Frenkelia

Frenkelia is a genus of apicomplexan parasites belonging to the family Sarcocystidae. These protozoan parasites are known for forming cysts within the intermediate host's tissues, most commonly in the brain and muscles. The definitive hosts are typically carnivorous animals, where the parasite undergoes sexual reproduction.

The life cycle of Frenkelia involves two hosts. Herbivores, often rodents, act as intermediate hosts, becoming infected by ingesting sporocysts shed by the definitive host through fecal contamination. Within the intermediate host, the parasite undergoes asexual reproduction, eventually forming cysts, known as "Frenkel bodies," primarily in the brain. Carnivorous animals, such as foxes, cats, and other predators, become infected by consuming the infected tissues of the intermediate host. In the definitive host's intestine, the parasite undergoes sexual reproduction, producing oocysts that are then shed in the feces, completing the cycle.

Frenkelia infections in intermediate hosts can cause neurological symptoms, although these are not always apparent. The cysts within the brain can impact behavior and motor function, potentially increasing the risk of predation. In definitive hosts, infection is usually asymptomatic.

The genus is related to Sarcocystis, and distinguishing between the two can sometimes be challenging based on morphology alone, requiring molecular techniques for accurate identification. The specific species of Frenkelia and their respective host ranges can vary depending on the geographical location.