The most common internal parasites in dogs are roundworms (especially the Toxocara species), hookworms (primarily Ancylostoma), and whipworms (Oxyuris). Tapeworms are not as common but they are just as worrisome. These parasites live in the intestines and drain vital nutrients that growing puppies need.

• ROUNDWORMS: These parasites can infect puppies before they are born and can also be transmitted via the dam's milk. Adult dogs get roundworms by accidentally ingesting eggs deposited on the ground. The immature larvae migrate through your dog's body and can cause damage to the live and lungs. Puppies with roundworms often show a bloated abdomen, dull coat, diarrhea, and possibly intestinal blockages. Adult dogs develop some resistance, but even they can show the effects of roundworms.

• HOOKWORMS: These are smaller than roundworms but have a set of moth hooks that dig into the intestines and drain nutrients and blood. Again, puppies can be infected in utero or via their dam's milk. Hookworms can be ingested and can also penetrate the skin, and they cause skin lesions in people as they migrate through the body. Hookworms can actually kill a puppy by making it severely anemic. Dogs with hookworms will show anemia, possibly bloody diarrhea, weight loss, and poor coats.

• WHIPWORMS: Not as prevalent as roundworms or hookworms, these are small intestinal parasites with a whip-like, tapering tail. The eggs need to be ingested to complete their life cycle, but they can survive in the ground for long periods of time. Whipworms cause diarrhea, often with mucus and blood. Dogs with whipworms may defecate frequently and strain to do so. A large number of whipworms can be a serious drain on an adult dog, let alone a puppy. Whipworms are resistant to treatment, so repeated treatments may be necessary.

• TAPEWORMS: The most common tapeworms are Dipylidium caninum and Taenia pisiformis. These two have different life cycles, and differentiating them is important for treating your dog and preventing future cases of tapeworm infestation. Dipylidium use fleas as their intermediate host. Dogs that have fleas often accidentally eat one while grooming and scratching. Taenia use rodents as their intermediate host, and dogs that hunt mice or rabbits can pick them up while hunting if they eat their prey. Tapeworms are often discovered when you see what appear to be dried rice segments around your dog's tail and rectum.

A fecal sample from your dog is often the best way to diagnose intestinal parasites. You need to bring a small amount of stool (about a tablespoon, preferably fresh) to your veterinarian. This will be mixed with a special salt solution and either run through a centrifuge or allowed to sit. The final solution will be examined under a microscope to see if it contains eggs passed by adult parasites living inside your dog.

Mark down the dates and details of any worm problems your dog has had. This information will be useful to the veterinarian if he finds any problems with your dog.

Protozoan Problems

Protozoal parasites are small single-cell organisms that can't exist very well outside their given host or a specialized environment. Many of the common protozoa we may find in our dogs can also affect people. Good hygiene is very important in dealing with these and other parasites:

• GIARDIA: This protozoal parasite is quite hardy and can exist for long periods of time in a wet environment. Streams and ponds are its favorite sites. Drinking infected water may lead to severe diarrhea, sometimes with blood or mucus. The cysts are then passed into the feces and may contaminate other bodies of water. There are treatments for giardia, but it can be difficult to diagnose. This parasite can be spread to people as well, so you and your dog should both avoid drinking water from streams or ponds in areas where this parasite is known to exist. There is now a vaccine for dogs in epidemic areas.

• COCCIDIA: There are many species, but virtually all work the same way. Dogs that live in a less-than-clean environment, especially puppies, may ingest cysts through contaminated food or fecal material. Dogs with coccidia may show diarrhea, sometimes with blood. In puppies this can be a debilitating disease. People are resistant, but kennel areas still need to be kept immaculately clean to prevent puppies picking up this protozoan.

The best way to diagnose protozoal infections is with a fresh fecal sample. In this case, your veterinarian will take a small sample directly from your dog's rectum. The sample will be mixed with saline and examined under a microscope for protozoa actively moving around. A regular fecal test would kill the protozoa and make them virtually impossible to detect.

Mark down the dates and details of any protozoal problems your dog has had. This information will be a useful part of your dog's medical history.

Treating Intestinal Parasites

As always, one of the best treatments for disease problems is prevention. Keeping your dog's play area clean, picking up after your dog on walks, yearly or even twice-yearly fecal checks, and helping your dog to stay in the best condition possible all reduce parasite problems. Still, it is possible for your dog to pick up parasites just by walking where a dog deposited eggs days before. So even the best-cared-for dog may have parasites at some time.

Here is a list of some traditional treatments and prevention methods:

• YEARLY OR EVEN TWICE-YEARLY FECAL CHECKS ARE A QUICK, EASY, AND RELATIVELY INEXPENSIVE WAY TO MAKE SURE YOUR DOG NEVER GETS A SERIOUS PARASITE LOAD.

• ALWAYS PICK UP AFTER YOUR DOG, AND ENCOURAGE OTHERS TO DO SO FOR THEIR DOGS AS WELL.

