Roundworms & Dogs - The most common dog digestive tract parasite

Dogs & Roundworms

Roundworms are the most common parasite that infects the digestive tract of canines. While talking about parasites may not be pleasant, owners need to educate themselves about their pet抯 health and wellbeing.

There are 2 types of Roundworms that effect dogs: Toxascaris leonine and Toxocara canis. This article will focus on Toxascaris Canis, as it is the more common of the two.

There are 4 ways a dog can contract T. Canis: ingestion of eggs, ingestion of a host, by larvae through the uterus, or by larvae as consumed through mother抯 milk.

• Ingestion of eggs: Infection through the ingestion of eggs can occur when a dog consumes soil or feces contaminated with roundworm eggs. The eggs then hatch and the larvae enter the wall of the small intestine. Then larvae move through the circulatory system. The larvae then head towards the respiratory system or towards other organs in the dog抯 body. In puppies the larvae most commonly move from the circulatory system to the respiratory system. Then they are coughed up and re-swallowed. In the stomach the larvae mature into adults. These adult worms lay eggs which are passed along in the feces of the dog.
• Ingestion of a host: This is similar to the process of ingesting eggs, except the dog actually consumes a host carrying T. Canis (for example, a small rodent). The host is digested and the larvae are released into the dog抯 system during that process.
• Infection through the uterus: When larvae enter a dog抯 body they can wall themselves off in internal tissues. This process is called encysting. The encysted larvae can remain dormant for long periods of time (months or years). A female dog that is infected with encysted T. Canis larvae can pass them to her litter of puppies. The first way this can occur is that the dormant larvae will become active and move through the uterus and placenta and infect the pup while in utero. Most puppies are born with roundworm because they are infected in this manner.
• Infection through the consumption of milk: Larvae can also travel to puppies when they nurse. The T. Canis larvae are consumed and then mature in the pup抯 small intestine.

It only takes about 4 weeks for a T. Canis egg to mature into an adult roundworm that is capable of laying eggs of its own and carrying on the lifecycle. One single female T. Canis can produce 200,000 eggs per day!

Symptoms: A pot belly is the most common sign of roundworms ?especially in puppies. This symptom occurs in adult dogs as well. Sometimes dogs will be skinny, with the exception of a large belly. The coat may be dull and some animals may develop loose stool or vomiting. If the migration of the larvae has continued into the lungs, it can lead to pneumonia.

In the case of a severe infection, roundworms are sometimes able to be seen in vomit or feces. They appear almost spaghetti-like and range from 3-8 inches in length. A fecal sample is taken and examined under a microscope to detect immature roundworm eggs.

Treatment: There are many wormers that kill adult roundworms, however they will not affect the larvae. This is why your veterinarian should recommend treating with repeat doses of worming medication. With puppies, it is routine for them to receive at least 3 doses of worming medication to ensure that the treatment is effective. For adult dogs, your veterinarian will advise you on the best course of action. Many heartworm preventatives also contain an ingredient that kills roundworms. This will help keep your dog free from future infestations. Yearly fecal exams are recommended.

Precautions: Humans can become infected with Roundworms! This is most common in children as they often play in dirt and will then put their hands in their mouths. If they ingest eggs, infection can occur. Do not allow children to play in areas which dogs use as a bathroom. Direct contact with an infected dog rarely leads to human infection. The eggs need to be ingested, thus diligent hygiene practices should be followed if your dog is being treated for a parasitic infection.