The Size of Some Mammalian Picornaviruses

It is generally assumed that viruses which are classified within the same group should have the same morphology. However, the accepted diameter (15 to 30 nm.) of picornaviruses (International Committee, 1963) allows for considerable variation in virus size. Nevertheless, this wide range does not include the reported size of a significant number of animal enteroviruses (Table 1). Since electron microscopy is used routinely in many diagnostic laboratories to speed the identification of viruses, it is of practical as well as theoretical importance to find if the established serotypes of enteroviruses are the same in size. Our interests, however, are limited to agents of farm animals, so we have examined strains of virus from cattle, pigs and sheep.

All micrographs were taken at an instrument magnification of × 100,000. This nominal magnification was corrected using a Bosch and Lomb 2160 lines per mm. X-grating.