[The initial phase of cyst formation in Sarcocystis dispersa sarcosporidians]

Area of Science:

• Veterinary Parasitology
• Cell Biology
• Microbiology

Background:

• Sarcocystis dispersa is an apicomplexan parasite that infects various mammals.
• Understanding the early developmental stages of Sarcocystis is crucial for disease control and prevention.

Purpose of the Study:

• To investigate the early intracellular development of Sarcocystis dispersa in mice.
• To characterize the morphology and location of early parasitic stages.

Main Methods:

• Oral inoculation of six white mice with Sarcocystis dispersa sporocysts.
• Necropsy and tissue sampling on days 10, 12, and 14 post-inoculation.
• Light microscopy to identify and characterize parasitic stages within host cells.

Main Results:

• Pre-cyst merozoites were identified in leukocytes and muscle cells by days 10 and 12 post-inoculation.
• These merozoites in muscle cells lacked a parasitophorous vacuole.
• Young sarcocysts, containing only metrocytes, were observed by days 12 and 14 post-inoculation.
• The transformation of merozoites into metrocytes occurred concurrently with sarcocyst wall development.

Conclusions:

• The early asexual proliferation of Sarcocystis dispersa occurs within leukocytes and muscular cells.
• The absence of a parasitophorous vacuole around muscle-invading merozoites is a key feature.
• Sarcocyst wall formation is initiated during the transformation of merozoites into metrocytes.