Study of dose effects

Although the doses of 10,000 and 33,000 spores per bee have been shown to produce infection in all exposed bees, it is common to use much higher doses, even an order of magnitude higher or more, to ensure infection (Alaux et al. 2010a; Alaux et al. 2010b, Paxton et al., 2007; Malone and Stefanovic 1999; Higes et al., 2007; Porrini et al., 2010; Webster et al., 2004; Woyciechowski and Moron, 2009). Depending on the type of experiment, it is often best not to use higher spore doses than is necessary to produce infection in individual bees, because when high spore doses are used, non-germinated spores may be retrieved and counted as spores produced from infection.

Honey bee queens become infected by both N. apis and N. ceranae. As with workers, a range of different doses have been used to study effects of infection on queens individually fed, although again, more spores were provided than were required (Alaux et al. 2010c; Webster, 2008). Using individual feeding, queens and worker bees have become infected using similar spore doses (Webster et al., 2004), but the infectious doses for queens have never been established for either of the two microsporidian infections discussed.