Practical Parasitology PDF

Practical Parasitology : Ciliophora, Luminal and Genital Flagellates Super Class: Ciliophora/ Balantidium coli Trophozoite Oval shape Course cilia Contractile vacuoles Kidney shaped macronucleus. Super Class: Ciliophora/ Balantidium coli Cyst Trophozoite Cyst Shape Oval, pointed at the anterior end...

Practical Parasitology : Ciliophora, Luminal and Genital Flagellates Super Class: Ciliophora/ Balantidium coli Trophozoite Oval shape Course cilia Contractile vacuoles Kidney shaped macronucleus. Super Class: Ciliophora/ Balantidium coli Cyst Trophozoite Cyst Shape Oval, pointed at the anterior end Spherical Surface Covered in cilia Covered with thick, hard cyst wall with cilia sometimes visible underneath Motility motile Non-motile Infectiveness Non-infective infective Diagnosis Occasionally found in feces, often found in tissue biopsies of infected individuals Found in feces of infected individuals Balantidiasis The intestinal protozoan Balantidium coli is the only member of the ciliate group that is pathogenic for humans. Disease produced by B. coli is similar to amebiasis, because the organisms elaborate proteolytic and cytotoxic substances that mediate tissue invasion and intestinal ulceration. Life cycle The life cycle of B. coli is simple involving ingestion of infectious cysts excystation, and invasion of trophozoites into the mucosal lining of the large intestine, caecum, and terminal ileum. Epidemiology B. coli are distributed worldwide. Swine and (less commonly) monkeys are the most important reservoirs. Infections are transmitted by the faeco-oral route; outbreaks are associated with contamination of water supplies with pig faeces. Person-to-person spread, including through food handlers, has been implicated in outbreaks. Risk factors associated with human disease include contact with swine and substandard hygienic condition. Laboratory Diagnosis Microscopic examination of feces for trophozoite and cysts is performed. Super class: Flagellates/ INTRODUCTION Flagellates are unicellular microorganisms. Their locomotion is by lashing a tail-like appendage called a flagellum or flagella and reproduction is by simple binary fission. There are three groups of flagellates: Luminal flagellates Giardia lamblia Hemoflagellates Trypanosoma species. Leishmania species. Genital flagellates Trichomonas vaginalis Luminal flagellates/ Giardia lamblia Trophozoite Bilaterally symmetrical. pear-shaped. Two nuclei (large central karyosome). Four pairs of flagella. two axoneme (serves as the skeleton). a suction disc with which it attaches to the intestinal wall. Luminal flagellates/ Giardia lamblia Cyst Oval in shape Thick smooth wall. Four nuclei. Contain parabasal bodies and flagella. Each cyst gives rise to two trophozoites during excystation in the intestinal tract. Giardia lamblia trophozoite and cyst. Life Cycle Giardia trophozoite Pathogenesis Infection with G. lamblia is initiated by ingestion of cysts. Gastric acid stimulates excystation, with the release of trophozoites in duodenum and jejunum. The trophozoites can attach to the intestinal villi by the ventral sucking discs without penetration of the mucosa lining, but they only feed on the mucous secretions. In symptomatic patients, however, mucosa-lining irritation may cause increased mucous secretion and dehydration. Metastatic spread of disease beyond the GIT is very rare. Epidemiology Giardia lamblia has a worldwide distribution, particularly common in the tropics and subtropics. It is acquired through the consumption of inadequately treated contaminated water, ingestion of contaminated uncooked vegetables or fruits, or person-to-person spread by the faeco-oral route. The cyst stage is resistant to chlorine in concentrations used in most water treatment facilities. Laboratory diagnosis Examination of diarrheal stool- trophozoite or cyst, or both may be recovered in wet preparation. In examinations of formed stool (e.g. in asymptomatic carriers) only cysts are seen. If microscopic examination of the stool is negative in a patient in whom giardiasis is highly suspected duodenal aspiration, or biopsy of the upper small intestine can be examined. In addition to conventional microscopy, several immunologic tests can be implemented for the detection of parasitic antigens. Genital flagellates/Trichomonas vaginalis Important features It exists only as a trophozoite (very important). pear-shaped organism. A central nucleus. Four anterior flagella. One posterior flagellum. An undulating membrane extends about two-thirds of its length. Infective stage is the quiescent form of the trophozoite. Transmission is by sexual intercourse. Trichomonas vaginalis/ trophozoite Pathogenesis The trophozoite is found in the urethra & vagina of women and the urethra & prostate gland of men. After introduction by sexual intercourse, proliferation begins which results in inflammation & large numbers of trophozoites in the tissues and the secretions resulting in vaginitis in woman and urethritis in men. Life Cycle Epidemiology This parasite has worldwide distribution, and sexual intercourse is the primary mode of transmission. Occasionally, infections can be transmitted by fomites (toilet articles, clothing), although this transmission is limited by liability of the trophozoite. Rarely Infants may be infected by passage through the mother’s infected birth canal. The prevalence of this flagellate in developing countries is reported to be 5% –20% in women and 2% –10% in men. Laboratory diagnosis In females, T. vaginalis may be found in urine sediment, wet preparations of vaginal secretions or vaginal scrapings. In males it may be found in urine, wet preparations of prostatic secretions. Contamination of the specimen with faeces may confuse T. vaginalis with T. hominis.