Trichinella spiralis and Trichinosis (Nematodes) – Helminths

by Vincent Racaniello, PhD

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    00:01 Let's move on to another helminth or worm infection, this one Trichinella spiralis.

    00:09 Trichinella spiralis is acquired by eating undercooked meat containing the cysts of trichinella, and a common theme, if you've listened to many of the videos that I have prepared for you, is that you have to be careful what you eat and how you cook it for sure. The kinds of meat that typically will harbor trichinella include pork, and of course pork is raised on farms and prepared for us, but also wild meat, wild pigs and bears, many people around the world like to catch these animals and eat them. Even polar bears, the Inuit's like to eat polar bears and there have been outbreaks of trichinella associated with eating polar bears in those populations. How do you acquire this infection? You eat undercooked meat, the meat contains larvae. We will see how those larvae get there in a moment. If you cook the meat really well, you will get rid of the larvae, alternatively, if you freeze your meat before cooking it, you kill larvae, so you can have rare-ish pork now, as long as the meat was frozen before you cook it. You eat the meat containing the larvae, the larvae go to your stomach, there your digestive juices release the larvae from the shell that they are in called the nurse cell and they moved through your stomach into your small intestines. There the adults mature and they live in your small intestine and there they mate and the female sheds newborn larvae that then enter your lymph circulation or your blood circulation and these worms can move to other tissues like the CNS, and the heart, and they can cause problems there, problems to your CNS and heart failure as well. The larvae are circulating through you and among the other places they like to go are muscle cells. The larvae penetrate the muscle cell and they curl up in a structure called a nurse cell. And there the larvae matures, and there it is forever. So if you eat trichinella contaminated meat and you survive the infection, you will have larvae in nurse cells in your muscle for the rest of your life. And as long as no one eats you, you won’t transmit the infection. But if this is a pig in which this cycle is occurring, of course the pig will be eaten and that is how the infection is transmitted. So the nurse cell complexes that remain viable in muscle specifically and if that is eaten, then it's transmitted to the next host. But as I've said humans don't eat each other, so we don't transmit it to other humans, but we certainly acquire this from animals. So there you go that's the lifecycle, again transmitted by undercooked meat. Now these Trichinella go through a cycle that involves intestinal passage into the blood and the formation of a cyst in the muscle. So if you reach again the cyst stage in the muscle, you've survived infection, but you can be killed earlier if worms get into other tissues.

    03:31 Some of the symptoms include diarrhea, abdominal pain, as these worms are moving about in your abdomen, muscle pain when the worms penetrate your muscle but once they form a nurse cell that goes away, and headache if they happen to enter your brain. As I said the worms can involve the heart and central nervous system, especially in cases where you've ingested more larvae, some meat can be more contaminated than other meats, and if you get a big dose of nurse cells, you can have more serious disease. How do you treat trichinella? So if you catch it early, you can treat it with albendazole, mebendazole and this will kill the adults that are in the intestine, but if you've passed that phase and now you have cysts, it will not kill the cysts. So you can get rid of the adults, so you can stop shedding eggs, but you won't get rid of the cysts in your muscle, you will live with those for the rest of your days.

    About the Lecture

    The lecture Trichinella spiralis and Trichinosis (Nematodes) – Helminths by Vincent Racaniello, PhD is from the course Parasites.

    Included Quiz Questions

    1. By eating uncooked meat
    2. By eating uncooked vegetables
    3. By drinking contaminated water
    4. Through skin penetration
    5. By eating uncooked rice
    1. Low pH in the stomach
    2. Macrophages in the small intestine
    3. Autolysis in the esophagus
    4. High pH in the stomach
    5. Enzymes released by neutrophils in the blood
    1. Muscles
    2. Liver
    3. Lungs
    4. Heart
    5. Kidney

    Author of lecture Trichinella spiralis and Trichinosis (Nematodes) – Helminths

     Vincent Racaniello, PhD

    Vincent Racaniello, PhD

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