Symptoms of Worms in Dogs

by Dr. Audrey Harvey, BVSc (Hons)

The symptoms of worms in dogs can vary, but in general they include diarrhea, weight loss, bloated stomach, and poor hair coat.

Dog intestinal worms are a frequent problem, and they can make dogs very sick, and may even be fatal. It is important that anyone who shares their life with a dog is aware of the symptoms of worms in dogs, and and how to treat them.

Intestinal Worms in Dogs

There are four types of worms that live in the intestines of dogs – hookworms, roundworms, tapeworms and whipworms. Veterinarians suggest that around 30% of dogs have intestinal parasites, and they may not show any symptoms.

Let's look at the characteristics of these worms one at a time.

• Hookworms. The most common hookworm in dogs is Ancylostoma caninum. These are small worms that attach themselves to the lining of the small intestine and drink blood.

Dogs become infected with hookworm when larvae in the ground migrate through their skin, usually the skin on their feet. Pups also acquire infection either in the uterus or by drinking milk from an infected mother.

Because these dog parasites feed on blood, symptoms of hookworm in dogs are related to blood loss through the intestine. Their feces are often black, tarry and sticky, because of the digested blood. They are often lethargic due to the anemia, and have pale gums.

Hookworm larvae can infect people but they don't live in our intestine. They migrate under our skin, causing an itchy red rash which often goes away by itself.

Hookworm Symptoms: black, tarry feces, lethargy, anemia, and pale gums.

• Tapeworms. The common flea tapeworm, Dipylidium caninum, doesn't often cause any harm to a dog, apart from an itchy bottom. This means that the main symptom is scooting – your dog will drag his bottom along the ground to try and relieve his itch. You may also see little white wriggly grains of rice around his bottom or in his feces.

It will come as no surprise to learn that the lifecycle of the flea tapeworm involves the flea! Tapeworm eggs are eaten by flea larvae, and by the time the flea is adult, the tapeworm is ready to infect their host dog. The flea makes the dog itch, and he bites at it, and swallows the flea whole, whereupon it is digested, releasing the immature tapeworm.

The only way for dogs to get infected with tapeworm is through fleas, so if you have a persistent tapeworm problem, it would pay to look closely at your flea control.

Tapeworm Symptoms: Itchy bottom, scooting, white grains of rice around anus or on feces.

• Roundworms. The two species of roundworms that affect dogs are Toxocara canis and Toxascaris leonina. Dogs are infected in four ways: when they are in the uterus, when they are nursing from their mother, when they consume an infected rodent, or when they eat infected eggs that are in their environment.

Roundworm are a common cause of vomiting, diarrhea, ill health, and other dog gi problems in young pups. Puppies may often vomit up roundworms, or pass them in their feces. Large bundles of roundworms can actually block their intestine, which is very serious.

Roundworm Symptoms: vomiting, diarrhea, poor coat, and enlarged abdomen.

• Whipworms. Dogs acquire infection with Trichuris vulpis when they eat infective eggs. Adult worms live in the colon, and in small numbers they don't cause too many problems. A large worm infestation can be responsible for diarrhea with blood and mucus.

The eggs can survive in the environment for many years, which means that reinfection can occur fairly easily. If whipworm is an ongoing problem for your dog, you may need to move him to a different part of your yard, or concrete his kennel area, to prevent him being exposed to eggs.

Whipworm Symptoms: diarrhea with blood or mucous.

Heartworm in Dogs

The lifecycle of Dirofilaria immitis involves the mosquito. The insects pick up baby worms, known as microfilaria, when they feed from an infected dog. These microfilaria develop further in the mosquito, until they are capable of infecting another dog. They are then transmitted to that dog when the mosquito feeds again.

The adult worms can grow up to 14 inches in length, and they live in the pulmonary arteries, carrying blood from the heart to the lungs. They cause severe inflammation of the lining of the arteries, which makes the blood clot inappropriately. A large worm burden can partially block the artery, making it very hard for the heart to pump blood effectively.

The main symptoms of heartworm infection in dogs are signs of heart failure, including a cough, and a reduced ability to exercise. As the disease progresses, fluid accumulates in their abdomen, and they may have a bluish tinge to their gums, because their blood isn't getting oxygenated effectively.

Diagnosing Worms in Dogs

Fecal Float for Dog WormsThe most common way of diagnosing intestinal worms in dogs is with a fecal examination. Feces are mixed with a solution such as Fecasol, which encourages any parasite eggs to float. A microscope cover slip is placed on top of the feces/Fecasol mix, and the eggs adhere to that. It is then examined under the microscope.

This is effective for hookworm, tapeworm and roundworm infections. The first sign of tapeworm infection in a dog is often an itchy bottom, or small white worm segments in his feces. Dogs with hookworm often present with diarrhea and anemia. Whipworms don't lay eggs all the time, so a fecal examination may be negative even if a dog has worms in his colon. It's a good idea to treat for whipworms in any dog with symptoms of infection.

Heartworm diagnosis involves blood tests which look for either microfilaria or proteins from adult worms in a dog's blood.

Treating Worms in Dogs

None of the worming products available to dog owners actually prevent infection with any of the worms we've discussed. They kill the worms before they cause a dog any harm. We need to worm our dogs regularly because they are constantly exposed to worm eggs and larvae.

Praziquantel is effective against tapeworms, while fenbendazole kills hookworm and whipworm. Roundworms are controlled by febantel. Intestinal worms are often treated with a combination product that wipes out all the types of worms at once. Drontal Plus is such a product. It can be given to adult dogs every three months, and this should avoid any health problems due to intestinal worms. Young pups need more frequent treatment, and ideally should be wormed two weekly until their vaccination schedule is complete.

There are many options for controlling heartworm in dogs, but all the products available to dog owners kill the larval stages of the worm before they develop into adults. Monthly dosing with ivermectin (Heartgard), selamectin (Revolution) or milbemycin (Interceptor) are effective at protecting your dog from heartworm disease, and they also kill some types of intestinal worms at the same time.

If you have a busy lifestyle, you may want to treat your dog with moxidectin (Proheart 6). This is an injection which will kill heartworm larvae for 6 months. It's a great choice if you are worried about forgetting your monthly heartworm treatment, but you do still need to treat for intestinal worms.

The American Heartworm Society recommends that puppies start heartworm prevention at 8 weeks of age.

Heartworms that have developed into adulthood are treated with melarsomine (Immiticide). Two or three injections of this drug will kill the worms, but the dead parasites can cause further inflammation in your dog's lungs. He will need to be kept very quiet for several months while his body clears the remains of the worms.

Lastly, any symptoms of worms in dogs should be treated. This can involve blood transfusions for anemia caused by hookworms, or anti-diarrhea mixes to soothe intestinal inflammation due to whipworms.

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