Alright, back to roundworms.
(nematodes or roundworms),
the example is
Up to 25% of the
has these worms
in your intestine.
Do you have one?
It's a good chance that you might,
depending on where you live,
you could look at this map and see the
parts of the world that are heavily
infested, Ascaris Lumbricoides.
Now if you have
one or a few worms,
you'll probably be okay,
you won’t have symptoms perhaps
and you wouldn't even know it, you might
live many years with such worm in you,
maybe one day it will pass out
of you and you'll be surprised.
On the other hand, you may have many
worms, by repeated infections,
in which case you will have serious
illness and we will talk about this.
Now here is a photograph I love,
which a colleague of mine gave to me,
this is a jar of ascaris adults,
so look closely at this
jar, it is a big jar,
you can see the size by the
stack of books next to it.
Alright, it looks like a foot or two
high, couple of gallons of liquid in it
and it is full of these ascaris roundworms,
you can see the individual worms,
looks like there's a thousand or more worms
in that jar, so where did these come from?
They're preserved in
formalin so they don't rot.
They came from people in a
small village in Bangladesh.
What happened is a few doctors and
scientists went to this village,
they gave the inhabitants of the
village a drug to kill the worm
and when the worm is dead,
it passes out of the intestine
and they collected all the worms
that the people in this village shed
in this day of treatment and
they put them in this jar.
So many, many villages have
this high burden of infection
and here in more developed countries
perhaps, you won’t have this,
but in other parts of the
world it's quite common.
So let's take a look at the
life cycle of an ascaris infection.
It typically begins when we
ingest the egg form of the worm
and we acquire this by fecal
contamination of our food and water.
So we eat the eggs, they are very
small, we can't see them,
they go into our stomach,
they pass through the stomach into
the small intestine where they hatch.
The eggs hatch,
they become larvae
and these penetrate the intestinal
wall and enter the bloodstream.
And then they go to the liver,
as all good things do when
they pass through the blood.
They migrate to the heart and eventually
are pumped through the lung capillaries.
In the capillaries they make
their way to those capillaries
that wrap around the alveolar spaces,
the terminal sacs of the lung,
that's where gas
exchange takes place,
so the capillaries are in
close proximity to the alveoli
and what do these tiny worms do?
They pierce their way out of
capillary into the airspace,
so now they're out of the blood,
they're in your lung, and what do they do?
They wiggle their way up into
the bronchi and the trachea,
all the way up to the
back of your throat.
So these little worms
are crawling up there
and then what happens,
you swallow them
and they go down
to your intestine.
They've been there before, that's right,
the first time they were just hatching,
this time they're going
to colonize your intestine
and grow into some of those large
adults that we saw in the photograph,
and the adults mature in your small
intestine and as I said if you have one,
it's not much of a problem, but the small
intestine is not very big in diameter
and if you have many worms,
this can be a problem.
It can obstruct your small
intestine and you will have disease.
These worms can also make
their way to the bile duct,
where the bile duct comes from the
gallbladder through the small intestine,
they can penetrate that and
clog it up and cause pathology,
as well as a consequence
of the obstruction.
So that is the
life cycle of ascaris
and it starts all over again,
you have worms in
they are producing eggs,
which you shed in your feces
and those eggs then contaminate
someone else's water or food
to start the cycle
all over again.
Fruits and vegetables
commonly can be contaminated.
In many countries where
ascaris is prevalent,
human feces are
used as fertilizer
because it's nutrient rich,
it's taken and spread over the fields,
it gets on the
leaves and the fruits
and in it are eggs of
ascaris, they are very stable
and then you go to eat them
without cleaning them very well,
bingo you have another
So you can see how you could get
many, many worms in you,
if you keep eating eggs
over and over again,
each one gives you a new worm and
you get multiple worms in you.
So light infections are
but the worms themselves as you get more
and more can cause biliary obstruction
or inflammation of
So the more worms the more problems
you have, heavy infections,
malnutrition, you can't absorb the food,
the worms are blocking the intestine,
bowel obstruction, you can't
defecate, aberrant migration.
So many worms are really problematic
and you need to get rid of them.
Now here is a very unfortunate little
girl whose belly is full of worms.
Look at the poor thing,
so sad whenever I see this picture,
she has been contaminated
over and over again;
she's obviously living in unsanitary
conditions where her food and water
is contaminated with ascaris eggs,
so she has many, many eggs in her belly.
You can see how swollen
and distended it is.
Now fortunately we
can take care of this.
This child was given an anti-ascaris
drug that kills the worms,
makes them leave her intestines
and here is the result.
They were all collected
and now she's better.
Look at all that worms,
all those worms that came out of her.
Unfortunately she will get
infected again and again,
because her lifestyle
She continues to eat
If the worms happen to
leave your intestinal tract
and penetrate other tissues,
which can happen
from time to time,
this can be fatal,
here's an example
of someone's liver filled
with ascaris worms.
This is someone who died
as a consequence of having
so many worms in the liver,
which disrupts the tissue
and its function, it's fatal.
Alright so how do you diagnose
and treat this infection?
Diagnosis is very simple,
you get some stool from a person
who has a swollen abdomen,
who you suspect has ascaris
and you look and you will see the
eggs of the ascaris in the stool.
Each adult female releases 200,000
eggs a day in your intestine.
One female, so if you have
10, well 2 million eggs a day,
you can certainly see that in someone’s
stool without being very skilled.
You can treat these infections
with a variety of drugs
that will cause
the worms to leave,
mebendazole, albendazole, ivermectin,
nitazoxanide and other drugs.
The thing is, you usually don't
treat unless you have lots of worms
and you have a swollen
belly or other symptoms.
I should point out that ivermectin
was discovered by William Campbell.
He was awarded the Nobel
Prize for that discovery.
Mebendazole selectively depolymerizes
so worms are invertebrates;
they have no vertebral column,
so this is a rather
How do we prevent infection?
Very simple, but not so easily achieved.
Sanitary disposal of feces,
keep human feces away from
your food and your water
and don't use it to
fertilize your crops.
Unfortunately in many parts of the
world, this simply isn't possible.