Bee-Inspired Healing: Apitherapy in Veterinary Medicine for Maintenance and Improvement Animal Health and Well-Being.

This review aims to present current knowledge on the effects of honey bee products on animals based on in vivo studies, focusing on their application in clinical veterinary practice. Honey's best-proven effectiveness is in treating wounds, including those infected with antibiotic-resistant microorganisms, as evidenced in horses, cats, dogs, mice, and rats. Propolis manifested a healing effect in numerous inflammatory and painful conditions in mice, rats, dogs, and pigs and also helped in oncological cases in mice and rats. Bee venom is best known for its effectiveness in treating neuropathy and arthritis, as shown in dogs, mice, and rats. Besides, bee venom improved reproductive performance, immune response, and general health in rabbits, chickens, and pigs. Pollen was effective in stimulating growth and improving intestinal microflora in chickens. Royal jelly might be used in the management of animal reproduction due to its efficiency in improving fertility, as shown in rats, rabbits, and mice. Drone larvae are primarily valued for their androgenic effects and stimulation of reproductive function, as evidenced in sheep, chickens, pigs, and rats. Further research is warranted to determine the dose and method of application of honey bee products in animals.

Bridging the buzz: In vivo EPR imaging unlocking the secrets of honey bee health.

Honey bees play a pivotal role in shaping ecosystems and sustaining human health as both pollinators and producers of health-promoting products. However, honey bee colony mortality is on the rise globally, driven by various factors, including parasites, pesticides, habitat loss, poor nutrition, and climate change. This has far-reaching consequences for the environment, economy, and human welfare. While efforts to address these issues are underway, the current progress in electron paramagnetic resonance (EPR) instrumentation affords using the immense potential of this magnetic resonance technique to study small samples such as honey bees. This paper presents the pioneering 2D in vivo EPR imaging experiment on a honey bee, revealing the ongoing redox-status of bees' intestines. This way, by monitoring the spatio-temporal changes of the redox-active spin-probes' EPR signal, it is possible to gain access to valuable information on the course of ongoing bees' pathologies and the prospect of following-up on the efficiency of applied therapies. Employing a selection of diverse spin-probes could further reveal pH levels and oxygen concentrations in bee tissues, allowing a noninvasive assessment of bee physiology. This approach offers promising strategies for safeguarding pollinators and understanding their biology, fostering their well-being and ecological harmony.

Potential of Wormwood and Oak Bark-Based Supplement in Health Improvement of Nosema ceranae-Infected Honey Bees.

Nosema ceranae, a microsporidian parasite, as one of the stressors that contribute to honey bee decline, has a significant negative impact on the longevity, productivity, and reproductive capacity of honey bee colonies. There are several different strategies for Nosema infection control, including natural-based and antibiotic-based products. In this study, we tested wormwood and oak bark-based supplement "Medenko forte" on survival, Nosema infection, oxidative stress, and expression of immune-related genes in artificially N. ceranae-infected bees. The results revealed a positive influence on the survival of Nosema-infected bees, irrespectively of the moment of supplement application (day 1, day 3, or day 6 after bee emergence), as well as reduction of Nosema loads and, consequently, Nosema-induced oxidative stress. Supplementation had no negative effects on bee immunity, but better anti-Nosema than immune-stimulating effects were affirmed based on expression levels of abaecin, defensin, hymenoptaecin, apidaecin, and vitellogenin genes. In conclusion, the tested supplement "Medenko forte" has great potential in the health protection of Nosema-infected bees. However, further investigations need to be performed to elucidate its mechanisms of action.

Genome-Wide Analysis of Milk Production Traits and Selection Signatures in Serbian Holstein-Friesian Cattle.

