Dogs are victims of several parasites. The most common are the roundworms that infest most puppies at some time in their young lives and tapeworms that can be a big problem when flea infestations are high.

Early diagnosis of the presence and species of intestinal parasite is important, for not all worms respond to the same treatment. Therefore, stool samples should be taken to the veterinarian for microscopic examination if worms are suspected.

Most worm infestations cause any or all of these symptoms: diarrhea, perhaps with blood in the stool; weight loss; dry hair; general poor appearance; and vomiting, perhaps with worms in the vomitus.  However, some infestations cause few or no symptoms; in fact some worm eggs or larvae can be dormant in the dog's body and activated only in times of stress, or in the case of roundworms, until the latter stages of pregnancy, when they activate and infest the soon-to-be-born puppies.

Roundworms                                                                                                   

Adult roundworms live in the dog's small intestine.

What they do:
Cause diarrhea, vomiting, stunted growth, rough coat, bloated belly.

How they spread:
Almost all puppies get roundworms from their mothers. Dogs can also pick up roundworms from the soil.

Defending against them: Once a month prevention is recommended.

Roundworms are active in the intestines of puppies, often causing a pot-bellied appearance and poor growth. The worms may be seen in vomit or stool; a severe infestation can cause death by intestinal blockage.

This worm can grow to seven inches in length. Females can produce 200 thousand eggs in a day, eggs that are protected by a hard shell and can exist in the soil for years. Dogs become infected by ingesting worm eggs from contaminated soil. The eggs hatch in the intestine and the resulting larva are carried to the lungs by the bloodstream.

The larva then crawls up the windpipe and gets swallowed, often causing the pup to cough or gag. Once the larvae return to the intestine, they grow into adults.

Roundworms do not typically infest adults. However, as mentioned above, the larvae can encyst in body tissue of adult bitches and activate during the last stages of pregnancy to infest puppies. Worming the bitch has no effect on the encysted larvae and cannot prevent the worms from infecting the puppies.

Hookworms

Enlarged hook worm mouth showing 'teeth'.

What they do:
Attach to the dog's intestinal lining, leaving bleeding internal wounds. Cause blood loss, anemia, and diarrhea. As few as 100 hook worms can kill a puppy.

How they spread:
Eggs pass through the feces of an infected dog into the soil where they are easily swallowed or can penetrate through a dog's feet.
 

These are small, thin worms that fasten to the wall of the small intestine and suck blood. Dogs get hookworm if they come in contact with the larvae in contaminated soil. As with roundworms, the hookworm larvae becomes an adult in the intestine. The pups can contract hookworms in the uterus and the dam can infest the pups through her milk.

A severe hookworm infestation can kill puppies, but chronic hookworm infection is usually not a problem in the older dog. When it does occur, the signs include diarrhea, weight loss, anemia, and progressive weakness. Diagnosis is made by examining the feces for eggs under a microscope.

Tapeworms

Shaped like rice, these parasites live in the small intestine.

What they do:

They may cause debilitation and weight loss when they occur in large numbers. Sometimes, the dog will scoot or drag its anus across the ground or carpet because the segments are irritating to the skin in this area. The adult worm is generally not seen, but the white segments which break away from the tapeworm and pass outside the body rarely fail to get an owner's attention!
 

Occasionally, a tapeworm will release its attachment in the intestines and move into the stomach. This irritates the stomach, causing the dog to vomit the worm. When this happens, a worm several inches in length will be seen.

The dog sheds segments of the tapeworm containing the eggs in its feces. These segments are flat and move about shortly after excretion. They look like grains of rice when dried and can be found either in the dog's stool or stuck to the hair around his anus. Tapeworms cannot be killed by the typical over-the-counter wormer; see the veterinarian for appropriate treatment.

How Tapeworms Are Transmitted 
The most common canine tapeworm is transmitted by fleas. Flea larvae become infected by ingesting tapeworm eggs that have been shed in the dog's feces. Dogs become infected if they swallow an infected flea while grooming. The tapeworms grow to maturity in the dog's gut. Tapeworm segments which contain eggs are then shed in the dog's feces. Tapeworms also can be transmitted when dogs eat the raw meat of infected intermediate hosts.   A dog who hunts or eats wildlife infested with fleas may get tapeworms.

Tapeworm Eggs
Adult tapeworms live in the guts of dogs, where they lay their eggs. The eggs are released with the dog's feces, where they then dwell.

Tapeworm Transmission and Growth
As the larvae grow within the eggs, the eggs may be ingested by flea larvae that are also present in the dog feces. If a dog ingests an infected flea, the tapeworm larvae may hatch and mature in the gut of the dog.

Adult Tapeworm
The larvae mature within the gut of the dog where they may travel as far down as the anus. They generally lay their eggs in the gut.

Whipworms

Shaped like whips, these parasites live in the large intestine.

What they do:
Cause bloody diarrhea, anemia, dehydration. loss of appetite.

How they spread:
A female whip worm can produce 2,000 eggs a day. Eggs are passed in feces, and can survive for years in the soil. Whip worms are very difficult to eradicate.
 

Adult whipworms look like pieces of thread with one end enlarged. They live in the cecum, the first section of the dog's large intestine. Infestations are usually light, so an examination of feces may not reveal the presence of eggs. Several checks may be necessary before a definitive diagnosis can be made.

Prevention

Several worms that infect and reinfect dogs can also infect humans, so treatment and eradication of the worms in the environment are important. Remove dog feces from back yards at least weekly, use appropriate vermicides under veterinary supervision, and have the dog's feces checked frequently in persistent cases. Do not mix wormers and do not use any wormer if your dog is currently taking any other medication, including heartworm preventative, without consulting the veterinarian.

When walking the dog in a neighborhood or park, remove all feces so that the dog does not contribute to contamination of soil away from home as well.

Dogs that are in generally good condition are not threatened by worm infestations and may not even show symptoms. However, it's a good idea to keep the dog as worm-free as possible so that if disease or stress do take a toll, you're not fighting worms in a sick pet.

[ Heartworm disease: an ounce of prevention beats a pound of cure]

Norma Bennett Woolf