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