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2.
Emerg Infect Dis ; 26(3): 472-480, 2020 Mar.
Artigo em Inglês | MEDLINE | ID: mdl-32091357

RESUMO

The relative roles that movement and proximity networks play in the spread of highly pathogenic avian influenza (HPAI) viruses are often unknown during an epidemic, preventing effective control. We used network analysis to explore the devastating epidemic of HPAI A(H5N8) among poultry, in particular ducks, in France during 2016-2017 and to estimate the likely contribution of live-duck movements. Approximately 0.2% of live-duck movements could have been responsible for between-farm transmission events, mostly early during the epidemic. Results also suggest a transmission risk of 35.5% when an infected holding moves flocks to another holding within 14 days before detection. Finally, we found that densely connected groups of holdings with sparse connections between groups overlapped farmer organizations, which represents important knowledge for surveillance design. This study highlights the importance of movement bans in zones affected by HPAI and of understanding transmission routes to develop appropriate HPAI control strategies.

4.
J Wildl Dis ; 2019 Oct 17.
Artigo em Inglês | MEDLINE | ID: mdl-31622187

RESUMO

Avian influenza and Newcastle disease viruses (AIV, NDV) are major pathogens of captive and wild birds worldwide. Wetlands and their associated bird communities, especially waterfowl and shorebirds, are known to play a central role in the epidemiology of these diseases as maintenance hosts. However, these viruses also circulate in places where these ecosystems and communities are uncommon, suggesting the involvement of other taxa in their epidemiological cycles. In the arid region of Abu Dhabi of the United Arab Emirates (UAE), both viruses are regularly detected, and represent a threat for local poultry and for the Houbara Bustard (Chlamydotis macqueenii) conservation breeding programs. To assess the presence, transmission, and maintenance of these viruses in such environments, 4,521 individuals from six resident and peridomestic wild bird species were sampled in the vicinity of two Houbara Bustard conservation breeding centers, and tested for AIV and NDV using real-time reverse transcriptase PCR and an enzyme-linked immunosorbent assay. A limited exposure to AIV was reflected in a virus prevalence below 0.4% and a serologic prevalence of 0.6%, and a moderate circulation of NDV was indicated by a virus prevalence of 0.9% and a serologic prevalence of 18.9% in the targeted peridomestic wild birds, suggesting different epidemiological roles for each taxa. Thus, some peridomestic species could actively participate in the epidemiological cycle of NDV in arid environments such as the UAE, challenging the conceptual epidemiologic framework centered on the involvement of waterfowl and shorebirds.

6.
Front Vet Sci ; 6: 66, 2019.
Artigo em Inglês | MEDLINE | ID: mdl-30895182

RESUMO

Risk factors are key epidemiological concepts that are used to explain disease distributions. Identifying disease risk factors is generally done by comparing the characteristics of diseased and non-diseased populations. However, imperfect disease detectability generates disease observations that do not necessarily represent accurately the true disease situation. In this study, we conducted an extensive simulation exercise to emphasize the impact of imperfect disease detection on the outcomes of logistic models when case reports are aggregated at a larger scale (e.g., diseased animals aggregated at farm level). We used a probabilistic framework to simulate both the disease distribution in herds and imperfect detectability of the infected animals in these herds. These simulations show that, under logistic models, true herd-level risk factors are generally correctly identified but their associated odds ratio are heavily underestimated as soon as the sensitivity of the detection is less than one. If the detectability of infected animals is not only imperfect but also heterogeneous between herds, the variables associated with the detection heterogeneity are likely to be incorrectly identified as risk factors. This probability of type I error increases with increasing heterogeneity of the detectability, and with decreasing sensitivity. Finally, the simulations highlighted that, when count data is available (e.g., number of infected animals in herds), they should not be reduced to a presence/absence dataset at the herd level (e.g., presence or not of at least one infected animal) but rather modeled directly using zero-inflated count models which are shown to be much less sensitive to imperfect detectability issues. In light of these simulations, we revisited the analysis of the French bovine abortion surveillance data, which has already been shown to be characterized by imperfect and heterogeneous abortion detectability. As expected, we found substantial differences between the quantitative outputs of the logistic model and those of the zero-inflated Poisson model. We conclude by strongly recommending that efforts should be made to account for, or at the very least discuss, imperfect disease detectability when assessing associations between putative risk factors and observed disease distributions, and advocate the use of zero-inflated count models if count data is available.

