Study System
V. ceranae is a microsporidian parasite with a nearly global
distribution. It was initially discovered in Apis ceranae and
later spilled over into A. mellifera honeybees, where it appears
to be more virulent than closely related parasites such as V.
apis (Paxton et al. 2007). Recent studies have shown that wild native
bees are also infected with V. ceranae , including many wild
bumblebees (Bombus spp.), stingless bees (Tetragonula
hockingsi , Tetragonisca spp., Scaptotrigona spp.,Melipona spp.), and solitary bees (Osmia bicornis )
(Plischuk et al. 2009, Graystock et al. 2013, Furst et al. 2014, Müller
et al. 2019, Purkiss and Lach 2019, Salvarrey et al. 2021, Cilia et al.
2022). Transmission of V. ceranae between individuals is
primarily fecal–oral or oral–oral, as it is spread through ingestion
of contaminated food or contact with the feces of diseased hosts (Chen
et al. 2008, Smith 2012). V. ceranae germinates in the midgut of
the bee, where the spore count can reach over 30 million, and it is then
excreted as feces (Paxton et al. 2007, Chen et al. 2008, Higes et al.
2008a), potentially contributing very large numbers of spores to the
environment (e.g., on floral surfaces). Symptoms of infection in
honeybees include digestive disorders, shortened life spans, atypical
breeding behavior, reduced sucrose sensitivity, and diminished honey
production; however, colony infection is often asymptomatic until sharp
depopulation occurs, often in autumn and winter (Chen et al. 2008, Higes
et al. 2008a, 2010, Graystock et al. 2013). Symptoms are generally
assumed to be the same for wild bees, but data on this is limited aside
from a few reports that V. ceranae may cause reduced survival,
learning impairment, sucrose sensitivity, and cellular immunosuppression
in bumblebees or stingless bees (Graystock et al. 2013, Piiroinen and
Goulson 2016, Macías-Macías et al. 2020). Furthermore, V. ceranaeinfections suppress the pollinator immune response, which can lead to
coinfection with other pathogens or parasites and an increased
likelihood of mortality (Antúnez et al. 2009). The drastic effects ofV. ceranae on pollinator health have been linked to the sudden
collapse of honeybee colonies (Higes et al. 2008a) and may be an
important factor in the recent declines of some wild bees (Graystock et
al. 2013, Furst et al. 2014, Goulson and Hughes 2015).