Vol. 8, Issue 10, Part E (2022)

Abstract
Bluetongue is an Office International Epizootics List A disease and described as an economically devastating affliction of sheep. The etiological agent of this disease is bluetongue virus which is the prototype species of the genus Orbivirus in the family Reoviridae. If the titre of the virus at various intervals is known, optimum inoculum and time of harvest can be calculated for maximum yield, which plays a crucial role in de If the titre of the virus at various intervals is known, optimum inoculum and time of harvest can be calculated for maximum yield development of vaccine. Therefore, an attempt was made to know the titre of the virus at periodic intervals of post infection by studying the growth pattern of two bluetongue virus vaccine strains. The titration of the two isolates M11 (BTV 2) and N12 (BTV 15) in BHK₂₁ cells was done for 5 passages. The time and titres were estimated as 10^4.55, 10^4.68, 10^6.12, 106.72 and 10^7.22 TCID₅₀/ml for M11 isolate (BTV 2) and 10^2.69, 10^3.58, 10^5.64, 10^7.55 and 10^7.56 TCID₅₀/ml for N12 isolate (BTV 15). Further one step growth curve experiments were conducted for the isolates in BHK21 cells. Both the viruses had maximum titres at 48 h. The inoculum size had no significant effect on the harvest in the dilutions tested.