7.
Sci Rep ; 9(1): 1031, 2019 Jan 31.
Artigo em Inglês | MEDLINE | ID: mdl-30705346

RESUMO

Live bird markets (LBMs) are major targets for avian influenza virus (AIV) surveillance programmes. While sampling the LBM environment has become a widely used alternative to the labour-intensive sampling of live poultry, the design of surveillance programmes and the interpretation of their results are compromised by the lack of knowledge about the effectiveness of these sampling strategies. We used latent class models and a unique empirical dataset collated in Vietnamese LBMs to estimate the sensitivity and specificity of five different sample types for detecting AIVs subtypes H5N1 and H5N6: oropharyngeal duck samples, solid and liquid wastes, poultry drinking water and faeces. Results suggest that the sensitivity of environmental samples for detecting H5N1 viruses is equivalent to that of oropharyngeal duck samples; however, taking oropharyngeal duck samples was estimated to be more effective in detecting H5N6 viruses than taking any of the four environmental samples. This study also stressed that the specificity of the current surveillance strategy in LBMs was not optimal leading to some false positive LBMs. Using simulations, we identified 42 sampling strategies more parsimonious than the current strategy and expected to be highly sensitive for both viruses at the LBM level. All of these strategies involved the collection of both environmental and oropharyngeal duck samples.

8.
Euro Surveill ; 23(26)2018 06.
Artigo em Inglês | MEDLINE | ID: mdl-29970219

RESUMO

IntroductionFrance is one of Europe's foremost poultry producers and the world's fifth largest producer of poultry meat. In November 2016, highly pathogenic avian influenza (HPAI) virus subtype H5N8 emerged in poultry in the country. As of 23 March 2017, a total of 484 confirmed outbreaks were reported, with consequences on animal health and socio-economic impacts for producers. Methods: We examined the spatio-temporal distribution of outbreaks that occurred in France between November 2016 and March 2017, using the space-time K-function and space-time permutation model of the scan statistic test. Results: Most outbreaks affected duck flocks in south-west France. A significant space-time interaction of outbreaks was present at the beginning of the epidemic within a window of 8 km and 13 days. This interaction disappeared towards the epidemic end. Five spatio-temporal outbreak clusters were identified in the main poultry producing areas, moving sequentially from east to west. The average spread rate of the epidemic front wave was estimated to be 5.5 km/week. It increased from February 2017 and was negatively associated with the duck holding density. Conclusion: HPAI-H5N8 infections varied over time and space in France. Intense transmission events occurred at the early stages of the epidemic, followed by long-range jumps in the disease spread towards its end. Findings support strict control strategies in poultry production as well as the maintenance of high biosecurity standards for poultry holdings. Factors and mechanisms driving HPAI spread need to be further investigated.


Assuntos
Surtos de Doenças/veterinária , Patos/virologia , Vírus da Influenza A Subtipo H5N8/patogenicidade , Influenza Aviária/epidemiologia , Doenças das Aves Domésticas/virologia , Animais , França , Vírus da Influenza A Subtipo H5N8/genética , Vírus da Influenza A Subtipo H5N8/isolamento & purificação , Influenza Aviária/virologia , Aves Domésticas/virologia , Doenças das Aves Domésticas/epidemiologia , Análise Espaço-Temporal
9.
Front Vet Sci ; 5: 51, 2018.
Artigo em Inglês | MEDLINE | ID: mdl-29675418

