Cyst of Giardia lamblia in Saline Preparation and Its Details
Cysts of Giardia lamblia
Cysts of Giardia lamblia in saline preparation as shown above picture.
Identification features
- Size: 12µm X 7 µm (length and breadth)
- Shape: Oval or elliptical
- Cyst wall: Refractile
- Nucleus: Four in number, forming a cluster at one end
- Axostyle: Set diagonally
Introduction of Giardia
Giardia is a genus of anaerobic flagellated protozoan parasites of the phylum metamonad that colonies and reproduce in the small intestines of several vertebrates, causing giardiasis. Their life cycle alternates between a swimming trophozoite and an infective, resistant cyst. Giardia were first described by the Dutch micrscopist Antonie van Leuwenhoek in 1681. The genus is named after French zoologist Alfred Mathieu Gird. Giardia lamblia is also known as:
Giardia intestinalis or
Lamblia intestinalis and
Giardia duodenalis.
Geographical distribution: It is cosmopolitan in distribution (Worldwide) and most common in warm climates.
Habitat: Duodenum and the upper part of the jejunum of man
Morphology
Giardia lamblia has two forms, cyst, and trophozoite.
Cyst
- Oval shaped
- 12 µm long and 7 µm broad
- Axostyle lie diagonally
- 4 nuclei
Remaining flagella and margin of the sucking disc
Trophozoites
- In flat view racket -shaped
- Side view resembles a split pear
- Dorsal surface convex
- Ventral view concave with sucking disc
- 14µm long and 7µm broad
- Anterior end broad
- Contains two axostyles, two nuclei, and four pairs of flagella
Life cycle
Unfavorable conditions of duodenum, encystment occur in the intestine. Ingestion of contaminated food containing cyst of Giardia. Within 30 minutes cyst hatches out 2 trophozoites. From stomach to the duodenum where cyst divides giving rise to 2 trophozoites. In the duodenum, multiplication of trophozoites occurs and colonization occurs.
Mode of transmission
Cysts
Direct transmission
Fomites
Contaminated water and/or food
Ingested cysts release trophozoites
Trophozoites multiply and encyst in intestines
Excreted in feces
Survival
Cysts
Survive well in cool, moist conditions
Remain viable for months in cold water
Two months at 8°C
One month at 21°C
Can also survive freezing
Susceptible to desiccation and direct sunlight
Pathogenicity of Giardia
Trophozoite attaches to the convex surface of epithelial cells of the intestine leading to disturbances of absorption function causing malabsorption of fat. There is also looseness of the bowel and steatorrhea. Trophozoite may cause the following effects toxic effects, traumatic and irritative effects.
Incubation period: 1-25 days
Clinical features
It may show the following features-
Asymptomatic
Intestinal symptoms – It may be further
acute enterocolitis and chronic enteritis
General features- Symptoms of clinical disease is of the following types-
- Mild to severe gastrointestinal sign
- Sudden onset diarrhea
- Foul-smelling stools
- Abdominal cramps
- Bloating, flatulence
- Nausea, fatigue
- Weight loss
- anemia
- Allergic manifestation
- Chronic cholecystography
Laboratory Diagnosis of Giardia
Microscopic examination
Stool (freshly passed)
Direct observation in feces
Trophozoites
“Teardrop” shape
Two nuclei and tumbling mobility
Cysts
Approximately 13 microns long
Oval, with 2-4 nuclei
Immunofluorescence
Note-Trophozoite may also see in
- Bile aspirated from the duodenum
- Bile from bile duct
Treatment of Giardia
Following antiprotozoal drugs are useful to treat giardiasis and they are-
Anti-protozoal drugs
- Metronidazole
- Tinidazole
- Ornidazole
- Chloroquine
- Secnidazole
Chronic cases
Maybe resistant
Prolonged therapy may be necessary.
Prevention and Control
Water
Do not drink contaminated water from the sources like
untreated lakes, rivers, shallow wells.
Treat potentially contaminated water
Heat (rolling boil for one minute)
Filter (absolute pore size of one micron)
Chlorinate
Food
Wash raw fruits and vegetables
Practice good hygiene
- Hand washing
- Don’t swim in recreational waters for at least two weeks after symptoms end.
- Avoid fecal exposure
Limit environmental contamination
Clean and promptly remove feces from the surface.
Related Videos
#Giardia lamblia cysts in iodine wet mount at center of the video-
#Trichome stained slide showing Trophozoite of Giardia lamblia as shown below-
Further Readings
- Isenberg clinical microbiology procedures Handbook
2nd edition. Vol. 2 - Merkell and Voge’s medical parasitology
9th edition. - Parasitology: 12th edition
By K. D. Chatterjee - District laboratory practice in Tropical countries –Part-I.
By Monica Chesbrough. - Atlas of Medical Helminthology and protozoology -4th edn -P.L. Chiodini, A.H. Moody, D.W. Manser
- Medical Parasitology by Abhay R. Satoskar, Gary L. Simon, Peter J. Hotez and Moriya Tsuji