0:00 Parasites are microorganisms that live on the living host and drive nutrition 0:09 from them 0:10 without any benefit to the host. 0:13 Parasites can cause harm to the infected host. 0:17 The host is defined as an organism such as you or me or even the dog where the 0:22 parasites 0:23 can live in or on. 0:26 There are parasites everywhere and some common ones include interobvious vermic 0:31 ulares which 0:32 is the pinworm parasite that causes the itchy bum and plasmodium the parasite 0:37 that causes 0:38 malaria. 0:44 We will mainly focus on parasites which causes infections in humans and there 0:51 are three main 0:52 classes of these parasites, these are protozoa, helmines and ectoparasides. 1:00 First of all, parasites can be described based on a few characteristics. 1:06 Human parasites can either be unicellular or multicellular. 1:11 Unicellular include protozoa meaning that they are made up of one single cell. 1:18 Parasites can also be described as living inside the host termed endoparasides 1:31 such 1:31 as entomiba histolytica, jiardia and helmines or parasites can live on the host 1:39 surface 1:40 and these are termed ectoparasides such as lysetics and mites. 1:45 So let's learn a bit more about the three classes of parasites that infect 1:52 humans, beginning 1:52 with protozoa. 1:55 Protozoa are unicellular microorganisms. 2:00 Protozoa can be either free living or parasitic in nature meaning they can live 2:05 in the environment 2:06 without a host or they can be parasitic in nature and infect a human or an 2:12 animal. 2:13 Protozoa are defined as having no really cell wall and are typically classified 2:18 based on 2:18 their mode of movement. 2:21 You have amoeba, proper term sarcodina, an example of this is intomiba histolyt 2:29 ica. 2:29 You have the flagellates, also known as mastagofora and these include jiardia 2:38 and lishmania. 2:41 You have the ciliates or the ciliophora which include valantidium. 2:49 And finally you have the sporozoa, the apecomplexa and these are organisms 2:55 whose adult stages 2:57 not really motile and they include plasmodium, cryptosporidium and taxoplasm 3:05 osis. 3:06 There will be separate videos that look into each of these protozoa parasites 3:10 in more detail. 3:16 The next class of parasites are the helminths. 3:19 When you think of helminths you should think of worm parasites. 3:23 Helminths comes from the Greek word helminths which means intestinal worms. 3:27 Today they refer to worms that cause problems in the intestines but also other 3:32 organs such 3:32 as the lungs and the liver. 3:35 Helminths are large multi cellular organisms that are generally visible to the 3:40 naked eye 3:41 in their adult stage. 3:43 Like the protozoa helminths can be either free living or parasitic in nature. 3:49 In their adult form helminths cannot multiply in humans. 3:54 Helminths are classified again into three main groups. 3:59 These are the flukes, also known as trematodes. 4:04 Adult flukes are leaf shaped flatworms. 4:09 Then you have tapeworms called cestoidies. 4:15 Cestoidies or tapeworms are elongated segmented flatworms that inhabit the 4:23 intestinal lumen. 4:25 It is important to know that flukes and tapeworms are both types of flatworms, 4:30 they are flat. 4:32 The last group of helminths are the roundworms called nematodes. 4:38 Roundworms are cylindrical worms, they inhabit intestinal and extra intestinal 4:44 site. 4:44 Examples are the pinworms, enterobius vermiculares that cause the itchy bum 4:49 that people get. 4:52 Endoparasites are typically referred to as endoparasites, because they live 4:57 inside the 4:57 host. 4:59 Endo is the Greek word for within, so endoparasites means parasites within the 5:04 body. 5:10 And this brings us to the third class of parasites, which are your ectoparas 5:17 ites. 5:18 And ectoparasites, on the other hand, live on the host outside. 5:22 Ecto is Greek for outside, so ectoparasites are parasites which live outside 5:27 the body. 5:28 Ectoparasites typically refer to parasites which attach or borrow into the skin 5:32 and remain 5:33 there for relatively long periods of time. 5:35 They often cause intense itchiness, causing considerable annoyance and 5:40 discomfort. 5:41 Examples of ectoparasites include scabies, the common bed bug, fleas and lice. 5:48 This vast majority of ectoparasites are othropods or insects. 5:52 Many ectoparasites are vectors for other pathogens, which means they can carry 5:57 other pathogenic 5:58 organisms, such as bacteria, for example. 6:01 These other microorganisms, such as the bacteria, are then typically 6:05 transmitted when the ectoparasites 6:07 are feeding on or from the host. 6:12 So in terms of pathophysiology, parasites are distributed worldwide, although 6:19 the tropical 6:21 latitudes are disproportionately affected. 6:25 Parasites can invade the human body in different ways, through the oral root, 6:30 the skin, arthropod 6:31 vectors or sexual contact. 6:35 Arthropod vectors include mosquitoes, fleas, sandflies, lice. 6:40 Parasites transmit parasites by injection into the bloodstream of the host 6:45 directly via the 6:46 salivary gland. 6:53 When a parasite enters the body, or the bloodstream in this case, the host 6:57 defense has a mechanism 6:59 consisting of innate immune systems, which mediates initial protection against 7:04 the infection, 7:06 and then the adaptive immunity, which is more effective. 7:09 Once the parasites have invaded, innate host defenses, adaptive cellular and 7:14 humoral immune 7:15 responses are promoted against a wide array of antigenic components of the 7:22 parasites, and 7:24 this will cause an inflammatory response. 7:31 Investigations when suspecting parasitic infection. 7:35 Well, to diagnose parasitic infections, you need to identify if a parasite is 7:40 present, 7:40 and this can be either through identifying ova, the parasite's eggs, larvae, 7:47 which is 7:47 an immature worm form of the parasite, or identifying the adult parasite itself 7:54 . 7:55 And you can identify each of these either in stool, blood, or tissue. 8:02 And you identify it through a microscope, for example, as well as stains. 8:07 There's also other investigations such as looking for presence of antibodies in 8:11 serum 8:11 against those specific parasites. 8:14 Nowadays, you can look at parasite antigen and DNA material to identify 8:20 parasites within 8:21 the body. 8:23 For example, you can look at genetic material in the stool or in the blood, and 8:28 this is 8:29 the stool PCR, or blood PCR. 8:32 Finally, sometimes gastroscopy and colonoscopy is used for parasites that 8:36 infect the gastrointestinal 8:38 tract, including trying to identify helmets and giadiolamblia. 8:45 During the endoscopic procedure, specimens can be collected and then analyzed. 8:50 There is a blood test which may identify presence of ease and aphyllia, and it 8:54 can be common, 8:55 however, it's mostly seen in multicellular parasitic infections, as they're 9:00 migrating 9:00 into host tissue. 9:03 Treatment of parasites will depend on what the actual cause is, but typically 9:07 anti-parasitic 9:09 medications are used. 9:15 So in summary, parasites are microorganisms that live on a living host and 9:19 derive nutrition 9:20 from the host, without any benefit to them. 9:25 This can also cause harm to the infected host. 9:29 There are three classes of parasites that infect humans. 9:32 These include protozoa, helmets, and ectoparasides. 9:37 Thank you for watching.
