75 Bulletin UASVM, Veterinary Medicine 66(2)/2009 ISSN 1843-5270; Electronic ISSN 1843-5378 Influence of Temperature on the Viability of Cryptosporidium Parvum Oocysts from the Faeces Isolated from Calves AKAM A. 1 , Gh. DÃRÃBU 2 , V. COZMA 3 , E. UTEU 3 , R. KAIDI 4 , K. KHELEF 5 , BACHI F. 6 , Z. BOUCHENE 7 1 Département de biologie, Université Ziane Achour Djelfa, Algérie, a_hakem@hotmail.fr 2 Faculté de Médecine Vétérinaire, 119 Calea Aradului, Timioara, Roumanie. 3 Faculté de Médecine Vétérinaire, Cluj-Napoca, Str. Mãnãstur Nr. 3, 3400, Roumanie. 4 Département des sciences vétérinaire, Université Saad Dahlab, Blida, Algérie. 5 Ecole Nationale vétérinaire, Alger, Algérie. 6 Département de parasitologie, Institut Pasteur d’Alger, Algérie 7 Service de parasitologie, Hopital de Béni-Messous, Alger, Algérie. Abstract. Influence of temperature on viability of Cryptosporidium parvum oocysts originally isolated from calves faeces. Cryptosporidium parvum oocysts originally isolated from calves faeces were submitted to various temperatures at different times in order to estimate their viability and infectivity. The results of this study showed that cryptosporidia oocysts aren’t viable after 2 months if they are kept at +4 °C and after 3 weeks at 18-22 °C. However, the duration of viability of oocysts is increased until 6 and 1 month if they are maintained in addition with potassium dichromate (K 2 Cr 2 O) (2,5%) at +4 °C and 18-22 °C respectivelly. Contrary, the oocysts lose their infectivity when they are stored at -20 °C after 1 hour, -10 °C and 0 °C after 12 hours of incubation (with or without the solution of conservation), 23 °C after 3 weeks, 34 °C after 2 weeks, 40 °C after 4 days, 45 and 50 °C after 45 minutes, 51 and 55 °C after 35 minutes, 60 °C after 25 minutes, 65 °C after 15 minutes, 70 °C after 5 minutes and 75 °C after 3 minutes. However, the wet temperature 50 and 55 °C are effectif against cryptosporidia oocysts after 60 and 30 minutes of incubation respectively. The oocysts lose their normal morphology after 24 hours at -10 °C and 9 months at +4 °C when they are stored in potassium dichromate. On the other hand, no oocysts are morphologicaly damaged for other periods of exposure even when the latest are exposed in higher temperatures 70 and 75 °C. Keywords: Cryptosporidium parvum, oocysts, resistance, time of exposure, temperature, potassium dichromate. INTRODUCTION Les cryptosporidies sont des parasites coccidiens résistants aux facteurs physiques tels que la température et l’humidité [21, 4, 16]. Cette résistance est témoignée par leur caractère cosmopolite et leur incroyable adaptation aux divers climats. De nombreuses études ont montré la limite de tolérance des cryptosporidies vis-à-vis des différents degrés de températures [10, 21, 2, 4, 9, 8, 17, 6] et de l’humidité [17, 7]. Ce travail complète la précédente étude [1] et a pour objectifs d’: - évaluer la tolérance des oocystes de Cryptosporidium parvum aux différentes degrés de températures et de temps d’exposition; - estimer la résistance des cryptosporidies à l’action de la température humide élevée (50 et 55 °C) et du temps d’incubation; - apprécier les éventuels changements de l'aspect de l’oocyste après chaque épreuve de contact et, enfin;