To improve the genomic evaluation of milk-related traits in Holstein-Friesian (HF) cattle it is essential to identify the associated candidate genes. Novel SNP-based analyses, such as the genetic mapping of inherited diseases, GWAS, and genomic selection, have led to a new era of research. The aim of this study was to analyze the association of each individual SNP in Serbian HF cattle with milk production traits and inbreeding levels. The SNP 60 K chip Axiom Bovine BovMDv3 was deployed for the genotyping of 334 HF cows. The obtained genomic results, together with the collected phenotypic data, were used for a GWAS. Moreover, the identification of ROH segments was performed and served for inbreeding coefficient evaluation and ROH island detection. Using a GWAS, a polymorphism, rs110619097 (located in the intron of the CTNNA3 gene), was detected to be significantly (p < 0.01) associated with the milk protein concentration in the first lactation (adjusted to 305 days). The average genomic inbreeding value (FROH) was 0.079. ROH islands were discovered in proximity to genes associated with milk production traits and genomic regions under selection pressure for other economically important traits of dairy cattle. The findings of this pilot study provide useful information for a better understanding of the genetic architecture of milk production traits in Serbian HF dairy cows and can be used to improve lactation performances in Serbian HF cattle breeding programs.

Effects of Plant-Based Supplement on Oxidative Stress of Honey Bees (Apis mellifera) Infected with Nosema ceranae.

One of the most important approaches in the prevention and treatment of nosemosis is the use of herbal preparations as food supplements for bees. Therefore, the aim of this study was to investigate the effects of a plant-based supplement branded as "B+" on honeybees in a laboratory experiment. Four experimental groups were established: treated group (T), N. ceranae-infected and treated group (IT), N. ceranae-infected group (I) and non-infected group (NI). Survival, N. ceranae spore load and oxidative stress parameters together with expression levels of antioxidant enzyme genes and vitellogenin gene were monitored. The mortality in the T, IT and NI groups was significantly (p < 0.001) lower than in than in the I group. Within Nosema-infected groups, the IT group had a significantly lower (p < 0.001) number of N. ceranae spores than the I group. In addition, expression levels of genes for antioxidant enzymes were lower (p < 0.001) in the IT group compared to the I group. The concentration of malondialdehyde and the activities of antioxidant enzymes (superoxide dismutase, catalase and glutathione S-transferase) were significantly lower (p < 0.001) in the IT group compared to the I group. No negative effects of the tested supplement were observed. All these findings indicate that the tested supplement exerted beneficial effects manifested in better bee survival, reduced N. ceranae spore number and reduced oxidative stress of bees (lower expression of genes for antioxidant enzymes and oxidative stress parameters).

"Slow kill" treatment reduces DNA damage in leukocytes of dogs naturally infected with Dirofilaria immitis.

Parasitic diseases are considered to be a cause of oxidative stress which leads to oxidative damage of various molecules including DNA. This can result in mutations, replication errors, and genome instability. Therefore, aim of this study was to measure DNA damage induced by Dirofilaria immitis in the single cells such as dogs' leukocytes using the comet assay. Also, we monitored the effects of antiparasitic treatment on mitigation of sensitivity to DNA damage in leukocytes treated with H2O2 using the in vivo and ex vivo comet assay. The whole blood samples from 34 dogs from Serbia were used, both males and females, from one to 13 years old, both pure and mixed-breeds. A rapid immunochromatographic test (Antigen Rapid Heartworm Ag 2.0 Test Kit, Bionote, Minnesota, USA) was used for the detection of D. immitis antigens. The modified Knott's test and PCR were used in the aim of detecting D. immitis microfilariae in dogs' blood, and evaluating the number of circulating microfilariae during the treatment. The genotoxicity evaluation showed that D. immitis infection resulted in DNA damage in naturally infected dogs, with the highest DNA damage occurring in the group of dogs with severe clinical signs. Treatment with ivermectin and doxycycline decreased DNA damage in leukocytes of dogs in all groups, as the intensity of infection decreased due to applied therapy. Ex vivo comet assay results showed that leukocytes exhibited decreased sensitivity to H2O2-induced DNA damage during treatment. The results of the modified Knott's test and PCR in our study showed that treatment with ivermectin and doxycycline was successful in decreasing the average number of microfilariae during the time and at the end eliminating them from the dogs' blood.

Genotoxic Potential of Thymol on Honey Bee DNA in the Comet Assay.

