Survival of virus after thermoprocessing in capillary tubes

Abstract

A modification of the capillary tube heating technique described by Stern and Proctor was evaluated to determine its suitability for virus thermal inactivation studies. A suspension of coxsackie virus B5 (Faulkner strain) in tissue culture maintenance medium was placed into melting point capillary tubes and heated to 56, 60, 72, and 80 C for various time intervals. Surviving virus was quantitated by infection of cell culture. Lactating goats were inoculated with coxsackie virus B5 (Faulkner) or a mixture of coxsackie virus B5 and reovirus 3 (Abney) in an attempt to produce milk containing virus as a result of systemic infection. Reovirus 3 was recovered in the milk for five days after inoculation. Infection was further evidenced by elevated temperature, leukopenia, and production of reovirus 3 neutralizing antibodies. Antibodies were also detected in a kid nursing on the infected dam. Evidence of coxsackie virus infection was not detected. Reovirus titer on day 2 post inoculation was sufficient to conduct further thermal inactivation studies. Additional studies were conducted in which coxsackie virus B5 was added to goat, cow, and human milk. Samples were heated at several temperature and time intervals. No virus was detected in samples frozen prior to heating to 72 C, however, infectious virus was detected in samples which had not been frozen prior to heating. Coxsackie virus survived in cow and human milk heated to 72 C for 2 seconds and in goat milk heated to 72 C for 60 seconds. Thermal inactivation curves plotted for the coxsackie virus experiments were bi-phasic suggesting the possibility of a two step degradation process. In the final phase of the study, a comparison was made between the rates of heat inactivation of reovirus 3 in milk from the infected goat and in non-infected milk to which approximately the same quantity of virus had been added. Similar bi-phasic curves were observed for both infected and contaminated milk. Comparison of data would indicate that more virus survives heat processing in the milk from an infected animal than in milk to which virus has been added.