had exceeded the cost of an ounce of gold. That is why your veterinarian charges so much for a tablet or injection of the product.