The growing spread of the oriental hornet in Italy represents a serious threat to honeybees.
The oriental hornet (Vespa orientalis) is a predatory hymenopteran belonging to the Vespidae family and is considered deemed one of the most destructive of the numerous enemies of honeybees.
Global warming and the movement of people and goods are the primary factors that are facilitating the expansion and colonization of new territories by V. orientalis. Native to the southeast Mediterranean, northeast and east Africa, the Middle East, and Central Asia, this species has spread to Chile, Mexico, China, and several European countries, including Spain, Romania, France, and the Greek islands.
In Italy, V. orientalis has been established in Sicily for some time and from there it then spread to Calabria, Campania, and Lazio. It It subsequently extended its range to Tuscany, Sardinia, Liguria, and Friuli Venezia Giulia, becoming a neo-invasive species.
Risks for Honeybees
Honeybee colonies are an important food source for the oriental hornet (Vespa orientalis), which can also act as a mechanical or biological vector of Apis mellifera pathogens, favoring their spread in the colonies. A study by the IZSVe investigated the presence of pathogens by analyzing 9 specimens of V. orientalis captured in the province of Trieste (North-East of Italy) in 2018. Viral co-infections were detected in all samples, with the concomitant presence of 2 to 5 of the seven A. mellifera viruses investigated.
Adult hornets feed on carbohydrates and sugary substances, such as nectar, honeydew, and ripe fruits. In contrast, their larvae require a large supply of protein to grow. As a result, honeybee colonies are an important food source for these hornets. The negative impact on honeybees is not limited to the serious direct damage caused by predatory behaviour but also includes the hornets’ ability to act as potential mechanical or biological vectors of pathogens affecting Apis mellifera, thus contributing to the spread of diseases among colonies.
A study conducted by the IZSVe, published in the scientific journal Veterinary Medicine and Science, investigated the presence of pathogens carried by V. orientalis, whose stings could potentially pose a threat not only to honeybees but also to human health.
The study was conducted in the province of Trieste, where V. orientalis has been present since 2018, likely introduced through goods shipped to the city’s commercial port. The field experiment, conducted from spring (to capture the queens) to late summer (to capture the workers), used experimental apiaries as bait and traps to capture the hornets. A total of 10 V. orientalis queens and 5 workers were captured, but only 4 queens and 5 workers were found suitable for molecular and microbiological testing, followed by MALDI-TOF analysis to identify the bacterial species present.
The molecular analyses conducted to detect the presence of the most frequent bee pathogens (fungi, trypanosomatids, and viruses) highlighted only several viral co-infections in all the sampled hornets (both queens and workers), identifying 5 of the 7 investigated viruses most known to infect Apis mellifera. The presence of these viruses, commonly found in many apiaries across Italy, suggests that they may have been transmitted from honey bees to V. orientalis through the predation and cannibalization of infected bee specimens. These findings confirmed data recently published by other researchers.
Risks for Humans
The oriental hornet could also become a public health problem, both because it is capable of inflicting multiple and painful stings on humans, with a high risk of developing an allergic reaction, and because it is capable of carrying pathogens for humans as well.
The microbiological analyses of the isolated bacteria led to the identification of some bacteria that are not only opportunistic pathogens for animals, birds, and insects but could also cause infections in humans.
These findings confirmed that, in addition to causing significant damage to beekeeping by feeding on honeybees and stressing their colonies, V. orientalis could also act as a potential biological or mechanical vector of bee pathogens, contributing to their spread among apiaries. Furthermore, these hornets may pose a risk for human beings, not only because they are capable of inflicting painful stings, which can also cause allergic reactions, but also because they can potentially act as vectors of pathogens for humans.
To mitigate the negative effects of the abnormal growth of V. orientalis populations and their potentially harmful impact on honey bees and public health, an integrated, multifaceted management and control program is essential. This should include public awareness campaigns, monitoring and alert systems, queen reduction, nest identification, and removal.
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