43. Trichomonas vaginalis. Trichomonas tenax. Giardia lamblia (Lamblia intestinalis).

Genus Trichomonas. Giardia lamblia (Lamblia intestinalis).

• The genus Trichomonas belongs to the phylum Parabasala, which includes flagellated protozoa.
• These organisms are anaerobic, meaning they thrive in oxygen-poor environments like mucosal linings.
• They are found in human mucosal surfaces such as:
• The oral cavity
• The gastrointestinal tract
• The urogenital tract
• They are pear-shaped, with a central axostyle and multiple anterior flagella that help with motility.

Morphological Features

• Axostyle: A rod-like internal cytoskeletal structure running along the body length; supports cell shape and sometimes protrudes from the rear end.
• Flagella: Vary in number (typically four or more); provide locomotion.
• Undulating membrane: Present in some species (e.g., T. vaginalis); aids in movement in viscous environments.
• No cyst form: Trichomonas species exist only as trophozoites, which is unusual among protozoan parasites.
• Reproduce asexually through binary fission.

Genomic Insights

• Genome studies have revealed the presence of meiosis-specific genes, suggesting potential for genetic recombination, even though no sexual cycle has been directly observed.
• Genes similar to those involved in homologous recombination and crossing-over in eukaryotes have been detected.

Important Human Species

Trichomonas tenax

• Habitat: Found in the oral cavity, especially around dental calculus, periodontal pockets, or cavities.
• Size: Typically measures 6 to 10 micrometers in length.
• Nature: Considered a commensal organism; it survives in the mouth without causing active disease but may be opportunistic in poor hygiene.
• Association:
• Found more frequently in individuals with poor oral hygiene
• Associated with advanced periodontal disease
• Transmission:
• Occurs via saliva exchange, such as kissing
• Through droplet spray while speaking or sneezing
• Via shared utensils, contaminated drinking glasses, or water

Trichomonas hominis (Pentatrichomonas hominis)

• Habitat: Found in the large intestine (colon) of humans.
• Size: Ranges from 5 to 15 micrometers.
• Nature: Also a commensal, generally considered non-pathogenic
• Controversy: Occasionally found in diarrheal stools, but its role as a pathogen remains uncertain.
• Morphological Features:
• Has five flagella and a long undulating membrane that extends nearly the entire body length.
• Transmission:
• Occurs through fecal-oral route
• Ingestion of contaminated water, food, or utensils
• Cyst Form: Absent; transmission depends on the survival of trophozoites in favorable environments.

Giardia lamblia (also known as Lamblia intestinalis)

General Characteristics

• Giardia lamblia is a flagellated protozoan parasite that infects the small intestine of humans and various animals.
• Belongs to the phylum Metamonada, class Diplomonadida.
• It is a significant cause of protozoal diarrhea worldwide, especially in areas with poor sanitation.
• Infection by Giardia is referred to as giardiasis.

Morphological Forms