Avaliação da eficácia de nova estratégia de combate à varroose da abelha (Apis mellifera) em Portugal : tratamento combinado de acaricidas homologados

Dissertação de Mestrado Integrado em Medicina VeterináriaA morte e o desaparecimento de colónias de abelhas (Apis mellifera) e mesmo de apiários inteiros têm vindo a preocupar cientistas do mundo inteiro. Várias doenças e outros fatores foram associados ao colony collapse disorder (distúrbio do colapso das colmeias). Os ácaros da espécie Varroa destructor são apontados como um dos principais culpados deste problema.Com o crescente aparecimento de resistência aos acaricidas por parte de Varroa sp., devido à utilização sucessiva da mesma molécula ou por má aplicação destes, criou-se uma necessidade de desenvolver novos métodos de combate a este parasita. A utilização de protocolos de tratamento combinando mais de um acaricida, têm-se apresentado como uma boa alternativa à utilização convencional de apenas um medicamento. O principal objetivo deste estudo realizado no Posto Apícola da Tapada da Ajuda (em Lisboa), consistiu em determinar a eficácia e qual o melhor método de aplicação de dois acaricidas homologados em Portugal no controlo de Varroa destructor. Assim, foram estabelecidos dois grupos de colónias para o estudo, um deles em que foi aplicado em primeiro lugar timol (Thymovar®) e depois o fluvalinato (Apistan®) (TA; n=10) e outro em que se aplicou em primeiro lugar o fluvalinato e depois o timol (AT; n=10). Para determinar o valor de eficácia de tratamento, foi aplicado um terceiro acaricida como controlo (amitraz). Foi contabilizada a queda de Varroas três vezes por semana, do momento de aplicação do primeiro acaricida, até perfazer duas semanas após a aplicação do acaricida controlo. A média de eficácia do grupo TA foi de 87,3%, apresentando valores mínimo e máximo de 72,6% e 97,9%, respetivamente. O grupo AT apresentou média de eficácia 91,2%, com valores entre 72,1% e 99%. Comparando os valores de média dos dois grupos, conclui-se que não apresentaram diferença significativa (p=0,304), aplicando um teste-t não emparelhado. Foram medidas as temperaturas mínimas e máximas, e a partir daí a temperatura média. Vários picos de valores de queda de Varroa são consistentes com o aumento da temperatura, o que indica haver uma possível relação entre estes. Apesar de não ter sido encontrada diferença entre os dois grupos, os valores de eficácia obtidos foram superiores aos obtidos nos últimos anos em Portugal, aquando da aplicação de apenas um acaricida. Podemos assim concluir que estes protocolos terapêuticos são ambos uma boa escolha para o controlo de Varroa destructor, de preferência juntamente com outras técnicas de maneio que reduzam a reprodução destes ácaros.ABSTRACT - Efficacy evaluation of a new strategy against Varroa destructor in honey bees (Apis mellifera) in Portugal: combined treatment with approved acaricides - Death and disappearance of bee colonies (Apis mellifera) and entire apiaries increased worldwide. Several diseases have been associated to the Colony collapse disorder, and the mite Varroa destructor infestation has been noted as one of the main causes of the problem. The increasing emergence of tolerance to acaricides by Varroa sp., due to successive use of the same molecule or wrong use of these chemicals, lead to the development of new methods to control this parasite. New protocols combining more than one acaricide have shown to be a good alternative to conventional use of only one drug. The main objective of this study accomplished at Posto Apícola in Tapada da Ajuda (Lisbon, Portugal), was to determine the efficacy and the best method to fight Varroa destructor using two acaricides approved in Portugal. Thus, two groups of colonies were established, one that used first thymol (Thymovar®) and then fluvalinate (Apistan®) (TA, n=10), and the other using fluvalinate first and then thymol (AT, n=10). To assess the efficacy of treatment, a third treatment with amitraz was used as control. Mites fall was measured three times in a week, during the assay, starting at the first treatment and ending two weeks after the control treatment. The mean efficacy of the treatment protocol for TA group was 87.3%, with 72.6% as a minimum and 97.9% as a maximum. The group AT presented a mean efficacy of 91.2%, with values between 72.1% and 99%. It was concluded, after the statistical analysis with unpaired T-test, that no significant difference (p=0,304) was found between the two groups. The average temperature was calculated with measurement of minimum and maximum daily temperature, and indicated a possible link between these and mite population profile, as several peaks of Varroa fall were consistent with temperature peaks. Although no difference was found between the groups, efficacy results were higher than others obtained in the last years in Portugal, when only one acaricide is used. So, both protocols are a good choice to fight Varroa destructor, along with management techniques that reduce the reproduction of these mites

Noise-reduction techniques for 1H-FID-MRSI at 14.1T: Monte-Carlo validation & in vivo application

