00:01
Let's move on to a slightly smaller
worm, these are the hookworms.
00:05
These are nematodes also,
and these are not ingested,
they penetrate your skin
and you don't even know it.
00:17
One of them,
they’re two species we will look at.
00:20
Ancylostoma duodenale,
sounds a little bit Italian but it's not,
Ancylostoma duodenale.
00:29
They're on the left
is a female worm
and on the right is a male worm,
so these worms reproduce sexually.
00:37
And the other species that is considered
a hookworm, Necator americanus.
00:45
Almost a billion hookworm infections
globally at this moment in time,
so this is again another
prevalent parasitic infection.
00:56
Let's take a look at the
lifecycle of necator americanus.
01:01
Let's start at a point where larvae
are entering your blood stream.
01:07
How do they do that?
You walk on land that is
contaminated with them
and they burrow into your
hair follicles on your feet.
01:18
Many people are not fortunate to
have shoes that protect their feet
and they walk in areas that
are fecally contaminated.
01:26
The human feces contain
the larvae of the hookworm,
they go to your feet,
they look for a hair follicle
which you can see in this picture,
they go down the follicle and
they get into your bloodstream
and you have no idea that this
is happening, you can't feel it.
01:43
So you know, in this course
we've talked a lot about
cooking your food and
watching what you eat.
01:48
Now you should watch where you
walk and wear shoes for sure.
01:51
So the larvae enter your bloodstream,
they enter your lung capillaries
and they do a similar
thing to the ascaris,
they then enter your
alveolar spaces,
they go from the capillary they
penetrate through into the air space,
they go up the trachea,
and where it joins
the esophagus,
they turn back down,
they are swallowed,
the worms mature in
the small intestine.
02:18
Some of the pathology associated
with infection is anemia
and the eggs are produced by
the adults in the intestine,
they pass out in the feces,
they end up in the environment,
on grass or on the dirt and the
next person who walks along,
of course the eggs hatch
and become the larvae.
02:38
The next person walks along
they get onto their feet
and go into their
hair follicles.
02:43
So in the days when
people defecated outdoors,
they would go out of
their home and find a tree
and defecate against the tree
and their feces
had worms in them.
02:55
And the next person would come
out and walk on the same ground
and the worms would
penetrate their feet.
03:00
This is a common
means of infection.
03:11
In terms of clinical disease,
because of the anemia,
that's one of the symptoms,
iron deficiency anemia
and failure to thrive,
if you acquire this infection as a child,
you will not grow properly.
03:23
Very easy to diagnose,
you look again in
the feces for eggs,
there are lots of eggs in
the feces just like ascaris,
and you can see them there
and these infections can be
treated with Mebendazole,
it can get rid of the infection.
03:37
So how do we prevent
hookworm infections?
It's very simple.
03:43
Go to the bathroom in a toilet.
03:46
In the 20th century the
outhouse was invented.
03:49
The outhouse is a place where
you can go to the bathroom,
now we have plumbing and
toilets and so forth,
which brings the feces
away from where we live,
so we don't infect ourselves.
03:58
But in many parts of the world,
there was a time when we
didn't even have an outhouse
and people as I said went to
the bathroom in the woods.
04:06
Why is an outhouse work?
It turns out that the hookworm
larvae can travel about four feet,
so if you dig a six foot pit
under the toilet in the outhouse,
that is too deep for
the larvae to come up
and get into the next person who
is sitting there in the outhouse.
04:28
Six feet was the key.
04:30
Six feet down,
the larvae die and they never get up,
they can go four feet in any
direction, up or down or sideways,
but not six feet, so the outhouse solved
the problem of hookworm infections
in the southern United
States for many years.
04:44
Around the Civil War,
many many hookworm infections,
and then the outhouse was
built and it took care of them.
04:51
Very interesting way to
take care of an infection.