Bulletin of Insectology 79: 127-135, doi: 10.3897/bull.insectology.195045
High prevalence of Deformed Wing Virus A and Nosema ceranae in a red dwarf honey bee (Apis florea Fabricius, 1787) colony accidentally introduced in Malta
Giovanni Cilia‡, Cecilia Costa‡, Aleksandar Uzunov§|¶, Matthew Vella#, David Mifsud#‡ Consiglio per la ricerca in agricoltura e l’analisi dell’economia agraria (CREA), Research Center Agriculture and Environment (CREA-AA), Bologna, Italy§ Institute of Apicultural Research, State Key Laboratory of Resource Insects, Chinese Academy of Agricultural Sciences, Beijing, China| Ss. Cyril and Methodius University in Skopje, Faculty of Agricultural Sciences and Food, Skopje, Republic of North Macedonia¶ Macedonian Academy of Sciences and Arts, Research Center for Environment and Materials, Skopje, Republic of North Macedonia# Institute of Earth Systems, Division of Rural Sciences and Food Systems, University of Malta, Msida, Malta
Corresponding author: Giovanni Cilia ( giovanni.cilia@crea.gov.it ) Academic editor: Fabio Sgolastra © Giovanni Cilia, Cecilia Costa, Aleksandar Uzunov, Matthew Vella, David Mifsud. This is an open access article distributed under the terms of the Creative Commons Attribution License (CC BY 4.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited. Citation:
Cilia G, Costa C, Uzunov A, Vella M, Mifsud D (2026) High prevalence of Deformed Wing Virus A and Nosema ceranae in a red dwarf honey bee (Apis florea Fabricius, 1787) colony accidentally introduced in Malta. Bulletin of Insectology 79: 127-135. https://doi.org/10.3897/bull.insectology.195045 |  |
Abstract
The finding of Apis florea in Malta provides a unique opportunity to investigate early pathogen dynamics in a non-native honey bee species entering an insular ecosystem. A comprehensive molecular screening of adult workers was performed to assess pathogen prevalence, abundance, replication activity, and genetic identity. The analysis revealed a high prevalence of DWV genotype A and Nosema ceranae, alongside the detection of ABPV, CBPV, SBV, and BQCV. Strand-specific RT-PCR confirmed active viral replication for all detected viruses. Sequencing demonstrated complete homology among positive individuals for each viral species, suggesting a founder effect and introduction of a restricted pathogen genetic pool. Phylogenetic comparisons showed high similarity with globally distributed strains, including Asian-associated lineages, while DWV-B and Nosema apis were not detected. The overall pathogen assemblage appears defined and biologically coherent, supporting the hypothesis that infections were co-introduced from the area of origin rather than acquired from the Maltese environment. Given the ecological sensitivity of island systems, continued longitudinal monitoring will be essential to determine whether A. florea will become an established pathogen reservoir within the Maltese pollinator community or will remain a transient carrier of infections associated with a single introduction episode.
Keywords
alien species, biological invasion, DWV, island ecosystems, nosemosis, molecular epidemiology