One of the causes of bee mortality in sight: study results give hope that bees can be strengthened against the dreaded wing deformation virus with a natural active ingredient. Bees treated with the preparation show a significantly increased resistance to infection and are less affected by memory impairments caused by the virus. This improves the ability of infected bees to successfully return to the hive after searching for food, the scientists report.
Mankind looks with concern at its valued honey producers and pollinators – the insects suffer from the so-called bee deaths: Many colonies around the world are weakened and the loss rates are high. As shown by numerous studies, the problem is based on a mixture of different causes and their interactions. The so-called wing deformation virus is an important factor. Bees severely affected by the infection die within a few days. In the case of latent infestation, on the other hand, the wings, after which the virus is named, are incorrectly tied. Earlier studies have also shown that the pathogen can impair the bees’ ability to learn and remember.
Bee problems in sight
The strain from the wing deformation virus is in turn linked to the second major problem for bees: the infestation by varroa mites. The bloodsuckers transmit the viruses and weaken the bees, so that their resilience suffers. So far, attempts have been made to keep the mites in check by means of chemical control measures in order to indirectly help the bees against the disease. “But beekeepers shouldn’t use pesticides for food safety reasons. So we looked for ways to directly strengthen the bees’ resistance to the virus, ”explains first author Cheng-Kang Tang from the National Taiwan University.
As part of their study, he and his colleagues first looked at the fundamental effects of the virus infection. By analyzing the gene activity in infected bees, they were able to show that the pathogen suppresses the expression of genes that are related to the nervous system and cognitive processes in the insects. Obviously, this is the cause of the disorders of the learning and memory functions in the infections. Against the background of these results, the researchers were interested in a substance that has already been known to have a beneficial effect on immune functions and cognitive performance from other studies: sodium butyrate (NaB). This is a compound that occurs naturally in many plants, for example.
More resilience and cognitive performance
In order to sound out the possible effect of NaB on bees in connection with infections caused by the wing deformation virus, the scientists fed test animals with NaB-containing sugar water for a week. They were then infected with the virus in parallel with untreated control bees. The subsequent evaluations showed: More than 90 percent of the treated bees were still alive after five days, while 90 percent of the infected bees that had not received NaB died in the same period.
“Our results show that feeding the insects with NaB before exposure to the virus can counteract the negative effects of the pathogen,” sums up Wu. The background to this effect could also be uncovered through genetic analyzes: “We found that NaB upregulates some genes of the immune defense in bees, which can help suppress virus replication and improve the bees’ chances of survival,” says Wu. The researchers also found indications that the administration of the active ingredient favorably influenced genetic expression patterns in the infected bees, which are associated with cognitive abilities.
To what extent this is reflected in real improvements in the bees’ memory, the researchers investigated through experiments with bee colonies in the field: They installed monitors at the entrances to various hives to determine how many bees they leave in the course of a day and then return again Return home. The researchers found that, on average, only half of infected bees manage to return to the hive. Animals that were similarly affected by the virus but had previously been treated with NaB were much more successful when they returned home: more than 80 percent still found their way home, the researchers report. “What is special about the study is that we examined the effects of NaB at various levels – from gene expression and effects in the laboratory to behavior in the field under natural conditions,” says Wu.
He and his colleagues now see the active ingredient as an important bearer of hope in bee medicine. That is why they now want to further explore the potential through additional studies. “Sodium butyrate is very cheap. If the positive effects are confirmed, it would be a simple and affordable approach for beekeepers to keep their bees alive, ”says Wu.
Source: Cell Press, technical article: iScience, doi: 10.1016 / j.isci.2021.103056