RESUMO

Highly pathogenic avian influenza (HPAI) H5N1 virus has been circulating in Vietnam since 2003, whilst outbreaks of HPAI H5N6 virus are more recent, having only been reported since 2014. Although the spatial distribution of H5N1 outbreaks and risk factors for virus occurrence has been extensively studied, there have been no comparative studies for H5N6. Data collected through active surveillance of Vietnamese live bird markets (LBMs) between 2011 and 2015 were used to explore and compare the spatiotemporal distributions of H5N1- and H5N6-positive LBMs. Conditional autoregressive models were developed to quantify spatiotemporal associations between agroecological factors and the two HPAI strains using the same set of predictor variables. Unlike H5N1, which exhibited a strong north-south divide, with repeated occurrence in the extreme south of a cluster of high-risk provinces, H5N6 was homogeneously distributed throughout Vietnam. Similarly, different agroecological factors were associated with each strain. Sample collection in the months of January and February and higher average maximum temperature were associated with higher likelihood of H5N1-positive market-day status. The likelihood of market days being positive for H5N6 increased with decreased river density, and with successive Rounds of data collection. This study highlights marked differences in spatial patterns and risk factors for H5N1 and H5N6 in Vietnam, suggesting the need for tailored surveillance and control approaches.

10.
Ecohealth ; 15(1): 209-227, 2018 03.
Artigo em Inglês | MEDLINE | ID: mdl-29330676

RESUMO

Having gained momentum in the last decade, the One Health initiative promotes a holistic approach to address complex global health issues. Before recommending its adoption to stakeholders, however, it is paramount to first compile quantitative evidence of the benefit of such an approach. The aim of this scoping review was to identify and summarize primary research that describes monetary and non-monetary outcomes following adoption of a One Health approach. An extensive literature search yielded a total of 42,167 references, of which 85 were included in the final analysis. The top two biotic health issues addressed in these studies were rabies and malaria; the top abiotic health issue was air pollution. Most studies described collaborations between human and animal (n = 42), or human and environmental disciplines (n = 41); commonly reported interventions included vector control and animal vaccination. Monetary outcomes were commonly expressed as cost-benefit or cost-utility ratios; non-monetary outcomes were described using disease frequency or disease burden measurements. The majority of the studies reported positive or partially positive outcomes. This paper illustrates the variety of health challenges that can be addressed using a One Health approach, and provides tangible quantitative measures that can be used to evaluate future implementations of the One Health approach.


Assuntos
Saúde Ambiental/organização & administração , Saúde Única , Pesquisa/organização & administração , Saúde Ambiental/economia , Saúde Ambiental/normas , Prática Clínica Baseada em Evidências , Relações Interprofissionais , Pesquisa/normas
11.
Vet Rec ; 181(5): 117, 2017 Jul 29.
Artigo em Inglês | MEDLINE | ID: mdl-28754737

RESUMO

Pig production and pork consumption are very important to the People's Republic of China for both economic and cultural reasons. The incursion and spread of a disease such as African swine fever (ASF), which emerged in Eastern Europe in 2007, could have devastating socioeconomic consequences for both the Chinese and the global pig industry. The Chinese government consequently attributes a very high priority to ASF and is actively seeking to improve its preparedness. This paper discusses different drivers and pathways of potential emergence of ASF in China in light of the country's specificities, including international movements of people, pigs and pig products, swill feeding practices and wild boar populations. It suggests that effective ASF risk management in China will require a comprehensive and integrated approach linking science and policy and will need to involve all relevant stakeholders to develop realistic policies.


Assuntos
Febre Suína Africana/prevenção & controle , Febre Suína Africana/epidemiologia , Animais , China/epidemiologia , Humanos , Risco , Suínos
12.
PLoS One ; 12(6): e0178241, 2017.
Artigo em Inglês | MEDLINE | ID: mdl-28632789

RESUMO

Presence of ducks, and in particular of free-grazing ducks, has consistently been shown to be one of the most important risk factors for highly pathogenic avian influenza outbreaks which has compromised poultry production in South-East Asia since the early 2000s and continues to threaten public health, farmers' livelihood and food security. Although free-grazing duck production has been practised for decades in South-East Asia, there are few published studies describing this production system, which is suspected to play an important role in the maintenance of avian influenza viruses. This study aimed at describing quantitatively the long-distance free-grazing duck production system in South Vietnam, characterising the movement and contact patterns of the duck flocks, and identifying potential associations between farming practices, movement and contact patterns and the circulation of avian influenza viruses. We conducted interviews among stakeholders involved in the free-grazing duck production system (duck farmers, transporters and rice paddy owners) in combination with a virological cross-sectional survey in South Vietnam. Results show that both direct and indirect contacts between free-grazing duck flocks were frequent and diverse. The flocks were transported extensively across district and province boundaries, mainly by boat but also by truck or on foot. A third of the investigated flocks had a positive influenza A virology test, indicating current circulation of avian influenza viruses, but none were positive for H5 subtypes. The age and size of the flock as well as its location at the time of sampling were associated with the risk of influenza A circulation in the flocks. These findings should be considered when developing risk assessment models of influenza virus spread aimed at informing the development of improved biosecurity practices leading to enhanced animal health, sustainable animal production and reliable income for farmers.


