5.1. Introduction

The methods for propagating and purifying honey bee viruses in bees have not changed much from those described by Bailey and Ball (1991). Many viruses, including all of the important ‘picorna-like’ viruses, can be propagated by injection in either pupae or adult bees. Pupal injections are easier to manage than injection into adult bees, from pretty much every aspect: injection, incubation, homogenization and purification. Some viruses can only be infected orally and/or are only infectious in adult bees. The propagation criteria for each virus are listed in Table 3. Infectivity tests are essentially more precise versions of the propagation protocols. Another way to propagate and purify honey bee viruses is through tissue culture. This removes the potential for contamination and the dependence on the bee season that comes with propagating in bees, and allows for large volume propagation. It also is a highly effective tool for detailed laboratory experimentation at cellular level, without the influence of bee and hive effects. Attempts at virus propagation in bee tissue culture have so far met with limited success. However, significant progress has recently been made with Nosema cultivation in commercial (Lepidopteran) insect cell lines (see the BEEBOOK paper on cell culture (Genersch et al., 2013).