Trichomonas vaginalis
History:
¢ First observed by Donne in 1836 in
vaginal secretions.
Habitat:
¢ Inhabit
-
Female:
vagina and urethra
-
Male:
prostate gland, seminal vesicles and
urethra.
Morphology
¢ Exist only as trophozoites and
is infective form of parasite.
¢ Cyst form absent.
¢ Trophozoites:
-
Shape:
ovoid or pear-shaped.
-
Size:
7-23µm in length and 6-8µm wide.
-
Short
undulating membrane reaching upto the middle of the body.
-
Single
nucleus, located in the anterior portion .
-
Prominent
axostyle that runs throughout the length of
the body and projects posteriorly.
-
Presence
of five flagella, impart charcteristic motility known as wobbling or rotatory
movement.
-
Four
anterior free flagella, arising from a
shallow depression in the anterior end of the body called periflagellar canal.
-
Fifth
flagellum curves back along the margin of the undulating membrane and is called
the recurrent flagellum.
-
Not
enclosed by undulating membrane but lies in a shallow groove in the free margin
of the membrane.
-
Just
beneath the membrane lies the costa, a unique rigid cord, filamentous in
appearance that supports undulating membrane.
-
Cytoplasm
contains large numbers of chromatin granules around costa and axostyle.
-
Simple,
completed in a single host either male or female.
-
Infection
transmitted sexually from a women acting as a reservior of infection to man.
-
In
female, parasite gets nourishment from the mucosal surface of the vagina, and
from the ingested bacteria and erythrocytes.
-
Reproduce
by longitudinal binary fission, begins by division of nucleus, followed by
division of neuromotor apparatus and finally separation of cytoplasm into two
daughter trophozoites.
-
Trophozoites
are infective stages.
-
On
sexual contact, trophozoites transmitted to male and localise in the urethra
and prostate gland.
-
These
trophozoites under go replication in the same way as in vagina of female.
Pathogenesis
¢ Non invasive parasite, remains
adherent to the mucosal epithelium of the vagina or urethra and causes
superficial lesions. Infects squamous epithelium but not columnar epithelium.
¢ Virulence factor:
-
Protein
liquids and Proteases- helps in adherence of trophozoites to epithelial cells
of the genito-urinary tract.
-
Enzyme
cysteine protease- responsible for haemolytic activity.
-
Normally,vaginal
epithelial surface is rich in glycogen and lactobacillus. Lactobacillus
converts glycogen to lactic acid that maintains acidic pH of vagina.
-
Parasite
feed on host vaginal cells, results in disruption of the glycogen levels and
vaginal bacterial flora leading to rise in pH level. The parasite thrives at pH
levels that exceed 4.9.
-
May
occur epithelial erosion which lead to petechial haemorrhage and metaplastic
changes in the epithelium.
Clinical
disease
¢ Incubation period- ranges from 4-28 days.
¢ Cause trichomoniasis.
¢ In women,
-
altered
vaginal environment is common, have a scant, watery vaginal discharge.
-
Vaginitis may occur, with symptoms like
itching, burning and painful urination along with profuse, forthy and
malodorous discharge containg bacteria, pus and trophozoites.
-
PID
most important complication.
-
Pregnant
women infected with T.vaginalis , more likely to have premature rupture
of membranes, premature birth and pre-term or low birth weight baby.
¢ In men,
-
infections
are usually asymptomatic.
-
Occasionally
experience urethritis, prostatitis and cystitis.
-
May
occur infertility.
¢ Both in male and female, infection is
associated with gonorrhoea, chlamydia, and HIV infections.
Laboratory
diagnosis
¢ Specimen: vaginal and urethral
discharges, prostatic secretion, endocervical specimens or urine sediments.
¢ Microscopy:
-
Direct
wet mount: a small amont of freshly collected specimen is mixed with a drop of
saline on a microscope slide and covered with a coverslip. Examine under low
power for presence of actively motile trophozoites. If motility diminishes, it
may be possible to observe movement of undulating membrane, under high dry
power.
-
Staining:
stained (giemsa, papanicolaou) preparetion of dry smear may be examined, but
oragnisms may be difficult to recognise.
¢ Culture:
-
More
sensitive than wet mount (93% sensitivity), but not routinely used as it is
expensive and somewhat technically difficult.
-
Variety
of media like
Ø Bushley’s, Feinberg-Whittington,
Roiron’s and Johnson-Trussel etc can be used.
Ø CPLM (Cysteine peptone liver maltose)
medium is frequently employed.
Ø Plastic envelope medium is also used
and its sensitivity is reported to be superior to other available techniques.
¢ Other methods:
a)
Serological
test: indirect haemagglutination and gel diffusion test are used for antibody
detection.
b)
Gene
probes: monoclonal antibodies and DNA probes are also effective.
c)
PCR:
also used nowadays.
Treatment
¢ Metronidazole (200-250 mg orally
thrice daily for 5-7 days)
¢ To prevent recurrence, patient’s
sexual partner should be tested and trated.
¢ Strains resistant to metronidazole is
treated with tinidazole.
¢ During pregnancy, topical therapy
with clotrimazole, in a dose of 100mg daily for 6 days is effective.
