Influence of Temperature on the Viability of Cryptosporidium Parvum Oocysts from the Faeces Isolated from Calves

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 maintaine d in addition with potassium dichromate (K 2Cr 2O) (2,5%) at +4 °C and 18-22 °C respectivelly. Contrar y, the oocysts lose their infectivity when they are stored at -20 °C after 1 hour, -10 °C and 0 °C afte r 12 hours of incubation (with or without the solut ion 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 i ncubation 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 temperat ures 70 and 75 °C.