Roundworm Infection: How Toxacaris Spreads, Hookworm Treatment & Prevention in Dogs

How Toxascaris leonine spreads

stained sliced roundworm egg under microscopeToxascaris leonine has the simpler life cycle of the two round worms. It is much more common in cats than dogs. Unike Toxocara canis it is not passed from pregnant or nursing dogs to pups.

An infected dog sheds eggs from the gut

Eggs of Toxascaris leonine roundworms will pass out of the dog in the stool. The eggs are not infective in fresh feces, but usually take 3 to 6 days to become infective if the conditions (humidity and temperature) are suitable.

An egg is swallowed by a dog

If the eggs are swallowed by a dog the larval and adult development all occur in the gut. Unlike Toxocara canis, the larval stages do not pass out of the intestine into the body. After the eggs hatch, the larvae enter the intestinal wall and develop there. When they are adults they move out of the wall back into intestine.

If a dog eats another animal that is infected with Toxascaris leonine

If another animal that is not a canid (dog, fox, coyote etc) or a feline (cat, bobcat etc.) eats infective eggs then the larvae move out of the gut and encyst in tissues of the animal.

The most common intermediate hosts for Toxascaris leonine are rodents such as mice and rats.

When a dog eats an infected animal the larvae are activated in the gut, develop into mature worms and start to lay eggs. As with direct infection of a dog the Toxascaris leonine larvae do not leave the gut.

What are the symptoms of a roundworm infection?

Symptoms of Toxocara canis infection

In very young puppies

In very young puppies, if there a heavy Toxocara canis infection there will be severe illness and perhaps death. Puppies with a moderate to severe infection will often have slowed development, a reduced rate of growth, are often anemic, are very lethargic and have a poor-looking coat. They will usually have a pot belly and may have abdominal pain.

Vomiting and diarrhea can occur, and the worms may be obvious.

If there is a heavy infestation a puppy may get pneumonia when the larva are migrating through the lungs.

In puppies older than about 2 months

In puppies that older than 2 months the symptoms of Toxocara canis infestation are usually not as severe and diarrhea and vomiting may come and go.

Pneumonia is possible when the larvae migrate.

In adult dogs

In most healthy adult dogs there are usually few symptoms.

Symptoms of Toxascaris leonine infection

All ages of dogs

Dogs with low levels of Toxascaris leonine infection may not show any obvious signs of being infected.

Heavy infestation with Toxascaris leonine in any age dog, but particularly puppies can cause vomiting and diarrhea, often obviously containing worms.

The presence of lots of worms removes significant amounts of nutrients from the gut, resulting in less nutrition of the dog. A dog can have some or all of the following symptoms; a dull coat, be lethargic, become anemic and have a pot bellied appearance.

Diagnosis of roundworm infections

If a dog has vomited up roundworms or they are present in diarrhea, they can easily be identified. They look like strands of spaghetti.

Routinely to check for a roundworms infection a stool sample is analyzed. Eggs are separated from the rest of the stool by flotation. Under the microscope roundworm eggs can be identified by their shape and size.

Treatment of dogs with roundworms

Ingredients such as febantel, fenbendazole, pyrantel, piperazine, milbemycin oxime, ivermectin, moxidectin and mebendazole will kill adult worms. Praziquantal does not kill roundworms.

Different products have different dosing schedules.

Since the products kill worms in the gut but do not kill migrating larvae, treatments are usually repeated at 2 to 4 week intervals. As new worms mature they are killed and only a few eggs will be laid and pass out in the stool.

Generally it is assumed that pregnant dogs are infected. The most common treatment is fenbendazole daily to prevent transmission of larvae to the uterus and the unborn pups, and to the mammary glands, so that the milk is not infectious. Mothers are usually treated while they are nursing too.

Prevention of roundworm infection

Roundworm infection cannot be prevented directly by medication. The medications used are de-wormers. However, by killing the adult worms this stops more eggs ending up in the environment and so help prevent other animals getting infected.

Newborn Puppies

Newborn puppies should be first treated with a de-wormer suitable for puppies within 2 weeks of their birth. If a puppy is infected, after about 2 weeks they will start to have eggs in their stool. This can lead to contamination of any areas that the puppies go.

Follow up treatments at least for 4, 6 and 8 weeks are usually recommended. Larvae that are still maturing and larvae that come with the milk of the mother are not killed by de-worming until they mature into adult worms. Therefore repeated de-worming treatments will kill newly matured adult worms and minimize the number of eggs that pass out of the intestine.

If eggs or worms are detected in the stool after 8 weeks, more treatments are necessary.

The treatment of choice for young puppies is usually pyrantel.

Older puppies and adults

Vets usually recommend a regular deworming to eliminate any adult roundworms.

If you live in an area that gets heartworm, then most heartworm medications will kill roundworms (the major exception is Revolution – see Heartworm – Table of Common Preventative Medicines: Note: most heartworm medications do not kill tapeworms.). Therefore, if your dog is on heartworm medication they are getting de-wormed for roundworms once per month.

There are a number of over the counter medications that kill roundworms, if a dog is not on heartworm medication. Something like WormX that also kills hookworms and tapeworms, in addition to roundworms is probably a good idea.

A New Dog

When you get a dog, whether it a young puppy or a dog from a shelter, unless you are absolutely certain that they have been on de-worming medication on an appropriate schedule it is important to start a course of de-worming. Talk to your vet about what they recommend. The usual schedule is immediately, 2 weeks later and then at intervals thereafter. A stool check at about 4 weeks is a good precaution, to make sure that if they were infected that all worms have been eliminated.

A clean outside environment

Since roundworm infections are so common in dogs there are a lot of eggs on the ground.

Keeping your yard picked up will mean that the most of the eggs will be removed before they become infectious. This will help stop your dog getting re-infected.

If possible keep your dog away from areas in parks where there is a lot of stool on the ground. Picking up after your dog also helps.

Since the eggs can survive harsh conditions, decontamination of an area is not easy. Measures include covering in concrete or asphalt, removal of top soil and burning.

Can humans get roundworms from dogs?

Occasionally humans can get infected with roundworms, if they accidently swallow an egg that contains a larva of Toxocara canis or Toxascaris leonine. The vast majority of cases in humans are Toxocara canis.

Small children are more likely to be infected than adults since they are more likely to put things in their mouth and crawl, play etc on the ground. Keeping your yard picked up and not letting young children play in areas of parks that heavily used by dogs will reduce the risk.

In adults there are usually no symptoms. Young children are more likely to get symptoms. The presence of symptoms is called toxocariasis. The symptoms can range from mild to more severe and though they will usually last a few weeks, occassionally the effects may remain.

Humans are much more likely to get an infection from puppies rather than adult dogs since usually they will be more actively shedding eggs.

Occasionally humans can get roundworms from eating undercooked game or possibly from a fly that happens to be carrying an egg landing on food that is then eaten.

In conclusion

Toxocara canis is more common in dogs than Toxascaris leonine.

The majority of puppies when they are born are already are infected with roundworm. It is important to treat puppies within 2 weeks of birth and several times thereafter to minimize the number of eggs that are produced and pass out of the intestine.

Heavy roundworms infections can have serious health consequences, particularly puppies under 3 months.

All dogs should be regularly de-wormed to control the spread of roundworms. Most heartworm medications will kill adult roundworms.

 
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See also Worms Of The Digestive System: General Information