Giardia Lamblia Medical Parasitology PDF

GIARDIA LAMBLIA MEDICAL PARASITOLOGY HISTORY AND DISTRIBUTION The flagellate was first observed by Dutch scientist Antonie von Leeuwenhoek (1681) in his own stools. It is named 'Giardia' after Professor Giard of Paris and 'lamblia' after Professor Lamble of Prague, who gave a detailed descript...

GIARDIA LAMBLIA MEDICAL PARASITOLOGY HISTORY AND DISTRIBUTION The flagellate was first observed by Dutch scientist Antonie von Leeuwenhoek (1681) in his own stools. It is named 'Giardia' after Professor Giard of Paris and 'lamblia' after Professor Lamble of Prague, who gave a detailed description of the parasite. It is the most common protozoan pathogen and is worldwide in distribution. Endemicity is very high in areas with low sanitation, especially tropics and subtropics. Visitors to such places requently develop traveller's diarrhea caused by giardiasis through contaminated water. HABITAT Giardia lamblia lives in the duodenum and upper jejunum It is the only protozoan parasite found in the lumen of the human small intestine TROPHOZOITE It measures 15 μm x 9 μm wide and 4 μm thick. Dorsally, it is convex and ventrally, it has a concave sucking disc, which helps in its attachment to the intestinal mucosa. It is bilaterally symmetrical and possesses. 1 pair of nuclei, 4 pairs of flagella, Blepharoplast, from which the flagella arise (4 pairs), 1 pair of axostyles, running along the midline, Two sausageshaped parabasal or median bodies, lying transversely posterior to the sucking disc. The trophozoite is motile, with a slow oscillation about its long axis, often resembling falling leaf. CYST It is the infective form of the parasite. The cyst is small and oval, measuring 12 μm x 8 μm and is surrounded by a hyaline cyst wall. Its internal structure includes 2 pairs of nuclei grouped at one end. A young cyst contains 1 pair of nuclei. The axostyle lies diagnonally, forming a dividing line within cyst wall. Remnants of the fl agella and the sucking disc may be seen in the young cyst. MODE OF TRANSMISSION: Man acquires infection by ingestion of cysts in contaminated water and food. Direct transmission from person to person Enhanced susceptibility to giardiasis is associated with blood group A, achlorhydria, use of cannabis, chronic pancreatitis, malnutrition, and immune defects  PATHOGENICITY They may cause abnormalities of villous architecture by cell apoptosis and increased lymphatic infiltration of lamina propria. Variant specific surface proteins (VSSP) of giardia play an important role in virulence and infectivity of the parasite. Giardia may lead to mucus diarrhea, fat malabsorption (steatorrhea), dull epigastric pain, and flatulence. The stool contains excess mucus and fat but no blood. Children may develop chronic diarrhea, malabsorption of fat, vitamin A, protein, and weight loss. Giardia may colonize the gall bladder, causing biliary colic and jaundice. Incubation period is variable, but is usually about 2 weeks. LIFE CYCLE Within half an hour of ingestion, the cyst hatches out into two trophozoites, which multiply successively by binary fission and colonize in the duodenum. The trophozoites live in the duodenum and upper part of jejunum, feeding by pinocytosis. During unfavorable conditions, encystment occurs usually in colon. Cysts are passed in stool and remain viable in soil and water for several weeks. There may be 200,000 cysts passed per gram of feces. Infective dose is 10–100 cysts. TREATMENT Metronidazole (250 mg, thrice daily for 5–7 days) and tinidazole (2 g single dose) are the drugs of choice. Cure rates with metronidazole are more than 90%. Tinidazole is more effective than metronidazole. Furuzolidone and nitazoxamide are preferred in children, as they have fewer adverse effects. Parmomycin, an oral aminoglycoside can be given to symptomatic pregnant females. PROPHYLAXIS Proper disposal of waste water and feces. Practice of personal hygiene like hand-washing before eating and proper disposal of diapers. Prevention of food and water contamination. Community chlorination of water is ineffective for inactivating cysts. Boiling of water and filtration by membrane filters are required.