Induced liver tumour deaths by subgroup A Rous sarcoma virus in chicks inoculated via chorioallantoic membrane, a genetic marker.

A study was made using two strains of light breed (White Leghorn strains, A and B) and four heavy beeds (Rhode Island Red, New Hampshire, Australorp, Columbian) to evaluate the breed difference in survival potential of chicks that were infected as 11-day-old embryos via chorioallantoic membranes (CAMs) with a subgroup A Rous sarcoma virus. Of the 1185 chicks hatched over multiple hatch-replicates, 845 chicks died rapidly of a fibrosarcomatous liver tumour (LT) with a peak mortality about 74% attained by the second week, post-hatch, in the heavy breeds and more than 90% by the second week in the light breed. The breeds did not differ in induced LT mortality when the chicks hatched from eggs that had at least 25 pock counts on CAMs, apparently genetically susceptible, i.e. 25 biologically active virus particles were enough to induce an unpreventable fatal LT. However, low pock-count on CAMs did not act as a pointer for predicting genetic resistance to infection because about 23% of chicks developed from eggs that had no pocks on CAMs, apparently genetically resistant, also died of LT, requiring further studies.