Lapinised rinderpest virus and a vaccine: Some observations in East Africa: II. Field Trials with Lapinised Vaccine

Abstract

Summary In East Africa, freeze-dried, lapinised virus vaccine was used successfully for the control of rinderpest in the field. These results confirm the findings of Cheng and Fischman (1948) in China. Indigenous Zebu cattle, high and low-grade crosses of European breeds with Zebu cattle, pure-bred European cattle and hypersusceptible Ankole cattle were successfully immunised. Of these, only the Ankole cattle exhibited a marked clinical reaction as a result of inoculation with lapinised virus. When vaccinated cattle were challenged by the subcutaneous injection of virulent rinderpest, the duration of the immunity was shown to last for between 8 and 15 months. When tested by exposure to cattle infected with rinderpest, the immunity lasted 13 months. The injection of lapinised virus had no adverse effect on pregnant cattle, and did not reduce the yield of cows in milk. One experiment indicated that lapinised virus could be used for the reimmunisation of cattle which had received a triple course of formolised-spleen vaccine one year previously. Many thousands of cattle have been vaccinated with lapinised virus but so far comparatively few have been obtained for immunity tests at the laboratory. However, when lapinised virus has been used in Kenya, in areas where natural rinderpest was present, it has not once failed to protect the cattle. On one occasion, in a herd of 1886 grade cattle some of which were infected with rinderpest, vaccination curtailed extension of the disease and considerably reduced fatalities.