Effect of Magnesium Sulfate and Casein Hydrolysate on Thermoinactivation of Newcastle Disease Virus Vaccine

Abstract

In spite of widespread use of Newcastle disease (ND) vaccine in Mexico there are a large number of outbreaks of the disease. From January 1969 to June 1971, 267 cases of ND were diagnosed in this laboratory (1). The majority of the outbreaks occurred in birds that had been vaccinated at least once, and in many cases the birds had received two or more live-virus vaccinations (1). The failure to withstand exposure to ND in the field may be due to inadequate amounts of virus in the vaccines. In some instances, low titer of the vaccine may be due to mishandling. Villaseinor (8) found a 3.0 log drop in virus titer when the reconstituted vaccines were held at 30 C for one hour, a temperature that can be readily reached within a poultry house in Mexico. Winterfield and Seadale (11) also studied the effect of temperature on the stability of ND vaccines administered in the drinking water and found a drop in titer when no stabilizer was added.