Protozoa Biology Study Guide PDF

Protozoa Protozoa are single- celled eukaryotes where a single cell is capable of performing all functions necessary for life. Protozoa are divided according to their means of locomotion into : 1. Rhizopoda: move by pseudopodes. 2. Ciliates: move by cilia. 3. Flagellates: move by flagella a...

Protozoa Protozoa are single- celled eukaryotes where a single cell is capable of performing all functions necessary for life. Protozoa are divided according to their means of locomotion into : 1. Rhizopoda: move by pseudopodes. 2. Ciliates: move by cilia. 3. Flagellates: move by flagella and can be classified into intestinal, urogenital, blood and tissue flagellates. 4. Sporozoan: have no locomotory organ. 1  Protozoa can also be classified according to site of infection into : 1. Intestinal and/or urogenital protozoa include: Entamoeba histolytica, Balantidium coli, Giardia lamblia, Trichomonas vaginalis. 2. Blood protozoa include: Leishmania sp., Trypanosoma sp., Plasmodium sp. and Toxoplasma gondii. 2  A- Class Rhizopoda Example: Entamoeba histolytica Move by pseudopodia. Asexual reproduction. E. histolytica, as its name suggests ( histo – lytic = tissue destroying ). Disease : Amoebiasis, amoebic dysentery. Habitat : Large intestine. DH : Man. 3 E. histolytica (cont.) 4 E. histolytica (cont.) Pathogenicity: I. Intestinal amoebiasis ( primary lesion ): Trophozoite secrete proteolytic enzymes which enable them to penetrate the gut wall and multiply in the submucosa forming a minute ulcer. Extensive ulceration can be followed by secondary bacterial infection. II. Extraintestinal amoebiasis ( secondary lesions ): a) Hepatic amoebiasis in the form of amoebic hepatitis and amoebic liver abscess. b) Amoebic lung abscess. c) Amoebic brain abscess. 5 E. histolytica (cont.) Symptoms: I. Intestinal amoebiasis : Infection may be: 1. Asymptomatic (cyst passer): in healthy carrier who discharge cysts with no ulcers. They are active source of infection. 2. Acute amoebic dysentery: There are fever, colic, abdominal pain with or without tenesmus, mucus, blood, pus in stool. 3- Chronic amoebic dysentery: only cysts pass in stool, flatulence, recurrent attacks of dysentery at long intervals with normal bowel movements. II. Extraintestinal amoebiasis : The organism may invade the skin, liver, lung and brain where it produces abscesses that result in liver dysfunction, pneumonitis and encephalitis. 6 E. histolytica (cont.) Mode of infection: 1. Ingestion of mature cyst through contaminated food or water. 2. Autoinfection ( hand to mouth infection ). Diagnosis: 1- Stool examination by direct smear stained or unstained with iodine to find cysts and trophozoites. 2- Serological tests: ELISA. 3- CT scan for liver in hepatic amoebiasis and ultrasonography or aspiration of liver abscess. 7 E. histolytica (cont.) Treatment: 1. Asymptomatic carriers (Cyst passers): treated with luminal amoebicide drugs such as diloxanide furoate which acts locally in the intestinal lumen. 2- Standard treatment for invasive amoebiasis (amoebic dysentery; hepatic amoebiasis) is metronidazole (Flagyl®), tinidazole or other 5-nitroimidazole derivatives, combined with a luminal amoebicide (e.g.Diloxanide furoate) (Furazol®) to eradicate any surviving organisms from the lumen of the large intestine and prevent relapse. Because of their rapid absorption from the gastrointestinal tract, the nitroimidazoles are less effective against parasites in the lumen and a luminal amoebicide should be used in combination. 8 E. histolytica (cont.) In severe cases of amoebic dysentry, tetracycline can be combined with metronidazole to reduce the risk of superinfection, intestinal perforation, and peritonitis. N.B.: Entamoeba coli is another non-pathogenic protozoa which commonly lives in the large intestine in humans and differs from E. histolytica in having 8-nucleated mature cysts as the diagnostic and infective stage. 