"Roundworms and Their Public Health Significance"
This week we would like to discuss an extremely common intestinal parasite of dogs and cats and many other animals. Almost all mammals can have some form of roundworms. Typically, these are the "spaghetti-like worms" you can see in the vomitus and feces of puppies and kittens. Since they can cause serious problems in humans (usually children) I wanted to bring attention to the dangers they can present.
What are they?
Roundworms are big worms. Typically they are white, about the diameter of a spaghetti-strand and about 4 inches in length. Often times kittens or puppies vomit one up or we are horrified when we see them in the feces.
How do our pets get roundworms?
Kittens or puppies may be born with roundworms! We know that Roundworm larva are tiny enough to migrate through the placental blood supply to the fetal liver or lungs. Soon after birth the juvenile roundworms begin migrating from the liver and lungs to the intestine where they grow to adults and begin laying eggs. Within three weeks after birth, puppies and kittens can begin shedding roundworm eggs into the environment.
A second source of infection is through the mother's milk - Roundworm larva can gain entry into the mammary glands and then be passed to the puppies or kittens as they nurse.
A third possibility is if the young animal should eat an embryonated egg found in fecal contamination of food or water bowls, the nesting box or other environmental sources. The egg hatches within the intestine and a "Blood-Lung" migration begins as described below.
In the three cases above we are talking about a "Blood-Lung" migration. In other words, from wherever the roundworm larva gains entry into the pet's body the larva then migrate to the liver via the portal blood system (the portal blood system is the one draining from the stomach, intestines and leading to the liver) . The larva are then carried by the circulatory system to the lungs where they can pierce the walls of tiny lung blood vessels (capillaries) and gain entry into the airways (alveoli and bronchioles). The cilia (little whiskers that move foreign objects) lining the airways then move the larva up the bronchi and windpipe until they are coughed up and swallowed. Once they are swallowed they have become large enough that they can continue their maturation to adult egg-laying roundworms in the small intestine.
Somatic cycle... A second type of roundworm life cycle occurs when dogs or cats develop "age resistance" at about 6 months of age or older. Instead of the larval form reaching the lungs via the blood and going through the "coughing up, swallowing and growing to adult in the intestine" phase another phenomenon occurs. The so-called "age resistance" alerts the dog or cats immune system to the possible presence of roundworm larva. When a larva enters the body, the immune system traps it in walled-off granuloma's that may appear in nearly any tissue. I have personally seen them in liver tissue when doing post-morteum exams. Once trapped in granuloma's, the larva can live for years occasionally escaping to become re-trapped in other granuloma's. During the last 1/3 of pregnancy this migration of these juvenile roundworms is greatly accelerated allowing them to find their way into the placenta and fetus or into the mammary glands to infect nursing puppies. When the bitch cleans the puppies she also may swallow infective eggs.
What are the signs of roundworm infestation?
Actually, adult roundworms do little damage. They do not attach to the intestine wall and drain the pet's blood or nasty things like that. They just move around in the intestine and eat some of the nutrients intended for the pet or brouse on the mucous lining the intestine wall. Occasionally they will cause irritation inside the intestine & transient diarrhea or if they are in great enough numbers they can actually block the intestine and constipate the anim. If they find their way up into the stomach they can cause the pet to wretch and vomit the worm up.
More important to the pet's health are the migrating juveniles. As they pass thru the liver and lungs they can cause verminous pneumonia or hepatitis. Signs of roundworm infestation include: dull hair coat, pot-bellied unthrify appearance, poor weight gain, vomiting, coughing, intermittant diarrhea or constipation. Heavily infested puppies or kittens occasionally die of worm-related pneumonia.
What is the treatment?
It is easy to get rid of roundworms in the intestine. Just give any oral wormer effective against roundworms. My favorite is any brand with pyrantel pamoate as the active ingredient. This is generally well tolerated by the pet, safe and effective, but... Once again the "migrating juvenile worms are the problem". Nothing at all will kill the juvenile worms trapped in granuloma's. It is best to worm breeding female dogs and cats before breeding and again 3, 6 and 9 weeks after welping. Juveniles migrating through the liver and lungs also will not be killed by conventional wormers. This is why we like to worm puppies and kittens twice three weeks apart and then check a fecal specimen three weeks later. This allows all migrating juveniles to reach the intestine where they are easily killed.
So what's the big deal with public health significance?
Here is where it gets a bit frightening! Roundworm larva have actually blinded young children and caused countless other problems. The humans most affected are children from early neonatal age to four or five years of age, however any age can be affected. Why is this? The secret lies in hand-to-mouth ingestion of roundworm eggs. Lets say the cat uses the sandbox for a litter area. Kids playing in the sand very easily can pick up eggs on their hands and where do their hands go? Right in the mouth without being washed.
Once the embryonated roundworm egg reaches the intestine of the human it hatches and the larva penetrates the intestine wall. From there it gains entry into the blood stream and may end up just about anywhere in the body including vital organs such as the eye, brain, liver, kidneys, heart wall, lungs, etc. Since humans are an unnatural host for the roundworm larva, their body reacts and walls off the larva in little granuloma's (similar to what occurs in adult dogs and cats). These granuloma's may cause sudden dysfunction of any of these organs resulting in illness.
The most often diagnosed illness is loss of sight in one eye. The roundworm larva is trapped in the optic disk behind the retina of the eye and a granuloma forms. These granuloma's have been mistaken for retinoblastoma's (cancer of the retina) and the eye was mistakenly removed. I believe the reason the problem is so often diagnosed in the eye is because we know it is happening. We experience loss of vision; the eye is removed and the larva is discovered.
Remember what I said above? When roundworm larva are encased in granuloma's they are impossible to kill with any anti-parasitic drugs and they are also impossible to detect. How many cases of persons seizuring with no apparent cause could be related to roundworm larva? It is impossible to know because the granuloma's are impossible to detect. We can't remove the brain and search for the larva microscopically.
I hope I didn't scare you by making you aware of this problem. The problem is rare, but it "can" happen at any time. This is an important reason for people to always wash their hands before eating or putting a finger in the mouth. Who knows, it could save your eye!
Be Safe - Be Sure - Have Your Vet Check Your Pet for Intestinal Worms Twice a Year!
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Sorry this happened to your baby.
