Intestinal Parasites in Dogs

Dogs

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A parasite is a plant or animal that lives upon or within another living organism. There are a variety of parasites that infect various organs or body systems. Parasites can be either internal or external parasites – living primarily on the skin (fleas), in the respiratory tract (lungworms), or in the blood vessels and heart (heartworms).

Some gastrointestinal parasites are microscopic, and the only way to diagnose them is by microscopic examination of your dog's feces for the eggs shed by the adult worms. Others are large enough to be observed in your dog's bowel movements or after he vomits. Moreover, some tapeworms produce proglottids, which are the segments making up their body. These segments can be seen around the hair on the anus or in the stool, appearing as bits of moving "white rice."

Among the important gastrointestinal parasites of dogs are roundworms (Toxocara species), hookworms (Ancylostoma caninum, Ancylostoma braziliense and Uncinaria stenocephala), whipworms (Trichuris vulpis, T. campanula, T. serrata), stomach worms (Physaloptera spp.), tapeworms (Diplylidium caninum, Taenia pisiformis), and microscopic parasites Coccidia, Giardia and Strongyloides species.

How Parasites Are Acquired

  • Ingestion of eggs. Most infections are acquired by ingestion of microscopic eggs. This occurs when a dog licks areas where other dogs have defecated, like yards, parks or grass.

  • At birth. Many puppies are born with intestinal parasites (usually roundworms) that have been passed from the mother, where the parasite was in an encysted, quiet state.

  • From intermediate host. Tapeworms are transmitted by an intermediate host when a dog swallows a flea or eats a rabbit.

    It should be emphasized that some parasites – especially roundworms and hookworms – can also affect people, especially children. For that reason, it is essential to prevent intestinal parasites in our pets and to treat any resultant infection.

    Parasitic diseases range from trivial to fatal disease. Parasites can cause severe disease in immature puppies, sick or debilitated pets, or in pets with a suppressed immune system. Younger pets often get acute disease (vomiting, diarrhea, dehydration, and anemia) whereas older pets get chronic disease such as intermittent diarrhea.

    What to Watch For

  • Nausea
  • Vomiting
  • Diarrhea
  • Anemia
  • Skin lesions

    Diagnosis

    Because parasitism is easily confused with other debilitating conditions, diagnosis depends on the following:

  • Medical history and physical examination, including observations of worms in the stool or vomitus.

  • Fecal examination for microscopic eggs or larvae. This is the most common approach to diagnosis as most pets do not appear ill.

  • CBC – Complete blood count if anemia is suspected (as with a hookworm infection) or if the pet is showing symptoms of illness.

  • Other blood tests may reveal concurrent problems.

    Treatment

    Treatments for intestinal parasites may include one or more of the following:

  • Routine deworming in puppies – This is the ideal approach. All immature pets should treated at the first veterinary examination and regularly dewormed during the first year. In general, every dog less than one year of age should be given an anthelmintic (anti-parasite drug) for ascarids regardless of fecal results. This is in part to protect the environment from contamination with microscopic eggs that might infect children.

  • A yearly fecal check and treatment is recommended for adult pets, especially if they are not taking heartworm preventatives that would prevent development of intestinal worms.

  • Other treatments may include fluid therapy for debilitated pets or blood transfusion and iron supplementation (if necessary for severe blood loss as with hookworm infections).

    Home Care and Prevention

    At home administer any prescribed medications and follow-up with your veterinarian for examinations and repeated fecal (stool) tests as needed.

    Some microscopic eggs can live in the environment (such as the yard) for weeks to months and cause re-infection. Clean up yard weekly and minimize roaming of pets in places like parks where exposure and infection are possible.

    Many health care specialists recommend a fecal sample from all adult animals at least yearly, a sample at each puppy vaccination visit, and a follow up sample at the appropriate interval after the last deworming medication has been given.

    With primarily outdoor dogs, it may be advisable to evaluate stool samples every three to six months if risk of infection is high. One may also consider heartworm preventatives that also prevent intestinal parasites.

    • Photograph of hookworm eggs seen on fecal flotation.

    • Photograph of a packet of tapeworm eggs as seen under a microscope.

    • Fecal preparation previous to slide examination

    • Evaluation of fecal slides under a microscope.

    Intestinal parasites are a common cause of vomiting and diarrhea in dogs; however, other medical problems can lead to similar symptoms.

  • One must exclude disorders such as viral infection, ingestion of spoiled or toxic food, ingestion of irritating or toxic substances, or bacterial infections, before establishing a definite diagnosis of disease from parasite infection.

  • Remember too that many pets have more than one problem. For example, in a young dog, a viral infection of the intestine (such as parvovirus or coronavirus infections) is very likely to be complicated by a pre-existing intestinal parasite problem.

