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Preventing & Treating Common Parasites in Dogs

Many of the common intestinal parasites of dogs can easily be spread to people. Children are especially prone to acquiring these parasites because they tend to spend more time with their hands in their mouths. Many can cause gastrointestinal problems; others can migrate through the skin and organs of people. It important to be aware of the possible human health implications of our pets, and always do as much as possible to prevent infestations of our animals and our environment.


Routine deworming
Good sanitation of our homes and our pet’s living area.
Cover sandboxes when not in use
Keep dogs indoors when not under direct supervision to minimize exposure 
Do not allow dogs to consume wildlife
Monthly flea and tick prevention (for tapeworms)
While diluted bleach or ammonia is effective at killing many of the parasite eggs, some require extreme heat (boiling water, steam, propane treatment). Therefore sanitation, treatment, and prevention are the best methods for environmental control.
Clean up all feces immediately. Many of the common intestinal parasites can actually inhabit the environment, or may not become infective for the first 24 hours. Therefore immediate cleaning of feces in your backyard or in public places is very important to prevent environmental contamination.



  • Deworming at 2, 4, 6, 8 weeks of age, then monthly heartworm preventative

  • Fecal testing 2-4 times in the first year of life

  • Puppies require repeated treatment because they are repeatedly exposed to hookworms and roundworms while nursing, and many of these parasites have complex life cycles. During the early stages of infection (first 2-3 weeks) hookworms and roundworms are migrating through their body and treatment will ONLY kill the parasites present within their gastrointestinal system.

  • Also important to deworm pregnant dogs and cats during their pregnancy.


    Adult dogs

  • Monthly heartworm preventative

  • Fecal testing every 6-12 months.

  • Adult dogs that are positive for roundworms and hookworms on routine testing should be dewormed once, and then 2-3 weeks later before considering retesting to ensure adequate treatment

  • Intestinal Parasites

    Types of Intestinal Parasites:

        • Acquired from ingestion of contaminated soil, stool, or wildlife; also during gestation and while nursing
        • Signs start within 2 1/2- 3 weeks of age.
        • Even if an animal has been appropriately dewormed throughout its entire life, it is common for worms to form cysts in their tissue. These cysts are very resistant to treatment. These will become activated when an animal is pregnant, and travel to the fetuses and mammary tissue.
        • Distended (enlarged) abdomen
        • Poor body and coat condition
        • Diarrhea/Vomiting
     Human Health Concerns:
        • Acquired from handling/consuming soil containing cat/dog/raccoon feces,
        • Most commonly affect children.




        • Eggs in stool from an infected animal,
        • Puppies acquire via nursing, through ingestion of larvae worms in infected wildlife, or through the larval worms penetrating their skin.
        • Time from ingestion/skin penetration to laying eggs is approximately 2-3 weeks, but can be as soon as 10 days in puppies
        • Hookworms feed on the blood from the lining of the intestines, causing anemia (low red blood cells)
        • Pale gums
        • Distended (enlarged) abdomen
        • Poor coat and body condition
        • Diarrhea, vomiting, poor appetite
        • Respiratory signs (pneumonia) through larval migration
     Human Health Concerns:
        • Larvae in environment penetrate and travel through skin of children, adults. Red, itchy, infected skin especially along bottoms of feet, legs, or hands. These will not develop into adult parasites, and tend not migrate to other organs or the gastrointestinal tract.


        • Tapeworms require an intermediate host, which is often prey of the affected animal (Example: Cat and Mouse.) Infected animals shed sections of adult worms (proglottids) which contain eggs. When these are consumed by the appropriate intermediate host, the larval cysts develop. When these intermediate hosts (fleas, lice, rodents etc) are ingested by a dog, they will develop into mature intestinal tapeworms.
        • Time from infection to shedding of proglottids is usually 2-3 weeks.
        • Weight loss
        • Perianal (around the anus) irritation
    Human Health Concerns:
        • Ingestion of infected fleas can cause mild gastrointestinal signs in children
        • Rare human infections will develop cestode cysts that require drainage or surgical removal.



        • Only affects dogs in the United States
        • Direct fecal to oral life cycle
        • Once eggs are produced and are in the environment they are very resistant to temperature, dryness and sunlight.
        • Become infective within 9-21 days,
        • Can remain in the environment for years
        • Common in urban areas with high volumes of dogs (dog parks etc.)
        • Symptoms can occur without egg production causing negative fecal float
        • Very long period from exposure to signs (74-90 days)
        • Diarrhea
        • Blood in stool
        • Can be asymptomatic
        Human Health Concerns: None


        • Protozoan single celled organism.
        • Complex life cycle with many different stages
        • Transmission via contaminated environment and through ingestion of intermediate hosts (mice, rats, etc)
        • Very host specific, therefore coccidia cannot be spread from dogs to cat or vice versa.
        • Invade and destroy intestinal cells, causing poor digestion and absorption. 
        • Eggs can survive in the environment for very long periods of time (1+ year) in the right conditions.
        • Diarrhea, weight loss, dehydration, rarely bloody stool
        • Can progress to vomiting, depression, and loss of appetite.
        • Puppies are most commonly affected, and will eventually clear the parasite as their immune system develops.
        • Adult dogs do not usually show clinical signs of coccidia unless their immune system is compromised.
     Human Health Concern: None

        • Protozoan single celled organism
        • Most commonly found in stagnant and running water
        • Signs usually dose dependant (more exposure = more likely to have signs)
        • Most adult dogs have natural immunity
        • Watery diarrhea
        • Occasionally vomiting
        Human Health Concerns:
        • Different strains of Giardia infect dogs, cats, and people
        • It’s unlikely, but possible for a dog with Giardia to spread it to their owners
        • Most Giardia is spread from human to human, or from drinking contaminated water.


    External Parasites