Development of Ox‐Coyote Cycle of Sarcocystis cruzi¹

Abstract

The ox‐coyote cycle of Sarcocystis cruzi was studied by killing 38 calves between 4 and 153 days postinoculation (DPI) with 55 × 103‐5 × 108 sporocysts from the intestines of coyotes. At 4 DPI, a zoite was found within the lumen of a mesenteric lymph node artery. At 7 DPI, zoites were found in mononuclear cells and in endothelial cells in mesenteric arteries. First generation meronts (41.0 × 17.5 μm in diameter) occurred 7–26 DPI in mesenteric lymph nodes. At 19–46 DPI, second generation meronts occurred in kidneys, muscles, and other tissues: renal meronts were 19.6 × 11.0 μm, and intramuscular meronts were 25.0 × 11.1 μm. Merozoites were found in the peripheral blood 17 DPI and later at 24–46 DPI. They divided by endodyogeny in mononuclear cells. Sarcocysts were seen first in the heart at 45 DPI and contained one or two metrocytes. At 55 DPI, sarcocysts containing only metrocytes were found in striated muscles, heart, and in smooth muscles of the urinary bladder, rumen, omasum, abomasum, and small intestine. At 67, 87, 112, and 153 DPI, sarcocysts were found only in striated muscles and in the heart. At 67 DPI, sarcocysts were up to 360 μm long. They contained only metrocytes and were not infective to the dog. At 86 DPI, sarcocysts contained mostly bradyzoites, a few metrocytes, and were infective to a coyote. The thin‐walled sarcocysts grew to a maximum length of 800 μm and contained bradyzoites that were 10.9 × 3.0 μm. At 90 DPI, two mature sarcocysts were found in 2 of 73 sections of brain and spinal cord; hundreds of sarcocysts were present in sections of tongue and heart of this calf. Gametogony occurred in the small intestine of the coyote. Macro‐and microgamonts were found in goblet cells of the small intestines of coyotes 6 h after the ingestion of infected meat. Microgamonts were few and contained 3–11 slender gametes. Oocysts were seen at 12 h and sporulation was completed 9 DPI. The prepatent period in the coyote was 8 days. The ox‐coyote cycle is compared with ox‐dog cycle.

Sarcocystis cruzi (Hasselmann, 1923) Wenyon, 1926: redescription, molecular characterization and deposition of life cycle stages specimens in the Smithsonian Museum

“…In view of the recent development and recognition of several Sarcocystis species in cattle, we reevaluated histologic sections and obtained new morphological and genetic data from parasites used by Dubey (1982 a ). Life cycle stages were photographed using a digital DP73 camera (Olympus Optical Ltd., Tokyo, Japan) fitted on an Olympus AX 70 microscope (Olympus Optical Ltd.), and deposited in the Smithsonian Museum.…”

“…Materials and methods were the same as described in detail previously (Dubey, 1982 a ). Briefly, 38 Holstein–Friesian newborn calves were inoculated with 275 000–500 000 000 sporocysts of 7 isolates (BI–B7) of S. cruzi obtained from laboratory-raised coyotes fed naturally infected hearts of cattle raised in Montana (Tables S2 and S3).…”

“…In the 1980s, one of us (J. P. D.) studied the full life cycle of a S. cruzi transmissible from coyotes to cattle in Bozeman, Montana, USA. For the life cycle studies with the Bozeman isolates of S. cruzi , newborn calves and coyotes were raised in captivity to strictly monitor their diets (Dubey, 1982 a ) (Table S2).…”

“…While reevaluating histologic slides from the 1982 study (Dubey, 1982 a ), a paraffin block of a kidney of a calf 383 fed 150 000 000 S. cruzi sporocysts from coyote no. 27 (Table S2) and euthanized on day 24 p.i.…”

“…Among these species of bovine Sarcocystis , a complete description of the life cycle is known only for S. cruzi . The life cycle of S. cruzi was completed in 1982 (Dubey, 1982 a ) experimentally in cattle before the advent of molecular diagnostics (Dubey et al ., 1989); to our knowledge, no archived frozen tissues from the cattle employed in the original descriptions remain for DNA characterization. Current DNA characterization is based on naturally infected cattle (Rosenthal et al ., 2008; Gjerde, 2016; reviewed in Dubey and Rosenthal, 2023).…”