RATE AND COURSE OF SPORULATION OF OOCYSTS OF EIMERIA-ACERVULINA UNDERDIFFERENT ENVIRONMENTAL-CONDITIONS

An experiment was conducted to determine the rate and maximum percenta ge of sporulation of Eimeria acervulina oocysts at various environment al conditions relating to temperature (21 Versus 33 degrees C) and rel ative humidity (RH) (40 versus 80%). Measurements were made during 44 h after excretion of oocysts in 3 substrates: dry litter, clammy litte r and pure faeces respectively. Maximum sporulation percentage in both dry (22.6%) and clammy litter (19.5%) was higher (P < 0.005) than in pure faeces (11.6%). Neither temperature nor RH had a significant infl uence on percentage of oocysts that sporulated. Under these simulated practical conditions approximately 25% of all oocysts sporulated, wher eas sporulation under optimal conditions (29 degrees C, aeration, 2% K 2Cr2O7) showed a higher (68%) sporulation ability of oocysts. At 33 de grees C sporulation proceeded at a faster pace than at 21 degrees C (P < 0.005). With respect to RH and substrate, once sporulation started, the rate of increase to maximum percentage was not different. Time of onset of sporulation was influenced by temperature (P < 0.0001) and R H (P < 0.001). Time of onset occurred 15 h later at 21 degrees C compa red with 33 degrees C and 5 h later at 40% RH compared with 80%. Also, an interaction effect (P < 0.01) was found with effect of RH being st ronger at 21 degrees C compared with 33 OC, It was concluded that the most important aspect in the epidemiology of E. acervulina during a fl ock cycle is the time of onset of sporulation with temperature being t he most important factor.