Ewww... Worms

Lisa Radosta, DVM, DACVB
By Lisa Radosta, DVM, DACVB on Dec. 14, 2011

Is there anything grosser than worms? Even as a veterinarian they disgust me. At one time or another, your dog will get some type of intestinal parasite. For puppy owners, intestinal worms are a real concern. Infections that would be unlikely to make an adult dog sick can kill a puppy.

This week, we are talking about roundworms. In future blogs, we will talk about hookworms, tapeworms and heartworms.

Roundworm (ascarid) infections are the most common intestinal parasitic worm infection in pups. There are two main culprits: Toxocara canis (T. canis) and Toxascaris leonina (T. leonina).

Roundworm infections can cause pneumonia, intestinal obstruction, pot-bellied appearance, vomiting, and diarrhea. In some cases, infected pups will have no clinical signs at all. If your pup vomits up a long, white or light brown worm, be highly suspicious that she has round worms. As gross as it is, put the worm in a bag (without touching it) and bring it, and your pup, to your veterinarian’s office.

In addition to the clinical signs above, roundworms ingest the nutrients meant for your puppy. This, in combination with diarrhea, results in weight loss. What makes roundworms even more dangerous is that you can get them too.

Puppies can get roundworms in utero from the mother, through the milk while nursing, by eating an animal that is infected, or by ingesting soil that is contaminated.

Roundworms have a life cycle and a hardiness that is hard to beat. For example, larvae can hide in the muscle of infected hosts like rodents for years. Roundworm eggs are tough little buggers too. They can stay in the environment, laying dormant through hostile climates, only to develop into larvae years later under the right conditions. It is for this reason that you can’t just treat your puppy; you have to eliminate the worms, eggs and larvae from the environment, too.

It helps to understand the life cycle of the parasite so that you can understand how to eliminate it.

An infected dog defecates in the grass in your neighborhood, depositing microscopic eggs in the fecal material. It rains and time passes, degrading the fecal material and leaving the eggs. In about a month, the larvae develop within the T. canis egg. Along comes your pup, minding her own business while out on a walk with her owner. She walks through the grass and picks up dirt and T. canis eggs on her feet. When she gets home, she licks her paws and legs. Boom! She is infected. It is that simple. Once your pup is infected, the larvae migrate to the liver and lungs. (Are you grossed out yet?) Once they are in the lungs they can cause respiratory disease. But, it is not over yet. Without your knowledge, your little pup coughs up the worms and then swallows them. In your pup’s intestines, the worms find food and love. They chow down and find a mate so that they can make eggs. Then, your pup poops the eggs out, contaminating the environment. If you are not careful about cleaning up, your pup will reinfect herself again and again.

Veterinarians diagnose roundworms either by identifying a worm in the vomitus of a puppy or by finding eggs on a fecal float test (called a "fecal" for short). Unfortunately, eggs are shed intermittently, depending on the life cycle of the worm. That means that even if your pup is infected, eggs may not be detectable on the fecal float test.

Treating roundworms seems simple. Your dog is infected with an intestinal worm - just give a dewormer right? If it was that easy, roundworms wouldn’t be such a problem. Unfortunately, dewormers only kill the worms that are in the intestine, leaving the larvae in other body parts untouched.  So basically, you are waiting for the larvae to grow up, get coughed up, get swallowed and end up in the intestine so that you can kill them with a dewormer. If your dog doesn’t get reinfected, a couple of dewormings should do it, but if she keeps getting infected, it will take more than that. Proper deworming for T. canis includes two or three doses about two weeks apart to treat roundworms.

You can prevent roundworm infections by walking your pup in clean areas, keeping her from eating small animals, verifying with the breeder that the mother is on a monthly preventative and that the puppies have been properly dewormed, keeping up with regular dewormings after adoption, and cleaning up after your pup when she poops. When you go to socialize your pup, bring her to places where she can meet dogs with a known health history — such as daycare and puppy class — and avoid places with dogs that you don’t know — such as dog parks, dog beaches and pet supply stores.

The cool thing is that most monthly heartworm preventatives control roundworms as well. Unfortunately, the dosage of dewormer in the heartworm preventative is not enough to treat a severe infection, but it will prevent your pup from becoming infected in the first place. Puppies should be dewormed at two week intervals from the age of 2-8 weeks to clear any early infections. For more information on roundworms, go to the Companion Animal Parasite Council.

In addition to the tactics described above, your pup needs some basic skills to keep from being infected with roundworms. First, she should know how to defecate on cue so that you can collect her fecal samples and bring them to the veterinarian’s office. That way, she can avoid the dreaded fecal loop (the plastic loop that we insert you-know-where to collect fecal samples). You can find information on teaching your dog to eliminate on cue in some of my previous blogs.

After coming in from walking in areas where unfamiliar dogs may have defecated, your pup should have her footpads wiped. If you are walking her in her own yard, this is probably not necessary. You will need a soft cloth, treats, and a mat. Ask your pup to lie down on the floor on a mat. Take some time to teach her to stay on the mat as well. When she is able to lie down and stay comfortably, you are ready to start working on handling her paws. Then, say "paw" and hold her paw in your hand. If she is calm, hand her a treat and let go of her paw. Repeat this procedure on all four paws. If she pulls her paw away a little, hold it gently. When she stops pulling, let go immediately and give her a treat. Make a note that you held her paw for too long and hold it for less time next time.

If your pup reacts violently and starts to really pull her paw away, stands up, or uses her mouth to get you to stop, let go of her paw immediately. She has been conditioned to react when her paws are handled and will need special treatment. For this type of pup, start by holding her elbow or knee lightly and rewarding. Then, work your way down to the paw. When you can hold her paw gently for about 15 seconds before she gets a treat, you are ready for the next step. At this point, you can start to wipe the areas between the toes and pads very gently with a wet cloth. As always, start slow and then increase the time and pressure. And don’t forget to be generous with the rewards.

Dr. Lisa Radosta

Image: Geoff Hardy / Shutterstock

Lisa Radosta, DVM, DACVB


Lisa Radosta, DVM, DACVB


Dr. Radosta is a board certified veterinary behaviorist and owner of Florida Veterinary Behavior Service since 2006.  She is a well known...

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