Proton magnetic resonance spectroscopic imaging (1H-MRSI) is a powerful tool that enables the multidimensional non-invasive mapping of the neurochemical profile at high-resolution over the entire brain. The constant demand for higher spatial resolution in 1H-MRSI led to increased interest in post-processing-based denoising methods aimed at reducing noise variance. The aim of the present study was to implement two noise-reduction techniques, the Marchenko-Pastur principal component analysis (MP-PCA) based denoising and the low-rank total generalized variation (LR-TGV) reconstruction, and to test their potential and impact on preclinical 14.1T fast in vivo 1H-FID-MRSI datasets. Since there is no known ground truth for in vivo metabolite maps, additional evaluations of the performance of both noise-reduction strategies were conducted using Monte-Carlo simulations. Results showed that both denoising techniques increased the apparent signal-to-noise ratio SNR while preserving noise properties in each spectrum for both in vivo and Monte-Carlo datasets. Relative metabolite concentrations were not significantly altered by either methods and brain regional differences were preserved in both synthetic and in vivo datasets. Increased precision of metabolite estimates was observed for the two methods, with inconsistencies noted on lower concentrated metabolites. Our study provided a framework on how to evaluate the performance of MP-PCA and LR-TGV methods for preclinical 1H-FID MRSI data at 14.1T. While gains in apparent SNR and precision were observed, concentration estimations ought to be treated with care especially for low-concentrated metabolites.Comment: Brayan Alves and Dunja Simicic are joint first authors. Currently in revision for NMR in Biomedicin

Fast high-resolution metabolite mapping in the rat brain using 1H-FID-MRSI at 14.1T

Magnetic resonance spectroscopic imaging (MRSI) enables the simultaneous non-invasive acquisition of MR spectra from multiple spatial locations inside the brain. While 1H-MRSI is increasingly used in the human brain, it is not yet widely applied in the preclinical settings, mostly because of difficulties specifically related to very small nominal voxel size in the rodent brain and low concentration of brain metabolites, resulting in low signal-to-noise ratio SNR. In this context, we implemented a free induction decay 1H-MRSI sequence (1H-FID-MRSI) in the rat brain at 14.1T. We combined the advantages of 1H-FID-MRSI with the ultra-high magnetic field to achieve higher SNR, coverage and spatial resolution in the rodent brain, and developed a custom dedicated processing pipeline with a graphical user interface: MRS4Brain toolbox. LCModel fit, using the simulated metabolite basis-set and in-vivo measured MM, provided reliable fits for the data at acquisition delays of 1.3 and 0.94 ms. The resulting Cram\'er-Rao lower bounds were sufficiently low (<40%) for eight metabolites of interest, leading to highly reproducible metabolic maps. Similar spectral quality and metabolic maps were obtained between 1 and 2 averages, with slightly better contrast and brain coverage due to increased SNR in the latter case. Furthermore, the obtained metabolic maps were accurate enough to confirm the previously known brain regional distribution of some metabolites. The acquisitions proved high repeatability over time. We demonstrated that the increased SNR and spectral resolution at 14.1T can be translated into high spatial resolution in 1H-FID-MRSI of the rat brain in 13 minutes, using the sequence and processing pipeline described herein. High-resolution 1H-FID-MRSI at 14.1T provided reproducible and high-quality metabolic mapping of brain metabolites with significantly reduced technical limitations.Comment: Dunja Simicic and Brayan Alves are joint first author

Detection tube for small HF RFID tags, based on mutual coupling with a coil resonator

This communication concerns the detection of 13.56 MHz (HF) RFID “small” tags. Herein, the term “small” refer to an effective area below 1 cm2 and the detection principle is in volume, especially inside a tube of 9 cm in diameter and 2m in length. The ability to detect the “small” tags in the tube is achieved by using a coil resonator conformed on the tube surface, following a principle of multiple magnetic coupling, also referred as magnetic field guide. Theoretical considerations on mutual coupling formula and electrical model fit to CST simulations and VNA measurements concerning the evaluation of impedance and coupling factors range. Detection tests with an RFID reader (from IB technology) and NXP SLI-X chip confirm the possibility of detection by providing a first result of 2 cm range. This detection was impossible inside the tube without using the resonator. Perspectives of improvement evocated at the end of the paper are numerous for that structure

Implications of asymptomatic infection for the natural history of selected parasitic tropical diseases

Progress has been made in the control or elimination of tropical diseases, with a significant reduction of incidence. However, there is a risk of re-emergence if the factors fueling transmission are not dealt with. Although it is essential to understand these underlying factors for each disease, asymptomatic carriers are a common element that may promote resurgence; their impact in terms of proportion in the population and role in transmission needs to be determined. In this paper, we review the current evidence on whether or not to treat asymptomatic carriers given the relevance of their role in the transmission of a specific disease, the efficacy and toxicity of existing drugs, the Public Health interest, and the benefit at an individual level, for example, in Chagas disease, to prevent irreversible organ damage. In the absence of other control tools such as vaccines, there is a need for safer drugs with good risk/benefit profiles in order to change the paradigm so that it addresses the complete infectious process beyond manifest disease to include treatment of non-symptomatic infected persons