Thymol is a natural essential oil derived from the plant Thymus vulgaris L. It is known to be beneficial for human and animal health and has been used in beekeeping practice against Varroa mite for years. In this study, the genotoxic and antigenotoxic potential of thymol were evaluated on the honey bee (Apis mellifera L.) continuous cell line AmE-711 for the first time. Using the Comet assay, three increasing concentrations (10, 100, and 1000 µg/mL) of thymol were tested. Negative control (non-treated cells) and positive control (cells treated with 100 µM H2O2) were also included. The absence of thymol cytotoxicity was confirmed with the Trypan blue exclusion test. Thymol in the concentration of 10 µg/mL did not increase DNA damage in AmE-711 honey bee cells, while 100 and 1000 µg/mL concentrations showed genotoxic effects. For testing the antigenotoxic effect, all concentrations of thymol were mixed and incubated with H2O2. The antigenotoxic effect against was absent at all concentrations (10, 100, 1000 µg/mL) tested. Moreover, thymol enhanced the H2O2-induced DNA migration in the Comet assay. The obtained results indicate genotoxic effects of thymol on cultured honey bee cells suggesting its careful application in beekeeping practice to avoid possible negative effects on honey bees.

Contact varroacidal efficacy of lithium citrate and its influence on viral loads, immune parameters and oxidative stress of honey bees in a field experiment.

With an almost global distribution, Varroa destuctor is the leading cause of weakening and loss of honey bee colonies. New substances are constantly being tested in order to find those that will exhibit high anti-Varroa efficacy at low doses/concentrations, without unwanted effects on bees. Lithium (Li) salts stood out as candidates based on previous research. The aims of this study were to evaluate Li citrate hydrate (Li-cit) for its contact efficacy against Varroa, but also the effect of Li-cit on honey bees by estimating loads of honey bee viruses, expression levels of immune-related genes and genes for antioxidative enzymes and oxidative stress parameters on two sampling occasions, before the treatment and after the treatment. Our experiment was performed on four groups, each consisting of seven colonies. Two groups were treated with the test compound, one receiving 5 mM and the other 10 mM of Li-cit; the third received oxalic acid treatment (OA group) and served as positive control, and the fourth was negative control (C group), treated with 50% w/v pure sucrose-water syrup. Single trickling treatment was applied in all groups. Both tested concentrations of Li-cit, 5 and 10 mM, expressed high varroacidal efficacy, 96.85% and 96.80%, respectively. Load of Chronic Bee Paralysis Virus significantly decreased (p < 0.01) after the treatment in group treated with 5 mM of Li-cit. In OA group, loads of Acute Bee Paralysis Virus and Deformed Wing Virus significantly (p < 0.05) increased, and in C group, loads of all viruses significantly (p < 0.01 or p < 0.001) increased. Transcript levels of genes for abaecin, apidaecin, defensin and vitellogenin were significantly higher (p < 0.05-p < 0.001), while all oxidative stress parameters were significantly lower (p < 0.05-p < 0.001) after the treatment in both groups treated with Li-cit. All presented results along with easy application indicate benefits of topical Li-cit treatment and complete the mosaic of evidence on the advantages of this salt in the control of Varroa.

Zika vector competence data reveals risks of outbreaks: the contribution of the European ZIKAlliance project.

First identified in 1947, Zika virus took roughly 70 years to cause a pandemic unusually associated with virus-induced brain damage in newborns. Zika virus is transmitted by mosquitoes, mainly Aedes aegypti, and secondarily, Aedes albopictus, both colonizing a large strip encompassing tropical and temperate regions. As part of the international project ZIKAlliance initiated in 2016, 50 mosquito populations from six species collected in 12 countries were experimentally infected with different Zika viruses. Here, we show that Ae. aegypti is mainly responsible for Zika virus transmission having the highest susceptibility to viral infections. Other species play a secondary role in transmission while Culex mosquitoes are largely non-susceptible. Zika strain is expected to significantly modulate transmission efficiency with African strains being more likely to cause an outbreak. As the distribution of Ae. aegypti will doubtless expand with climate change and without new marketed vaccines, all the ingredients are in place to relive a new pandemic of Zika.

