Francesco Nazzi

University of Udine, Udine, Friuli Venezia Giulia, Italy

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Publications (38)68.67 Total impact

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    ABSTRACT: The tick Ixodes ricinus (L.) is the most important vector of tick-borne zoonoses in Europe. Apart from factors related to human behavior, tick abundance is a major driver of the incidence of tick-borne diseases in a given area and related data represent critical information for promoting effective public health policies. The present study analyzed the relationship between different environmental factors and tick abundance in order to improve the understanding of I. ricinus autecology and develop spatial predictive models that can be implemented in tick-borne disease prevention strategies. Ticks were sampled in 27 sites over a four-year period and different environmental variables were studied. Five simple models were developed that explain a large part of variation in tick abundance. Precipitation seems to play the most important role, followed by temperature, woodland coverage, and solar radiation. Model equations obtained in this study may enable the spatial interpolation and extension of tick abundance predicted values to sites of the same area, in order to build regional predictive maps. They could also be useful for the validation of large-scale spatial predictive maps. © 2015 The Society for Vector Ecology.
    Journal of Vector Ecology 06/2015; 40(1):107-116. DOI:10.1111/jvec.12138 · 1.44 Impact Factor
  • Francesco Nazzi, Francesco Pennacchio
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    ABSTRACT: The widespread losses of honeybee colonies recorded over the past number of years in the northern hemisphere represent a major concern for the beekeeping industry and, more importantly, may have a severe impact on ecological services and biodiversity. There is now a general consensus about the multifactorial origin of colony losses, but the mechanistic basis of this complex phenomenon still remains largely elusive. In this review, we propose a functional framework for interpreting how different stress agents can interact to adversely affect bee immunity and health. This provides a new background rationale in which to develop an integrated approach to bee protection, as part of a more comprehensive strategy for the conservation of insect pollinators. Copyright © 2014 Elsevier Ltd. All rights reserved.
    Trends in Parasitology 12/2014; 30(12):556-561. DOI:10.1016/j.pt.2014.09.006 · 6.22 Impact Factor
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    ABSTRACT: Honeybee colonies (Apis mellifera) host a number of parasites, among which the mite Varroa destructor has been implicated in colony losses recorded around the world in recent years. Although many studies have been carried out on the direct and indirect damage caused by the mite to its host, the possible influence of mite infestation on the in-hive behaviour of honeybees has received little attention so far; moreover, to our knowledge, no behavioural study has been performed on adult bees infested during the pupal stage, which is when the mite causes most of its detrimental effects. In order to assess any possible consequence of infestation on the in-hive behaviour of honeybees, we carried out detailed observations on adult bees artificially infested during the pupal stage. We recorded a higher proportion of inactive bees among the infested ones; moreover, we observed that infested bees are less involved in tending larvae and dealing with hive duties compared to their uninfested mates. These results allow to draw some hypotheses which could be tested using the infestation method presented here.
    Apidologie 10/2014; 46(3). DOI:10.1007/s13592-014-0323-0 · 1.54 Impact Factor
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    ABSTRACT: The decline of honeybee colonies and their eventual collapse is a widespread phenomenon in the Northern hemisphere of the globe, which severely limits the beekeeping industry. This dramatic event is associated with an enhanced impact of parasites and pathogens on honeybees, which is indicative of reduced immunocompetence. The parasitic mite Varroa destructor and the vectored viral pathogens appear to play a key-role in the induction of this complex syndrome. In particular, the Deformed Wing Virus (DWV) is widespread and is now considered, along with Varroa, one of the major causes of bee colony losses. Several lines of evidence indicate that this mite/DWV association severely affects the immune system of honeybees and makes them more sensitive to the action of other stress factors. The molecular mechanisms underpinning these complex interactions are currently being investigated and the emerging information has allowed the development of a new functional model, describing how different stress factors may synergistically concur in the induction of bee immune alteration and health decline. This provides a new logical framework in which to interpret the proposed multifactorial origin of bee colony losses and sets the stage for a more comprehensive and integrated analysis of the effect that multiple stress agents may have on honeybees.
    10/2014; 2(2). DOI:10.4081/entomologia.2014.203
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    ABSTRACT: Support to small farmers is at the heart of the fight against poverty. However, the continuous provision of support poses a major challenge which greatly affects the sustainability of development-related projects. Using a research and education approach, in which beekeeping was introduced into the curriculum of two secondary schools, we tested the potential of knowledge transfer as a means of promoting beekeeping. In this paper, we show that, with an educational program tailored to the audience needs, knowledge transfer and self-start-ups ensure better sustainability than material support. We further discuss the implications of these results in the sustenance of beekeeping as a development-related activity.
