Intestinal, Oral, Genital, Blood and Tissue Flagellates

Vocabulary flashcards covering flagellate taxonomy, general structures, Giardia lamblia morphology, life cycle stages, and host immune response.

Giardia lamblia

An intestinal flagellate parasite (also known as G. duodenalis or G. intestinalis) that inhabits the duodenum and upper jejunum of humans and causes giardiasis, a diarrheal disease.

Trichomonas vaginalis

A genital flagellate parasite responsible for trichomoniasis, a sexually transmitted infection.

Blood and Tissue Flagellates

Flagellate parasites transmitted by sandflies that cause leishmaniasis.

Old World Leishmaniasis

Form of leishmaniasis caused by parasites such as Leishmania donovani and Leishmania tropica.

New World Leishmaniasis

Form of leishmaniasis caused by members of the Leishmania braziliensis complex.

Flagella

Long whip-like cytoplasmic extensions used by flagellates (Class Mastigophora) for movement and sometimes feeding.

Blepharoplasts

Basal bodies from which flagella arise.

Axostyle

A central supporting rod found in some flagellate species that provides rigidity.

Undulating membrane

A fin-like structure supported by a basal fibre that aids in locomotion, especially in parasitic forms.

Sucking disc

A concave structure located on the ventral surface of the Giardia lamblia trophozoite that acts as an organelle of attachment.

Giardia lamblia Trophozoite

The active feeding form of G. lamblia; pear-shaped with a rounded anterior and pointed posterior end, convex dorsal surface, concave ventral sucking disc, and bilaterally symmetrical with 1 pair of nuclei, 1 pair of axostyles, 1 pair of parabasal bodies, 4 pairs of flagella, and 4 pairs of blepharoplasts.

Giardia lamblia Cyst

The transmission stage or infective form of G. lamblia; oval in shape, measuring $11\text{--}14\text{ }\frac{1}{10^6}\text{m} \times 7\text{--}10\text{ }\frac{1}{10^6}\text{m}$ ($11\text{--}14\text{ }\times 10^{-6}\text{m} \times 7\text{--}10\text{ }\times 10^{-6}\text{m}$ or $11\text{--}14\text{ }\frac{1}{\text{m}} \times 7\text{--}10\text{ }\frac{1}{\text{m}}$), containing two pairs of nuclei (4 total) and resistant to external environmental conditions.

Morphological forms of Giardia lamblia

The two structural stages of G. lamblia: the flagellated feeding trophozoite with sucking disc and axostyles, and the infective oval cyst containing nuclei.

Excystation

The process occurring in the duodenum within 30 minutes of cyst ingestion, where each G. lamblia cyst hatches out two trophozoites.

Encystation

The process occurring during transit down the colon as intestinal contents lose moisture, resulting in the formation of cysts passed in formed stools.

Variant-specific surface proteins (VSPs)

Cysteine-rich zinc finger proteins involved in surface antigenic variation in Giardia lamblia that help the parasite evade the host immune response.

IgA (in Giardiasis)

An antibody critical for host defense and clearance of G. lamblia by inhibiting parasite adherence; highly present in breast milk to protect breast-fed infants.

Athymic mice

Mice lacking T cells that suffer from chronic infection when infected with G. lamblia due to absent cellular immunity.