Cyclospora – Protozoa (GI Infection)

by Sean Elliott, MD

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    00:01 Cyclospora. A parasite.

    00:04 The Cyclospora are also in the genus of Eimerildae family, Say that three times fast.

    00:10 And if you've watched the session on isospora, you'll see a lot of similarities.

    00:15 In fact, these all behave exactly the same.

    00:18 The Cyclospora are also a coccidian protozoan parasite, such as you see on the image in front of you.

    00:25 A very densely-walled structure for a parasite.

    00:30 The Cyclospora undergo a fecal-oral spread of the oocysts for their transmission, very much like most of the parasites that we talked about.

    00:39 So they come from dirty or contaminated water and are ingested by their host.

    00:45 Incubation after that ingestion typically is for 2-11 days, depending probably on the load the amount of Cyclospora oocysts that are ingested.

    00:56 The typical human pathogen that we talked about is Cyclospora cayetanesis.

    01:02 Say that three times fast as well.

    01:14 So, if you will, if you haven't already, I urge you to do so.

    01:18 But to look at several slides from the isospora lifecycle, because we'll describe the same process here, but in bullet form.

    01:28 So the oocysts are ingested and assist sort of excysts itself.

    01:34 It opens up to release two sporozoites.

    01:36 These attach as a primary infection stage to the brush border of epithelial cells in the gastrointestinal tract.

    01:45 Next, those intracellular spores.

    01:48 So they enter into the cytoplasm of their target cell.

    01:52 They undergo asexual reproduction to create merozoites.

    01:56 The merozoites excyst.

    01:59 So they exit or lyse their host cell, creating a first stage in inflammatory reaction, and then autoinfect.

    02:08 So within the lumen of the gut, they will then target another epithelial cell, enter the cell, the cytoplasm of the cell, and then go to sexual reproduction, to create first zygote, and then together and another oocyst.

    02:22 The oocyst, then ruptures that host cell.

    02:26 So that's two rupture steps, two lytic steps after the asexual, and then after the sexual reproduction stages, and the cysts will either passage into the stool or potentially autoinfect again, further down the intestine.

    02:41 So the system cells undergo a sporulation step outside the human body.

    02:47 So it's not our problem, although, we've already had plenty of problem with the initial stages of inflammation, but ultimately, the cysts then become infectious, contaminating the water and another host or another victim can become infected.

    03:03 So diagnosis for Cyclospora is to demonstrate presence of the oocysts in stool.

    03:10 And it's important and somewhat difficult to distinguish the appearance of those cysts from other possible pathogens, especially including Cryptosporidium parvum.

    03:21 There are then clinical manifestations which are important to distinguish, although believe it or not, they are very much like other parasitic gastrointestinal infections.

    03:31 So because of the rupture of the cells, there is ongoing sort of scarring of the tissues, and the gastrointestinal epithelial cells lose the ability to absorb water and nutrients as well as they did.

    03:45 So the diarrhea associated as with others, is watery, it's a water loss malabsorptive diarrhea, and it also is associated with loss of fat and some protein.

    03:59 Now, as with other parasites, there are still normal bacterial flora, which are able to process this new load of food.

    04:08 And so one gets gas production, crappy abdominal pain, bloating, and because of loss of appetite and malabsorption, weight loss.

    04:17 So there is a flatulence along with the nausea and fatigue.

    04:21 Low-grade fever is really a byproduct of this low level inflammatory reaction to to sequential epithelial cells being ruptured by the process of the parasite.

    04:33 Treatment.

    04:34 Well, fortunately, Cyclospora infections are usually self-limited, lasting up to 10 to maybe 14 days at the most.

    04:42 So treatment could be just supportive.

    04:45 So providing fluids, providing nutrition, and then providing lots of comfort and solace.

    04:51 For those severe cases that are not getting better and certainly for those patients who are immunocompromised in any way, then use of a sulfonamides, such as trimethoprim-sulfamethoxazole is effective.

    05:04 So cyclosporiasis or Cyclospora-associated gastrointestinal disease is another nasty associated with contaminated water.

    05:14 The key things to remember about this particular parasite are that it is coccidian in nature and it undergoes both asexual and then sexual replication steps with autoinoculation or autoinfection occurring in between.

    05:28 Again, watch what you drink.

    About the Lecture

    The lecture Cyclospora – Protozoa (GI Infection) by Sean Elliott, MD is from the course Parasites.

    Included Quiz Questions

    1. Eimeriidae
    2. Cryptosporidiidae
    3. Cayetanensis
    4. Coccidia
    5. Cercopitheci
    1. ...2.
    2. ...1.
    3. ...3.
    4. ...4.
    5. ...5.
    1. Merozoite
    2. Sporozoite
    3. Trophozoite
    4. Schizont
    5. Zygote

    Author of lecture Cyclospora – Protozoa (GI Infection)

     Sean Elliott, MD

    Sean Elliott, MD

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