Parasitology
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| obligate | when an organism can live only in association with a host
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| facultative | when an organism can live both in or on a host as well as in a free form
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| those that benefit from the host without causing it any harm are known as | commensals
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| Parasites which live inside the body are termed | endoparasites
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| those parasites which exist on the body surface are called | ectoparasites
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| the host in which a parasite lives as the larval and asexual stage is the | intermediate host
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| The host in which the parasite lives its adult and sexual stage is the | definitive host
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| Other hosts that harbor the parasite and thus ensure continuity of the parasite's life cycle and act as additional sources of human infection are known as | reservoir hosts.
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| An organism (usually an insect) that is responsible for transmitting the parasitic infection is known as the | vector
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| direct wet mount | detects motile organisms (Giardia) usually in duodenal drainage , with saline or iodine
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| concentration | formalin ethyl acetate sedimentation or zinc flotation method, with saline or iodine
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| Permanent Stained smear | Trichrome or Iron-hemotoxylin stains
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| Thick and thin blood films | for Plasmodium, Babesia, Trypanosomes etc
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| Entamoeba histolytica (Protozoa) | the major cause of amebic dysentery
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| The metacyst divides into | four and then eight amoebae which move to the large intestine
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| Iodoquinol is used to treat | asymptomatic infections
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| metronidazole is used for | symptomatic and chronic amebiasis
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| Trophozoite: | This form has an ameboid appearance and is usually 15-20 micrometers in diameter, although more invasive strains tend to be larger. The organism has a single nucleus with a distinctive small central karyosome .
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| Entameba histolytica cysts are | spherical, with a refractile wall; the cytoplasm contains dark staining chromatoidal bodies and 1 to 4 nuclei with a central karyosome and evenly distributed peripheral chromatin.
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| Entamoeba coli | not pathogenic, larger troph usually 20-25 m, cyst 15-25 m ,>4 nuclei Commensal
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| Endolimax nana | cyst 5-10 m , 4 nuclei, no peripheral chromatin Commensal
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| Giardia lamblia (flagellate) | It is the most frequent protozoan intestinal disease in the US and the most common identified cause of water-borne disease associated with breakdown of water purification systems. Infection occurs by ingestion of cysts, usually in contaminated water.
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| Giardia cysts | 9 to 12 m. ellipsoidal cells with a smooth well-defined wall. The cytoplasm contains four nuclei and many of the structures seen in the trophozoite.
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| Giardia Trophozoite | a 12 to 15 m., half pear-shaped organism with 8 flagella and 2 axostyles arranged in a bilateral symmetry. There are two anteriorly located large suction discs. The cytoplasm contains two nuclei and two parabasal bodi.
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| Metronidazole is the drug of choice for | Giardia
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| Trichomonas vaginalis | colonizes the vagina of women and the urethra (sometimes prostate) of men. Wet prep or Giemsa stain of vaginal/urethral discharge, prostatic secretions or urine sediment.
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| Cryptosporidium parvum | Found in the gastrointestinal tract of many animals and causes epidemics of diarrhea in humans via contaminated food and water. Humans are infected by ingestion of C. parvum oocysts containing many sporozoites.
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| Isospora belli | rare infection of normal humans, although it is being seen in increasing numbers in AIDS patients. Infection via the oro-fecal route The infective stage of the organism is an oval oocyst which, upon ingestion, follows the same course as C. parvum.
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| Cyclospora cayetanensis | outbreaks linked to ingestion of contaminated food.
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| Demonstration of oocysts in feces is usually made using modified acid fast stains or immunoassays. |
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| Toxoplasma gondii | cats are the definitive host, can cause serious congenital defects if mother is exposed to cat feces.
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| TRYPANOSOMA | These are hemoflagellates and can be demonstrated in peripheral blood smears
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| T.brucei gambiense, rhodesiense, congolense AFRICAN - Causes African sleeping sickness | Parasites invade all organs of the body including heart and CNS. Leads to apathy, mental dullness, tremors, convulsions and sleepiness, coma.
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| AMERICAN (Southern U.S., Mexico, Central and S. America)- T. cruzi | causes Chagas disease-The vector is the reduvid bug. Chagas diease is a chronic or acute infection characterized by neurological disorders (including dementia). Chagas' disease is often fatal unless treated.
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| Four Plasmodium species are responsible for human malaria These are | P. falciparum, P. vivax, P. ovale and P. malariae.
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| Plasmodium is transmitted by | the female anopheline mosquito which injects sporozoites present in the saliva of the insect. Malaria can also be transmitted by transfusion and transplacentally.
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| The chill and fever follow a cyclic pattern (paroxysm). Fever is associated with severe headache, nausea (vomiting) and convulsions are indicative of which disease? | Malaria
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| Without treatment, all species of human malaria may ultimately result in spontaneous cure except with | P. falciparum
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| Chronic malaria results in | splenomegaly, hepatomegaly and nephritic syndromes
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| Diagnosis of Plasmodium is based on detection of parasite in what? | Giemsa stained blood smears.
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