GIARDIA LAMBLIA & TRICHOMONAS

TABLE OF CONTENT

GIARDIA LAMBLIA

Giardia lamblia causes giardiasis associated with diarrheal manifestations. It bears flagella as the organ of locomotion.

G. lamblia lives in duodenum and upper jejunum and is only protozoan parasite found in the lumen of human small intestine.

MORPHOLOGY

It exists in two forms :

  • Trophozoite form
  • Cyst form

TROPHOZOITE

Presence of trophozoites indicate active stage of the disease.

Measure :  10-20µm in length and 5-15µm in width.

Shape: In front view, it is pear shaped or tear drop or tennis racket shaped.

              In lateral view ,its appears as a spoon or sickle shaped

Motility: it has a falling leaf like motility

Symmetry ;

•One  pair of nuclei

•Adhesive or sucking disk 

•Four pair of flagella

•Pair of axonemes

CYST FORM

The cyst is oval in shape and it is 12 µm long and 7 µm broad.

There are four nuclei.

The axoneme lie diagonally, forming a dividing line within the cyst .

LIFE CYCLE

Host: giardia completes its life cycle in one host.

Infective form    :        cyst  

Pathogenic form :  trophozoite

LIFE CYCLE OF GIARDIA LAMBLIA

LAB DIAGNOSIS

  • Microscopic examination
  • Antigen detection
  • Antibody detection

1. MICROSCOPIC EXAMINATION

Demonstration of giardia cysts in the formed stools and the trophozoites of the parasite in diarrhoeal stools by wet preparation (normal saline and iodine) is useful for diagnosis.

ENTEROTEST

It uses a gelatin capsule attached to a thread containing a weight.

The patient is asked to swallow a gelatin capsule which contains a nylon thread at one end.

The free end of the nylon thread is attached to the cheek of the patient.

The capsule passes through stomach to the duodenum.

In the stomach, the capsule is dissolved and thread remains in the duodenum and jejunum.

After two hours, the thread is withdrawn and places in a tube containing saline and mechanically shaken.

The centrifuged deposit of the saline is examined microscopically for motile trophozoites of G. lamblia.

2. ANTIGEN

Fluorescent method using monoclonal antibodies and ELISA test have been developed for detection of giardia antigen in feces.

The triage micro parasite panel is an enzyme immunoassay kit that can detect E. histolytica , E. dispar, Giardia lamblia and cryptosporidium parvum in the stool specimen.

It is a rapid test as results are available within 15 minutes.

3. ANTIBODY DETECTION

Anti-giardia antibodies may be detected in the patient serum.

ELISA and indirect fluorescent antibody test have been used.

However, it cannot differentiate present or past infection and hence is not useful in diagnosis.

TREATMENT

Tinidazole is considered as the drug of choice .

Metronidazole or nitrazoxanide is gurazolidone is given alternatively.

Furazolidone is given to children and auranofin, paromomycin can be given in pregnancy.

PREVENTION

Improved food and personal hygiene .

Boiling or filtering of potentially contaminated water.

Treatment of asymptomatic carriers.

No vaccine is currently available.

TRICHOMONAS

Trichomonas differs from other flagellates , as they exist only in trophozoite stage . Cystic stage is not seen .

Genus trichomonas has divided into three species :

  1. Trichomonas vaginalis ( T. vaginalis )
  2. Trichomonas hominis ( T. hominis)
  3. Trichomonas tenax ( T. tenax )

MORPHOLOGY

It is pear shaped about 10-30µm in length and 5-20µm in breadth with short undulating membrane reaching upto the middle of the body.

It has four anterior flagella and one lateral flagellum called as recurrent flagellum which traverses the parasite as an undulating membrane than in turn supported at the base by rod like structure named “costa”.

The single ovoid nucleus is present at the anterior end and the posterior end is pointed.

The axostyle runs down the middle of the body and end in the pointed tale like extremity.

It is motile with a jerky movement. It divides by binary fission.

The trophozoite is the infective form as there is no cystic form.

MODE OF TRANSMISSION

The trophozoite cannot survive outside and so infection has to be transmitted directly from person to person . Sexual transmission is the usual mode of infection.

Trichomoniasis often coexist with the other sexually transmitted diseases like candidiasis, gonorrhea, syphilis or HIV.

Babies may get infected during birth.

Vaginal pH of more than 4.5 facilitate infection.

LIFE CYCLE

Trophozoite has two forms:

1.Flagellated trophozoite : it is the infective form as well as the diagnostic form.

2.Amoeboid trophozoite : it is an actively replicating form, found in the tissue feeding stages of the life cycle.

Asymptomatic females are the reservoir of infection.

Human acquire infection by  sexual route flagellated trophozoite after entry , transform into amoeboid forms.

These forms which multiply in the genital tract  cause infection. They again transform back to flagellated trophozoite that are discharge in vaginal secretions.

PATHOGENESIS AND CLINICAL FEATURES

T. vaginalis particularly infects squamous epithelium .

It secrets adhesins proteins which helps in attachment to the vaginal epithelium .

In females, it may produce vulvovaginitis characterized with an offensive yellowish discharge.

Colpitis macularis : strawberry appearance of vaginal mucosa is observed in 2% of patients .

The infection is often asymptomatic especially in males, although some may develop urethritis , epididymitis and prostatitis.

LAB DIAGNOSIS

Microscopic examination

a)Wet mount preparation:

  • Vaginal or urethral discharge is examined microscopically in a drop of saline for characteristic motile trophozoite with jerky movement. It is named “wet mount” preparation.
  • Specimen should be examined within 10-20minutes of collection.

STAINING METHODS

•Fixed smears stain with Giemsa stain and observed under light microscope.

•Direct fluorescent antibody (DFA) test is another method for detection of parasite. It is more sensitive than wet mount preparation.

Acridine orange fluorescent stain can be used it is rapid and sensitive comparable to wet mount.

CULTURE

Culture is considered as a gold standard method for diagnosis of t. vaginalis infection.

The parasite can be isolated from urethral and vaginal discharge on a variety of media.

CPLM (cysteine, peptone, liver, maltose) medium is often used.

“In pouch TV” is selective culture device for inoculation of specimen at point of care

Antigen detection

ELISA is used for demonstration of Trichomonas antigen.

Rapid immunochromatographic (ICT) is also available for detection of antigen.

Molecular methods

 Nucleic acid hybridization method and polymerase chain reaction for the diagnosis of trichomoniasis.

OTHER SUPPORTIVE TEST

Positive whiff test: fishy odor is accentuated when a drop of 10% KOH is added to production of amine.

It is positive in more than 75% of cases.

It is also positive in bacterial vaginosis

Treatment

Metronidazole or tinidazole is the drug of choice.

Prevention :

1.Treatment of both the partners.

2.Safe sex practices like use of condoms .

3.Avoidance of sex with infected person .

4.There is no effective vaccine licensed so far.

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