Assuntos
Criação de Animais Domésticos/métodos , Surtos de Doenças/veterinária , Patos/virologia , Vírus da Influenza A/patogenicidade , Influenza Aviária/epidemiologia , Doenças das Aves Domésticas/epidemiologia , Animais , Anticorpos Antivirais/sangue , Estudos Transversais , Patos/fisiologia , Influenza Aviária/virologia , Doenças das Aves Domésticas/virologia , Prevalência , Fatores de Risco , Vietnã/epidemiologia
13.
Sci Rep ; 7(1): 1111, 2017 04 19.
Artigo em Inglês | MEDLINE | ID: mdl-28424454

RESUMO

Effective control of many diseases requires the accurate detection of infected individuals. Confidently ascertaining whether an individual is infected can be challenging when diagnostic tests are imperfect and when some individuals go for long periods of time without being observed or sampled. Here, we use a multi-event capture-recapture approach to model imperfect observations of true epidemiological states. We describe a method for interpreting potentially disparate results from individuals sampled multiple times over an extended period, using empirical data from a wild badger population naturally infected with Mycobacterium bovis as an example. We examine the effect of sex, capture history and current and historical diagnostic test results on the probability of being truly infected, given any combination of diagnostic test results. In doing so, we move diagnosis away from the traditional binary classification of apparently infected versus uninfected to a probability-based interpretation which is updated each time an individual is re-sampled. Our findings identified temporal variation in infection status and suggest that capture probability is influenced by year, season and infection status. This novel approach to combining ecological and epidemiological data may aid disease management decision-making by providing a framework for the integration of multiple diagnostic test data with other information.


Assuntos
Doenças Transmissíveis/diagnóstico , Tuberculose Bovina/diagnóstico , Animais , Técnicas Bacteriológicas , Bovinos , Doenças Transmissíveis/epidemiologia , Feminino , Masculino , Modelos Estatísticos , Mustelidae/microbiologia , Mycobacterium bovis , Dinâmica Populacional , Tuberculose Bovina/epidemiologia
14.
Spat Spatiotemporal Epidemiol ; 19: 70-77, 2016 11.
Artigo em Inglês | MEDLINE | ID: mdl-27839582

RESUMO

African swine fever (ASF) is a viral disease of swine that has been present in the Russian Federation since 2007. Counts of ASF outbreaks reported in the Southern regions of the country (2007-2014) were aggregated to a grid of hexagons, and a zero-inflated Poisson model accounting for spatial dependence between hexagons was used to identify factors associated with the presence of ASF outbreaks and factors associated with the number of ASF reports in affected hexagons. Increasing density of pigs raised on low biosecurity farms was found to be positively associated with the probability of occurrence of at least one ASF outbreak in a hexagon and with the average number of reported ASF outbreaks amongst affected hexagons. Increasing human population density and increasing distance from the closest diagnostic laboratory were additional variables associated with number of reported ASF outbreaks amongst affected hexagons. The model was shown to have good predictive ability.


Assuntos
Febre Suína Africana/epidemiologia , Surtos de Doenças , Febre Suína Africana/etiologia , Agricultura , Animais , Fazendas , Humanos , Incidência , Vigilância da População , Fatores de Risco , Federação Russa/epidemiologia , Análise Espaço-Temporal , Suínos
15.
Vet Res ; 47(1): 109, 2016 11 04.
Artigo em Inglês | MEDLINE | ID: mdl-27814754

RESUMO

The transmission tree of the Israeli 2015 epidemic of highly pathogenic avian influenza (H5N1) was modelled by combining the spatio-temporal distribution of the outbreaks and the genetic distance between virus isolates. The most likely successions of transmission events were determined and transmission parameters were estimated. It was found that the median infectious pressure exerted at 1 km was 1.59 times (95% CI 1.04, 6.01) and 3.54 times (95% CI 1.09, 131.75) higher than that exerted at 2 and 5 km, respectively, and that three farms were responsible for all seven transmission events.


