EXPERIMENTAL MODES OF CARYOSPORA-BIGENETICA (APICOMPLEXA, EIMERIIDAE)INFECTION IN SWINE AND THE EFFECTS OF TEMPERATURE AND SALINITY ON PARASITE INFECTIVITY IN PORCINE TISSUE

Four crossbred pigs (Sus scrofa) were inoculated orally with Caryospor a bigenetica oocysts derived from snake and mouse feces, and with C. b igenetica infected mouse tissue. One pig also was given i.m. injection s of methylprednisolone acetate. All four pigs displayed clinical sign s including erythema, edema, and lethargy. Caryocysts were observed hi stologically in numerous tissues including ear, tongue, jowl, shoulder , loin, intercostal, ham, hock, and feet. The four pigs each were butc hered into six commercial cuts: shoulder, loin, side, ham, hock, and f eet. Raw 10 g samples from each cut were bioassayed by pepsin digestio n and s.c. inoculation into 12 Swiss-Webster mice (Mus musculus) and 1 2 cotton rats (Sigmodon hispidus). Seventeen of 24 mice and cotton rat s exhibited clinical signs and C bigenetica tissue infections. Remaini ng portions of the six commercial cuts were temperature or saline trea ted, and 10 g samples were bioassayed in 16 mice and 12 cotton rats. N o clinical sign or tissue infection was observed in these animals. Our study presents evidence that swine can be infected with C. bigenetica by ingesting oocysts present in snake feces or mouse feces (following inoculation of mice with snake-derived oocysts) or by ingesting C. bi genetica infected rodent tissue, that endogenously produced C. bigenet ica oocysts are not excreted in the feces of swine, and that C. bigene tica in pork can be rendered noninfective by freezing at -20-degrees-C (-4-degrees-F) for 21 days, frying at 84-degrees-C (183-degrees-F) fo r 17 min, microwaving at 88-degrees-C (190-degrees-F) for 17 min, gril ling at 82-degrees-C (180-degrees-F) for 48 min, baking at 95-degrees- C (203-degrees-F) for 230 min, boiling at 100-degrees-C (212-degrees-F ) for 60 min, or by curing at 4-degrees-C (39-degrees-F) for 20 days.