Parasitology and the Protozoans
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kjordan9097 on September 29, 2011
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28 terms
Terms | Definitions |
|---|---|
 Parasite | organism that lives on or inside of a host. Is metabolically dependent on the host. |
| Vector (biological) | organism that transmits the parasite to humans, usually an arthropod (insect) |
| Incidental parasite | organism that doesn't usually infect humans (maybe infect horses or dogs) |
| Reservoir host | organism that harbor same stage of parasite found in humans - serves as a reservoir for possible transmission |
| definitive or final host | harbors the adult (sexually reproducing) stage of the parasite |
| intermediate host | organism harbors immature (asexually) reproducing stage of the parasite |
| fomite | inanimate object that transmits disease |
| Life cycles - Parasitic organisms exhibit two types of life cycles: | 1) Simple/direct life cycle 2) Complex life cycle note - sometimes host provides hormone to progress to next stage in development in life cycle |
| Simple/direct life cycle | Many of the protozoan parasites have simple life cycles (for example, Entamoeba histolytica and Giardia lamblia). In the simple life cycle the parasite is transferred from one host to another without the involvement of another organism such as an intermediate host. In the case of entamoeba histolytica a human becomes infected when they ingest the cyst form of the protozoan in fecal contaminated water or food. |
| Complex life cycle | Some protozoan parasites (ex. Plasmodium spp.) and many of the helminths have complex life cycles. One or more intermediate hosts are involved in complex parasitic life cycles. Refer to the life cycle of D. caninum for an example of a complex life cycle. Usually dogs and cats are infected. |
| Protozoans (Survey of some parasitic protozoans) | 1) Phylum Sarcodina 2) Phylum Mastigophora 3) Phylum Ciliata 4) Phylum Sporozoa |
| Phylum Sarcodina - The amoebas. Motile by means of pseudopods (extensions of cytoplasm). | Entamoeba histolytica |
| Entamoeba histolytica | Causes amoebic dysentery. The only amoeba that can cause intestinal parasite in humans. Cosmopolitan - 10% of the world population are infected - 85-95% of them infected are asymptomatic = normal flora. But sometimes it's a big problem, most of the time they don't kill their host (they need the host to continue living) they just suck the life blood out of the host. When entamoeba become invasive they produces proteolytic enzymes - literally digest host tissues. they digest holes I the lining of the intestine over a period of time they produce an ameboma - (flask shaped lesions) * Life cycle stages - trophozoite and cysts - trophozoit has a large sucking disc on its back side, this is used to attach to lining of intestine * Symptom 1) - clinical dysentery -diarrhea plus blood and mucus - from holes in the intestine, when irritated - the body makes more mucus * Symptom 2) abdominal pain and gas * Symptom 3) secondary infection oft those lesions with normal flora accompanied by a fever * Symptom 4) hepatomegaly - swollen and tender liver because it has a tendency to end up in the liver which makes the liver very unhappy * To avoid infection with E. histolytica - don't drink the water. * Treatment - Flagyl (metronidazole) - flagyl is a potential carcinogen if used in high doses, but worth the risk if you make sure you have it. Very useful drug - treats bacteria in low dose and parasitic - quite difficult to cure, needs a high dose for a long course - potential carcinogen. |
| Phylum Mastigophora | The flagellates. Motile by means of flagella. Examples: Giradia lamblia Trichomonas vaginalis Trichomonas vaginalis |
| Girdia lamblia | Causes giardiasis and/or giardial malabsorption syndrome. Most common intestinal parasite in humans because there are many animal reservoirs. Can get from contaminated mountain water and sometimes well water. * Life cycle stages - tropozoite and cyst (when you have a tropozoit and a cyst it is always the infective stage) incubation typically last 7-15 days * Symptoms - diarrhea (abundant) foul smelling, grey or orange in color, high fat content (a layer of oil on surface of toilet water because it is high in lipids because of the malabsorption syndrome) * Treatment - flagyl (metronidazole) |
| Trichomonas vaginalis | Causes trichomoniasis, a disease that is usually an STD 80% of infected women are asymtematic for significant amount of time, months to years, but she is actually infected Men take a few days to show signs Symptoms - Women - vaginal discharge, red spots, painful itching of vaginal mucosa Symptoms - Men - dishcarge from penis, irritation and painful itching of penis Treatment - Same as for Entamoeba - Flagyl / metronidazole |
