Giardia lamblia(( 蓝氏贾第鞭毛虫蓝氏贾第鞭毛虫))
Intestinal flagellateIntestinal flagellate
Giardia lambilia Giardia lambilia lives in small intestinelives in small intestine
GiardiasisGiardiasis
Diarrhea Diarrhea
“traveler’s diarrhea”
1. MorphologyNucleus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
921×525μm
Ventral surfaceVentral surface Lateral surfaceLateral surface
Tail flagellaTail flagellaventral flagellaventral flagella
Behind side Behind side flagellaflagella
Front side Front side flagellaflagella
Cyst :
ball-shaped or oval , thick wall , 2-4 nuclei,
10 14µm ×7.5 9µm
Nucleus
AxostylesFlagella
Cyst in stool
(Stained with haematoxylin)
2. Life Cycle
Mature cystPassed 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 )
onset of diarrhea (Water--like stoolsWater--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:
①Duodenal 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
贾第虫感染率的地区分布
(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 900x106 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 25-39 year age groups, and travelers, and immunodeficiency persons
So called: “hikers disease”, “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