Differing Susceptibilities of Eimeria acervulina, Eimeria maxima, and Eimeria tenella Oocysts to Desiccation

Outbreaks of avian coccidiosis may occur when susceptible chickens are raised on litter containing viable Eimeria oocysts. The purpose of this study was to compare the relative sensitivities of Eimeria acervulina, Eimeria maxima, and Eimeria tenella oocysts to dessication. Sporulated E. acervulina, E. maxima, or E. tenella oocysts were incorporated into gelatin beads and incubated at 32 C for 0, 1, 2, or 3 days. In vitro oocyst excystation rates were measured for each combination of Eimeria species and incubation time. Day-old broiler chicks were allowed to ingest the oocysts-containing beads, and total oocyst production was measured from days 5-8 post-inoculation. Although no effect on excystation was observed, E. maxima oocysts displayed greater resistance to drying compared to E. acervulina and E. tenella oocysts. Eimeria acervulina oocyst production decreased 100-fold after 1-2 days incubation. Eimeria tenella oocysts were slightly more resistant to drying in that a 100-fold decrease in oocyst production was delayed until 2 days. For both E. acervulina and E. tenella, very few oocysts were observed after 3 days incubation. Eimeria maxima oocyst production remained high at all time points. Subsequent studies revealed E. maxima oocyst production was ablated only after 5 days incubation. These findings may explain in part the observed prevalence of E. maxima in litter from commercial poultry operations.