Subphylum: Mastigophora(flagellates)

↓Oro-intestinal- Uro-genital

↓

Haem-osomatic

Trichomonas tenax T. vaginalis

Giardia intestinalis

Chilomastix mesnili.

Trichomonas hominis

Dientamoeba fragilis

Embadomonas intestinalis.

Enteromonas hominis.

A- Oro-intestinal- urogenital flagellates:

General Characters:1- Infection occurs in the buccal cavity, the

intestine or the uro-genital tract.

2- The infective stage is either the vegetative or the cystic form.

3- Transmission of infection is direct one.

1- Giardia intestinalis(Giardia lamblia)

Geographical distribution: world-wide.

It is considered the main cause of diarrheal outbreaks from contaminated water supplies.

Morphology: Tow forms can be visualized microscopically.

A- Trophozoite

B- Cyst

A- Trophozoite:- The body is bilaterally symmetrical.- Size: 12 x 6 μ.- It is pear-shaped with an anterior rounded and

posterior tapering parts. - It has a convex dorsal surface and a flat ventral

one which is modified in its anterior part forming a sucking disk acting as an attachment organ.

Trophozoite:

- Two vesicular nucleus.

- Two median bodies

(curved rods)

called parabasal bodies.

- Four pairs of flagella.

-The intracytoplasmic part

(axonemes) of posterior

two flagellae (axostyle)

extend through the body

dividing it and become

free posteriorly.

B- Cyst:

- Size is 10 x 5 μ.- It has double-colourless wall.- It contains four nuclei usually gathered at one pole.- Cytoplasm is often retracted at one side.- Remnants of the flagellae, median bodies and axostyle are

clearly seen.

Giardia trophozoite & cyst

Life Cycle:

Habitat: -In the upper part of small intestine (duodenum

and upper jejunum).

- Trophozoites stick closely to the mucosa and they may

penetrate the crypts of mucosa.

- They may be found in the gall bladder and bile ducts.

Definitive host: Man is the natural host.

Reservoir hosts: Many animals (dogs, rodents,

monkeys, pigs….ect.) Giardia is a zoonotic disease.

Infective stage: Mature quadrinucleated cyst.

Mode of infection: faeco-oral transmission cycle:

1) Cysts may be ingested with contaminated food and water or transmitted by house flies, cockroaches…ect.

2) Person to person transmission occurs especially among school children, prisoners and in nurseries.

3) Autoinfection by hand-to-mouth transmission.

- Trophozoites replicate by longitudinal binary fission.- Excystation occurs in upper part of the small intestine

stimulated by alkaline pH there. - Cyst → two trophozoites.

Pathogenecity and Clinical Picture:

- Trophozoites live closely to intestinal mucosa attached by their sucking discs→ mechanical irritation.

- Attachment is facilitated by a parasite secreted lectin which is activated by duodenal secretion→ derangement of normal villous architecture.

- Shortening, blunting of villi up to total atrophy.- Inflammatory foci in crypts and lamina propria.

Resistance to giardiasis:It is indicated by spontaneous cure of the disease

that may occur after about 40 days.- Lymphocytes, macrophages and secretory IgA

are important for resistance. - Human Milk is able to kill Giardia trophozoites

via lipase and IgA, so it can afford protection to breast fed babies.

The prepatant period is 10-36 days.The disease may be asymptomatic in many

cases.

Symptoms

may be:1) Diarrhea, flatulance, distension, epigastric

pain, crampy abdominal pain, anorexia and weight loss.

2) Sreatorrhea (fatty diarrhea) and malabsorption syndrome (Steatorrhea → greasy, pale yellow, frothy foul smelling and bulky stool) may occur due to:

a- Physical occlusion of mucosa by attached parasites.

b- Enterotoxin secretions by the parasite.c- Deconjugation and consumption of the bile salts.d- Villous atrophy.

This patient has: - ↓ absorption of carotene, folate and vit B12

- ↓ activity of lipase, ↓ secretion of disaccharidases, lactose and other enzymes → Lactose intolerance.

3) Severe symptoms: (in immunocompromized)- Persistent steatorrhea.- Fat-soluble vitamins deficiency. - Hypoproteinaemia- Cholangitis and cholecystitis → jaundice &

biliary colic

Predisposing factors to symptomatic giardiasis:1- Achlorohydria, hypogammaglobinaemia and relative

↓ secretory IgE.2- Young age (infants and children).3- Bacterial colonization ↑ damage by Giardia

trophozoites.