    Environment Development and Sustainability 06/2014; 16(3). DOI:10.1007/s10668-013-9497-2
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    ABSTRACT: Large-scale losses of honey bee colonies represent a poorly understood problem of global importance. Both biotic and abiotic factors are involved in this phenomenon that is often associated with high loads of parasites and pathogens. A stronger impact of pathogens in honey bees exposed to neonicotinoid insecticides has been reported, but the causal link between insecticide exposure and the possible immune alteration of honey bees remains elusive. Here, we demonstrate that the neonicotinoid insecticide clothianidin negatively modulates NF-κB immune signaling in insects and adversely affects honey bee antiviral defenses controlled by this transcription factor. We have identified in insects a negative modulator of NF-κB activation, which is a leucine-rich repeat protein. Exposure to clothianidin, by enhancing the transcription of the gene encoding this inhibitor, reduces immune defenses and promotes the replication of the deformed wing virus in honey bees bearing covert infections. This honey bee immunosuppression is similarly induced by a different neonicotinoid, imidacloprid, but not by the organophosphate chlorpyriphos, which does not affect NF-κB signaling. The occurrence at sublethal doses of this insecticide-induced viral proliferation suggests that the studied neonicotinoids might have a negative effect at the field level. Our experiments uncover a further level of regulation of the immune response in insects and set the stage for studies on neural modulation of immunity in animals. Furthermore, this study has implications for the conservation of bees, as it will contribute to the definition of more appropriate guidelines for testing chronic or sublethal effects of pesticides used in agriculture.
    Proceedings of the National Academy of Sciences 10/2013; DOI:10.1073/pnas.1314923110 · 9.81 Impact Factor
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    ABSTRACT: Summary In this article we provide guidelines on statistical design and analysis of data for all kinds of honey bee research. Guidelines and selection of different methods presented are, at least partly, based on experience. This article can be used: to identify the most suitable analysis for the type of data collected; to optimise one’s experimental design based on the experimental factors to be investigated, samples to be analysed, and the type of data produced; to determine how, where, and when to sample bees from colonies; or just to inspire. Also included are guidelines on presentation and reporting of data, as well as where to find help and which types of software could be useful. Guia estadistica para estudios en Apis mellifera Resumen En este trabajo se proporcionan directrices sobre el diseño estadístico y el análisis de datos para todo tipo de investigación sobre abejas. Tanto las directrices como la selección de los diferentes métodos que se presentan están basadas, al menos en parte, en la experiencia. Este artículo se puede utilizar: para identificar el análisis más adecuado para el tipo de datos recogidos; para optimizar el diseño experimental basado en los factores experimentales a ser investigados, las muestras a analizar, y el tipo de datos que se producen; para determinar cómo, dónde , y cuando muestras abejas de las colonias, o simplemente para inspirar. También se incluyen directrices para la presentación y comunicación de los datos, así como dónde encontrar ayuda y distintos software que puedan ser útiles. 西方蜜蜂研究的统计指南 摘要 在本文中,我们提供了针对蜜蜂所有研究的统计设计和数据分析指南。这些指南和方法的选择至少部分基于我们的经验。本文也可用于:针对收集到的数据类型选择最优分析方法;基于所研究的实验因素、待分析的样本和获得的数据类型优化实验设计;确定从蜂群中采集蜜蜂样本的地点、时间和方式;或者仅为实验提供参考。另外,也包含展示和报告数据时的指南,以及如何寻求帮助和选用何种软件。 Keywords: COLOSS, BEEBOOK, honey bees, sampling, sample size, GLMM, robust statistics, resampling, PCA, Power, rule of thumb
    Journal of Apicultural Research 09/2013; 52(4). DOI:10.3896/IBRA.1.52.4.13 · 1.36 Impact Factor
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    Simone Del Fabbro, Francesco Nazzi
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    ABSTRACT: Tick-borne zoonoses are considered as emerging diseases. Tick repellents represent an effective tool for reducing the risk of tick bite and pathogens transmission. Previous work demonstrated the repellent activity of the phenylpropanoid eugenol against Ixodes ricinus; here we investigate the relationship between molecular structure and repellency in a group of substances related to that compound. We report the biological activity of 18 compounds varying for the presence/number of several moieties, including hydroxyl and methoxy groups and carbon side-chain. Each compound was tested at different doses with a bioassay designed to measure repellency against individual tick nymphs. Both vapor pressure and chemical features of the tested compounds appeared to be related to repellency. In particular, the hydroxyl and methoxy groups as well as the side-chain on the benzene ring seem to play a role. These results are discussed in light of available data on chemical perception in ticks. In the course of the study new repellent compounds were identified; the biological activity of some of them (at least as effective as the "gold standard" repellent DEET) appears to be very promising from a practical point of view.
