Guest Post: The Roundworm Toxocara (part 1: pets and people)

Time to cap off our Intestinal Issue month at Embrace with an article on worms. Who better to write the post than someone who knows much more than I do (which is pretty well everyone!); hence a guest post by Dr. Anna M. van Heeckeren, founder and Executive Director of The van Bakeren Foundation.

Anna had so much "juicy" content, I split it into 2 posts. This one on roundworm in pets and people and tomorrow's on roundworm prevention and treatment. Now over to Anna...

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As a veterinarian researching and blogging about the problem of diseases that are spread from animals to people (zoonoses), I am happy to give you the straight poop about roundworms (pun fully intended).

What is the roundworm Toxocara?

It’s one of the parasitic intestinal worms that make us squirm at The van Bakeren Foundation. The reason we care about this creepy crawly is that Toxocara is the most common roundworm found in our pets and can accidentally be spread to people, causing some rather nasty consequences. So let’s find out more so we can protect our pets, our families, and ourselves.

What are the symptoms in pets?

It depends. According to the Companion Animal Parasite Council (the leading expert in providing veterinarians with guidelines about getting rid of parasites like roundworms affecting dogs and cats) most of the time you can’t tell by looking at them that they are infected; however, dogs and cats with lots of roundworm (usually puppies and kittens) commonly lose weight, their fur looks dull, and they may have a potbellied appearance. Your dog or cat may cough if the roundworms move into the lungs (which is one step to the roundworm becoming an adult). Also, you may notice the adult roundworms in your dog or cat’s poop or after they throw up. Yes, it's pretty gross!

What do roundworms look like?

The adult worms (pictured to the right) look a bit like spaghetti (the boys are smaller than the girls) that live in the intestines of dogs and cats; they are white or light brown in color and may be several inches long (hopefully I haven’t stopped you from ever wanting to eat pasta again!)

The adults lay a lot of eggs, which are also found in the animal’s poop. These eggs are very small (like a pinprick) so you cannot see them easily without the help of a microscope (pictured to the left).

They almost look like very small hen’s eggs with the yolk inside. After a week or so (depending on the specific kind of roundworm), these eggs become what’s called “infective.” (pictured to the right)  That is, the egg contains a young, immature roundworm, or larva, and then if accidentally eaten the worms can cause disease. That’s why it’s so important that you pick up after your cat or dog as soon as possible (daily is best). The bad news is that the infective eggs can live in the environment for a very long time (years), and are very hard to kill.

(pictures courtesy of CAPC)  

How do roundworms spread to dogs and cats?

Usually, it is something they accidentally get from their mother when they’re puppies or kittens. So you might ask - how many puppies and kittens are infected with roundworms? The answer is nearly all of them! That’s why the Companion Animal Parasite Council recommends treating puppies and kittens with worming medications that you can get from your veterinarian.

Dogs and cats can also get infected again by eating dirt containing the microscopic eggs, or by eating small animals like mice that are infected with roundworms. The Companion Animal Parasite Council recommends treating dogs and cats once monthly with worming medications that you can get from your veterinarian. Adult pets are much less likely to be infected (as few as 2.6% or 2-3 out of 100 of owned pets), especially if they see a veterinarian regularly. Homeless animals are much more likely to be infected.

How do roundworms spread from animals to people?

Usually it’s through indirect contact. That is, usually people accidentally eat dirt contaminated with infective roundworm eggs where dogs and cats have been pooping.

Who tends to get infected with roundworms?

Usually children ages 2-6 years old; however, people who cannot naturally fight off infections very well, otherwise known as those who are “immunosuppressed.” This would include the very young (i.e. children), pregnant women, people taking chemotherapy for cancer treatment (a.k.a. chemo), and the elderly (guess that would depend on your definition of elderly) can also be infected.

How many people get infected with roundworms?

The Centers for Disease Control and Prevention (CDC) are concerned about this often overlooked disease called toxocariasis because it’s more common than you may want to know. They cite research indicating that about 1 in 7 people (about 14%) in the United States are infected with Toxocara (or rather, have been exposed to it and their body’s immune system is fighting off the infection).

While this is very scary to learn, luckily it’s not too common that people have any problems if infected; one study indicates that up to one person out of 1,000 infected people actually get any signs of disease; however, in those few cases the disease symptoms can be terrifying, such as seizures and blindness, from worms penetrating the brain and eyes. It’s better to be safe than sorry and prevent from getting infected in the first place.

Which is our topic for tomorrow. Stay tuned...

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Dr. Anna M. van Heeckeren has degrees in biology, genetics, and veterinary medicine. She is founder and Executive Director of The van Bakeren Foundation, a 501(c)(3) public non-profit with a mission to prevent the spread of diseases between animals and people through research, education and outreach, and providing veterinary medical care to animals in underserved communities using a One Health approach. She is also Chair of the American Veterinary Medical Foundation, which is committed to embracing and advancing the well-being and medical care of animals. She lives her husband Ned and two children Marta and Elise, along with her two cats, Bing (pictured with Anna) and Eva (camera shy), her rabbit Wallace, and several fish.