A CERTAIN PARASITICAL INDEX VOL 2 Flashcards
Name the known parasitic flagellates
①Intestinal and Urogenital system:
– Giardia and Trichomonas
➁Blood and Tissues:
– Trypanosoma and Leishmania
Flagellates Phylum:
Sarcomastigophora
Flagellates Subphylum:
Mastigophora
Flagellates Class:
Zoomastigophora (mastix:whip)
Flagellates Suborder:
Diplomonadina
Flagellate Genus:
Giardia, Trichomonas, Chilomastix,
Enteromonas
Giardia lamblia( G. intestinalis and G. duodenalis) Habitat:
upper duodenum, adherent to microvilli
Giardia species
G. muris, G. agilis and G. lamblia
Morphology of G. lamblia
trophozoites & cysts
G. lamblia trophozoite morphology
- Trophozoites: contains 4 pairs of flagella, directed posteriorly that aid the parasite in moving, bilaterally symmetrical, pear shaped (pyriform), rounded anteriorly, tapering posteriorly
- Dorsal surface convex
- Ventral surface concave
- Sucking disc half anterior
- 9 – 21µm long x 5 – 15 µm
broad x 1.5µm thick
Two trophozoites hatch from one cyst
G. lamblia cyst morphology:
immature and mature with four nuclei
* Thick smoothed cyst wall, ovoid in shape or elliptical
* 8 – 12µm long x 7 – 12µm wide
* 4 pairs curved bristles, 4 nuclei either clustered at one end or present in pairs at opposite ends
* Cytoplasm off the wall anteriorly
* Axostyle runs diagonally through the cyst
* Flagella shorten and are retracted within cyst
– Provide internal support
What are the risk factors of developing Giardiasis?
- Travel in developing world
- Changing diapers
- Eating food without cooking
- Eating fruits or vegetables without washing
- Owning a dog
- Other groups at increased risk for infection include:
– children in day care institutions, homosexual men,
individuals with immunoglobulin deficiency states
(inherited or acquired)
What is the infective form of Giardia lamblia?
Infective form – mature cyst passed in faeces of man. It is a zoonosis.
more suscepitible is blood group A AND IMMUNIE DEFIECEINT
In the human body, where does Giardia spp excystation and encystation occur?
- Excystation occurs in stomach & duodenum within 30minutes
- Encystation occurs in transit down the colon
- Trophozoites multiply by longitudinal binary fission & colonize in duodenum & upper jejunum
Giardiasis infection timeline:
- Incubation period: Averages 1 – 2 weeks
- Average duration of symptoms ranges from 3-10weeks
- The infective dose: In humans about 10-25 cysts &are capable of causing clinical disease in 8 of 25
subjects
World wide: Leningrad’s curse, traveller’s diarrhoea
Giardiasis pathogenesis:
*Enterocyte damage, villi atrophy, crypt hyperplasia, intestinal hyperpermeability and brush boarder damage that causes a reduction in disaccharide enzyme secretion
*Lectins and other cytopathic substance secreted by parasite also causes indirect damage to intestinal epithelium
*Giardiasis results in decreased jejunal electrolyte water and glucose absorption, and damage to intestinal epithelium leads to malabsorption of electrolyte and fluids, resulting in osmotic diarrhoea known as giardiasis
*Occasionally, trophozoites can enter gall bladder, bile duct leading to jaundice
Diagnosis of Giardiasis:
①Microscopy of stool, duodenal aspirates
* Direct faecal smear: ideally 3 specimens from different days should be examined
– both saline and iodine
* Concentration Methods:
– ZnSo4 Floatation reveals cysts
– Formol ether sedimentation
* Trophozoites in soft, diarrhoeic stool
* Cysts in formed stool
➁Entero test (string test) – gelatin capsule containing a nylon string with a weight swallowed by the patient. Free end of the string is fixed to the mouth. Capsule
dissolves & the string is released in the duodenum. After overnight string is removed & bile stained mucus collected
③Culture
– Not done routinely
– Diamonds medium
④Serological methods
- An enzyme-linked immunosorbent assay (ELISA) to detect IgM in serum provides evidence of current infection
- A polyclonal antigen-capture ELISA can be used to demonstrate submicroscopic infections in feces and an IgA-based ELISA will detect specific antibodies in saliva
⑤Molecular diagnosis
– DNA probes & PCR for research purposes
Trichomonad general morphology:
a. Typically with four to six flagella (one flagellum in one genus and none in another)
b. In typical genera, one flagella recurved. free or with proximal or entire length adherent to body surface.
c. Undulating membrane, if present associated with adherent segment with curved flagellum
Trichomonas hominis (Pentatrichomonas hominis) Habitat:
Caecum, feeds on enteric bacteria
* Second commonest intestinal flagellate
next to Giardia.
* feeds on enteric bacteria
Morphology of T. hominis:
Only the trophic stage
1. Pyriform, semi rigid axostyle, cytosomal cleft, 5-14 microns
2. 4 anterior + 1 posterior flagella, posterior flagella free, undulating membrane
Trichomonas vaginalis Habitat:
vagina, urethra,
Prostate gland, preputial glands
Feeds on mucosal bacterial
- Obligate parasite
- Infects squamous epithelium but not columnar epithelium
- Facultative anaerobic parasite
- It produces energy by fermentation of
sugars in a structure called hydrogenosome - A modified mitochondria in which enzyme of oxidative phosphorylation is replaced by enzyme of anaerobic fermentation
T. vaginalis morphology
Only trophozoites
1. Pyriform flagellate
2. 4 anterior flagella + 1 on body margin
undulating membrane
3. posterior flagella does not extend beyond posterior of body
4. thick curved axostyle
5. cytostome small and inconspicuous
costa ( chromatin basal body)
6. Chromatin granules present in cytoplasm.
Diagnosis of T. vaginalis:
1.Finding Trich. in exudates, saline smear,
swim with undulating membrane
2. Pap smear
3. Fecal samples
4. In uretheritis Trich. seen in urine
5. No discharge in males – massage
needed
6. Antigen detection
7. PCR
8. Culture
Trichomonas tenax
Habitat: Mouth, Gingivals, margins of gums Tartar around teeth, cavities of carious teeth, tonsilar crypts
Transmission: close personal contact,
kissing, sharing utensils
Treatment: oral hygiene