Use of Thymol in Nosema ceranae Control and Health Improvement of Infected Honey Bees.

Nosema ceranae is the most widespread microsporidian species which infects the honey bees of Apis mellifera by causing the weakening of their colonies and a decline in their productive and reproductive capacities. The only registered product for its control is the antibiotic fumagillin; however, in the European Union, there is no formulation registered for use in beekeeping. Thymol (3-hydroxy-p-cymene) is a natural essential-oil ingredient derived from Thymus vulgaris, which has been used in Varroa control for decades. The aim of this study was to investigate the effect of thymol supplementation on the expression of immune-related genes and the parameters of oxidative stress and bee survival, as well as spore loads in bees infected with the microsporidian parasite N. ceranae. The results reveal mostly positive effects of thymol on health (increasing levels of immune-related genes and values of oxidative stress parameters, and decreasing Nosema spore loads) when applied to Nosema-infected bees. Moreover, supplementation with thymol did not induce negative effects in Nosema-infected bees. However, our results indicate that in Nosema-free bees, thymol itself could cause certain disorders (affecting bee survival, decreasing oxidative capacity, and downregulation of some immune-related gene expressions), showing that one should be careful with preventive, uncontrolled, and excessive use of thymol. Thus, further research is needed to reveal the effect of this phytogenic supplement on the immunity of uninfected bees.

Effects of Agaricus bisporus Mushroom Extract on Honey Bees Infected with Nosema ceranae.

Agaricus bisporus water crude extract was tested on honey bees for the first time. The first part of the cage experiment was set for selecting one concentration of the A. bisporus extract. Concentration of 200 µg/g was further tested in the second part of the experiment where bee survival and food consumption were monitored together with Nosema infection level and expression of five genes (abaecin, hymenoptaecin, defensin, apidaecin, and vitellogenin) that were evaluated in bees sampled on days 7 and 15. Survival rate of Nosema-infected bees was significantly greater in groups fed with A. bisporus-enriched syrup compared to those fed with a pure sucrose syrup. Besides, the anti-Nosema effect of A. bisporus extract was greatest when applied from the third day which coincides with the time of infection with N. ceranae. Daily food consumption did not differ between the groups indicating good acceptability and palatability of the extract. A. bisporus extract showed a stimulative effect on four out of five monitored genes. Both anti-Nosema and nutrigenomic effects of A. bisporus extract were observed when supplementation started at the moment of N. ceranae infection or preventively (before or simultaneously with the infection).

Potential of Fumagillin and Agaricus blazei Mushroom Extract to Reduce Nosema ceranae in Honey Bees.

Depending on the infection level and colony strength, Nosema ceranae, a microsporidian endoparasite of the honey bee may have significant consequences on the health, reproduction and productivity of bee colonies. Despite exerting some side effects, fumagillin is most often used for Nosema control. In this study, in a cage experiment, N. ceranae infected bees were treated with fumagillin or the extract of Agaricus blazei mushroom, a possible alternative for Nosema control. Bee survival, Nosema spore loads, the expression levels of immune-related genes and parameters of oxidative stress were observed. Fumagillin treatment showed a negative effect on monitored parameters when applied preventively to non-infected bees, while a noticeable anti-Nosema effect and protection from Nosema-induced immunosuppression and oxidative stress were proven in Nosema-infected bees. However, a protective effect of the natural A. blazei extract was detected, without any side effects but with immunostimulatory activity in the preventive application. The results of this research suggest the potential of A. blazei extract for Nosema control, which needs to be further investigated.

Plant-based supplement containing B-complex vitamins can improve bee health and increase colony performance.

It is common knowledge that nutritive stress resulting from decreased diversity and quality of food, pollution of food sources and beekeeping errors may lead to increased susceptibility of bees to pathogens and pesticides. The dearth of adequate food is frequently compensated with supplements. Thus, this research was aimed to study the effects of the plant-based supplement B + on colony strength (assessed according to open and sealed brood area, honey and pollen/bee bread reserves, and the number of adult bees). In addition, Nosema ceranae spores and viruses were quantified and the level of infestation with Varroa destructor assessed. The experiment was conducted in late summer and early spring. In colonies which were given B + in feed a significant increase (p < 0.05) in the parameters of colony strength were noticed in comparison to the control (colonies fed on sugar syrup). Moreover, it was proven that the bees from these colonies had significantly lower (p < 0.05) N. ceranae spore counts, and acute bee paralysis, deformed wing and sacbrood virus loads. Our results suggest that the addition of B + supplement to the colonies provide them with nutrients, contribute to their strengthening, might prevent nutritive stress and increase the success of bees in combating pathogens.