Assuntos
Epidemias/veterinária , Virus da Influenza A Subtipo H5N1/fisiologia , Influenza Aviária/transmissão , Doenças das Aves Domésticas/transmissão , Perus/virologia , Animais , Influenza Aviária/epidemiologia , Israel/epidemiologia , Modelos Estatísticos , Doenças das Aves Domésticas/epidemiologia , Doenças das Aves Domésticas/virologia
16.
Prev Vet Med ; 122(3): 253-6, 2015 Dec 01.
Artigo em Inglês | MEDLINE | ID: mdl-26597092

RESUMO

In epidemiology, data are often aggregated using administrative boundaries or regular spatial lattices. Iso-population partitioning methods allow the aggregation of small units for which population data are available into larger units that are contiguous, as compact as possible, and have a similar population size. The objective of this paper was to study the influence of three spatial data aggregation approaches on data visualization and data analysis: iso-populated units (IPUs), administrative units, and iso-geometric units. This study was conducted using results and simulations from the brucellosis clinical surveillance system for dairy cattle in France. Our findings indicate that using spatial partitioning methods for generating IPUs enhances the ability to interpret the spatial distribution of epidemiological indicators under study. In addition, it provides information on population density and improves the consistency of the power of statistical tests across units. By defining the target population size per spatial unit, IPUs can be used to control the statistical power of a study. Finally, by adding criteria based on environmental factors to generate spatial units, they can be used to control the variation of exposure to these factors within the units.


Assuntos
Brucelose/veterinária , Doenças dos Bovinos/epidemiologia , Coleta de Dados/métodos , Monitoramento Epidemiológico/veterinária , Análise Espacial , Animais , Brucelose/epidemiologia , Brucelose/microbiologia , Bovinos , Doenças dos Bovinos/microbiologia , Indústria de Laticínios , França/epidemiologia
17.
Prev Vet Med ; 120(3-4): 253-64, 2015 Jul 01.
Artigo em Inglês | MEDLINE | ID: mdl-25962955

RESUMO

In disease surveillance, capture-recapture approaches have been used to estimate the frequency of endemic diseases monitored by imperfect surveillance systems. A standard output of these techniques is an estimate of the sensitivity of the surveillance. In addition, capture-recapture applications contribute to a better understanding of the disease detection processes and of the relationships between different surveillance data sources, and help identify variables associated with the under-detection of diseases. Although capture-recapture approaches have long been used in public health, their application to livestock disease surveillance is only recent. In this paper, we review the different capture-recapture approaches applied in livestock disease surveillance, and discuss their benefits and limitations in the light of the characteristics of the surveillance and control practices used in animal health.


Assuntos
Doenças dos Animais/epidemiologia , Gado , Doenças dos Animais/etiologia , Animais , Vigilância da População
18.
Prev Vet Med ; 120(1): 70-85, 2015 Jun 01.
Artigo em Inglês | MEDLINE | ID: mdl-25623970

RESUMO

Surveillance systems produce data which, once analysed and interpreted, support decisions regarding disease management. While several performance measures for surveillance are in use, no theoretical framework has been proposed yet with a rationale for defining and estimating effectiveness measures of surveillance systems in a generic way. An effective surveillance system is a system whose data collection, analysis and interpretation processes lead to decisions that are appropriate given the true disease status of the target population. Accordingly, we developed a framework accounting for sampling, testing and data interpretation processes, to depict in a probabilistic way the direction and magnitude of the discrepancy between "decisions that would be made if the true state of a population was known" and the "decisions that are actually made upon the analysis and interpretation of surveillance data". The proposed framework provides a theoretical basis for standardised quantitative evaluation of the effectiveness of surveillance systems. We illustrate such approaches using hypothetical surveillance systems aimed at monitoring the prevalence of an endemic disease and at detecting an emerging disease as early as possible and with an empirical case study on a passive surveillance system aiming at detecting cases of Highly Pathogenic Avian Influenza cases in Vietnamese poultry.


