Dogs can be afflicted by many kinds of worms and worm-like parasites . In this section, we detail the many common kinds.
Coccidia
Not really a worm but a one-celled microscopic organism, this parasite is not especially common in dogs, but it can strike young puppies, particularly when they’re living in crowded conditions with lax sanitation. The disease is picked up through contaminated water, food, or surroundings. Coccidia produce eggs in the dog’s intestinal tract, which are then passed into the environment in the stool. Coccidia can lie dormant, causing no symptoms, but they can be activated by some sort of stress. Once they swing into action, these little protozoans start doing their dirty work, causing diarrhea , weakness, lack of appetite, anemia , and dehydration . Your vet will probably treat Coccidia with sulfa drugs and antibiotics . Good hygiene is the key to containing and preventing Coccidia. Pick up the stool immediately, making sure there’s no opportunity for food or water to be contaminated by it. If your dog is diagnosed with Coccidia, a thorough cleaning of her living area, using strong (but canine-safe) disinfectants or boiling water, is needed.
Giardia
This is another protozoal parasite – and it can affect dogs and people. Giardia is often waterborne, entering the water supply through contamination by wild animals, dogs, and people. Signs of Giardia infection are diarrhea, which may appear bloody or slimy, and sometimes a mild stomach upset. Your vet will treat Giardia with antiprotozoal drugs. Protect your dog from Giardia by not letting your dog drink from streams, rivers, or lakes, no matter how clean they may look.
Heartworm
Once restricted to the more hot and humid area s of the United States, and of most concern for dogs who spent a lot of time in the woods, heartworm is now prevalent in every part of the country.
The life cycle of the heartworm, Dirofilaria immitis, begins with the bite of a mosquito carrying heartworm larvae. The larvae enter the skin, going through several stages of development and eventually riding through the dog’s bloodstream to the right side of the heart. Here they stay and become mature worms. If not detected, the population of adult worms can grow, creating a mass that blocks blood flow, decreases the heart’s efficiency, and eventually causes the right side of the heart to fail.
When the adult worms breed, they produce microfilaria. These are offspring that enter the circulating blood and are small enough to be sucked up by a mosquito that bites the infected dog. Within 10 to 48 days, the microfilaria develop into infectious larvae. The next time the mosquito bites a dog, these heartworm larvae are passed along and the cycle begins all over again.
Dogs infested with heartworms may go for years without showing signs. When the heartworms eventually start to cause a dog trouble, an early sign may be a deep, soft cough that gets worse with exertion. As the cycle progresses, the dog becomes lethargic, loses weight, and sometimes coughs up blood. In the later stages of heartworm disease, the dog has trouble breathing, her chest bulges, and she develops congestive heart failure . Without treatment, she’ll die.
Fortunately, a routine blood test can detect heartworm even before any signs appear. And heartworm can be easily prevented. Every dog should be tested for heartworm (your veterinarian can tell you when and how often). Most dogs will test negative, but your vet may still recommend a heartworm preventative. Diethylcarbamazine (DEC, which is sold under brand names such as Filaribits) kills the infectious larvae. It must be given daily during mosquito season to make sure no larvae survive to mature into adult worms.
If a dog is diagnosed with heartworm, treatment depends on how far along things are. If there’s heart failure or liver or kidney damage, those problems must be attended to first. The treatment for a full-blown case of heartworms is very stressful, and the dog must be in the best possible condition in order to survive it. Follow-up care is crucial, too. About six weeks after initial treatment, the recovering dog gets another drug to kill any microfilaria produced by the adult worms. A blood sample is checked to make sure all the microfilaria are gone. If it comes up positive, additional treatments are given until the dog is completely free of worms and microfilaria.
Hookworms
Hookworms are most often found in warm, humid areas of the country but can show up anywhere. These worms, the most common of which is known as Ancylostoma caninum, usually affect puppies, although adult dogs can have them, too. They’re usually passed in the mother’s milk or even through the skin and take up residence in the pup’s small intestine. Once in the dog’s belly, they hook onto the intestinal wall, sucking in tissue and blood. This causes one of the classic signs of hookworm infestation: dark, tarry, or bloody stool. In serious cases of hookworm disease, dogs suffer severe anemia.
