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Hookworms

by Vincent Racaniello, PhD
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    00:00 your crops. Unfortunately in many parts of the world, this simply isn't possible.

    00:00 That is ascaris, let's move on to a slightly smaller worm, these are the hookworms.

    00:07 These are nematodes also, and these are not ingested, they penetrate your skin and you don't even know it. One of them, they’re two species we will look at, Ancylostoma duodenale, sounds a little bit Italian but it's not, Ancylostoma duodenale. There on the left is a female worm and on the right is a male worm, so these worms reproduce sexually. And the other species that is considered a hookworm, Necator americanus. Almost a billion hookworm infections globally at this moment in time, so this is again another prevalent parasitic infection. Let's take a look at the lifecycle of necator americanus. Let's start at a point where larvae are entering your blood stream. How do they do that? You walk on land that is contaminated with them and they burrow into your hair follicles on your feet, many people are not fortunate to have shoes that protect their feet and they walk in areas that are fecally contaminated.

    01:27 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. So you know in this course we've talked a lot about cooking your food and watching what you eat. Now you should watch where you walk and wear shoes for sure. 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, where it joins the esophagus, they turn back down, they are swallowed, the worms mature in the small intestine. Some of the pathology associated with infection is anemia, shown on this slide, a reduction in the number of red blood cells 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 at the larvae, the next person walks along they get onto their feet and go into their hair follicles. 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 and the next person would come out and walk on the same ground and the worms would penetrate their feet. This is a common means of infection. 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. 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.

    03:34 So how do we prevent hookworm infections. It's very simple. Go to the bathroom in a toilet. In the 20th century the outhouse was invented. 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. 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. 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. Six feet was the key, 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 around the Civil War. Many many hookworm infections, and then the outhouse was built and it took care of them. Very interesting way to take care of an infection.


    About the Lecture

    The lecture Hookworms by Vincent Racaniello, PhD is from the course Parasites.


    Included Quiz Questions

    1. Anemia
    2. High fever with chills
    3. Jaundice
    4. Rhinitis
    5. Conjunctivitis
    1. 4 feet
    2. 2 feet
    3. 18 feet
    4. 24 feet
    5. 30 feet
    1. Mebendazole
    2. Itraconazole
    3. Methotrexate
    4. Propranolol
    5. Aspirin

    Author of lecture Hookworms

     Vincent Racaniello, PhD

    Vincent Racaniello, PhD


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