Chronic exposure to sublethal doses of imidacloprid combined with the microsporidium Vairimorpha ceranae affects immunity, gut microbiota and survival of Africanized honey bees

In recent years, there has been growing concern over the use of pesticides such as the neonicotinoid imidacloprid, which is commonly used to combat pests worldwide. Different studies have shown the great impact that sublethal doses of this pesticide have on the health of non-target insects such as honey bees. In this study we investigated the sublethal effects of chronic exposure of imidacloprid on the immune response of Africanized honey bees and its impact on exposure to pathogens such as Vairimorpha ceranae and the deformed wing virus (DWV), the gut microbial community and in honey bee survival. Our results showed that imidacloprid affected the immunity of Africanized honey bees, increasing the expression of lysozyme and decreasing the expression of hymenoptaecin, generating an abnormal physiological state. Imidacloprid together with V. ceranae decreased the expression of vitellogenin. Furthermore, imidacloprid did not affect V. ceranae infection or DWV replication. On the other hand, imidacloprid causes changes in the gut microbiota specially in V. ceranae infected bees. These alterations were reflected in the high mortality rates caused by imidacloprid alone or in combination with V. ceranae. These results corroborate previous findings in European honey bees, which showed the negative effects of imidacloprid. This study carried out on Africanized honey bees, it is a contribution to visualize the extent of the impact of imidacloprid on other honey bees lineages affected by the intensive use of pesticides.