Submitted to: International Journal for Parasitology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: March 25, 2003
Publication Date: May 12, 2003
Citation: Dubey, J.P., Lindsay, D.S. 2003. Development and ultrastructure of besnoitia oryctofelisi tachyzoites, tissue cysts, bradyzoites, schizonts and merozoites. International Journal for Parasitology. 33:808-819.
Interpretive Summary: Besnoitia are single-celled parasites that cause mortality in animals. Scientists at the Beltsville Agricultural Research Center discovered a new species of Besnoitia, B. oryctofelisi that causes disease in domestic rabbits. In this paper they describe the parasite structure in detail. These findings will be of interest to biologists, pathologists and parasitologists.
Development and structure of different life cycle stages of Besnoitia oryctofelisi which has a rabbit-cat life cycle was studied by light and transmission electron microscopy. For light microscopy, B. oryctofelisi- infected tissues were stained with H & E, periodic acid Schiff (PAS) reagent, and immunohistochemically with rabbit anti-B. oryctofelisi polyclonal antibodies and anti-BAG-1 antibodies. In vitro and in vivo-derived tachyzoites were 5-6 µm long and they were found to divide by endodyogeny. In tachyzoites, the nucleus was often central, and micronemes were few and located anterior to the nucleus. Earliest tissue cysts were seen in gerbils starting 12 days p.i. Early tissue cysts had an outer PAS-positive cyst wall, a middle PAS-negative host cell layer, an inner PAS-negative parasitophorous vacuolar membrane. Organisms in early tissue cysts were PAS-negative, did not stain with anti-BAG-1 antibodies, and amylopectin granules and enigmatic bodies were absent. Tissue cysts beginning 17 days p.i. contained organisms that became PAS-positive and reacted with anti-BAG-1 antibodies, indicating they were bradyzoites. Immunoreactivity with polyclonal anti-B. oryctofelisi antibodies suggested that Besnoitia species bradyzoites are encapsulated by the host cell. Bradyzoites (10 ¿m) were about twice the length of tachyzoites and contained enigmatic bodies characteristic of Besnoitia bradyzoites. Unlike tachyzoites and tissue cysts, schizonts were located intravascularly in the lamina propria of the small intestine of cats. Merozoites were 5-6 ¿m long, had few rhoptries and amylopectin granules, had numerous micronemes and had a terminal nucleus.