There are two different Roundworms. Their scientific names are Toxocara canis and Toxascaris leonina. The control and treatment of these worms are the same, but since Toxacara canis is the most common of the two types, we will focus our information here.
The adult Roundworm can achieve a length of up to 10 cm and live in the small intestines of the host dog. Upon entry into the intestines they are around 2cm but within ten days can grow 250+%, around 5 or 6 cm. For pups that are severely infected with these worms they will have a potbellied appearance. Because the worm affects the nutritional intake of the puppy another symptom that may be present is the development of a poor starting coat of fur. For some where this worm is very severe, blockage of the gut may occur, which can lead to death.
For one to understand how to control and treat a pet with roundworm infection it is important to know the lifecycle of the worm. As mentioned before the adult roundworm lives in the small intestines. In one day while in the small intestines a female can lay up to 200,000 eggs. These eggs are subsequently passed through the bowels and deposited upon the ground. While in and on the ground a two-stage larvae begins to develop in the egg and this egg is very sticky and easily clings to the fur or paws of the unsuspecting dog. Once it attaches to a dog it often finds its way into the mouth when the dog licks these regions.
Because the egg has a thick and durable shell it is well protected against environmental factors and disinfectants.
If the larvae is in its second stage when digested the shell will dissolve and the larvae then find their way to the small intestines. Once in the small intestine they dig their way through the intestine walls and into the surrounding blood vessels.
From the blood vessels they move to the liver where they burrow through the tissue and begin to molt into a third stage larvae. This third stage larvae then find their way through a blood vessel, through the heart, and into the lungs.
While in the lungs the larvae grow for a number of weeks and finally break out into the air spaces in the lungs and can be severe enough to cause bronchitis. During this time the dog will cough the worms up and re-swallow them where they will then find their way back to the small intestines.
The reason it is important to understand the lifecycle is because while the worm is moving through the tissue it is unable to be treated. The only time that treatment is effective is when the worm is an adult and in the gut of the dog.
When looking for a good de-wormer medicine our vet has advised us to purchase products with the active ingredient of Pyrantel Pamoate. Under the theory that "more is better" it is our opinion that medicines with a higher level of this ingredient are probably more affective and worth the extra $1 or $2. If advised differently by your vet we certainly recommend that you follow their directions.
While in the small intestine the larvae develop into adults. Within 2-3 weeks the female adults begin to lay their eggs where the whole cycle begins again. As long as a puppy is exposed to these eggs that puppy will face an issue of infection with worms in various stages of development.
Because only adult worms can be treated if medicated, the dog will only expel live eggs and dead adults. Those larvae in development in the dog will remain developing and the dog will remain infected. Because each female can lay a large amount of eggs within a very small amount of time the dog will be re-colonized and infected with worms in various stages of development.
Because only adult worms can be treated, it is of the utmost importance to realize that a single treatment will not be effective in the treatment of an infected puppy. Because of this it is important to treat the puppy on a regular and continual basis for a certain period of time to insure that the infection has been taken care of properly.
After the puppy reaches about twelve weeks of age their immune system is developed to a significant enough level to take care of infections and treatment can stop.
One exception to this is pregnant and lactating female dogs, who once again become susceptible to infection. Because of this, the risk to new pups is significant since they can pick up the eggs through the mothers’ droppings or through larvae that have stuck to her fur.
Another way a pup may be susceptible to infection is inutero (while in the uterus). This happens when the female dog has had worms when she was a pup and some larvae have hibernated in the tissue of the female until she becomes pregnant. This hibernation can last for many years. Upon pregnancy, for reasons not fully understood, these larvae once again become active and find their way to the uterus and burrow through to infect the pup. Because of this it is possible for a pup as early as two weeks old to have an active infestation of adult Roundworms.
Because adult Roundworms can be found in a pup as early as two weeks of age this is usually the time when the de-worming process should begin. Beginning treatment early will not only help the puppy out early in its life but also decrease the chances of it developing hibernating larvae, which could infect future litters.
Because worms can exist in various stages of development it is important for the purchaser to realize that worms are a common occurrence and have very little to do with the care of the pup by the breeder. It is also equally important for the breeder to have been regularly treating for worms and advise the purchaser of the potential for Roundworm infection and the appropriate treatment cycle.
In order to help reduce the chances of worms and other various diseases, such as Parvo and Distemper, the following steps should be taken:
Collect all droppings.
Reduce exposure to other animals and areas frequented buy other animals.
Reduce exposure to unnecessary human contact, as they may be carriers.
When possible, eliminate dirt runs. Where elimination is not possible make these runs as large as possible to help dilute the potential of infection.
Maintain a strict treatment program.
A good worming program should begin as early as two weeks and continue on the third, fourth, sixth, eighth, tenth, and twelfth week with a Pyrantel Pamoate based de-wormer which is also effective against Hookworms.
Breeding females should be treated at least three times. Once before mating, another time after giving birth, and once again shortly before the pups are weaned. Because of the reduced level of immunity in older dogs treatment should also be given them on occasion.
Because humans can also become infected with the Roundworm it is important to realize the health risk involved. Because the worm can not pass through human tissue as it can through a dog’s tissue, the larvae tend to remain in various parts of the human body. These larvae are known as "visceral larvae migrans". These larvae often infect nervous system tissue and can cause blindness if they reach the optic nerve.
Because of the risk of infection and its possible side effects it is important that we try to avoid infection. Human infection comes through the swallowing of eggs, which may either be picked up from the soil or off the fur of an animal. Young children are most susceptible because they often ignore proper hygiene and are often the ones most interactive with animals. When you have children who play with animals it is important that you stress the importance of proper hygiene and the washing of hands to help reduce the likelihood of infection.
Some statistics everyone, especially those with children, should be aware of:
25% of park soil may contain eggs.
40-60% of urban dogs carry this parasite.
