[1] His findings were not initially interpreted as involving a protist, and the literature referred to the structures he described as "Miescher's tubules".

Similar structures were found in pig muscle in 1865, but these remained unnamed until 1899, when the name Sarcocystis miescheriana was proposed for them.

This uncertainty was resolved in 1967 when electron microscopic studies showed that they were protozoa, related to Toxoplasma and Eimeria.

The lifecycle remained unknown until 1970, when bradyzoites from sarcocysts in bird muscles were inoculated into cultured mammalian cells and seen to undergo development into sexual stages and oocysts.

[citation needed] Merozoites entering muscle cells round up to form metrocytes and initiate sarcocyst formation.

As the sarcocyst matures, the small, rounded, noninfectious metrocytes give rise to crescent-shaped bodies called bradyzoites (also known as "bradyzoic merozoites"[4]) that are infectious for the definitive host.

[citation needed] In species in which symptoms develop, these typically occur 20–40 days after ingestion of sporocysts and during the subsequent migration of sporozoites through the body vessels.

[citation needed] A second lifecycle has more recently been described whereby carnivores and omnivores pass the infectious stages in their faeces.

[citation needed] Related genera include: Besnoitia, Caryospora, Cystoisospora, Frenkelia, Isospora, Hammondia, Hyaloklossia, Lankesterella, Neospora, and Toxoplasma.

[citation needed] Sarcocystis is the largest genus within the family Sarcocystidae and consists of species that infect a range of animals, including mammals, birds, and reptiles.

[citation needed] Besnoitia, Hammondia, Neospora, and Toxoplasma apparently form a single clade.

Because of this pattern, the genus may have evolved in the Northern Hemisphere from a pre-existing protozoan species that infected mammals.

Because of initial confusion over the nature of this parasite, the organism in the intestine was originally referred to as Isospora hominis .

Infections have been reported from Africa, Europe (Germany, Spain and Poland), the United States (California), Central and South America, China, India, Tibet, Malaysia, and Southeast Asia.

[citation needed] Stool examinations in Thai laborers showed that Sarcocystis infection had a high prevalence of around 23%, reflecting ingestion of raw or undercooked meat.

A study of 100 human tongues obtained post mortem in Malaya revealed an infection rate of 21%.

Two species are currently considered to be capable of causing human intestinal infection: S. bovihominis (S. hominis) and S. suihominis.

The invasive form may involve a wide variety of tissues including lymph nodes, muscles, and the larynx.

These included anorexia, nausea, abdominal pain, distension, diarrhea, vomiting, dyspnea, and tachycardia.

[citation needed] Amprolium and salinomycin were effective in preventing severe illness and death in experimentally infected calves and lambs.

Four recognised species infect cattle: S. bovifelis, S. bovihominis (S. hominis), S. cruzi (S. bovicanis), and S. hirsuta.

Typical clinical signs of acute bovine sarcocystosis are: anorexia, pyrexia (42 °C or more), anemia, cachexia, enlarged palpable lymph nodes, excessive salivation, and loss of hair at the tip of the tail.

[13] Sheep may be infected by four recognized species of Sarcocystis: S. arieticanis and S. tenella (S. ovicanis) are pathogenic; S. gigantea (S. ovifelis) and S. medusiformis are nonpathogenic.

The usual pathological findings in such cases are multifocal spinal cord white matter oedema and necrosis, glial nodules and mild to moderate nonsuppurative encephalomyelitis.

The diagnosis may be established finding protozoan bodies (12.7–23.0 μm) that stain immunocytochemically for Sarcocystis epitopes.

[citation needed] Five species infect horses: S. asinus, S. bertrami, S. equicanis, S. fayeri, and S. neurona (S. falcatula).

Symptoms include lethargy, shortness of breath, tail bobbing, yellow-tinted droppings, and sudden death.

In some species, the cysts may be visible to the naked eye (ducks, mice, rabbits and sheep), but in most, microscopic examination is required.

[citation needed] Several other genera of heteroxenous and cyst-forming coccidia are known,[26] including Besnoitia, Cystoisospora, Frenkelia, Hammondia, Neospora and Toxoplasma.

Amprolium (100 mg/kg, daily for 30 days), fed prophylactically, reduced illness in cattle inoculated with S. cruzi.