• Parasites, Hosts and Diseases
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• v.60 no.4
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• pp.241-246
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• 2022

Felids are the unique definitive host of Toxoplasma gondii. The intestine of felid is the only site for initiating Toxoplasma gondii sexual reproduction. T. gondii excretes millions of infectious oocysts from the intestine, which are the primary source of infection. There are many difficulties in developing vaccines and drugs to control oocyst excretion due to the lack of an appropriate experimental model. Here, we established an in vitro feline intestinal epithelial cell (IEC) infection system and an efficient animal model of T. gondii Chinese 1 genotype, Wh6 strain (TgCtwh6). The Kunming mice brain tissues containing TgCtwh6 cysts were harvested 42-day post-infection. The bradyzoites were co-cultured with cat IECs in vitro at a ratio of 1:10. Five 3-month-old domestic cats were orally inoculated with 600 cysts each. The oocysts were detected by daily observation of cat feces by microscopy and polymerase chain reaction. We found that the parasite adhered and invaded cat IECs in vitro, transformed into tachyzoites, and then divided to form rose-like structures. These parasites eventually destroyed host cells, escaped, and finished the asexual reproduction process. Schizonts associated with sexual reproduction have not been observed during development in vitro cultured cells. However, schizonts were detected in all infected cat intestinal epithelial cells, and oocysts were presented in all cat feces. Our study provides a feasible cell model and an efficient infection system for the following studies of T. gondii sexual reproduction, and also lays a foundation to develop drugs and vaccines for blocking excretion and transmission of oocysts.

• Applied Microscopy
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• v.29 no.2
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• pp.211-221
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• 1999

The ultrastructural changes of cuticular surface, excretory and digestive organs of Anisakis simplex larvae chronologically recovered from experimental cats were observed with a SEM and TEM. The larva recovered from an experimental cat at 3 days post-infection (PI) retained the cuticular surface with regular transverse striations and a longitudinal groove on the lateral side of body. This finding suggests that the molting of the 3rd stage larva of A. simplex to 4th one occurred from the 3rd day after infection in cats. The excretory organ (renette cell) consisted of a large cell with numerous ductules ramified from the main duct, mitochondria and secretory granules in cytoplasm. Secretory granules in the renette cell of larvae recovered at 24 hours PI were round whereas those of control and larvae recovered at 6 hours PI were amorphous. Muscular esophagus and ventriculus also retained many secretory granules in the cytoplasm. The secretory granules in these organs of larvae recovered at $6\sim24$ hours PI were electron-dense and widely distributed whereas those of control worm were packed in a pocket and retained various electron densities. In the cytoplasm of intestinal epithelial cells, numerous fine glycogen particles and mitochondria were distributed. The chronological changes of secretory granules in renette cell, muscular esophagus and ventriculus seem to be related with the worm penetration into host tissue.