A rapid decline of Apis mellifera, a keystone pollinator of wild plant species and
agricultural crops, was recorded worldwide in recent years. The massive use of
insecticides and fungicides in agriculture associated with pollution generated by
other human activities and presence of parasites can cause toxicological effects in
bees including a decrease of the immune defences, leading to the collapse of the
colonies. Effective assessment of the ecotoxicological impacts of anthropogenic
contaminants requires an approach that combines different biomarkers that enable
a more precise diagnosis of exposure to environmental stressors through a
combination of different biological responses. The aim of this study was to
develop and apply a set of biomarkers to study the ecotoxicological status of
honey bees. In the first phase, we investigated in the laboratory the effects of
EMS, cadmium and a commercial fungicide (azoxistrobin 18.2% and
ciproconazole 7.3%) in adult honey bees, evaluating eventual variation in
glutathione S-transferase (GST), carboxylesterase (CaE), acetylcholinesterase
(AChE) activities, alkaline phosphatase (ALP), lysozyme, erythrocyte nuclear
abnormalities (ENA) assay and differential haemocytes count (DHC). Genotoxic
effects, as well as alteration of the immune system, were found in bees treated
with EMS, cadmium or the fungicide. Cadmium and the fungicide also inhibited
AChE and CaE activities, GST was induced by all the compounds investigated. In
the second phase, adult honey bees were collected from apiaries located in four
environments characterized by different chemical input: a wooded environment
(low input), an urban site, an orchard and a cultivated countryside site. Honey
bees from the urban site were also collected and analyzed before and after
treatment for parasites. ENA assay showed that bees taken from the countryside
and the orchard had a greater number of abnormalities compared to the forest,
confirming the presence of genotoxic substances in agricultural environments
compared to control environments. GST activity was induced in bees from the
urban environment, AChE was inhibited in the countryside compared to the forest,
suggesting the presence of substances with neurotoxic effect in this environment.
ALP activity was induced in all sites in comparison to wooded one. The bees
collected after the parasites treatment showed an increase for GST activity as well
as AChE inhibition