Evaluation of interventions and vaccination strategies for low pathogenicity avian influenza: spatial and space–time analyses and quantification of the spread of infection

Mulatti, Paolo; Bos, Marian E. H.; Busani, Luca; Nielen, M.; Marangon, Stefano

doi:10.1017/s0950268809991038

Cited by 19 publications

(19 citation statements)

References 32 publications

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“…Our R f estimates are applicable to the Dutch layer chicken industry. The estimated R f in areas with high flock density in the Netherlands are in accordance with the R f estimates using data of LPAI outbreaks in areas with high flock densities in Italy (Mulatti et al, 2010). In addition, our estimates are further supported by the fact that no large LPAI epidemic in poultry has been observed in the Netherlands in the past 10 years.…”

Section: Tablesupporting

confidence: 88%

Risk based surveillance for early detection of low pathogenic avian influenza outbreaks in layer chickens

Gonzáles

Boender

Elbers

et al. 2014

Preventive Veterinary Medicine

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Current knowledge does not allow the prediction of when low pathogenic avian influenza virus (LPAIV) of the H5 and H7 subtypes infecting poultry will mutate to their highly pathogenic phenotype (HPAIV). This mutation may already take place in the first infected flock; hence early detection of LPAIV outbreaks will reduce the likelihood of pathogenicity mutations and large epidemics. The objective of this study was the development of a model for the design and evaluation of serological-surveillance programmes, with a particular focus on early detection of LPAIV infections in layer chicken flocks. Early detection is defined as the detection of an infected flock before it infects on average more than one other flock (between-flock reproduction ratio Rf<1), hence a LPAI introduction will be detected when only one or a few other flocks are infected. We used a mathematical model that investigates the required sample size and sampling frequency for early detection by taking into account the LPAIV within- and between-flock infection dynamics as well as the diagnostic performance of the serological test used. Since layer flocks are the target of the surveillance, we also explored whether the use of eggs, is a good alternative to sera, as sample commodity. The model was used to refine the current Dutch serological-surveillance programme. LPAIV transmission-risk maps were constructed and used to target a risk-based surveillance strategy. In conclusion, we present a model that can be used to explore different sampling strategies, which combined with a cost-benefit analysis would enhance surveillance programmes for low pathogenic avian influenza.

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Section: Tablesupporting

confidence: 88%

Risk based surveillance for early detection of low pathogenic avian influenza outbreaks in layer chickens

Gonzáles

Boender

Elbers

et al. 2014

Preventive Veterinary Medicine

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“…For estimation of β h , the relation R h = β h *AUC can be reversed for a known value R h ' during an epidemic, and a mean AUC' of actual flocks during that same epidemic: β h = R h '/AUC'. For this calculation, we used a published value of R h ' of 2.15, which was the farm reproduction number at the beginning of the Italian 2000–2001 LPAI epidemic, when no control measures were in place yet [12]. The value of AUC' was estimated as the average AUC of 1000 simulated outbreaks in 1000 single-flock farms with different flock sizes and gender of birds (randomly selected from a list of single-flock turkey farms available at the Regional poultry farm registry), assuming the absence of any control measure.…”

Section: Methodsmentioning

confidence: 99%

“…Sampling for active surveillance was assumed to start at day 60 of the production cycle (based on the results of Comin et al [9]) and to be performed on a monthly basis (as in Mulatti et al [12]). At each sampling, we assumed that 10 birds were tested by means of both serological and virological assays (assuming perfect accuracy for both tests, which was relaxed in sensitivity analyses, see below).…”

Section: Methodsmentioning

confidence: 99%

Evaluating Surveillance Strategies for the Early Detection of Low Pathogenicity Avian Influenza Infections

