Bee stings in Brazil: Epidemiological aspects in humans

Bees are insects of the order Hymenoptera and are involved in human accidents. In Brazil, bees that cause accidents are crosses derived from Europeans with African bees and are known for their aggressive behavior. Despite being considered an important public health concern, epidemiological studies at the national level are scarce. The objective of this study was to verify the epidemiological profile of bee accidents in humans in Brazil, using data from 2009 to 2019 of the Brazilian Ministry of Health. It was found that bee accidents increased by 207.61% from the first to the last year of the present study. The incidence varied according to the geographical region; the southern region had more bee accidents, but the Northern region had more deaths caused by bee accidents. Besides, climatic conditions were associated with susceptibility to bee stings; the incidence was higher during spring and summer. Age was also associated with fatality rate, with the elderly being the group with the highest fatality rate. Our results demonstrate that accidents caused by bees involve factors related to patients, the environment, and the behavior of bees. It is important to know the epidemiological aspects to help prevent apidic accidents.

The effects of crude propolis, its volatiles and ethanolic extracts on the ecto-parasitic mite, Varroa destructor and health of the African savannah honey bee, Apis mellifera scutellata

Propolis is a hive product composed of biologically active plant resins, and has been shown to enhance individual honey bee (Apis mellifera L.) health. Propolis has also been demonstrated to mitigate, in part, the negative effects caused by the ecto-parasitic mite Varroa destructor and its associated viruses on the health of managed European honey bee colonies. However, its effect on the health status of African honey bees remains largely unknown. Here, we found that the African savannah honey bees, A. m. scutellata in Kenya, deposited approximately two and half-fold more propolis in their colonies during periods of increased than reduced worker brood rearing. This finding suggested that A. m. scutellata may use high quantities of propolis prophylactically to protect their young brood; yet, we observed no significant correlation between the quantity of propolis and the amount of worker brood or mite-infestation level on adult workers. Furthermore, whereas propolis volatiles or propolis placed in direct contact with the mites had no effect on mite survival under laboratory conditions, the ethanolic extract of propolis significantly reduced mite survival when compared with untreated control. These results suggest the presence of mite deterrent compounds in the ethanolic extract of the African honey bee propolis.

Population genomics and morphometric assignment of western honey bees (Apis mellifera L.) in the Republic of South Africa

BACKGROUNDS

Apis mellifera scutellata and A.m. capensis (the Cape honey bee) are western honey bee subspecies indigenous to the Republic of South Africa (RSA). Both bees are important for biological and economic reasons. First, A.m. scutellata is the invasive "African honey bee" of the Americas and exhibits a number of traits that beekeepers consider undesirable. They swarm excessively, are prone to absconding (vacating the nest entirely), usurp other honey bee colonies, and exhibit heightened defensiveness. Second, Cape honey bees are socially parasitic bees; the workers can reproduce thelytokously. Both bees are indistinguishable visually. Therefore, we employed Genotyping-by-Sequencing (GBS), wing geometry and standard morphometric approaches to assess the genetic diversity and population structure of these bees to search for diagnostic markers that can be employed to distinguish between the two subspecies.

RESULTS

Apis mellifera scutellata possessed the highest mean number of polymorphic SNPs (among 2449 informative SNPs) with minor allele frequencies > 0.05 (Np = 88%). The RSA honey bees generated a high level of expected heterozygosity (Hexp = 0.24). The mean genetic differentiation (FST; 6.5%) among the RSA honey bees revealed that approximately 93% of the genetic variation was accounted for within individuals of these subspecies. Two genetically distinct clusters (K = 2) corresponding to both subspecies were detected by Model-based Bayesian clustering and supported by Principal Coordinates Analysis (PCoA) inferences. Selected highly divergent loci (n = 83) further reinforced a distinctive clustering of two subspecies across geographical origins, accounting for approximately 83% of the total variation in the PCoA plot. The significant correlation of allele frequencies at divergent loci with environmental variables suggested that these populations are adapted to local conditions. Only 17 of 48 wing geometry and standard morphometric parameters were useful for clustering A.m. capensis, A.m. scutellata, and hybrid individuals.

CONCLUSIONS

We produced a minimal set of 83 SNP loci and 17 wing geometry and standard morphometric parameters useful for identifying the two RSA honey bee subspecies by genotype and phenotype. We found that genes involved in neurology/behavior and development/growth are the most prominent heritable traits evolved in the functional evolution of honey bee populations in RSA. These findings provide a starting point for understanding the functional basis of morphological differentiations and ecological adaptations of the two honey bee subspecies in RSA.