Assessing the role of two populations of Aedes japonicus japonicus for Zika virus transmission under a constant and a fluctuating temperature regime.

BACKGROUND: Since the huge epidemic of Zika virus (ZIKV) in Brazil in 2015, questions were raised to understand which mosquito species could transmit the virus. Aedes aegypti has been described as the main vector. However, other Aedes species (e.g. Ae. albopictus and Ae. japonicus) proven to be competent for other flaviviruses (e.g. West Nile, dengue and yellow fever), have been described as potential vectors for ZIKV under laboratory conditions. One of these, the Asian bush mosquito, Ae. japonicus, is widely distributed with high abundances in central-western Europe. In the present study, infection, dissemination and transmission rates of ZIKV (Dak84 strain) in two populations of Ae. japonicus from Switzerland (Zürich) and France (Steinbach, Haut-Rhin) were investigated under constant (27 °C) and fluctuating (14-27 °C, mean 23 °C) temperature regimes. RESULTS: The two populations were each able to transmit ZIKV under both temperature regimes. Infectious virus particles were detected in the saliva of females from both populations, regardless of the incubation temperature regime, from 7 days post-exposure to infectious rabbit blood. The highest amount of plaque forming units (PFU) (400/ml) were recorded 14 days post-oral infection in the Swiss population incubated at a constant temperature. No difference in terms of infection, dissemination and transmission rate were found between mosquito populations. Temperature had no effect on infection rate but the fluctuating temperature regime resulted in higher dissemination rates compared to constant temperature, regardless of the population. Finally, transmission efficiency ranged between 7-23% and 7-10% for the constant temperature and 0-10% and 3-27% under fluctuating temperatures for the Swiss and the French populations, respectively. CONCLUSIONS: To the best of our knowledge, this is the first study confirming vector competence for ZIKV of Ae. japonicus originating from Switzerland and France at realistic summer temperatures under laboratory conditions. Considering the continuous spread of this species in the northern part of Europe and its adaptation at cooler temperatures, preventative control measures should be adopted to prevent possible ZIKV epidemics.

Oxidative Stress, Endoparasite Prevalence and Social Immunity in Bee Colonies Kept Traditionally vs. Those Kept for Commercial Purposes.

Commercially and traditionally managed bees were compared for oxidative stress (superoxide dismutase (SOD), catalase (CAT), glutathione S-transferase (GST) and malondialdehyde (MDA)), the prevalence of parasites (Lotmaria passim, Crithidia mellificae and Nosema ceranae/apis) and social immunity (glucose oxidase gene expression). The research was conducted on Pester plateau (Serbia-the Balkan Peninsula), on seemingly healthy colonies. Significant differences in CAT, GST and SOD activities (p < 0.01), and MDA concentrations (p < 0.002) were detected between commercial and traditional colonies. In the former, the prevalence of both L. passim and N. ceranae was significantly (p < 0.05 and p < 0.01, respectively) higher. For the first time, L. passim was detected in honey bee brood. In commercial colonies, the prevalence of L. passim was significantly (p < 0.01) lower in brood than in adult bees, whilst in traditionally kept colonies the prevalence in adult bees and brood did not differ significantly. In commercially kept colonies, the GOX gene expression level was significantly (p < 0.01) higher, which probably results from their increased need to strengthen their social immunity. Commercially kept colonies were under higher oxidative stress, had higher parasite burdens and higher GOX gene transcript levels. It may be assumed that anthropogenic influence contributed to these differences, but further investigations are necessary to confirm that.

Exposure of honey bee larvae to thiamethoxam and its interaction with Nosema ceranae infection in adult honey bees.

