1. Intestinal flagellates
Mrs. Dalia Kamal Eldien
Msc in Microbiology
Lecture NO 5

2. Objectives Over view on flagellate, main species& their taxonomy
Giardia lamblia as an example for flagellate
Normal habitat, mode of transmission& epidemiology
Morphology of Giardia lamblia include cyst& trophozoite
Life cycle of Giardia lamblia
Sings& symptoms of Giardiasis
Laboratory diagnosis
Treatment of Giardiasis
Prevention control of Giardiasis

3. Amoebae Flagellates Ciliates Coccidia Microsporidia
The basic generally accepted practical classification of the medically important parasitic protozoa
Amoebae
Entamoeba histolytica
Acanthamoeba species
Naegleria species
Flagellates
Giardia lamblia
Trichomonas vaginalis
Trypanosoma species
Leishmania species
Ciliates
Balantidium coli
Coccidia
Blood and tissue coccidia:
Plasmodium species
Toxoplasma gondii
Intestinal coccidia:
Isospora belli
Cryptosporidium parvum
Cyclospora cayetanensis
Microsporidia
Encephalitozoon species
Enterocytozoon species

4. The Flagellates
The flagellates belong to the Mastigophora Subphylum and possess more than one flagellum.
Beating these flagella enable them to move.
A cytosome may be present which helps in the identification of the species.
Flagellates possess one advantage over their amoeboid relatives in that they can swim. Therefore, enabling them to invade and adapt to a wider range of environments unsuitable for other amoebae.

5. The trophozoites are easily recognized in saline preparations by their motility.
However, accurate identification is done on a stained fecal smear.
Cysts are more commonly seen than the trophozoite.

6. Main species
There are pathogenic and commensal species of flagellates. The flagellates which are encountered in the intestinal tract are
 Giardia lamblia
 Chilomastix mesnili
Trichomonas hominis
Retortamonas intestinalis 
 Enteromonas hominis

7. Taxonomy Kingdom Animalia Subkingdom Protozoa Phylum Sarcomastigophora
Subphylum Mastigophora
Class Zoomastigophora
Order Diplomonadida
Family Hexamitidae
Genus Giardia
Species lamblia

8. Giardia lamblia
Is a flagellated protozoan parasite that colonizes and reproduces in the small intestine, duodenum and jejunum.
Worldwide distribution, common in tropics & subtropical countries. It is more common in warm climate .
It is the most common flagellate of the intestinal tract, causing Giardiasis. 

9. Transmission:-
Infection occurs by ingestion of cysts (generally from fecal contaminated food or water)
Sources of infection:
Contaminated water
Contaminated food  

10. Epidemiology
Giardia infection is the most common intestinal parasitic disease affecting humans
Giardiasis is a global disease.
Common in children 6-10 years age.
Also prevalent in homosexual males.
Primary immuno-deficiency (IgA deficiency)
Recent increase in Giardia infection in Backpackers or campers who drink untreated water from lakes or river

11. Morphology Trophozoite:
The trophozoites of G. lamblia are flattened pear shaped and are an average size of 15 µm long, 9 µm wide and3 µm thick.
 When stained, the trophozoite is seen to have 2 nuclei, 2 slender median rods (axostyles), and 8 flagella arising from the anterior end.
They have been described as looking like tennis rackets without the handle (they are often seen has having a comical face-like appearance when looking at the front view)
The movement of the trophozoites are described as tumbling leaf motility

12. Trophozoite

13. Trophozoite

14. Morphology
Cyst
Cysts are small, oval, 8-14 x 5-10 µm , thick cyst wall, with four nuclei and fibrils and flagella longitudinally oriented.
The cyst environmentally resistant and responsible for disease transmission. (The infective stage of Giardia lamblia )

15. Cyst

16. Cyst

17. Life cycle
Definitive hosts are humans & a wide range of animals with no intermediate hosts or vectors
Giardia spp. have two stages, cysts and trophozoites.
The infection is acquired by ingesting cysts.
As few as cysts are sufficient to establish an infection in some humans.
Trophozoites are released from the ingested cysts in the small intestine.

18. Trophozoites colonize the small intestine, attaching to the mucosa of the bowel using a ventral sucking disks.
The trophozoites then multiply by longitudinal binary fission
As the Giardia trophozoites move toward the colon, they retreat into the cyst stage (known as encystation) and the new cysts are excreted in the feces
Cysts can appear in the feces from 3 days to 3 weeks after infection

20. Clinical disease
Giardia lamblia colonies in the small intestine where the trophozoites adhere to the mucosal surface by means of their sucking disc, and absorb their nutrients from the lumen of the small intestine causing Giardiasis.
Giardiasis does not spread via the bloodstream, nor does it spread to other parts of the gastrointestinal tract, but remains confined to the lumen of the small intestine
Cysts are produced as the parasites descend the intestinal tract although trophozoites can be passed in the faeces in severe infections.
Cysts can survive outside the body for several weeks under favorable conditions.

21. Symptoms
infection with Giardia lamblia can range from asymptomatic to severe diarrhea.
1-Asymptomatic infections:
are responsible for the continued transmission of the parasite as numerous cysts are produced. 

22. 2-Symptomatic infections:
Giardia lamblia generally does not penetrate the intestinal wall, but may cause inflammation and shortening of the villi in the small intestine.
Extremely large numbers of trophozoites may be present and may lead to a direct, physical blockage of nutrient uptake, especially in fat soluble substances such as vitamin B12. 
Symptoms include severe diarrhea, nausea and flatulence.

23. Laboratory diagnosis
Giardiasis can be diagnosed by direct observation of the trophozoites or cysts in the feces- several specimens-
Trophpzoite: usually present in Water-like faeces
Cyst: usually present in Formed faeces
Duodenal fluid aspirate examination for chronic gardiasis
For Fresh sample either do Saline wet mounts with or without iodine or MIF (Merthiolate-iodine-formaldehyde) stain and permanently stained preparations (e.g., trichrome).

24. G. lamblia cyst

25. G. lamblia trophozoite

26. Immunodiagnosis (ELISA).
Direct fluorescent antibody (DFA) assay.
Culture system using Diamond medium.
Molecular analysis by PCR-based assays.

27. Treatment
Giardiasis can be treated with a number of drugs, such as Metronidazole form 5-7 days or Tinidazole

28. Prevention control Improving environmental sanitation
Good hygiene, such as hand washing reduces the risk of infection
Boiling suspect water for one minute is the surest method to make water safe to drink and kill disease-causing microorganisms such as Giardia lamblia if in doubt about whether water is infected