Neonicotinoids decrease sucrose responsiveness of honey bees at first contact

For two decades, neonicotinoid insecticides have been extensively used worldwide. Targeting neuronal receptors, they have deleterious effects on the behaviour and physiology of many insects. Bees are exposed to these insecticides in pollen and nectar while providing pollination services to agricultural crops, and neonicotinoids have been shown to impair navigation and decrease their foraging activity. We have previously reported the effect of dietary thiamethoxam on sucrose responsiveness of young worker bees. Here, we exposed caged foragers to sublethal acute doses of clothianidin, imidacloprid, and thiamethoxam, then tested them individually for sucrose responsiveness using standard methods. In addition, we tested the response to a range of sucrose solutions laced with neonicotinoids on bees previously unexposed to neonicotinoids. This paradigm mimics the situation where foragers would first encounter poisoned nectars varying in sugar concentration. Bees were exposed to the insecticides in the feeding solution for 24 h before testing, or in the test solutions, or both. The three compounds had a detrimental effect on responses to mid-to-high sucrose concentrations under all experimental conditions, and unexposed bees tested with laced sucrose displayed unexpected low responses to the higher sucrose concentrations tested. This attenuation of sucrose response is further evidence that neonicotinoids are multisensory disruptors, with potent actions against pollinators and other beneficial insects at first contact.

The metabolic fate of nectar nicotine in worker honey bees

Honey bees (Apis mellifera) are generalist pollinators that forage for nectar and pollen of a very large variety of plant species, exposing them to a diverse range of secondary metabolites produced as chemical defences against herbivory. Honey bees can tolerate high levels of many of these toxic compounds, including the alkaloid nicotine, in their diet without incurring apparent fitness costs. Very little is known about the underlying detoxification processes mediating this tolerance. We examined the metabolic fate of nicotine in newly emerged worker bees using radiolabeled nicotine and LC-MS/MS analysis to determine the kinetic distribution profile of nicotine as well as the absence or presence and identity of any nicotine-derived metabolites. Nicotine metabolism was extensive; virtually no unmetabolised nicotine were recovered from the rectum. The major metabolite found was 4-hydroxy-4-(3-pyridyl) butanoic acid, the end product of 2'C-oxidation of nicotine. It is the first time that 4-hydroxy-4-(3-pyridyl) butanoic acid has been identified in an insect as a catabolite of nicotine. Lower levels of cotinine, cotinine N-oxide, 3'hydroxy-cotinine, nicotine N-oxide and norcotinine were also detected. Our results demonstrated that formation of 4-hydroxy-4-(3-pyridyl) butanoic acid is quantitatively the most significant pathway of nicotine metabolism in honey bees and that the rapid excretion of unmetabolised nicotine does not contribute significantly to nicotine tolerance in honey bees. In nicotine-tolerant insects that do not rely on the rapid excretion of nicotine like the Lepidoptera, it is possible that the 2'C-oxidation of nicotine is the conserved metabolic pathway instead of the generally assumed 5'C-oxidation pathway.

Differences in Varroa destructor infestation rates of two indigenous subspecies of Apis mellifera in the Republic of South Africa

Varroa destructor Anderson & Trueman (Varroa) is a damaging pest of the Western honey bee, Apis mellifera, in North America, Europe, and Asia. However, Varroa infestations have not produced equivalent colony losses of African subspecies of honey bee throughout Africa and parts of the Americas. We surveyed the Varroa infestation rates (number of Varroa per 100 adult honey bees) in colonies of A. m. scutellata, A. m. capensis, and hybrids of the two subspecies throughout the Republic of South Africa in the fall of 2014. We found that A. m. scutellata colonies had significantly higher Varroa infestations than did A. m. capensis colonies. Furthermore, hybridized colonies of the two subspecies had Varroa infestations intermediate to those of A. m. scutellata and A. m. capensis. This is the first documentation of a clear difference in Varroa infestation rates of A. m. scutellata, A. m. capensis, and hybridized colonies in South Africa. Furthermore, our data confirm that Varroa populations in A. m. scutellata colonies are within the range of populations that are damaging to European honey bees.

Resistance rather than tolerance explains survival of savannah honeybees (Apis mellifera scutellata) to infestation by the parasitic mite Varroa destructor

Varroa destructor is considered the most damaging parasite affecting honeybees (Apis mellifera L.). However, some honeybee populations such as the savannah honeybee (Apis mellifera scutellata) can survive mite infestation without treatment. It is unclear if survival is due to resistance mechanisms decreasing parasite reproduction or to tolerance mechanisms decreasing the detrimental effects of mites on the host. This study investigates both aspects by quantifying the reproductive output of V. destructor and its physiological costs at the individual host level. Costs measured were not consistently lower when compared with susceptible honeybee populations, indicating a lack of tolerance. In contrast, reproduction of V. destructor mites was distinctly lower than in susceptible populations. There was higher proportion of infertile individuals and the reproductive success of fertile mites was lower than measured to date, even in surviving populations. Our results suggest that survival of savannah honeybees is based on resistance rather than tolerance to this parasite. We identified traits that may be useful for breeding programmes aimed at increasing the survival of susceptible populations. African honeybees may have benefited from a lack of human interference, allowing natural selection to shape a population of honeybees that is more resistant to Varroa mite infestation.

