Epidemiological studies of coccidiosis in the domesticated fowl (Gallus gallus): II. Physical condition and survival of Eimeria acervulina oocysts in poultry-house litter.

The survival of coccidial oocysts in poultry-house litter has been examined. The experimental design ensured that viable oocysts were not continuously replenished by multiplication in chicks. Hence, reliable oocyst survival data were obtained, which is not possible in a commercial house where there is a continuously changing population of coccidia. Litter was seeded directly from infected chicks with unsporulated oocysts of Eimeria acervulina. Whilst sporulation proceeded rapidly, oocysts simultaneously began to deteriorate after only 24 h. After five days, most oocysts were disintegrating. Viable oocysts were, however, detected (using sentinel birds) up to day 23, although subsequently the viability of the oocyst population began to wane. Few viable oocysts were detectable after 38 days, despite some intact sporulated oocysts being evident up to 54 days. The physical condition of oocysts is therefore not a reliable indication of their viability. The surface temperature of the litter was 25-28 degrees C throughout and the moisture content varied from 31.0 to 62.1%; these conditions were not limiting factors for oocyst sporulation.