9  B- Class ciliates Balantidium coli Disease : Balantidiasis, Balantidial dysentery. Habitat : Large intestine. DH : Pigs and man. Pathogenicity: it is the only known ciliated parasite to infect humans. Symptoms and pathogenesis are similar to those seen in amoebiasis. However, liver, 10 lung and brain abscesses are not seen. B. coli (cont.) Mode of infection: man gets infected via ingestion of cyst (infective stage) through contaminated food, drinks or contaminated hands. Because pigs are an animal reservoir, human infections occur more frequently in areas where pigs are raised, Diagnosis: cysts and trophozoites in faeces. Treatment: tetracycline; metronidazole or diiodohydroxyquinoline 11 B. coli (cont.) 12  C- Class flagellates General characteristics: Move by flagella. Asexual reproduction. Classification according to habitat: Intestinal: Giardia lamblia Urogenital: Trichomonas vaginalis Blood and tissue flagellates: leishmania sp., Trypanosoma sp. 13 Flagellates (cont.) 1- Giardia lamblia (Giardia intestinalis) Disease : Giardiasis. Habitat : Small intestine at duodenal level. DH : Man especially children. RH : Mammalian hosts as cows, deer, sheep, pigs, monkeys, cats & dogs. 14 G. Lamblia (Flagellates cont.) 15 G. Lamblia (Flagellates cont.) Pathogenicity: flatulence, abdominal distension, nausea, diarrhea, indigestion and malabsorption especially of fats. Pus, mucus and blood are not commonly present in stool which contains excessive lipid (steatorrhea ). There is increased incidence of infection in immunodeficient patients. Mode of Infection: man gets infected by ingestion of mature cyst in contaminated food and water, autoinfection, mechanical transmission of vectors as houseflies. 16 G. Lamblia (Flagellates cont.) Diagnosis: 1. Stool examination : Macroscopically : pale, yellow, loose, frothy stool with excessive fat ( Lentil soup appearance). Microscopically : to detect cysts and trophozoites in severe diarrhea. Cysts are more commonly found in formed stool. 2. ELISA to detect Giardia lamblia antigen in stool. Treatment: Metronidazole or tinidazole. 17 T. vaginlais (Flagellates cont.) 2- Trichomonas vaginalis Disease : Trichomoniasis. Habitat : Vagina, cervix, urethra and urinary bladder of female; prostate, urethra, urinary bladder and seminal vesicles of male. DH : Man. The organism favors slight acidity (PH ≥ 5.9 ). PH of vagina is 3.5-4.5 which is maintained by lactic acid production via vaginal normal flora (so not favourable for Trichomonas).. Pathogenicity: T.vaginalis cannot live in the normal acidity of vagina. Any factor leading to decrease lactic acid production is a predisposing factor to T. vaginalis. Hormonal changes, decrease in vaginal secretory IgA and decrease of vaginal normal flora are predisposing factors. 18 qqq 19 T. vaginlais (Flagellates cont.) 20 T. vaginlais (Flagellates cont.) Pathogenesis and clinical picture: Trophozoites cause mechanical and toxic irritation of vagina causing vaginitis known as strawberry vagina. Surface is covered with frothy creamy or yellowish discharge resulting in: In female patients: They usually complain of itching, burning sensation, dysuria, yellow green vaginal discharge. In male patients: They are usually symptomless and act as carriers. Some complain of dysuria, urethritis and prostatitis. 21 T. vaginlais (Flagellates cont.) Mode of infection: Infection occurs via sexual contact, swimming pool, contaminated toilet seat, passage through birth canal in new born. Diagnosis: Demonstration of trophozoites in Giemsa- stained smears of vaginal discharge, urine, semen or prostatic secretions. Prevention and control: Personal hygiene, health education. Disinfection of toilet seats. Treatment: - Metronidazole or tinidazole are effective in both males and females (spouses should be treated at the same time). 22 - Lactic acid douche may be useful. 23