LONG TERM VIABILITY OF CRYOPRESERVED Eimeria SPOROCYSTS

R. M. Poston, L. K. Griffin, C. Heggen-Peay, J. E. Hutchins, A. Martin, and
V. W. Doelling
Embrex, Inc., P.O. Box 13989, Research Triangle Park, NC 27709
rposton@embrex.com

As Eimeria oocysts have limited viability and cannot be effectively cryopreserved, sporocysts from individual Eimeria strains are the desired life stage for cryopreservation. However, little data are available in the literature indicating the effects of long-term frozen storage on the viability of different Eimeria strains. Our laboratory has used standard sporocyst preparation and cryopreservation techniques on several Eimeria strains including E. acervulina, E. maxima, and E. tenella. After freezing, sporocysts were held in the vapor phase of liquid nitrogen for long-term storage prior to testing. To determine viability of the frozen stock cultures, sporocysts were thawed, washed one time, and administered by oral gavage to broiler chickens at one of two doses. Fecal material from inoculated birds was collected during the appropriate patent period and oocyst output per bird determined. All species tested were viable after three years and oocyst output trended with sporocyst dosage used for gavage. Oocyst output data from sporocysts stored for three months in the vapor phase of liquid nitrogen were comparable to oocyst output from stocks frozen for three years. These data indicate frozen sporocyst stocks from Eimeria acervulina, E. tenella, and E. maxima can be maintained with acceptable viability for at least three years.