    PLoS ONE 07/2013; 8(6):e67832. DOI:10.1371/journal.pone.0067832 · 3.53 Impact Factor
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    ABSTRACT: Very rapidly after Varroa destructor invaded apiaries of Apis mellifera, the devastating effect of this mite prompted an active research effort to understand and control this parasite. Over a few decades, varroa has spread to most countries exploiting A. mellifera. As a consequence, a large number of teams have worked with this organism, developing a diversity of research methods. Often different approaches have been followed to achieve the same goal. The diversity of methods made the results difficult to compare, thus hindering our understanding of this parasite. In this paper, we provide easy to use protocols for the collection, identification, diagnosis, rearing, breeding, marking and measurement of infestation rates and fertility of V. destructor. We also describe experimental protocols to study orientation and feeding of the mite, to infest colonies or cells and measure the mite’s susceptibility to acaricides. Where relevant, we describe which mite should be used for bioassays since their behaviour is influenced by their physiological state. We also give a method to determine the damage threshold above which varroa damages colonies. This tool is fundamental to be able to implement integrated control concepts. We have described pros and cons for all methods for the user to know which method to use under which circumstances. These methods could be embraced as standards by the community when designing and performing research on V. destructor.
    Journal of Apicultural Research 11/2012; 52(1):1-54. DOI:10.3896/IBRA.1.52.1.09 · 1.36 Impact Factor
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    ABSTRACT: Several factors threaten the health of honeybees; among them the parasitic mite Varroa destructor and the Deformed Wing Virus play a major role. Recently, the dangerous interplay between the mite and the virus was studied in detail and the transition, triggered by mite feeding, from a benign covert infection to a devastating viral outbreak, characterized by an intense viral replication, associated with some characteristic symptoms, was described. In order to gain insight into the events preceding that crucial transition we carried out standardized lab experiments aiming at studying the effects of parasitization in asymptomatic bees to establish a relationship between such effects and bee mortality. It appears that parasitization alters the capacity of the honeybee to regulate water exchange; this, in turn, has severe effects on bee survival. These results are discussed in light of possible novel strategies aiming at mitigating the impact of the parasite on honeybee health.
    Journal of insect physiology 10/2012; 58(12). DOI:10.1016/j.jinsphys.2012.09.008 · 2.50 Impact Factor
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    ABSTRACT: Author Summary Honeybees are of capital importance for humans since crop production significantly depends upon pollination by these insects. In recent years, widespread collapses of honeybee colonies have been reported throughout the world; unfortunately, despite intense research efforts, the causal agents of such losses are not yet identified, although parasites seem to play a key-role. We combined molecular, field-longitudinal and theoretical approaches to describe the mechanistic basis and dynamical properties of collapse-causing interactions within the multi-parasite community infecting the honeybees. We found that the parasitic mite Varroa destructor can de-stabilise the within-host dynamics of Deformed wing virus (DWV), transforming a cryptic and vertically transmitted virus into a rapidly replicating killer. The de-stabilisation of DWV infection results from a widespread immunosuppression characterized by a strong down-regulation of a member of the gene family NF-κB. This gene family not only plays a central role in insect immunity, but is also involved in intricate cross-talks with a number of physiological and stress response pathways. This suggests that different stress factors may alter the critical balance between viral pathogens and host-defences, promoting intense viral replication in bees harbouring silent infections and subsequent colony collapse. The model we propose can potentially explain the multifactorial origin of bee losses.
    PLoS Pathogens 06/2012; 8(6):e1002735. DOI:10.1371/journal.ppat.1002735 · 8.06 Impact Factor
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    ABSTRACT: A 2-year study was conducted in a mountainous area of northeast Italy to evaluate the occurrence and distribution of ticks, as well as to assess the prevalence of the spirochaete Borrelia burgdorferi sensu lato. All ticks collected were Ixodes ricinus L. (Parasitiformes: Ixodidae). In general, most nymphs and adult ticks were collected from April to July. Tick density was highly variable among sites; however, two areas with different infestation levels were recognized. Prevalences of B. burgdorferi s.l. in nymphal stages were rather variable between sites; overall the prevalence of infected nymphs in the whole area was slightly higher than 20%. The prevalence of B. burgdorferi s.l. in nymphs does not seem to be correlated with nymph density. The correlation between the incidence of Lyme borreliosis (reported human cases/1000 inhabitants/year) and Borrelia prevalence in nymphs was not significant, although a significant correlation was found between borreliosis incidence and nymph density.