• IF YOU ARE ADDING A NEW DOG TO YOUR FAMILY, DO A FECAL CHECK AS SOON AS POSSIBLE SO YOU DON'T CONTAMINATE YOUR YARD WITH PARASITE EGGS OR LARVAE.

• SOME SAFE MEDICATIONS THAT WILL KILL THE PARASITES AND LEAVE YOUR DOG IN GOOD HEALTH INCLUDE PYRANTEL PAMOATE, IVERMECTIN, AND FEBENDAZOLE. DIFFERENT MEDICATIONS ARE USED FOR DIFFERENT PARASITES, AND SOME PARASITES MAY DEVELOP DRUG RESISTANCE, REQUIRING YOU TO TRY A SECOND, DIFFERENT MEDICATION.

• IF YOU SEE WORMS OR SUSPECT A PARASITE PROBLEM CHECK WITH YOUR VETERINARIAN. MANY OVER-THE-COUNTER DEWORMERS ARE NOT VERY EFFECTIVE.

• CERTAIN PARASITES. SUCH AS WHIPWORMS, MAY REQUIRE REPEATED TREATMENTS ON A SET SCHEDULE TO TOTALLY CLEAR YOUR DOG.

• DO A F0LLOW-UP FECAL CHECK AFTER FINISHING A COURSE OF TREATMENT TO BE SURE IT WAS EFFECTIVE.

There are also some herbal and homeopathic medications that are believed to be effective for dewormings. Remember, just because something is natural or organic does not mean it is safe! Do not try any of these remedies without consulting a veterinarian experienced in their use. Black walnut is often touted for dewormings, along with garlic, but used incorrectly both of these could be toxic to your dog (as could many traditional dewormers if used incorrectly). Follow-up fecal checks are important to determine that treatment was successful.

Heartworms

Heartworms, Dirofilaria immitis, are potentially life-threatening parasites in dogs. Adult heartworms live and thrive in the heart and pulmonary arteries of dogs. Some may also be in the lungs in large blood vessels. These are long-lived parasites, some living as long as five years!

During this time, if there are both males and females present, they produce many tiny young, called microfilaria. The microfilaria get into the bloodstream and are picked up when a mosquito bites your dog. These microfilaria develop in the mosquito and then move to its mouth so that they can be injected into another dog when the mosquito feeds. In other words, this parasite can only be spread from dog to dog with the help of a mosquito.

Dogs with a mild case of heartworm will cough, lose some of their stamina, and may be weak or short of breath. The worms block the blood supply of fresh oxygen to other tissues, including the lungs, heart, kidneys, and liver. By the time these clinical signs show up, some of the damage is irreparable. Dogs may die from a heavy load of heartworms.

Prevention

Certainly, the ideal situation is to prevent heartworms from infecting your dog to begin with. There are numerous preventive medications. These range from daily pills to monthly medications. Work is also being done on even longer-range products.

Some of these medications require that your dog test negative for heartworm first, as a rapid die-off of the parasites could cause shock reactions. These products may be effective against some of the intestinal parasites your dog is susceptible to as well. Some practitioners use black walnut herbal preparations and homeopathic remedies along with twice-yearly blood tests to catch early infections.

Check with your veterinarian about a safe product for your dog. Some breeds are sensitive to ivermectin, a common ingredient in heartworm preventives, and should use other medications.

Keep track of any preventive heartworm medications you've used with your dog.

Diagnosis

Heartworm diagnosis may involve multiple specialized tests. There are a few simple and easy tests your veterinarian can run right in the clinic. The first is to check a blood sample for antigens. This test picks up protein in the blood shed by adult heartworms. This test will pick up infections early — with luck before the adults are even reproducing. This test specifically looks for proteins from female worms.

If your dog only has one or two worms, there may not be enough antigen to detect. A second test screens a blood sample for actual microfilaria. While microfilaria found in a blood sample are almost always from heartworms, they do need to be clearly identified before any treatment is started.

Keep track of your dog's blood test results in the following space:

Your veterinarian may also want to do X rays or even an echocardiogram (special ultrasound of the heart) to look for worms or the damage they cause. Enlargement of the heart and the large blood vessels that go to the lungs are highly suggestive of heartworm infection. A complete blood panel may be done before any treatment is started to see if your dog already has liver or kidney damage.

Treatment

Dogs that are diagnosed with heartworm infections will need treatments to kill both the adults and the microfilaria. Currently the only approved treatment for the adults is an organic arsenic compound — obviously a drug to be used with care, as you want to poison the worms but not your dog! This medication requires intravenous administration and your dog may need to be hospitalized for care and observation. Dogs must be kept quiet after this treatment.

While the adult heartworms are now dead, your dog's body must absorb the remains and keep any pieces from shedding off and causing trouble. Some veterinarians have been successful using ivermectin at higher than preventive dosages as well.