What are worms in dogs and cats?

Dog and puppy health care questions and answers, articles, videos and images

Worms in dogs and cats 
Questions and answers about worms in dogs and cats

     There's a huge variety of worm species on planet Earth.  Each kind of worm has found a niche in the biological environment including a number of worm species that utilize canines and felines for their personal survival!  Most intestinal worms  do not kill their hosts because if they did the worms themselves would perish.
     Intestinal worms in dogs and cats, then, often exist without doing much harm.  In other cases, especially in young dogs and cats, stressed or debilitated pets, or pets consuming poor quality diets do suffer from worm infestations.  In certain circumstances, worms that inhabit dogs and cats can be a source for human infestation.  It's important to keep pets worm free.

Kitten and cat health care questions and answers, articles, videos and images

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 Are all dogs and cats born with worms?  Someone told me their vet worms all puppies and kittens at their first and second exams but I don't want my cats to get worm medication if they don't have any.
Answer:    dogs... cats... worms... worming...
No, not all dogs and cats are born with worms.  For a newborn pup or kitten to have worms the mother must harbor worms herself.  Some kinds of worms such asDogs and cats can harbor intestinal worms and show no signs of worms in the stool. roundworms and hookworms have a tiny larval stage that begins when they actually leave the egg in the intestine, penetrate the intestine wall, migrate to the lungs, are transported up the bronchial tree to the throat and swallowed.  They then grow to adults in the intestine.  Pretty awesome way to mature to an adult, isn't it?
     These migrating larvae can become entrapped (encysted) in the adult dog's tissues including the mammary glands.  When a newborn pup or kitten nurses, encysted worms in the mammary glands can escape with the milk and develop into adult worms in the pup or kitten's intestines!  Occasionally, worm larvae can penetrate into the fetus, too.  This is called transplacental migration.
     Because today's intestinal wormers are so safe to use many veterinarians make it a habit to routinely worm all pups and kittens for roundworms and hookworms.  Tapeworm and heartworm (which is not an intestinal worm) life cycles are different and are dealt with when the pups and kittens are about 6 weeks of age.

Doctor's Notes
       It is common practice to check stool samples under the microscope.  Although not 100% accurate, is one of the best ways to detect intestinal parasites. 
Numbers of worm eggs...
do not always correlate with the numbers of adult worms present. 
are not found in the intestines so a "fecal sample check for worms" won't display heartworm infection.  


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intestinal worms in dogs and cats intestinal worms in dogs and cats tapeworm in dogs intestinal worms in dogs and cats
If the mother dog is worm free her 
pups will not be born with worms
Tapeworm segments are seen in this stool sample; tapeworm eggs are not readily seen under the microscope. Dipylidium tapeworm showing the numerous segments that eventually drop away from the chain  Various stool and vomit samples from a cat with gastroenteritis

Below you can see what the veterinarian or technician is looking for through the microscope in a fecal analysis
intestinal worm eggs in dogs and cats intestinal worm eggs in dogs and cats intestinal worm eggs in dogs and cats intestinal worm eggs in dogs and cats
Toxascaris roundworm eggs at low power microscopic view Toxascaris roundworm egg at high power microscopic view Toxocara canis roundworm egg at high power microscopic view Dipylidium tapeworm egg packet
intestinal worm eggs in dogs and cats intestinal worm eggs in dogs and cats intestinal worm eggs in dogs and cats intestinal worm eggs in dogs and cats
Paragonimus egg at high 
power microscopic view
Whipworm egg... easily mistaken for a Capillaria worm egg Looks like a worm egg, right?  
It's a pine pollen grain.
Another  worm egg look-alike... a ragweed pollen grain among whipworm eggs

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I have wormed my dog recently with products from my vet.  How would my dog get worms in the future and what does the vet look for in a stool sample?


dog parks and worms
Dog parks can be a source of contact with contaminated feces 


Fecal analysis results...
     Toxoplasma gondii
, Giardia,  Neospora caninum,  Cryptosporidium, Mesocestoides are not worm organisms.  They can be identified in stool analyses and are single celled organisms.




A disease that can be transmitted between man and animals, for example Rabies, is called a zoonosis.

Answer:  worm eggs... kinds of worms... dogs and cats
Tapeworms, roundworms, hookworms and whipworms are the most common intestinal worms in dogs and cats in the USA.  Each has a unique life cycle and all can impact your pet's health.  Intestinal worms are usually contracted via ingesting infective eggs from another animal's stool or during self-cleaning when egg-contaminated soil or feces is licked from the fur or paws.  Tapeworms usually are spread via ingestion of fleas that have eaten tape worm eggs, or by ingestion of small animals such as mice or rabbits that themselves have intestinal tapeworms.

Below is a list of common intestinal worms seen in dogs and cats:

worms in dogs and cats  ROUNDWORMS
Toxocara canis...
adults are present in the small intestine of the dog and fox; infection is via oral, transmammary and transplacental routes.  Infective larvae migrate through tissues, including to the fetus where they can establish a prenatal infection!. They eventually  pass through the lungs and then to the alimentary tract. In hosts other than the dog and fox, migration of larvae occurs but the life cycle is not completed in the intestinal tract. Is the cause of ocular and visceral larval migrans in humans.

Toxascaris leonina... are found in the small intestine of dogs, cats, foxes and wild carnivora. Causes toxascariasis.

Strongyloides cati... are found in the small intestine of the cat.

worms in dogs and cats  HOOKWORMS
Ancylostoma caninum is the most  common hookworm of dogs.

Medical Name Common Name Hosts Infected
Ancylostoma caninum Canine hookworm Dog, fox, possibly humans
Ancylostoma braziliense Canine and feline hookworm Dog, cat, fox, human (skin)
Ancylostoma tubaeforme Feline hookworm Cat
Uncinaria  stenocephala Northern canine hookworm Dog, cat, fox

worms in dogs and cats  WHIPWORMS
The whipworm called Trichuris vulpis usually affects dogs and rarely the cat.  It attaches to the cecum, a blind ended pouch at the start of the large intestine (colon). It is a very tiny worm of no longer than two inches in length.
  Dogs and cats can be infected with a whipworm called Trichuris trichiura. Whipworm eggs can live in an environment for up to a few years and are present in soil, food, or water, animal feces or animal flesh.  

worms in dogs and cats  LUNGWORMS and BLADDER WORMS
Capillaria plica...
eggs are occasionally found  in urine sediments from cats and dogs.  They can be mistaken for eggs of Trichuris vulpis (whipworms) from fecal contamination.

Capillaria aerophila and Aelurostrongylus abstrusus are parasitic nematodes; these two kinds of lungworms in cats are common worldwide.

worms in dogs and cats  TAPEWORMS
Taenia pisiformis... is a type of  tapeworm found in the small intestine of the dog, fox, and other wild carnivores, and very rarely in cats. The infective stage, Cysticercus pisiformis, can be present in rabbits' liver and peritoneal cavity.

Dipylidium caninum...  is a world-wide parasite that requires a flea as part of its life cycle to develop fully. Depending on the presence of appropriate flea and vertebrate hosts the eggs can survive outside of the host if conditions are right.

Echinococcus granulosus and Echinococcus multilocularis... although rare in dogs in the United States, cases have been reported in California, Arizona, New Mexico, and Utah.  Humans become infected when they swallow eggs in contaminated food. The infection is carried to the liver where cysts form. 

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