Isolation and Morphologic Differentiation of Blastocystis from Insect
Vectors Using Staining Media
Sherwin B. Toriano, Jeannette C. Fabian, Myrna D. Matira, and Felicitas C. Aquino
School of Medical Laboratory Science, The Manila Times College of Subic
Received: 27 November 2025; Accepted: 02 December 2025; Published: 20 December 2025
ABSTRACT
The complexity of Blastocystis morphology, its presence in various insect vectors, and the need for accurate
detection methods warrant further research. This comparative, cross-sectional study aimed to detect Blastocystis
species in domestic insect vectors, including Periplaneta americana (cockroach), Musca domestica (housefly),
and Drosophila melanogaster (fruit fly). The study also evaluated the effectiveness of various staining
techniques, namely Acid Fast staining, Gram staining, Methylene blue wet mount, and Direct smear using
Lugol's solution, for differential enumeration and morphologic assessment of Blastocystis cysts. The results
showed that Blastocystis cysts were recovered from Periplaneta americana and Musca domestica. Notably,
Methylene blue and Lugol's Iodine in Direct smear yielded higher morphologic scores, suggesting that these
staining methods may be more effective for visualizing Blastocystis cysts in insect vectors.
Keywords: Blastocystis; insect vectors; staining media; external washings; intestinal contents.
INTRODUCTION
Blastocystis species is a unicellular, polymorphic protozoan that inhabits the large intestine of humans and
various animals [1]. Its diverse morphological forms, including vacuolar, granular, amoeboid, and cyst forms,
contribute to its complex life cycle and pathogenicity [2]. Transmission occurs through the fecal-oral route, often
in poor hygienic conditions, and can involve human-human or animal-human transmission [3]. Blastocystis is a
prevalent parasite in human fecal samples, with higher rates in developing countries [4]. Close contact with
domestic animals and livestock can also facilitate transmission [5]. Insect vectors, such as houseflies and
cockroaches, can contaminate food and transmit diseases, including parasites like Blastocystis [6].
The role of Blastocystis in human disease remains debated, with symptoms including diarrhea, abdominal
cramps, and nausea [7]. While some studies suggest pathogenic potential, others have raised doubts due to
concomitant presence of other pathogens [8].
Various techniques can detect intestinal Blastocystis, including DNA probes, PCR, and direct fluorescent
antibody methods [9]. However, these methods are often expensive and inaccessible in developing countries.
Direct fecal smear microscopy is a widely used and cost-effective method, but requires skilled microscopists to
identify the parasite's diverse morphologic forms [10].
Several studies have investigated the sensitivity and specificity of direct fecal smear in detecting Blastocystis in
human fecal samples, with varying results. Staining methods have been less frequently explored, but notable
studies include the standardization of Blastocystis hominis diagnosis using Gram and May-Grünwald-Giemsa
staining [11]. Giemsa stain was used to diagnose Blastocystis in domestic bird species [12]. Khalifa et al. [13]
evaluated various staining methods, including Giemsa, trichrome stain, and others, finding Safranin-Methylene
blue to be a promising option.
This study differs from previous research in several key aspects. The Blastocystis used in this study was obtained
from insect vectors, not from humans or a specific Blastocystis subtype from a stock culture. While various
staining techniques have been explored, there is still no considered ideal method for routine use in detecting
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