UTTAR PRADESH JOURNAL OF ZOOLOGY

Blastocystis hominis is an anaerobic, single-celled protist classified under the class Blastocystea. It is globally recognized as a significant intestinal protozoan associated with gastrointestinal disturbances and is considered the most commonly detected non-fungal microeukaryote in human fecal specimens. Clinical presentations among infected individuals are frequently asymptomatic or mild; however, symptomatic cases may involve diarrhea, abdominal discomfort, bloating, and altered bowel habits. In the Philippine setting, B. hominis continues to be a noteworthy public health issue, particularly in communities lacking adequate sanitation and hygiene. Reported infection rates vary widely, with higher prevalence noted among immunocompromised populations such as the elderly in urban settings and even more so in rural areas. Specific subpopulations, including inmates and food service workers, have also shown measurable infection rates. Subtype ST3 is the most prevalent, in line with global findings, and may have pathogenic potential. Zoonotic transmission is supported by its detection in a range of animals, including poultry, swine, non-human primates, insects, and domestic dogs, with pigs exhibiting the highest carriage rates. Although molecular methods like PCR have improved detection accuracy, microscopy remains the most commonly used diagnostic tool in Philippine laboratories, largely due to economic and logistical limitations. However, microscopy has markedly lower sensitivity compared to PCR, potentially contributing to underdiagnosis and underreporting. Addressing these diagnostic constraints alongside implementing targeted public health strategies is essential. Given the limited scope of local studies on B. hominis from 2011 to the present, this review underscores critical research gaps and emphasizes the need for comprehensive national surveillance and intervention programs to mitigate the parasite’s impact.