During their lifetime honey bees (Apis mellifera) rarely experience optimal conditions. Sometimes, a simultaneous action of multiple stressors, natural and chemical, results in even greater effect than of any stressor alone. Therefore, integrative investigations of different factors affecting honey bees have to be carried out. In this study, adult honey bees exposed to thiamethoxam in larval and/or adult stage and infected with Nosema ceranae were examined. Newly emerged bees from colonies, non-treated or treated with thiamethoxam, were organized in six groups and kept in cages. Thiamethoxam treated bees were further exposed to either thiamethoxam or Nosema (groups TT and TN), or simultaneously to both (group TTN). Newly emerged bees from non-treated colonies were exposed to Nosema (group CN). From both, treated and non-treated colonies two groups were organized and further fed only with sugar solution (groups C and TC). Here, we present the expression profile of 19 genes in adult worker honey bees comprising those involved in immune, detoxification, development and apoptosis response. Results showed that gene expression patterns changed with time and depended on the treatment. In group TC at the time of emergence the majority of tested genes were downregulated, among which nine were significantly altered. The same gene pattern was observed on day six, where the only significantly upregulated gene was defensin-1. On day nine most of analyzed genes in all experimental groups showed upregulation compared to control group, where upregulation of antimicrobial peptide genes abaecin, defensin-1 and defensin-2 was significant in groups TT and TTN. On day 15 we observed a similar pattern of expression in groups TC and TT exposed to thiamethoxam only, where most of the detoxification genes were downregulated. Additionally RNA loads of Nosema and honey bee viruses were recorded. We detected a synergistic interaction of thiamethoxam and Nosema, reflected in lowest honey bee survival.

Efficacy of oral fluralaner for the treatment of canine generalized demodicosis: a molecular-level confirmation.

BACKGROUND: Canine generalized demodicosis is a common parasitic disease caused by the proliferation of Demodex mites. The introduction of isoxazoline class treatments in veterinary dermatology has resulted in apparently effective treatment of generalized demodicosis. The objective of this study was to evaluate the effectiveness of fluralaner for the treatment of canine generalized demodicosis using real-time PCR for the detection and quantification of Demodex DNA. METHODS: Twenty privately owned dogs with clinical symptoms of generalized demodicosis and deep skin scrapings positive for Demodex canis mites were enrolled in the study. Following diagnosis (day 0) each dog was treated with fluralaner at the recommended commercial dose for tick and flea treatment (25-56 mg/kg) based on body weight. Clinical and mite count assessments, and hair sampling for molecular analyses were performed on days 0, 28, 56, 84 and 112. Demodex DNA was detected and quantified using real-time PCR. RESULTS: A single oral dose of fluralaner reduced Demodex mite counts in skin scrapings by an average of 98.9% in all dogs by day 28. No mites were recovered from skin scrapings from any treated dog by day 56, at which time the dog was considered to be clinically cured, with total hair regrowth. There were significant differences among examined dogs in qPCR cycle threshold (Ct) values on days 0, 28, 56, 84 and 112. Demodex DNA levels decreased (increasing Ct values) throughout the study. Mite DNA was present on day 112, possibly from dead mites, at values significantly lower than in samples taken on days 0, 28 and 56. Based on qPCR testing of diluted samples, the Demodex mite population was reduced by approximately 1000-fold on day 112. CONCLUSIONS: Oral administration of fluralaner at the recommended dose to dogs with generalized demodicosis is highly effective for reducing Demodex mite populations and resolving clinical signs of generalized demodicosis. The presence of mite DNA may indicate that treatment did not kill all Demodex mites.

Response of adult honey bees treated in larval stage with prochloraz to infection with Nosema ceranae.

