Intestinal Flagellates: Life Cycle and Giardia Lamblia

Intestinal Flagellates General Information

• Most inhabit the large intestine, with exceptions like Giardia lamblia (small intestine), Trichomonas vaginalis (urogenital), and Trichomonas tenax (mouth).
• All undergo encystation except Trichomonas species and Dientamoeba fragilis.
• Most are commensals except Giardia lamblia, Dientamoeba fragilis, and Trichomonas vaginalis.
• Flagella attaches to the blepharoplast on the parasite's body.
• All undergo asexual reproduction through binary fission.

Intestinal Flagellates Life Cycle

• Infection occurs with the ingestion of cysts.
• Excystation happens in the small intestine, releasing trophozoites.
• Reproduction occurs through binary fission (longitudinal) in the small intestine.
• Parasite exits body via stool as either a cyst or trophozoite, depending on the parasite species and stool type.

Giardia Lamblia (A Man with Eyeglasses)

• First discovered in 1859 by French scientist Dr. F. Lambl.
• Also known as G. duodenalis and G. intestinalis.
• It is the most common cause of intestinal infection and most common protozoan pathogen worldwide.
• Only protozoan parasite found occupying the lumen of the small intestine.
• Humans get it by ingesting cysts in contaminated water and food.
• It resides in the small intestine (duodenum, jejunum, and upper ileum).
• Low infective dose of 8-10 cysts needed to cause outbreaks of diarrhea.
• Reproduces through binary fission, longitudinal.
• Prefers alkaline pH (7.8-8.2); more alkaline aids its attachment.

Giardia Lamblia Trophozoite

• Has 2 ovoidal nuclei.
• Pear/pyriform shaped, resembling an old man's face with eyeglasses.
• Possesses an axostyle for support.
• Has 1 pair of anterior flagella, 2 pairs of lateral flagella, and 1 pair of conal/posterior flagella.
• Has 2 ventral sucking discs which are virulence factors.
• Contains median/parabasal bodies shaped like a clawhammer.

Giardia Lamblia Cyst

• Has 4 nuclei.
• Refractile/clear cyst wall (hyaline), oval shaped.
• Contains median/parabasal bodies (2).
• Has energy structures and an axoneme (multiple axostyles).
• Deeply stained curved fibrils are present.
• Exhibits "Falling Leaf Motility”.
• Nonmotile.

Giardia Lamblia Epidemiology

• G. intestinalis is found worldwide in water sources.
• Major cause of parasitic diarrheal outbreaks in the United States, especially among children.
• Cysts are resistant to routine chlorination procedures used in most water plant facilities.
• The parasite is transmitted through contaminated water, fruits, and vegetables, as well as oral-anal sexual practices or fecal-oral route.

Giardia Lamblia Clinical Symptoms

• Organism now considered the only known pathogenic intestinal flagellate.
• Infections can be asymptomatic.
• Symptomatic infections (Traveler's Diarrhea) are characterized by varied clinical symptoms, ranging from mild diarrhea, abdominal cramps, anorexia, and flatulence to tenderness of the epigastric region, steatorrhea, and malabsorption syndrome.
• Patients may produce light-colored stools with high fat content, caused by secretions from the irritated mucosal lining.
• May lead to fat-soluble vitamin and folic acid deficiencies, hypoproteinemia, and structural changes of the intestinal villi.
• Blood is rarely present in the stool.
• Incubation period: 10-36 days, followed by watery, foul-smelling diarrhea, steatorrhea, flatulence, and abdominal cramping.

Giardia Lamblia Treatment and Control

• Treatments of choice include metronidazole (Flagyl), tinidazole (Tindamax), and nitazoxanide (Alinia).
• Prevention includes steps similar to those for Entamoeba histolytica.
• Includes water treatment with chemical therapy and filtration.
• Prevention involves guarding water supplies against contamination by potential reservoir hosts.
• Prevention include exercising good personal hygiene, proper cleaning, and proper cooking of food.
• Avoidance of unprotected oral-anal sex is key.

Giardia Lamblia Laboratory Diagnosis

• Usual specimens: stool/feces.
• Collect 3 specimens within 10 days.
• Examine feces using direct fecal smear (DFS) to detect trophozoites and cysts.
• To concentrate, use concentration techniques (FECT).
• Use a stained smear (permanent).
• Perform Entero-test/String Test if DFS is negative.
• Usually done if negative in DFS.
• Perform Beale’s String Test
• Swallow a capsule (has string and yarn inside)
• Loose end placed on face
• Yarn will go to the duodenum (where the parasites are
• After 4 hours, pull the string
• Prepare smear from the string and look for the parasite
• String should be green
• Can also check by duodenal aspirate, serology, molecular methods, or biopsy.

Dientamoeba Fragilis

• Classified as ameboflagellate without external flagella, based on electron microscope study.

• Primarily found worldwide and is most common intestinal protozoan parasite in Canada.

• Does not have a cyst stage.

• The trophozoite has one or two nuclei (binucleate trophozoite is more common).