Antioxidant supplementation can reduce the survival costs of excess amino acid intake in honeybees

Over-consuming amino acids is associated with reduced survival in many species, including honeybees. The mechanisms responsible for this are unclear but one possibility is that excessive intake of amino acids increases oxidative damage. If this is the case, antioxidant supplementation may help reduce the survival costs of high amino acid intake. We tested this hypothesis in African honeybees (Apis mellifera scutellata) using the major antioxidant in green tea, epigallocatechin-3-gallate (EGCG). We first determined the dose-range of EGCG that improved survival of caged honeybees fed sucrose solution. We then provided bees with eight diets that differed in their ratio of essential amino acids (EAA) to carbohydrate (C) (0:1, 1:250, 1:100, 1:75, 1:50, 1:25, 1:10, 1:5 EAA:C) and also in their EGCG dose (0.0 or 0.4 mM). We found that bees fed sucrose only solution survived better than bees fed EAA diets. Despite this, bees preferred a diet that contained intermediate ratios of EAA:C (ca. 1:25), which may represent the high demands for nitrogen of developing nurse bees. EGCG supplementation improved honeybee survival but only at an intermediate dose (0.3-0.5 mM) and in bees fed low EAA diets (1:250, 1:100 EAA:C). That EGCG counteracted the lifespan reducing effects of eating low EAA diets suggests that oxidative damage may be involved in the association between EAAs and lifespan in honeybees. However, that EGCG had no effect on survival in bees fed high EAA diets suggests that there are other physiological costs of over-consuming EAAs in honeybees.

Resistance of developing honeybee larvae during chronic exposure to dietary nicotine

The effects of pesticides on honeybee larvae are less understood than for adult bees, even though larvae are chronically exposed to pesticide residues that accumulate in comb and food stores in the hive. We investigated how exposure to a plant alkaloid, nicotine, affects survival, growth and body composition of honeybee larvae. Larvae of Apis mellifera scutellata were reared in vitro and fed throughout development on standard diets with nicotine included at concentrations from 0 to 1000μg/100g diet. Overall mortality across all nicotine treatments was low, averaging 9.8% at the prepupal stage and 18.1% at the white-eyed pupal stage, but survival was significantly reduced by nicotine. The mass of prepupae and white-eyed pupae was not affected by nicotine. In terms of body composition, nicotine affected water content but did not influence either protein or lipid stores of white-eyed pupae. We attribute the absence of consistent negative effects of dietary nicotine to detoxification mechanisms in developing honeybees, which enable them to resist both natural and synthetic xenobiotics.

Honeybees prefer warmer nectar and less viscous nectar, regardless of sugar concentration

The internal temperature of flowers may be higher than air temperature, and warmer nectar could offer energetic advantages for honeybee thermoregulation, as well as being easier to drink owing to its lower viscosity. We investigated the responses of Apis mellifera scutellata (10 colonies) to warmed 10% w/w sucrose solutions, maintained at 20-35°C, independent of low air temperatures, and to 20% w/w sucrose solutions with the viscosity increased by the addition of the inert polysaccharide Tylose (up to the equivalent of 34.5% sucrose). Honeybee crop loads increased with nectar temperature, as did the total consumption of sucrose solutions over 2 h by all bees visiting the feeders. In addition, the preference of marked honeybees shifted towards higher nectar temperatures with successive feeder visits. Crop loads were inversely proportional to the viscosity of the artificial nectar, as was the total consumption of sucrose solutions over 2 h. Marked honeybees avoided higher nectar viscosities with successive feeder visits. Bees thus showed strong preferences for both warmer and less viscous nectar, independent of changes in its sugar concentration. Bees may benefit from foraging on nectars that are warmer than air temperature for two reasons that are not mutually exclusive: reduced thermoregulatory costs and faster ingestion times due to the lower viscosity.

Seasonal prevalence of pathogens and parasites in the savannah honeybee (Apis mellifera scutellata)

The loss of Apis mellifera L. colonies in recent years has, in many regions of the world, been alarmingly high. No single cause has been identified for these losses, but the interactions between several factors (mostly pathogens and parasites) have been held responsible. Work in the Americas on honeybees originating mainly from South Africa indicates that Africanised honeybees are less affected by the interplay of pathogens and parasites. However, little is known about the health status of South African honeybees (A. m. scutellata and A. m. capensis) in relation to pathogens and parasites. We therefore compared the seasonal prevalence of honeybee pathogens (viruses, bacteria, fungi) and parasites (mites, bee lice, wax moth, small hive beetles, A. m. capensis social parasites) between sedentary and migratory A. m. scutellata apiaries situated in the Gauteng region of South Africa. No significant differences were found in the prevalence of pathogens and parasites between sedentary and migratory apiaries. Three (Black queen cell virus, Varroa destructor virus 1 and Israeli acute paralysis virus) of the eight viruses screened were detected, a remarkable difference compared to European honeybees. Even though no bacterial pathogens were detected, Nosema apis and Chalkbrood were confirmed. All of the honeybee parasites were found in the majority of the apiaries with the most common parasite being the Varroa mite. In spite of hosting few pathogens, yet most parasites, A. m. scutellata colonies appeared to be healthy.