Alien plant species: environmental risks in agricultural and agro-forest landscapes under climate change

Alien plant species have been essential for farming and agro-forestry systems and for their supply of food, fiber, tannins, resins or wood from antiquity to the present. They also contributed to supporting functions and regulating services (water, soil, biodiversity) and to the design of landscapes with high cultural and scenic value. Some of those species were intentionally introduced, others arrived accidentally, and a small proportion escaped, naturalized and became invasive in natural ecosystems—these are known as invasive alien species (IAS). Here, invasive means that these species have some significant negative impact, either by spreading from human-controlled environments (e.g. fields, gardens) to natural ecosystems, where they can cause problems to native species, or to other production systems or urban areas, impacting on agricultural, forestry activities or human health. Socio-environmental impacts associated with plant invasions have been increasingly recognized worldwide and are expected to increase considerably under changing climate or land use. Early detection tools are key to anticipate IAS and to prevent and control their impacts. In this chapter, we focus on crop and non-crop alien plant species for which there is evidence or prediction of invasive behaviour and impacts. We provide insights on their history, patterns, risks, early detection, forecasting and management under climate change. Specifically, we start by providing a general overview on the history of alien plant species in agricultural and agroforestry systems worldwide. Then, we assess patterns, risks and impacts resulting from alien plants originally cultivated and that became invasive outside cultivation areas. Afterwards, we provide several considerations for managing the spread of invasive plant species in the landscape. Finally, we discuss challenges of alien plant invasions for agricultural and agroforest systems, in the light of climate change.Joana R. Vicente was supported by POPH/FSE and FCT (Post-Doc grant SFRH/BPD/84044/2012). Ana Sofia Vaz was supported by FSE/MEC and FCT (Ph.D. grant PD/ BD/52600/2014). Ana Isabel Queiroz supported by FCT—the Portuguese Foundation for Science and Technology [UID/HIS/04209/2013 and IF/00222/2013/CP1166/CT0001]. This work received financial support from the European Union (FEDER funds POCI-01-0145-FEDER-006821) and National Funds (FCT/MEC, Fundação para a Ciência e Tecnologia and Ministério da Educação e Ciência) under the Partnership Agreement PT2020 UID/BIA/50027/201

Design of 1cm2 coils for HF RFID instruments tracking with detection range improvement

This paper concerns an application of magnetic coupling RFID technology at 13.56 MHz (HF band) for tracking devices such as instruments. The tag size is defined to be ergonomically small compared to the hand, and fixed inside a maximum surface of 1 cm 2. The case of multiple detections is considered, and consequently the reader surface of control is considered wide enough to include several instruments at the same time during a logistic control process. The use of such a small RFID tag is almost impossible using a large reader loop of 15×30 cm 2, as chosen for the tests. The key idea of the paper is then the addition of a resonator that enables to create the mandatory physical link by means of magnetic coupling between the tag coil and the resonator coil and between the resonator coil and the reader loop. Finally the detection range is highly improved by the presence of this resonator and results demonstrate that it is possible to detect these small RFID “1 by 1 cm 2 tags” at a distance of 1.5 cm to 3 cm, depending on their orientations

Seroprevalence of anti-SARS-CoV-2 IgG at the first epidemic peak in French Guiana, July 2020.

Funder: National Research AgencyFunder: Regional Health Agency of French GuianaFunder: Institut Pasteur Urgence COVID-19 fundraisingBACKGROUND: While Latin America has been heavily affected by the pandemic, only a few seroprevalence studies have been conducted there during the first epidemic wave in the first half of 2020. METHODOLOGY/PRINCIPAL FINDINGS: A cross-sectional survey was performed between 15 July 2020 and 23 July 2020 among individuals who visited 4 medical laboratories or 5 health centers for routine screening or clinical management, with the exception of symptomatic suggestive cases of covid-19. Samples were screened for the presence of anti-SARS-CoV-2 IgG directed against domain S1 of the SARS-CoV-2 spike protein using the anti-SARS-CoV-2 enzyme-linked immunosorbent assay (ELISA) from Euroimmun. CONCLUSIONS/SIGNIFICANCE: The overall seroprevalence was 15.4% [9.3%-24.4%] among 480 participants, ranging from 4.0% to 25.5% across the different municipalities. The seroprevalence did not differ according to gender (p = 0.19) or age (p = 0.51). Among SARS-CoV-2 positive individuals, we found that 24.6% [11.5%-45.2%] reported symptoms consistent with COVID-19. Our findings revealed high levels of infection across the territory but a low number of resulting deaths, which can be explained by French Guiana's young population structure