Blastocystosis

Blastocystis hominis, although previously regarded as a yeast, has the morphological and biological characteristics of a protozoon. Very little is known of the basic biology of this organism. Several morphological forms have been recognised: ameboid, vacuolar, avacuolar, multivacuolar, granular, cyst). The life cycle is not well known. Which of the forms is responsable for transmission is not known. Molecular typing has revealed extensive genetic diversity in morphological identical strains.

Until about 1930 it was regarded as a cause of diarrhoea, but thereafter it was generally considered to be an apathogenic commensal. The parasite colonises chiefly the caecum and to a lesser extent the distal colon. Since 1975, Blastocystis hominis has once more been regarded as responsible for long-term but less specific cases of diarrhoea. The pathogenicity appears to depend on the parasitic load (more than 5 Blastocystis per 40x field). The pathogenicity of Blastocystis nevertheless remains controversial. For some clinicians it is only an indication of the presence of one or other parasite or microorganism which is responsible for the symptoms of disease. If considered necessary, imidazoles such as metronidazole or otherwise clioquinol are used for treatment

Category: Medicine Notes