Kidney tumour virus—tumour or mycobacterial tubercle?

Abstract. Bacteriologically sterile filtrates of 'tumorous' fish elicited formation of 'tumours' in vivo which were morphologically indistinguishable from those described by Wessing & Bargen (1959). Attempts to isolate the putative aetiologic 'Virus' in primary and established cell cultures failed. When the lesions were examined for other compatible aetiologies, acid-fast stains revealed acid-fast bacilli and cultures grew Mycobacterium fortuitum . It is suggested that the 'kidney tumour virus' is actually soluble mycobacterial cell-fractions capable of eliciting tubercle formation in vivo .