International Union for the Study of Social Insects (IUSSI2018), August 5-10, 2018 in Guarujá, Brazil.

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Viruses are not the cause of the annual Melipona quadrifasciata syndrome

Author(s):
Lílian Caesar, Lílian Caesar , Samuel Paulo Cibulski , Cláudio Wageck Canal , Betina Blochtein , Aroni Sattler , Karen Luisa Haag
Institution(s):
Programa de Pós-Graduação em Genética e Biologia Molecular, Instituto de Biociências, Universidade Federal do Rio Grande do Sul, Porto Alegre, RS, Brazil; Programa de Pós-Graduação em Genética e Biologia Molecular, Instituto de Biociências, Universidade Federal do Rio Grande do Sul, Porto Alegre, RS, Brazil ; Faculdade de Veterinária, Laboratório de Virologia, Universidade Federal do Rio Grande do Sul, Porto Alegre, RS, Brazil ; Faculdade de Veterinária, Laboratório de Virologia, Universidade Federal do Rio Grande do Sul, Porto Alegre, RS, Brazil ; Faculdade de Biociências, Departamento de Biodiversidade e Ecologia, Pontifícia Universidade Católica do RS, Porto Alegre, RS, Brazil ; Faculdade de Agronomia, Laboratório de Apicultura, Departamento de Fitossanidade, Universidade Federal do Rio Grande do Sul, Porto Alegre, RS, Brazil ; Programa de Pós-Graduação em Genética e Biologia Molecular, Instituto de Biociências, Universidade Federal do Rio Grande do Sul, Porto Alegre, RS, Brazil
Viruses are linked to colony losses of Apis mellifera, but their impact on the health of native bees is unknown. The brazilian stingless bee Melipona quadrifasciata suffers from an annual syndrome that ultimately leads the colony to collapse. The syndrome affects managed bees from a wide and heterogeneous region in Southern Brazil, where the species hasn’t been found in its natural environment since decades. The observed symptoms of adult bees show similarity with those associated with viral infections in A. mellifera. Therefore, the aim of this work is to investigate whether the annual colony collapse of M. quadrifasciata is caused by a viral infection. For this, we sequenced the virome of workers from healthy and unhealthy colonies collected during the outbreak period (late summer) of 2017. Reads were trimmed and assembled into contigs for taxonomic characterization. Viral contigs were annotated and coverage was used as a proxi for abundance. Overall, the abundance of virus contigs was higher in the metagenomes of unhealthy than in healthy stingless bees. Contigs showing coverage higher then 8x and encoding proteins with similarity to arthropod viruses were retrieved for phylogenetic analyses and primer design. Sequences similar to arthropod viruses, including pathogenic bee viruses, were observed mainly in the unhealthy RNA virome, but none of them showed a significant identity with A. mellifera virus sequences. Samples from three different meliponaries were collected before, during and after the outbreak and submited to RT-PCR for viral diagnosis based on the sequences identified in the virome. Virus diagnosis did not show a correlation with disease manifestation, occurring in individuals of both healthy and unhealthy colonies. Furthermore these viruses occur mainly in bees from a single meliponary. We conclude that the M. quadrifasciata viruses identified in our study were not acquired from A. mellifera and are not the direct cause of the syndrome.
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