Like most other intestinal worms, hookworms are diagnosed by examining a stool sample under a microscope. If hookworm eggs are found, your vet will probably prescribe medication to kill the adult worms. In areas of the country where hookworm is extremely common, a healthy dog with a mild case may not be treated, since she’ll probably be reinfected quickly anyway. The best prevention for hookworm is being diligent in picking up after your dog. The longer an infected dog’s stool sits, the more likely it is that any hookworm eggs will hatch out into larvae and find their way under your dog’s skin.
Roundworms
Roundworms (Toxocara canis) are common in dogs, especially young puppies. Roundworm eggs are found in the soil, where they can survive for years. The life cycle of the roundworm seems unnecessarily difficult. The dog swallows the eggs from nosing around on the ground or picking something up in her mouth. The eggs hatch into larvae, ride through the bloodstream to the lungs and from there up the windpipe, where they’re swallowed again, return to the intestine, and become mature adult worms. Roundworm larvae can also be passed from mother to puppies through the placenta (the pups are actually born with roundworms) or through the mother’s milk.
Adult dogs can carry roundworms without much in the way of symptoms. But puppies with a load of them may vomit , have diarrhea, and lose weight. They have a noticeable pot belly (more than the usual “puppy tummyâ€), their coats are dull, and they don’t thrive like other pups. Occasionally, a dog may pass some of the worms in her stool. These worms look like strands of wriggling white spaghetti.
Responsible breeders and shelters check their dogs and puppies for roundworms and other parasites, and give them the regimen of medication to knock out the uninvited guests. Puppies should have had a fecal exam and worming before they’re old enough to be adopted, although follow-up doses of the medication may be needed. As with other types of worms, good sanitation is the key to prevention.
Tapeworms
Fleas are the most common carriers of tapeworm, although they can also be transmitted in small rodents or raw meat. So be careful in handling raw meat, and never feed your dog raw or undercooked meat or animal parts. If your dog has been treated for fleas , there’s a good chance she’s got tapeworms, too. The head — or scolex — of the tapeworm (the most common one in dogs is called Dipylidium caninum) hooks onto the intestine and begins producing a series of flat egg-filled segments resulting in a single worm with a length that can vary from a few inches to several feet. The most common way of diagnosing tapeworm is finding these segments — which look like grains of rice — in the dog’s stool or clinging to the fur around the dog’s anus.
Since the eggs are shed in the segments, a fecal exam can easily miss a tapeworm infestation. It’s up to you to keep a close eye out for the segments themselves and for other possible signs, such as digestive trouble (usually seen in younger dogs with large infestations) and scooting. This type of behavior is defined by the dog dragging her rear end along the ground. Scooting can be a response to irritation from tapeworms, but it can also be a sign of an impacted anal gland — something your vet or groomer can remedy easily. Once tapeworm has been detected (or suspected), treatment is simple and effective. Prevention includes flea control and not feeding the dog raw or undercooked meat and animal products.
Whipworms
Skinny little things with a bulge at one end, whipworms (Trichuris vulpes) are so named because their shape suggests a tiny whip. Dogs pick up whipworm eggs from the environment. The eggs hatch in a pooch’s intestinal tract, where the worms latch onto the wall of the large intestine and start producing eggs all over again. Like other kinds of worms, whipworms are usually only noticeable in young or debilitated dogs. A heavy infestation may cause diarrhea, anemia, or weight loss.
Once again, treatment is a simple medication, usually repeated at least one more time to catch any recently hatched worms before they reinfect the dog. Since the eggs are shed in the infected dog’s stool, prevention is a matter of common sense and common courtesy: Keep your dog away from the stools of other dogs, and pick up after your dog promptly. Regular fecal exams — twice a year is best — will catch a case of worms before it gets out of control.
