BackgroundBlastocystis sp., a widely prevalent intestinal protozoan parasite is found in a wide range of animals, including humans. The possibility of zoonotic transmission to human from birds especially ostriches led us to investigate on the cross infectivity of Blastocystis sp. isolated from the ostrich feces as well as the phenotypic and subtype characteristics. There is a need to investigate this especially with the rising number of ostrich farms due to the growing global ostrich industry.Findings100% of the ostriches were found to be positive for Blastocystis sp. using the in-vitro cultivation method. Transmission electron microscopy revealed high electron dense material in the central body of the vacoular forms. The membrane layer of the ostrich isolate was significantly (p = 0.003) thicker as compared to human isolate. Sudan staining revealed that this was lipid accumulation. We provide evidence for the first time, the existence of subtype 6 which has been previously reported only in pigs and cattle. Cysts, ranging from 3.0 to 7.0 μm in diameter caused experimental infection in Sprague Dawley rats implicating that Blastocystis sp. isolated from ostriches exhibits low host specificity.ConclusionThe study for the first time demonstrates that Blastocystis sp. subtype 6 do exist in ostriches and show high lipid storage in the vacuoles of the parasites. The study further provides evidence for potential zoonotic transmission in ostrich farms as Blastocystis subtype 6 can infect rats and the same subtype have been previously reported in humans.

Blastocystis sp., an intestinal organism is known to cause diarrhea with metronidazole regarded as the first line of treatment despite reports of its resistance. The conflicting reports of variation in drug treatment have been ascribed to subtype differences. The present study evaluated in vitro responses due to metronidazole on ST3 isolated from three symptomatic and asymptomatic patients, respectively. Symptomatic isolates were obtained from clinical patients who showed symptoms such as diarrhea and abdominal bloating. Asymptomatic isolates from a stool survey carried out in a rural area. These patients had no other pathogens other than Blastocystis. Ultrastructural studies using transmission electron microscopy (TEM) and scanning electron microscopy (SEM) revealed drug-treated ST3 from symptomatic patients were irregular and amoebic with surface showing high-convoluted folding when treated with metronidazole. These organisms had higher number of mitochondrion-like organelle (MLO) with prominent cristae. However, the drug-treated ST3 from asymptomatic persons remained spherical in shape. Asymptomatic ST3 showed increase in the size of its central body with the MLO located at the periphery.

Background: Blastocystis sp., a widely prevalent intestinal protozoan parasite is found in a wide range of animals, including humans. The possibility of zoonotic transmission to human from birds especially ostriches led us to investigate on the cross infectivity of Blastocystis sp. isolated from the ostrich feces as well as the phenotypic and subtype characteristics. There is a need to investigate this especially with the rising number of ostrich farms due to the growing global ostrich industry.