2.0 Some methods for studying animal viruses

Viruses are too small to be seen except by electron microscopy (EM) and this requires concentrations in excess of 1011 particles per ml, or even higher if a virus has no distinctive morphology, some fancy equipment, and a highly skilled operator. Thus viruses are usually detected by indirect methods. These fall into three categories: (i) multiplication in a suitable culture system and detection of the virus by the effects it causes; (ii) serology, which makes use of the interaction between a virus and antibody directed specifically against it; and (iii) detection of viral nucleic acid. However these days the polymerase chain reaction (PCR) is more likely to be employed as it is much quicker provided that the appropriate oligonucleotide primers are available (Section 2.3). Many viruses are uncultivatable, particularly those occurring in the gut, but some of these occur in such high concentration that they were actually discovered by EM. This chapter is not intended to be a technical manual, but to illustrate the principles governing the study of animal viruses.


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