Histopathological Features of Symptomatic and Asymptomatic Honeybees Naturally Infected by Deformed Wing Virus

Abstract

Deformed wing virus (DWV) is capable of infecting honeybees at every stage of development causing symptomatic and asymptomatic infections. To date, very little is known about the histopathological lesions caused by the virus. Therefore, 40 honeybee samples were randomly collected from a naturally DWV infected hive and subjected to anatomopathological examination to discriminate between symptomatic (29) and asymptomatic (11) honeybees. Subsequently, 15 honeybee samples were frozen at −80° and analyzed by PCR and RTqPCR to determinate the presence/absence of the virus and the relative viral load, while 25 honeybee samples were analyzed by histopathological techniques. Biomolecular results showed a fragment of the expected size (69bp) of DWV in all samples and the viral load was higher in symptomatic honeybees compared to the asymptomatic group. Histopathological results showed degenerative alterations of the hypopharyngeal glands (19/25) and flight muscles (6/25) in symptomatic samples while 4/25 asymptomatic samples showed an inflammatory response in the midgut and the hemocele. Results suggest a possible pathogenic action of DWV in both symptomatic and asymptomatic honeybees, and a role of the immune response in keeping under control the virus in asymptomatic individuals.

Detection of Honeybee Viruses in Vespa orientalis

“…Conversely to what previously reported in other species ( Genersch et al., 2006 ; Forzan et al., 2017 ), none of our samples showed any lesions at the macroscopical examination, indicative of the presence of viruses. However, as demonstrated by a previous study, we cannot exclude that, as in honeybees, viruses are generating damage to tissues in asymptomatic individuals ( Power et al., 2021 ). In honeybees, common sources of viral infections are pollen, nectar, bee bread, royal jelly and honey ( Mazzei et al., 2014 ; Schittny et al., 2020 ) as well as transmission mediated by Varroa destructor ( Shen et al., 2005 ; Santillán-Galicia et al., 2010 ).…”

“…The same samples where then subjected to molecular biology analysis to detect the possible presence of honeybee viruses. For each animal, head, legs and wings were removed while the thorax and the abdomen were cut into small pieces with a sterile blade to ease homogenization with the TissueLyser mechanical homogenizer (Qiagen, Hilden, Germany), as previously described ( Power et al., 2021 ). RNA was extracted and purified from genomic DNA using the RNeasy Plus Mini Kit (Qiagen, Hilden, Germany), according to the protocol provided by the manufacturer, and subjected to reverse transcription (RT) PCR as reported elsewhere ( Altamura et al., 2018 ).…”

Special Issue: “Infection in Honey Bees: Host–Pathogen Interaction and Spillover”

“…The results showed degenerative alterations of hypopharyngeal glands (in 19 specimens) and flight muscles (in 6 specimens) in symptomatic samples, while in 4 asymptomatic samples, evidence revealed an inflammatory response in the midgut and hemocele. All these findings suggested a possible pathogenic action of DWV in both symptomatic and asymptomatic honey bees, improving their immune response by keeping the virus under control in asymptomatic honey bees [8].…”

Essential Oils for a Sustainable Control of Honeybee Varroosis

“…Unfortunately, we are witnessing the loss of numerous bee colonies worldwide [ 3 , 4 ]. Although the causes of the losses are numerous, the parasite Varroa destructor and the infections it carries are one of the main ones [ 5 , 6 , 7 , 8 , 9 ].…”