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).