22.214.171.124. Longevity of infected bees
There is a surprising lack of data on the actual longevity of infected honey bees, probably because the mortality is rarely assessed per se. When the mortality takes place 10 to 14 days or more after the exposure to the spores, the researchers usually decide to sacrifice the tested honey bees. For N. ceranae, 100 % mortality of infected bees have been reported within this time frame (Higes et al., 2007; Martin-Hernandez, et al. 2011), but significantly lower mortality rates have also been observed (Dussaubat et al., 2010; Forsgren and Fries, 2010; Paxton et al., 2007; Porrini et al., 2010). There is a profound need for more mortality data from Nosema spp. infections, to better understand the impact from infection on colony viability. Possibly, cage experiments are less well suited for such tests because cage effects on longevity cannot be excluded, even if proper controls are used. An alternative would be to use marked bees, with and without infection, and introduce them to small functioning colonies and then study the rate at which such honey bees disappear compared to uninfected bees (see the section on statistics for survival analyses in the BEEBOOK paper on miscellaneous methods (Human et al., 2013)).
Only a few studies have investigated the longevity of queens when infected with N. apis. spores. Young infected queens that were allowed to lay eggs all died about 50 days after the onset of oviposition, with an average age when found dead or removed by the bees of about 25 days (Loskotova et al., 1980). The impact from infection on queen as well as colony performance also need further studies to assess the impact on colony performance from these infections.