    Medical and Veterinary Entomology 09/2010; 24(3):220-6. DOI:10.1111/j.1365-2915.2010.00877.x · 2.33 Impact Factor
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    ABSTRACT: The parasitic mite, Varroa destructor, is the most important threat for apiculture in most bee-keeping areas of the world. The mite is carried to the bee brood cell, where it reproduces, by a nurse bee; therefore the selection of the bee stage by the parasite could influence its reproductive success. This study investigates the role of the cuticular hydrocarbons of the European honeybee (Apis mellifera) in host-selection by the mite. Preliminary laboratory bioassays confirmed the preference of the varroa mite for nurse bees over pollen foragers. GC-MS analysis of nurse and pollen bees revealed differences in the cuticular hydrocarbons of the two stages; in particular, it appeared that pollen bees have more (Z)-8-heptadecene than nurse bees. Laboratory experiments showed that treatment of nurse bees with 100 ng of the pure compound makes them repellent to the varroa mite. These results suggest that the mite can exploit the differences in the cuticular composition of its host for a refined selection that allows it to reach a brood cell and start reproduction. The biological activity of the alkene encourages further investigations for the development of novel control techniques based on this compound.
    Parasitology 02/2010; 137(6):967-73. DOI:10.1017/S0031182009991867 · 2.35 Impact Factor
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    ABSTRACT: In Alpine area of extreme North Eastern Italy the first autochthonous case of TBE was reported in 1998 and was followed by 45 cases during the period 2001-2007, thus defining this area as definitely endemic. An ecological survey evaluated the tick density and the Tick-borne encephalitis virus (TBEV) infection prevalence in tick collected in selected sites. In addition, TBE strains were characterized by sequencing and phylogenetic analysis. Overall, 2,361 ticks (2,198 nymphs and 163 adults) of the Ixodes ricinus L. species collected during 2005 and 2006 were examined. Five samples were positive for TBEV, corresponding to an overall prevalence rate of 0.21%. When analyzed by place, TBEV was discovered in three sites where the highest tick density was found. The difference of prevalence between high and low density areas tested to be statistically significant (P = 0.028). Phylogenetic analysis showed that four sequences clustered with the Neudoerfl prototype, while the other clustered with the Isosaari 17 strain and with a number of Slovenian isolates. In addition, a sequence detected in archival samples from one human case segregated with another variant, namely the Swedish Torö strain.
    Journal of Medical Virology 02/2009; 81(2):309-16. DOI:10.1002/jmv.21389 · 2.22 Impact Factor
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    ABSTRACT: The mite Varroa destructor Anderson & Trueman is a parasite of the honeybee Apis mellifera L. and represents a major threat for apiculture in the Western world. Reproduction takes place only inside bee brood cells that are invaded just before sealing; drone cells are preferred over worker cells, whereas queen cells are not normally invaded. Lower incidence of mites in queen cells is at least partly due to the deterrent activity of royal jelly. In this study, the repellent properties of royal jelly were investigated using a lab bioassay. Chemical analysis showed that octanoic acid is a major volatile component of royal jelly; by contrast, the concentration is much lower in drone and worker larval food. Bioassays, carried out under lab conditions, demonstrated that octanoic acid is repellent to the mite. Field studies in bee colonies confirmed that the compound may interfere with the process of cell invasion by the mite.
    Naturwissenschaften 01/2009; 96(2):309-14. DOI:10.1007/s00114-008-0470-0 · 1.97 Impact Factor
  • Simone Del Fabbro, Francesco Nazzi
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    ABSTRACT: Diseases transmitted by ticks are causing increasing concern in Europe and all around the world. Repellents are an effective measure for reducing the risk of tick bite; products based on natural compounds represent an interesting alternative to common synthetic repellents. In this study the repellency of sweet basil (Ocimum basilicum L.) was tested against the tick Ixodes ricinus L., by using a laboratory bioassay. A bioassay-assisted fractionation allowed the identification of a compound involved in the biological activity. Eugenol appeared to be as repellent as DEET at two tested doses. Linalool, which was identified in the active fraction too, failed to give any response. Repellency of eugenol was proved also in the presence of human skin odour using a convenient and practical bioassay.
    Experimental and Applied Acarology 09/2008; 45(3-4):219-28. DOI:10.1007/s10493-008-9182-6 · 1.82 Impact Factor
  • Francesco Nazzi, Federico Vidoni, Franco Frilli
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    ABSTRACT: A laboratory study on the chemical cues influencing the behaviour of Acanthoscelides obtectus (Coleoptera, Bruchidae) on dry bean seeds was carried out to identify possible semiochemicals affecting the oviposition of the beetle.In an olfactometer, A. obtectus females preferred the odour of clean beans to that of beans where conspecifics had developed; an ether extract of such beans was repellent to the insect. Some hydrocarbons that are repellent to females were identified; the effect of heptacosane on the oviposition was studied.
    Journal of Stored Products Research 01/2008; 44(2):108-114. DOI:10.1016/j.jspr.2007.06.004 · 1.49 Impact Factor