Occurrence of virus, microsporidia, and pesticide residues in three species of stingless bees (Apidae: Meliponini) in the field

Bees are important pollinators whose population has declined due to several factors, including infections by parasites and pathogens. Resource sharing may play a role in the dispersal dynamics of pathogens among bees. This study evaluated the occurrence of viruses (DWV, BQCV, ABPV, IAPV, KBV, and CBPV) and microsporidia (Nosema ceranae and Nosema apis) that infect Apis mellifera, as well as pesticide residues in the stingless bees Nannotrigona testaceicornis, Tetragonisca angustula, and Tetragona elongata sharing the same foraging area with A. mellifera. Stingless bees were obtained from 10 nests (two of N. testaceicornis, five of T. angustula, and three of T. elongata) which were kept in the field for 1 year and analyzed for the occurrence of pathogens. Spores of N. ceranae were detected in stingless bees but were not found in their midgut, which indicates that these bees are not affected, but may be vectors of the microsporidium. Viruses were found in 23.4% of stingless bees samples. APBV was the most prevalent virus (10.8%) followed by DWV and BQCV (both in 5.1% of samples). We detected glyphosate and its metabolites in small amounts in all samples. The highest occurrence of N. ceranae spores and viruses was found in autumn-winter and may be related to both the higher frequency of bee defecation into the colony and the low food resources available in the field, which increases the sharing of plant species among the stingless bees and honey bees. This study shows the simultaneous occurrence of viruses and spores of the microsporidium N. ceranae in asymptomatic stingless bees, which suggest that these bees may be vectors of pathogens.