et al. 2012

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In recent years, the early detection of low pathogenicity avian influenza (LPAI) viruses in poultry has become increasingly important, given their potential to mutate into highly pathogenic viruses. However, evaluations of LPAI surveillance have mainly focused on prevalence and not on the ability to act as an early warning system. We used a simulation model based on data from Italian LPAI epidemics in turkeys to evaluate different surveillance strategies in terms of their performance as early warning systems. The strategies differed in terms of sample size, sampling frequency, diagnostic tests, and whether or not active surveillance (i.e., routine laboratory testing of farms) was performed, and were also tested under different epidemiological scenarios. We compared surveillance strategies by simulating within-farm outbreaks. The output measures were the proportion of infected farms that are detected and the farm reproduction number (Rh). The first one provides an indication of the sensitivity of the surveillance system to detect within-farm infections, whereas Rh reflects the effectiveness of outbreak detection (i.e., if detection occurs soon enough to bring an epidemic under control). Increasing the sampling frequency was the most effective means of improving the timeliness of detection (i.e., it occurs earlier), whereas increasing the sample size increased the likelihood of detection. Surveillance was only effective in preventing an epidemic if actions were taken within two days of sampling. The strategies were not affected by the quality of the diagnostic test, although performing both serological and virological assays increased the sensitivity of active surveillance. Early detection of LPAI outbreaks in turkeys can be achieved by increasing the sampling frequency for active surveillance, though very frequent sampling may not be sustainable in the long term. We suggest that, when no LPAI virus is circulating yet and there is a low risk of virus introduction, a less frequent sampling approach might be admitted, provided that the surveillance is intensified as soon as the first outbreak is detected.

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“…Despite control measures, an HPAI virus of the same subtype was isolated in December 1999 and rapidly spread to additional production facilities before being eradicated officially in April 2000. Following depopulation and restocking of the HPAI-infected areas, LPAI reemerged in August 2000, and 78 outbreaks were diagnosed and eradicated (37). To reduce the economic impact of the H7N1 infection in poultry (38), a vaccination program was initiated from November 2000 to May 2002.…”

mentioning

confidence: 99%

Emergence of a Highly Pathogenic Avian Influenza Virus from a Low-Pathogenic Progenitor

Monne

Fusaro

Nelson

et al. 2014

J Virol

128

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Avian influenza (AI) viruses of the H7 subtype have the potential to evolve into highly pathogenic (HP) viruses that represent a major economic problem for the poultry industry and a threat to global health. However, the emergence of HPAI viruses from low-pathogenic (LPAI) progenitor viruses currently is poorly understood. To investigate the origin and evolution of one of the most important avian influenza epidemics described in Europe, we investigated the evolutionary and spatial dynamics of the entire genome of 109 H7N1 (46 LPAI and 63 HPAI) viruses collected during Italian H7N1 outbreaks between March 1999 and February 2001. Phylogenetic analysis revealed that the LPAI and HPAI epidemics shared a single ancestor, that the HPAI strains evolved from the LPAI viruses in the absence of reassortment, and that there was a parallel emergence of mutations among HPAI and later LPAI lineages. Notably, an ultradeep-sequencing analysis demonstrated that some of the amino acid changes characterizing the HPAI virus cluster were already present with low frequency within several individual viral populations from the beginning of the LPAI H7N1 epidemic. A Bayesian phylogeographic analysis revealed stronger spatial structure during the LPAI outbreak, reflecting the more rapid spread of the virus following the emergence of HPAI. The data generated in this study provide the most complete evolutionary and phylogeographic analysis of epidemiologically intertwined high-and low-pathogenicity viruses undertaken to date and highlight the importance of implementing prompt eradication measures against LPAI to prevent the appearance of viruses with fitness advantages and unpredictable pathogenic properties. IMPORTANCEThe Italian H7 AI epidemic of 1999 to 2001 was one of the most important AI outbreaks described in Europe. H7 viruses have the ability to evolve into HP forms from LP precursors, although the mechanisms underlying this evolutionary transition are only poorly understood. We combined epidemiological information, whole-genome sequence data, and ultradeep sequencing approaches to provide the most complete characterization of the evolution of HPAI from LPAI viruses undertaken to date. Our analysis revealed that the LPAI viruses were the direct ancestors of the HPAI strains and identified low-frequency minority variants with HPAI mutations that were present in the LPAI samples. Spatial analysis provided key information for the design of effective control strategies for AI at both local and global scales. Overall, this work highlights the importance of implementing rapid eradication measures to prevent the emergence of novel influenza viruses with severe pathogenic properties.

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Evaluation of interventions and vaccination strategies for low pathogenicity avian influenza: spatial and space–time analyses and quantification of the spread of infection

Cited by 19 publications

References 32 publications

Risk based surveillance for early detection of low pathogenic avian influenza outbreaks in layer chickens

Risk based surveillance for early detection of low pathogenic avian influenza outbreaks in layer chickens

Evaluating Surveillance Strategies for the Early Detection of Low Pathogenicity Avian Influenza Infections

Emergence of a Highly Pathogenic Avian Influenza Virus from a Low-Pathogenic Progenitor

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