Diagnosis:1) Clinical diagnosis: C/P of the disease.2) Laboratory diagnosis:A- Direct: - Stool examination by direct smear- concentration

methods. ** Repeated ex. for 3 times must be done (due to

intermittent shedding of the parasite). - Examination of duodenal fluid which may be taken by

duodenal aspiration or by Enterotest (string-test).

B- Indirect: - Serological tests: IFA and ELISA. - Detection of copro-antigen by ELISA.

Enterotest capsule

Treatment:1) Fasigyn as a single dose.2) Metronidazole (Flagyl). (Not given to pregnant women: teratogenic)3) Albendazole.

Prevention and Control:- Environmental sanitation as: anti-fly measures, proper

sewage disposal and safe water supply.

- Faeces must not be used as fertilizer.

- Health education for: washing of green vegetables, fruits and hands before eating.

- Treatment of cases especially the carriers.

The Non-Pathogenic Intestinal Flagellates

All inhabit large intestine. All are harmless commensals. Multiplies by binary fission. The cyst is the infective stage.

1- Embadomonas (Retortamonas) intestinalis

Trophozoite: elongate, pyriform, 6×4μ in size.

- Anterior cleft-like cytostome.

- One vesicular nucleus.

- Two blepharoplasts give rise to 2 flagellae

(one directed anteriorly & the other pass

through cytostome posteriorly free.

Cyst: uninucleated, pyriform, 5×4μ in size.

2- Chilomastix mesniliTrophozoite: asymmetrical pear shaped,

about 15×8μ in size.

- Anterior cleft-like cytostome.

- One vesicular nucleus.

- Six blepharoplasts (near nucleus)

give rise to 3 free flagellae anteriorly,

2 surround the margins of the cytostome

& the last pass through it.

Cyst: uninucleated, lemon-shaped,

6×8μ in size.

Chilomastix mesniliTrophozoite:

Cyst:

3- Enteromonas hominisTrophozoite: oval in shaped,

about 16×4μ in size.

- No cytostome.

- One vesicular nucleus.

- Four blepharoplasts (near nucleus)

give rise to 3 free flagellae anteriorly,

& the fourth pass posteriorly.

Cyst: ovoidal in shaped,

5×4μ in size.

Mature cyst is quadrinucleated.

Human Trichomonads

There are 3 species:1-Trichomonus vaginalis.

1-Trichomonus hominis (intestinalis).

2-Trichomonus tenax (buccalis).

-They have 4 anterior flagellae, an undulating membrane, an axostyle and a cytostome.

- There is no cyst formation but exist only in the trophozoite stage (The infective stage).

Trichomonas vaginalis (Pathogenic urogenital flagellates)

Disease: Trichomoniasis, trichomonad vaginitis, urethritis, prostate vesiculitis.

Geographical distribution: world wide.

Morphology:- It is colourless pyriform flagellate (robust)- Size is 17 × 10 μ, - Anterior cleft-like cytostome.- One vesicular nucleus.- Four flagellae directed anteriorly,- Another one attach to 1/3 of the body of the parasite

undulating membrane. - The 6th flagellum passes through the body as thin axostyle

and projects out posteriorly.- A thick rod called parabasal body present between axostyle

and the undulating membrane.

Trichomonas vaginalis trophozoite

UF

A

10 m

Life cycle:• Habitat: -In females: posterior fornix of the vagina, cervix and

sometimes urethra -In males: urethra, epididymis, prostate & seminal

vesicles.• Definitive host: only man (no intermediate host).• Infective stage: trophozoites.• Mode of infection:1- Transmission occur during sexual acts or through

contaminated inner clothes, towels, toilet seats…ect.2- Trichomonas conjunctivitis may affect babies that

acquired the infection while passing through the birth canal of their infected mothers.

• Multiplication: by longitudinal binary fission.

Pathogenesis & Clinical picture:• Up to 50% of infected females & 95% of infected

males are asymptomatic.• The parasite is able to produce contact dependent

cytopathic effect (kill cells without phagocytosis).• Also it produces a cell detaching factor (its amount

correlates with severity of the manifestation).

