What is roundworm?

Rounworms are nematodes from the Phylum Nematoda. There are over 20,000 described species of roundworm and over 15,000 of them are parasitic. As far as we know today, only two species of roundworms are capable of infecting dogs: Toxocara canis and Toxascaris leonina. Veterinarians rarely test the dog to determine which species of roundworm that has infected the dog, because both species of roundworm can be treated with the same medication protocol.

Toxocara canis roundworms have an intricate life cycle consisting of no less than four steps. During step one, roundworm eggs are passed in the host’s faeces and an embryonic worm develops inside the egg without needing any host. It takes time for the egg to become infectous – how long will depend on the environment. During step two, the embryonic worm will have developed into a second stage larva inside the egg. An animal – such as a dog – picks up the egg and the egg hatches in the animal’s intestinal tract. If the animal is a dog, the life cycle can proceed to stage three. If not, the roundworm larvae will encyst and wait for the animal to be eaten by a dog. In a dog, roundworm larvae will encyst in the dog’s liver until it is ready for step three. During stage three, roundworm larvae will shed the cyst and move to the lungs of the dog where they can develop into third stage larvae. They travel upwards through the small airways and induce coughing. When the dog coughs, it will cough up tiny worms into its own throat and consequently swallow them. The aim of the third stage larvae is to reach the intestinal tract of the dog. In the intestine, the roundworm larvae will mature and mate. New eggs will be laid and the cycle will start over again.

If a bitch is pregnant, the larvae will migrate to the uterus instead of the lungs and infect the lungs of the unborn puppies. In the case of nursing mothers, larvae can travel to the mammary gland instead of the lungs in order to infect the puppies via the milk. In most cases, the puppies will already be infected if their mother was infected during pregnancy.

Toxascaris leonine have a much less complicated lifecycle. This roundworm only needs a dog to consume its second larvae stage and will then mature inside the intestine of the dog. After 2-3 months, it will be ready to reproduce. Toxascaris leonine is capable of developing into third stage larvae not only in dogs, but in a wide range of other animals as well. (The development of Toxocara canis is halted if it is not inside a dog.)

Roundworm symptoms in dogs

• Diarrhoea
• Vomiting
• Worms can be vomited up
• Malnutrition
• A “pot-belly” look
• Pneumonia (in severe cases)
• Obstruction of the intestine (in severe cases)

Roundworm treatment for dogs

There exists a wide range of medications capable of killing roundworms. It should also be noted that if you regularly administer flea control products or anti-heartworm drugs to your dog, you should check the specific product that you are using – it might function as a monthly anti-roundworm cure as well.
Some of the most commonly used active ingredients in roundworm deworming treatments for dogs are Febantel, Fenbendazole, Milbemycin Oxime, Piperazine, and Pyrantel pamoate. Febantel is the active ingredients in two medications named Drontal and Drontal plus, while Fenbendazole is the active ingredient in Panacur. Milbemycin Oxime is found in Interceptor and Sentinel, while Pyrantel pamoate is used in products such as HeartgardPlus, Nemex, Strongid and similar. Piperazine is the active ingredient in most over the counter products used in the United States.

When treating your dog for roundworm, it is important to understand how the medication works. In most cases, the drug will sedate the worm and make it lose its grip inside the intestine of your dog. It will then be passed out during your dog’s next bowel movement. Deworming medication used for roundworms will therefore only kill the parasites in the intestines of your dog – not the parasites that might be located somewhere else in the dog’s body. Your must therefore follow up the initial treatment with at least 2-3 more treatments to get rid of the new parasites that will migrate to the intestines from other parts of the body. The second deworming is normally administered a few weeks after the first one. 

Parasites in dogs: (click for more info)
Cheyletiellosis in dogs
Chiggers in dogs
Ear Mites in dogs
Fleas in dogs
Heartworm disease in dogs
Hookworms in dogs
Mange in dogs
Roundworm in dogs
Tapeworms in dogs
Ticks in dogs
Trichinosis in dogs