( 蓝氏贾第鞭毛虫 ） Giardia lamblia ( 蓝氏贾第鞭毛虫 ） Intestinal flagellate Giardia lambilia lives in small intestine Giardiasis Diarrhea “traveler’s diarrhea”

1. Morphology Nucleus 核 Sucking disk 吸盘 Axostyle 轴柱 Flagellum 鞭毛 (two anterior, posterior, ventral and tail flagella) Trophozoite Median body 中体 Inverse Pear-shaped 9  21×5  25μm

Ventral surface Lateral surface Tail flagella ventral flagella Behind side flagella Front side flagella

Cyst ： ball-shaped or oval, thick wall, 2-4 nuclei, 10  14µm ×7.5  9µm Nucleus Axostyles Flagella

Cyst in stool (Stained with haematoxylin)

2. Life Cycle Mature cyst Passed in feces Contaminated food and water By mouth Ingested by man or animals Excystation in duodenum 2 trophzoites Attaching to duodenum, upper small intestine, multiply by binary fission Cyst

2. Life Cycle

Infective stage ： Mode of infection : Colonizing sites: Mature cyst Mouth, Fecal-Oral transmission (hand to mouth) duodenum, upper small intestine characteristics of life cycle

3. Pathogenesis (1) Pathogenic mechanism (not clear) 1 ） Different virulence: mechanical blockage of the intestinal mucosa lesion of the intestinal mucosa by suckers of G.l toxicity to the intestinal mucosa by the secretion and excretion of G.l Malabsorption (of fat and carbohydrate)

2 ） Physiological / immunity status e.g. Intestinal IgA deficiency ， susceptible to the infection (2) Pathologic changes There are shortening of microvilli ( 微绒毛 ), epithelial cell damage ， and low-grade inflammation of the duodenal mucosa

(3) Clinical Manifestation Incubation period: 1~2w （ 45d ） Water--like stools onset of diarrhea ( Water--like stools ) suddenly with terrible odour abdominal cramping, bloating ( 胃胀气 ), abundant flatus, nausea ( 恶心 ) and vomiting, low-grade fever, usually last 1 to 3 weeks 1 ） Acute giardiasis In young children, it may persist for months characterized by fatty and greasy stool, significant malnutrition and weight loss.

2 ） Chronic phase ： Intermittent bouts of mushy stools with foul smelling, abdominal pain, nausea, weight loss, may persist for a long period (years). In children, it may result in undergrown.

4. Diagnosis (1)Parasitic Diagnosis 1 ） Stool examination ： as same as in E.h 2 ） Duodenal fluid or bile examination: ① Duodenal aspiration( 十二指肠引流 ) ② Duodenal capsule technique ( 肠检胶囊法 ) (2)Immunologic test ： mainly Ab detection (3)Molecular method: DNA probe 、 PCR

6. Epidemiology (1)Distribution ： World wide The infection rate is 1~20%. There were several outbreaks in European and American countries. Estimated incidence in China of 2-10% Higher in areas of poor sanitation (rural higher than urban area) and in day care settings

(2)Transmission 1 ） The source of infection ： The hosts who can pass the cyst: patient and carrier, animals (cat, dog, cattle, sheep, pig, beaver, etc.) large number of cysts shed (some patients shed up to 900x10 6 per day) 2 ） The route of infection ： Contaminated water and food, Spread by insects By mouth Can remain infective in water for 2-4 days (up to 16d, including in tap water) and in the digestive tract of cockroach for 12d. But susceptible to high temperature and dryness The cysts are resistant to adverse environmental conditions :

3 ） Susceptible populations ： All populations are susceptible to But higher frequency of infection in < 5 year and year age groups, and travelers, and immunodeficiency persons So called: “hikers disease”, “traveler’s diarrhea”traveler’s diarrhea Transmission is also found in homosexual males ( STD )

6. Prevention and Treatment (1) Chemotherapy: Metronidazole, tinidazole (2) Block of routes of transmission Adequate disposal of human stools Safe and adequate water supply ( filtration, boiling) Control of flies and cockroaches (3) Protection of susceptible population Public health education Good personal hygiene