  • Diagnosis In-depth

    Diagnostic tests are needed to recognize intestinal parasites. When a pet is ill with gastrointestinal symptoms, other tests may be needed to exclude other diseases, even if worms are obvious. These tests can include:

  • A complete medical history and physical examination. This should involve questions about any vomiting, bowel movements, weight loss, health of littermates, previous deworming program, history of previous parasites and housing. Complete examination with abdominal palpation (feeling the abdomen) should be done.

  • Fecal analysis tests. The fecal sample is mixed with a solution that encourages microscopic ova (eggs) to float to the top and stick to a microscope slide for examination. A single fecal sample may not demonstrate the eggs in infected dogs in some circumstances. Some parasites-whipworms are a good example-shed ova intermittently. Some parasitic infections such as Giardia require a different approach to diagnosis (fresh sample of feces with examination of a saline smear under a microscope).

  • A complete blood count (CBC). In sick pets or those appearing anemic, a CBC can reveal anemia (as some worms cause intestinal blood loss) or elevated eosinophil count (common in parasitic infections). It is also helpful to screen for other infectious intestinal diseases (such as parvovirus).

    Additional diagnostic tests may be recommend on an individual pet basis to exclude or diagnose other conditions or to better understand this disease's impact on your pet:

  • A test for parvovirus should be considered in puppies with acute or severe diarrhea or vomiting, especially when there is fever or blood in the stool. This infection is a very common cause of diarrhea in dogs. Worms are often shed with this condition (from pre-existing intestinal parasite infection).

  • Abdominal X-rays may be needed in some cases of severe vomiting or if the abdomen is abnormal to palpation.

    Treatment In-depth

    The best course for managing intestinal parasites is prevention. Treatment of intestinal parasites must be individualized based on the severity of the condition and other factors that must be analyzed by your veterinarian. Treatment may include:

  • Deworming. Puppies are dewormed routinely for roundworms and hookworms at the time of "puppy shots, " but worms can also affect mature dogs. Regular stool examinations can detect intestinal worms in most cases. Some of the newer heartworm preventatives also prevent intestinal parasites (and some prevent fleas as well!).

  • Fecal exam. A yearly fecal sample is recommended for adult dogs. Adult dogs typically acquire worms when they lick up microscopic eggs present in contaminated soil or grass. Mature dogs develop resistance to most intestinal parasites, but the whipworm can still cause problems leading to signs of colitis. It is to detect this worm with a stool sample, but it responds to appropriate deworming medicine.
  • Drug therapy. Several drugs available concurrently prevent heartworm disease and prevent or treat intestinal parasites. See your veterinarian for details. These products include Interceptor® (Milbemycin), Heartguard Plus® (Ivermectin + pyrantel tartrate) and Revolution® (selamectin).

    Treatment for parasites is often based the fecal analysis. Common treatments may include:

  • Roundworms (Toxocara infections)-pyrantel pamoate (Nemex®) or fenbendazole (Panacur®) is commonly used to treat roundworms and hookworms.

  • Hookworms (Ancylostoma caninum, Ancylostoma braziliense and Uncinaria Stenocephala)-pyrantel pamoate is commonly used to treat roundworms and hookworms.

  • Whipworms (Trichuris vulpis, T. Campanula, T. Serrata)-Dogs are treated once daily for three consecutive days and repeated in 3 weeks with fenbendazole (Panacur®). Some veterinarians recommend a third treatment in 3 months. This drug also treats roundworms, hookworms and tapeworms (Taenia spp.).

  • Physaloptera (stomach worm)-this can be treated with pyrantel pamoate.

  • Strongyloides-often treated with fenbendazole (Panacur®) or pyrantel pamoate (Strongid T®, Nemex®) for 5 days.

  • Tapeworms (Diplylidium caninum, taenia pisiformis)-praziquantel (Droncit®), epsiprantel (Cestex®) or febantel + praziquantel (Versom®); fenbendazole is effective for taeniid infection. Dipylidium infections also require prevention with flea control (fleas are the intermediate host). Prevent dogs from unsupervised hunting (rabbits are the intermediate host of Taenia pisiformis).

  • Coccidia-can be treated with sulfadimethoxine for 10 days or trimethoprim-sulfa for 7 days.

  • Giardia-can be treated with various drugs including metronidazole (Flagyl®) for 5 to 10 days.

  • Optimal treatment for your pet requires a combination of home and professional veterinary care and follow-up is important. Administer prescribed veterinary medications as directed and be certain to contact your veterinarian if you are experiencing problems treating your pet. Your veterinarian should do a PCV or complete blood count (CBC) for anemic pets.

    Your veterinarian should do repeat fecal examinations. Administer any prescribed medications; give yourself a reminder for treatments needed in the future.

    Follow preventative veterinary recommendations.

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