Among numerous factors that contribute to honey bee colony losses and problems in beekeeping, pesticides and Nosema ceranae have been often reported. In contrast to insecticides, whose effects on bees have been widely studied, fungicides did not attract considerable attention. Prochloraz, an imidazole fungicide widely used in agriculture, was detected in honey and pollen stored inside hives and has been already proven to alter immune gene expression of honey bees at different developmental stages. The aim of this study was to simulate the realistic conditions of migratory beekeeping, where colonies, both uninfected and infected with N. ceranae, are frequently transported to the vicinity of crop fields treated with prochloraz. We investigated the combined effect of prochloraz and N. ceranae on honey bees that faced fungicide during the larval stage through food consumption and microsporidium infection afterwards. The most pronounced changes in gene expression were observed in newly emerged Nosema-free bees originating from colonies previously contaminated with prochloraz. As exclusively upregulation was registered, prochloraz alone most likely acts as a challenge that induces activation of immune pathways in newly emerged bees. The combination of both stressors (prochloraz and Nosema infection) exerted the greatest effect on six-day-old honey bees. Among ten genes with significantly altered expression, half were upregulated and half downregulated. N. ceranae as a sole stressor had the weakest effects on immune gene expression modulation with only three genes significantly dysregulated. In conclusion, food contaminated with prochloraz consumed in larval stage could present a threat to the development of immunity and detoxification mechanisms in honey bees.

Honey bee viruses in Serbian colonies of different strength.

Protection of honey bees is of great economic importance because of their role in pollination. Crucial steps towards this goal are epidemiological surveys of pathogens connected with honey bee losses. In this study deformed wing virus (DWV), chronic bee paralysis virus (CBPV), acute bee paralysis virus (ABPV) and sacbrood virus (SBV) were investigated in colonies of different strength located in five regions of Serbia. The relationship between colony strength and virus occurrence/infection intensity were assessed as well as the genetic relationship between virus sequences from Serbia and worldwide. Real-time RT-PCR analyses detected at least one virus in 87.33% of colonies. Single infection was found in 28.67% colonies (21.33%, 4.00%, 2.67% and 0.67% in cases of DWV, ABPV, SBV and CBPV, respectively). In the majority of colonies (58.66%) more than one virus was found. The most prevalent was DWV (74%), followed by ABPV, SBV and CBPV (49.30%, 24.00% and 6.70%, respectively). Except for DWV, the prevalence of the remaining three viruses significantly varied between the regions. No significant differences were found between colony strength and either (i) the prevalence of DWV, ABPV, SBV, CBPV and their combinations, or (ii) DWV infection levels. The sequences of honey bee viruses obtained from bees in Serbia were 93-99% identical with those deposited in GenBank.

Experimental evaluation of infection, dissemination, and transmission rates for two West Nile virus strains in European Aedes japonicus under a fluctuating temperature regime.

West Nile virus (WNV) is continuously spreading in Eastern and Southern Europe. However, the extent of vector competence of Aedes japonicus (Theobald, 1901) is controversial. In this work, we elucidated the dynamics of virus growth in this invasive mosquito species. Females of Ae. japonicus were reared from eggs collected in the field in Switzerland and fed on bovine blood spiked with two WNV lineage 1 strains (FIN, Italy; NY99, USA). Fully engorged females were incubated for 14 days under a fluctuating temperature regime of 24 ± 7 °C (average 24 °C), 45-90% relative humidity, which is realistic for a Central European mid-summer day. Infection, dissemination, and transmission rates were assessed from individual mosquitoes by analyzing the abdomen, legs and wings, and saliva for the presence of viral RNA. Saliva was also investigated for the presence of infectious virus particles. Overall, 302 females were exposed to WNV strain FIN and 293 to strain NY99. A higher infection rate was observed for NY99 (57.4%) compared to FIN (30.4%) (p = 0.003). There was no statistical evidence that the dissemination rate (viral RNA in legs and wings) was different between females infected with FIN (57.1%) compared to NY99 (35.5%) (p = 0.16). Viral RNA load of FIN compared to NY99 was significantly higher in the hemocoel (p = 0.031) of exposed females but not at other sites (legs and wings, saliva). This is the first study describing the vector competence parameters for two WNV strains in a European population of Ae. japonicus. The high dissemination and transmission rates for WNV under a realistic temperature regime in Ae. japonicus together with recent findings on its opportunistic feeding behavior (mammals and birds) indicate its potential role in WNV transmission in Central Europe where it is highly abundant.