Evaluation of the heat tolerance of a freeze-dried V4 vaccine against Newcastle’s disease

Abstract

A freeze-dried virus vaccine against Newcastle’s disease was prepared using the heat tolerant derivative V₄/276 of the virus strain V₄ (UPM). The viral mean titre was 10^10.4 EID₅₀ per vial after 14 days at+ 4°C and 10¹⁰ EID₅₀ after 126 days. Incubation at 45 °C for 7 and 14 days reduced the titre to 10^8.5 and 10⁸⁰² EID₅₀, respectively. In addition, this preparation was exposed to ambient temperature at Ouagadougou (Burkina Faso) during the first fortnight of July 1991 when the temperature ranged from 25 to 32 °C, but never exceeded 35 °C. After 7 and 14 days of storage, the viral mean titre was10^9.3 EID₅₀ per vial. This vaccine is intended to coat grains fed to African village chickens.