Assuntos
Doenças dos Animais/epidemiologia , Animais , Vigilância da População/métodos , Prevalência , Avaliação de Programas e Projetos de Saúde/métodos , Avaliação de Programas e Projetos de Saúde/normas
19.
Prev Vet Med ; 114(1): 28-36, 2014 Apr 01.
Artigo em Inglês | MEDLINE | ID: mdl-24472215

RESUMO

Logistic regression models integrating disease presence/absence data are widely used to identify risk factors for a given disease. However, when data arise from imperfect surveillance systems, the interpretation of results is confusing since explanatory variables can be related either to the occurrence of the disease or to the efficiency of the surveillance system. As an alternative, we present spatial and non-spatial zero-inflated Poisson (ZIP) regressions for modelling the number of highly pathogenic avian influenza (HPAI) H5N1 outbreaks that were reported at subdistrict level in Thailand during the second epidemic wave (July 3rd 2004 to May 5th 2005). The spatial ZIP model fitted the data more effectively than its non-spatial version. This model clarified the role of the different variables: for example, results suggested that human population density was not associated with the disease occurrence but was rather associated with the number of reported outbreaks given disease occurrence. In addition, these models allowed estimating that 902 (95% CI 881-922) subdistricts suffered at least one HPAI H5N1 outbreak in Thailand although only 779 were reported to veterinary authorities, leading to a general surveillance sensitivity of 86.4% (95% CI 84.5-88.4). Finally, the outputs of the spatial ZIP model revealed the spatial distribution of the probability that a subdistrict could have been a false negative. The methodology presented here can easily be adapted to other animal health contexts.


Assuntos
Galinhas , Surtos de Doenças/veterinária , Patos , Virus da Influenza A Subtipo H5N1/fisiologia , Influenza Aviária/epidemiologia , Modelos Teóricos , Doenças das Aves Domésticas/epidemiologia , Animais , Influenza Aviária/virologia , Modelos Logísticos , Distribuição de Poisson , Doenças das Aves Domésticas/virologia , Fatores de Risco , Análise Espacial , Tailândia/epidemiologia
20.
PLoS One ; 8(5): e63246, 2013.
Artigo em Inglês | MEDLINE | ID: mdl-23691004

RESUMO

The mandatory bovine abortion notification system in France aims to detect as soon as possible any resurgence of bovine brucellosis. However, under-reporting seems to be a major limitation of this system. We used a unilist capture-recapture approach to assess the sensitivity, i.e. the proportion of farmers who reported at least one abortion among those who detected such events, and representativeness of the system during 2006-2011. We implemented a zero-inflated Poisson model to estimate the proportion of farmers who detected at least one abortion, and among them, the proportion of farmers not reporting. We also applied a hurdle model to evaluate the effect of factors influencing the notification process. We found that the overall surveillance sensitivity was about 34%, and was higher in beef than dairy cattle farms. The observed increase in the proportion of notifying farmers from 2007 to 2009 resulted from an increase in the surveillance sensitivity in 2007/2008 and an increase in the proportion of farmers who detected at least one abortion in 2008/2009. These patterns suggest a raise in farmers' awareness in 2007/2008 when the Bluetongue Virus (BTV) was detected in France, followed by an increase in the number of abortions in 2008/2009 as BTV spread across the country. Our study indicated a lack of sensitivity of the mandatory bovine abortion notification system, raising concerns about the ability to detect brucellosis outbreaks early. With the increasing need to survey the zoonotic Rift Valley Fever and Q fever diseases that may also cause bovine abortions, our approach is of primary interest for animal health stakeholders to develop information programs to increase abortion notifications. Our framework combining hurdle and ZIP models may also be applied to estimate the completeness of other clinical surveillance systems.


Assuntos
Brucelose Bovina/epidemiologia , Notificação de Doenças/métodos , Animais , Bovinos , Feminino , França , Notificação de Abuso , Modelos Estatísticos , Probabilidade
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