Submitted to: Innovative Food Science and Emerging Technologies
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: November 21, 2006
Publication Date: March 8, 2007
Citation: Shearer, A.H., Wilkins, G.C., Jenkins, M.C., Kniel, K.E. 2007. Effects of high hydrostatis pressure on Eimeria acervulina pathogenicity, immunogenicity and structural integrity. Innovative Food Science and Emerging Technologies. 8:259-268.
Interpretive Summary: Avian coccidiosis is an intestinal disease of poultry caused by protozoa in the genus Eimeria. The disease has been controlled for decades by the medication of feed with ionophore drugs and synthetic chemicals. With increased drug resistance in Eimeria, and consumer pressure to discontinue antibiotic usage in animal feed, producers are increasingly relying on alternative means of controlling coccidiosis. One method that is gaining greater acceptance is oral immunization of day-old chickens with live oocyst vaccines. While vaccination is gaining greater acceptance in the poultry industry, virulent oocysts are introduced into a poultry operation. The present study describes a method to attenuate Eimeria oocysts using high pressure treatment. The results indicate that pressure treatment does not prevent an immune response to the parasite, but does affect the ability of the parasite to multiply. This information is valuable also to treatment of fresh fruits and vegetables for destroying Cyclospora cayetanensis, a close relative of Eimeria, which causes human cyclosporiasis.
Eimeria acervulina is a protozoan parasite that can cause intestinal lesions and reduced weight gain in chickens. E. acervulina oocysts were treated by high hydrostatic pressure and evaluated for pathogenicity, immunogenicity, and structural integrity. Pressure treatment of E. acervulina oocysts at 550 MPa for 2 min. at 4, 20, or 40oC rendered the parasites nonpathogenic to chickens. Pressure treatment at 40 oC also prevented fecal shedding oocysts. Upon challenge with non-pressurized E. acervulina oocysts, partial immunity was observed with a reduction in lesion severity in chickens that had been inoculated with pressure-treated oocysts. No changes to the fragility and permeability of the oocyst wall or excystation of sporocysts were observed as a result of pressure treatment. Light and scanning electron microscopy revealed no changes to the whole oocyst or sporocysts. Recovery and the morphology of the excysted sporozoites were altered by pressure treatment. These results suggest that pressure affects sporozoite integrity.