• Nuclear chromatin appears fragmented into three to five granules and without peripheral chromatin on the nuclear membrane.

• In some organisms, nuclear chromatin appear like E. nana, E. hartmanni, or C. mesnili, especially with overstained trichrome or iron hematoxylin stain.

• Cytoplasm is vacuolated and contains ingested debris and uniform granules.

• The stain to distinguish individual chromatin granules in the nuclei is iron hematoxylin.

• Colon/large intestine is habitat.

• Transmitted through oral-fecal route by ingesting trophozoites.

• Related to Trichomonas.

• Usually ingested with Enterobius and Ascaris.

• Acts as carrier of D. fragilis.

• Reproduction occurs through binary fission.

• High prevalence in countries with high sanitation standards (Israel, Holland, Germany, etc.).

• Hakansson phenomenon: D. fragilis returns to normal size after swelling in water preparations.

• The life cycle and mode of transmission are unknown, although transmission in helminth eggs is suspected.

• Common symptoms include intermittent diarrhea and fatigue.

Dientamoeba Fragilis Clinical Symptoms and Diagnosis

• Most infections are asymptomatic
• Some symptomatic infections include diarrhea and abdominal pain.
• Other Symptoms can be bloody or mucoid stools, flatulence, nausea or vomiting, weight loss, and fatigue, alternating with constipation, low-grade eosinophilia, and pruritus.
• The examination of stool samples for the presence of trophozoites is the chosen method.
• The exact mode of D. fragilis transmission is unknown; one unproven theory suggests its transmission via helminth eggs.
• Studies show D. fragilis-resembling organisms identified in patients also infected with E. vermicularis (pinworm).
• Data indicate that this organism is mostly distributed in cosmopolitan areas.
• Iodoquinol treat symptomatic infections, while tetracycline or paromomycin (Humatin) may be used as alternatives.

Dientamoeba Fragilis Prevention and Control

• Is difficult because the life cycle is not fully understood.
• Consistent public sanitation is key.
• If unproven transmission theory is valid, the primary prevention measure would be the eradication of helminth eggs, especially pinworm.

Dientamoeba Fragilis Trophozoite

• Two nuclei (hence Dientamoeba).
• Karyosome exhibits a rosette/rose-like appearance.
• Sometimes not detected/seen and is fragile that it is easily destroyed.

Chilomastix Mesnili

• Commensal parasite located in the colon/large intestine (cecal region).
• Infective stage via ingestion of a cyst.
• Excystation happens in the small intestine, while trophozoites then go to the large intestine.
• Worldwide distribution.
• No Treatment needed.
• Prevention and control measures by promoting improved sanitation and personal hygiene.

Chilomastix Mesnili Life Cycle and Diagnosis

• An infection starts with ingestion of cysts.
• Once ingested, it goes to the colon/large intestine, and develops to reproduce.
• It also exists the body via feces.
• Cysts usually contaminate water, food, hands of people, and other fomites.
• It is diagnosed based on traditional examination of freshly passed stool from patients.

Chilomastix Mesnili Characteristics

• Trophozoite possesses 1 nucleus, with a prominent karyosome.
• Pyriform, pear-shaped, curved posture, twisted jaw.
• Anterior flagella
• One flagella near cytostome (mouth of the parasite)
  • Cytostomal fibril appearance
• Exhibits a spinal groove
• Cyst stage has one nuclei.
• It has an American lemon appearance.
• Is nipple-shaped, 7-10 um size.
• Has a hyaline knob protruding.
• Shows K cytostomal fibril.

Retortamonas Intestinalis

• Is a lemon to pear-shaped trophozoite.
• Exhibits jerky motility and has one nucleus.
• Has two fused fibrils resembling a bird’s beak.
• Single, large nucleus in cyst stage.
• Has Cleftlike cytostome near nucleus
• Has two anterior flagella.
• Diagnosis needs a stained preparation of stool sample.
• Unfortunately, difficult to identify because of small size.
• Although R. intestinalis is rarely reported, it has been seen in warm climate worldwide. Transmission is accomplished by ingesting infected cysts and has no symptoms.
• Because R. intestinalis is a nonpathogen, no treatment needed.
• Most important prevention is to have good personal and public hygiene conditions.

Enteromonas Hominis

• It can be oval to elongated shape, and have one to four nuclei
• Diagnostic is made by examining stool samples, despite it being small.
• Also, can be distributed worldwide in warm climate.
• No treatment is needed, since it is a nonpathogen.
• Good personal hygiene and public sanitation is key for prevention.
• Pear-shaped/ovoid cyst occurs as a half-circle.
• Exhibits jerky motility with single nucleus.
• Has no Cytostome, with four flagella (three are directed anteriorly and one directed posteriorly)

Urogenital Flagellates General Information

• Includes Trichomonas vaginalis, Trichomonas hominis, and Trichomonas tenax.
• These species lack a cyst stage, so they only exist as trophozoites.