| Trypanosomes - | Blood tissue flagellates that are leaf-shaped. Their morphology is efficient for moving through the circulatory system. The trypanosomes are vectored to humans by a blood-sucking arthropod. The trypanosomes are pleoorphic (many shapes) and have several stages in their life cycle. we viewed the tryptomastigaote stage in the lab. They have complex life cycles. Examples - Trypanosoma gambiense, Trypanosoma rhodiense, Trypanosoma cruzi |
| Trypanosoma gambiense and Trypanosoma rhodiense | Both cause the disease African sleeping sickness. Vector - tse-tse-fly symptoms - incubation is variable, severe headache, apathy-no energy, over period of months expect convulsions, sleep more and more of the time, without treatment death occurs 2-3 years Treatment - Melarsprol |
| Trypanosoma cruzi | causes the disease known as Chagas disease AKA American trypanosominasis. Vector - kissing bug (not fly) Symptoms and development of Chagas disease; Human bitten by fly (and pooped on!) --> Incubation --> development of a chagoma (painful, red chancre) (this is where the disease ends for some people - their immune system eliminated the parasite) if not Lymphatic stage can live months to years if not treated acute stage - a stage of the parasite called the amasitgote is encysted in muscle tissue throughout body, especially the heart. This leads to weakening of the heart and possible death years after the initial infection - painful people die of heart failure due to weakening of the heart from the bugs Treatment - same as for African sleeping sickness - Melarsprol |
| Phylum Ciliata - The Ciliates | Motile by means of cilia. The Ciliates are the most highly evolved protozoans. Most can reproduce asexually (fission) and sexually (conjugation). |
| Balantidium coli | Example of Phylum Ciliata - The only ciliate that occasionally parasitizes humans. When it does it causes balantidium dysentery. Life cycle - simple life cycle - trophozoit and cyst (infectious) Symptoms - dysentery Treatment - Flagyl |
| Phylum Sporozoa - The Sporozoans | Non-motile when mature. The sporozoans are obligate (they have no other choice) intracellular (reside inside host cells) parasites. They have complex life cycles and many are vectored by a blood sucking arthropod. mosquito bites 1st person -->develops blood --> bites 2nd person and infects them |
| Plasmodium spp. (example of Phylum Sporozoa) | Four species cause malaria in humans. They reproduce asexually (schizogony - multiple fission - parent cell divides to form more than two daughter cells) and sexually (produce male and female sex cells called gametocytes). Vector - Anopheles sp. (mosquito) Life cycle stages - sporazoite - infectious stage Treatment - Quinine |
| Toxoplasma gondii | a fairly cosmopolitan parasite that usually causes a mild, even asymptomatic (sometimes) disease in which the patient experiences mild chills, fever and a rash called toxoplasmosis. 30-50% of the population may be infected. Life cycle stages - total life cycle can occur in cats oocyst -->transferred feces of cat --> wash your hands Treatment - Toxoplasmosis is also very serious in severely immunocompromised individuals (advanced AIDS and cancer patients). These are usually the only individuals who are treated (will cause serious disease of blood vessels. In previously uninfected pregnant women - if the woman was infected before - no issues - but if new, after she is prenant it crosses the placental barrier, enters the neurosystem - miscarriage of fetus or neuro damage such as spina bifida or hydrochepalasis (water on the brain) or baby may not survive after birth. (no drugs given to pregnant women) Drugs used - pyrimethamine or trisulfapyrimidine Because it is a relatively common infection the spinal fluid of miscarried fetuses are checked for Toxoplasma ( when practical). |
| metabolic dependence | 1) nutrition 2) developmental stimulus 3)co-factors and enzymes (vitamins) |
| Helminth | multicellular parasitic organisms (i.e. tapeworms, ringworms) AKA the worms |
| Most of the parasitic protozoans and a few helminths have what type of life cycle? | most of the parasitic protozoans and a few helminths have simple/direct life cycles. no vector involved in simple. Example of complex is malaria which is infected human --> mosquito --> another human |
| Protozoans (general info) | 1) symptoms - clinical dysentary - diarrhea plus blood and mucus - from holes in intestine - when irritated body makes more mucus 2) abdominal pain and gas 3) seconday infection of those lesions with normal flora accompanied by a fever 4) hepatomegaly - swollen and tender liver because has tendency to end up i the liver - unhappy liver |
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