[Evaluation of the thermo-tolerability of the lyophilized V4 vaccine against Newcastle disease].

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 degrees C and 10(10) EID50 after 126 days. Incubation at 45 degrees C for 7 and 14 days reduced the titre to 10(8.5) and 10(8.2) 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 degrees C, but never exceeded 35 degrees C. After 7 and 14 days of storage, the viral mean titre was 10(9.3) EID50 per vial. This vaccine is intended to coat grains fed to African village chickens.