Trichomonas Vaginalis

• Pathogenic and largest among 3.
• Causes Trichomoniasis (STD) which affects both males and females.
• Habitat in urogenital area (females: vagina. males: urethra and prostate).
• Transmitted through intimate contact, infant delivery, contaminated towels and underwear.
• Reproduces through longitudinal binary fission.
• Most prevalent nonviral sexually transmitted infection.

Trichomonas Vaginalis Trophozoite Characteristics

• Has 1 nuclei and is pear-shaped.
• 4 anterior flagella
• 1 flagella embedded in its undulated membrane which appears like wave.
• The flagella aids in motility.
• A key is its length, half of the body.
• Axosylte
• Cytostomal
• Has rib-like structure, an iron-rich sideophil near Axostyle with no function.
• Bacteria present.

Trichomonas Vaginalis Clinical Manifestations

• Incubation period is 4-28 days.
• Proliferating colonies degenerate the vaginal epithelium, causing leukocytic inflammation.
• Vaginal pruritus (vaginal itching) with a burning sensation and Mucopurulent discharge occurs in women.
• Trichomoniasis refers to ping-pong disease.
• The disease is Mucopurulent, dysuria, has abdominal pain, and atypical pelvic inflammatory.
• Can lead to sterility and strawberry cervix.

Trichomonas Vaginalis Pathogenesis

• Can be secondary bacterial infection in urogenital tract.
• Acute condition changes when it comes to secretion and it decreases Leukocytes.
• Trichomonads associated postpartum.
• Few symptomatic infections show non-gonococcal urethritis.
• Babies and infants are infected moms get neonatal pneumonia.
• Uses adhesins which bind urogenital cells to promote tissue disruption and immune to evade.
• Cells also contains cysteine proteinases while alkaline ph promote infections

Trichomonas Vaginalis Epidemiology and Lab Diagnosis

• Its main route is STD infectious.
• Found worldwide and is the humans are main host who has increased susceptibility.
• Has symbiotic relationship with bacteria who causes STD (mycroplasma hominis)
• Some symptoms come from inflammation and those who has sexual activity are at great risk.
• Prevalence higher for women of childbearing age.
• With diagnostic , it will need a wet mount, a stain, and culture test such: Diamond modified medium, Feinberg whittington, and semen cultures are gold.
• Best results are urine and vaginal discharge.

Trichomonas Vaginalis Diagnosis and Management

• Dx: Antigen detection, serology
• High +PCR and inpouchTV
• Treatment: Metronidazole and Tinidazole
• Prevention is monogamy, abstinence, being faithful

Trichomonas Hominis

• Commensal, known also as Pentatrichomonas hominis.
• Contains 5 flagella and is found in the colon with trophozoites contaminated from food, water, hands or fomites.
• In the trophozoite, there are four anterior and one posterior flagella.
• Has conical and axostyle with membrane but with No Peripheral chromatin.

Trichomonas Tenax

• Commensal found in mouth tartar, carious cavities and gingival.
• Has direct transmission via kissing or dish sharing and harmless.
• In immunocompromised patient, some reports are respiratory infections and thoracic abscesses with bacteria that allows it to proliferate.
• Smallest species that is resistant to water and can survive for hours
• Dx: swabbing tartar with treatment of metronidazole
• Troph is pear-shaped with one nuclei.
• Two anterior flagella
• A 2/3 body length

Balantidium Coli General Information

• Largest protozoan infecting man.
• Hosts: man and pigs (zoonotic).
• Route of infection: Ingestion of cysts through contaminated food or water.
• Colon (cecum) inhabits.
• Risk factors: close contact with pigs (in pig feces).
• Only ciliate known to cause human disease.

Balantidium Coli Trophozoite Information

• 2 nuclei: micronucleus (sexual reproduction) and macronucleus (asexual reproduction and vegetative function).
• Mucocysts located beneath cell membrane
• Ellipsoid with tapered anterior portion.
• Cytostome and cytopyge are important for waste egestion.
• Contractile and food Vaculoles
• Use ball-like motion
• Spherical cyst with refractive characteristics with internal encapsulated components.
• Cyst stage does not result in multiplication of nuclei.

Balantidium Coli Disease Progression

• Incubation is 4-5 days and causes Balantidiasis or Balantidial Dysentery.
• Extraintestinal spread may occur via hyaluronidase enzymes.
• Presence of Salmonella can further agravvate this process.

Balantidium Coli Manifestations and Diagnosis

• Asymptomatic, Acute and Chronic
• Can spread to extraintesinal areas through appenditicis.
• Biopsy spxs can direct exam via sedimentation and biowpsy
• Transmission includes humans and contaminated feces.
• Treat with metronidazole and avoid unsafe fertilizer usage

Blastocystis Hominis

• Currently known as commensal of GIT, and member of Stramenopiles class.
• MOT includes ingestion of thick-layered cysts which still has more research.
• Some includes the classical vacuolated of having granular, multivavular and and abemoid structure.
• Disease symptoms depends pathology .
• Some have irritable bowel syndrom.
• Most are zoonotic, found worldwide, culture test with subtype for humans
• Treat Metronidazole.