Predisposing factors for pathogenicity:

- Change of normal acidic vaginal pH: 3.8- 4.4 (due to lactic acids produced by Doderlein’s bacilli bacterial flora) in to alkaline side (↑ pH).

- Change of physiologic status of the vagina and ↓ the secretory IgA.

1) In Female:

- In Trichomonas vaginitis, vaginal walls are red, tender with hyperaemia and petechial haemorrhage.

- Mucosa shows erosion and necrosis- Vaginal surface is covered by seropurulent, frothy

creamy or yellowish exudates.

- Patients complaint of:

- Itching and burning sensation with profuse yellowish leucorrheic discharge.

- Dyspareunia (painful sexual intercourse), dysuria and frequency of micturation can occur, also cystitis.

( A relation to cervical carcinoma was suggested).

2) In Males:- Infection generally is asymptomatic but urethritis

vesiculitis, epididymitis and prostatitis may occur.

• Patients complaint of:

- Dysuria with thin discharge.

- Enlarged prostate with tender epididymis.

3) In New born:

- Trichomonas respiratory tract infection and conjunctivitis may occur.

Diagnosis:1) Clinical diagnosis: C/P of the disease.2) Laboratory diagnosis: A- Demonstration of the trophozoite. In females: - specimens obtained via vaginal speculum. In males: - examination of prostatic fluid.- Direct wet smear examination by phase-contrast

microscope ( motile trophozoites).- Staining with Giemsa, Leishman or Papanicolaou stains.- Examination of urine and urethral discharge in both.B- Culture of specimens on Modified Diamond media.C- Immunological tests for detection of T. vaginalis antigens

in the discharge by: - Direct fluorescent test using labeled monoclonal

antibodies(DFA). - Enzyme immunoassay.

Treatment:

1- Both partners must be treated at the same time.

2- Local vaginal suppositories as Silver picrate and Furazolidone.

3- Vaginal douching with lactic acid or vinegar for restoration of normal vaginal pH.

4- Metronidazole (most effective)

It is used after failure of local measures (?carcinogenic).

Prevention and control:- Attention to personal hygiene and health education.- Treatment of cases.- Abstinence from using common toilet articles.

Two other species of Trichomonas occur in humans

Pentatrichomonas hominis

Trichomonas hominis (T. intestinalis)

It is non pathogenic & inhabit the large intestine.

- Small, 12x8μ, pyriform.

- Has small antero-lateral cytostome (mouth), one nucleus, four free flagella anteriorly and one marginal forming undulating membrane along 2/3 length of the parasite with free end.

- Thick axostyle (flagellum) extends

antro-posteriorly along the middle

of the body, with no parabasal body.

-Transmission is direct,

through contaminated food

and drink by the vegetative form.

Trichomonas tenax(T. buccalis)

- It is non pathogenic parasite that inhabits the mouth especially in carious teeth & gums.

- It measures 10x6μ , pyriform in shape.

- Has cytostome, one nucleus, 4 free flagella and one marginal with undulating membrane 1/2 the lateral margin of the parasite with no free end.

- Slender axostyle and faint parabasal body.

- Transmission is by the use of

contaminated utensils with

the trophozoite or direct by kissing.

Dientamoeba fragilis

It was considered to be an amoeba, but its flagellate nature was discovered by electron microscope.

It is now classified among the trichomonads.

Geographical distribution: world wide.

Morphology:- It has no cyst stage.- Trophozoite: 7 × 12 μ, characterized by the presence of two

nuclei.- Their karyosomes are composed of granules 4-8 in

number.- Cytoplasm contains food vacuoles (contain bacteria).- Pseudopodia are leaf-like active in fresh stool.

Dientamoeba fragilis trophozoite

Habitat: mucosal crypts of large intestine of man.

(It may ingest RBCs but never invades the mucosa).

Infective stage: trophozoite.

Mode of transmission:

Transmission might occur via eggs of Entrobius vermicularis or Ascaris (trophozoite inside the egg)

as oral transmission failed.

Clinical picture: mucus diarrhea, abdominal pain, flatulence and weakness.

Diagnosis: careful examination of fresh saline smear of stool. Staining with iron haematoxylin is preferable.

Treatment:

- Idioquinol - Tetracycline - Paromomycin

Dientamoeba fragilis Life Cycle

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