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

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

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

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.

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.

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

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

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. 

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

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

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

Trophozoite

Trophozoite

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 )

Cyst

Cyst

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 10-25 cysts are sufficient to establish an infection in some humans. Trophozoites are released from the ingested cysts in the small intestine.

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

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.

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. 

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.

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).

G. lamblia cyst

G. lamblia trophozoite

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

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

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