The Fundamental Pathology of Infectious Myxomatosis

Abstract

Infectious myxomatosis of rabbits was first described by Sanarelli in 1898 (1). Despite the peculiar features of the disease and the interest which it merits, studies on infectious myxomatosis have resulted in but thirteen papers and in several discordant statements as to its fundamental pathologic manifestations. The term “myxomatosis” by common usage implies that the process is neoplastic. Yet Aragao (2) states that the myxomatous tumors are not truly neoplastic, but merely remarkable collections of edematous fluid due to the presence of an infectious agent. Rivers (3) believes that in certain respects the infectious myxomatosis of rabbits resembles the Rous sarcoma of fowls, whereas in others it is quite different. It may serve to bridge the gap between virus tumor and vesicular, destructive virus diseases. It occurred to the writer that the early stages of the disease still merited purely morphologic investigation. A number of rabbits were inoculated, intradermally at first and by scratch inoculation from rabbit to rabbit later on. To secure as many involved lymph nodes as possible, the infection was usually introduced at more than one point, i.e . the thoracic skin near the axilla, near the groin, and the ear, to make certain of spread to the preauricular and cervical nodes. The animals were usually killed by air embolus at stages between the development of orbital and conjunctival lesions and the intense dyspnea preceding death from the disease itself. All organs, the subcutaneous tissues and skin, and as many lymph nodes as possible, were preserved for study. Tissues were fixed in absolute alcohol for mucin, in 10 per cent formalin, and in Zenker's fluid. The stains employed were mucicarmine, hematoxylin and eosin, eosin-methylene blue, Wright's blood stain which was found to give excellent results on formalin-fixed tissues, Giemsa stain, and Mallory's phosphotungstic acid hematoxylin.