Studies on the Transmission of Avian Visceral Lymphomatosis I. Variation in Transmissibility of Naturally Occurring Cases

The term visceral lymphomatosis has been applied to the condition in chickens in which one or more of the visceral organs contain abnormally large accumulations of lymphoid cells (26). This condition has also been referred to as lymphatic leukosis (13), lymphadenoma (30), lymphocytoma (15), hepato-lymphomatosis (22), hemocytoblastoma (25), lymphosarcoma (36), and has been regarded by many (1, 16, 21, 30, 33) as a malignant neoplastic disease. Reports of results on attempts to transmit visceral lymphomatosis have either been highly contradictory or inconclusive. Some investigators (18, 30) were unable to transmit this disease by inoculation. Because of negative results obtained, other investigators (15-17) held the view that lymphomatosis is a nontransmissible disease. However, more recent reports (3-5, 22, 35, 36) indicate that lympholnatosis may be transmitted with cell-containing inocula under favorable conditions. Others (25, 28, 29, 32) have expressed the view that the various manifestations of lymphomatosis, erythroblastosis and granuloblastosis are expressions of the same disease process, and result from a common etiologic agent. These interpretations have been based in part on experiments in which lymphomatosis has occurred among the controls, and conclusions were drawn from statistical differences in incidence of the various manifestations between control and inoculated groups. No specific attempts were made to exclude the possibility that the investigators worked with a mixture of agents--a reasonable explanation for the diverse manifestations obtained. It has been shown repeatedly that erythroand granuloblastosis can be transmitted readily with filtrates [see reviews of Olson (33), EngelbrethHolm (14), and Furth (23)], and that the etiologic agent has many characteristics ascribed to viruses (20, 24, 27, 37). Thus, if one accepts the unitarian view (25) one may hypothesize that all forms of leukosis in chickens are produced by a virus-like agent; however, such reasoning has many weaknesses (21, 23) and is of much less significance than evidence obtained from well controlled experiments showing a high rate of, and direct transmission of, a particular form of the avian leukosis complex (26). In view of the controversial status of visceral lymphomatosis and the lack of conclusive evidence concerning its transmission, experiments were conducted to test the transmissibility of this manifestation. These experiments have been conducted with a uniformity of environment and host which has hitherto not been attained. It has already been reported (5) that, under certain conditions, cell-containing preparations from tumors of some cases of visceral lymphomatosis will induce a high incidence of tumors in a short time; whereas similar preparations from other cases will produce only a few, if any, tumors. Four inocula that elicited a high proportion of tumors were propagated by serial transfer through 15 to 19 passages made at intervals of 7 to 14 days. Experiments described herein further demonstrate the variation in the transmissibility of visceral lymphomatosis by cellular inocula from different naturally occurring cases. They also show that cell-free preparations from certain cases of visceral lymphomatosis, when injected into chicks, will produce lymphomatous involvement of the viscera and, in some instances, osteopetrosis.