Risk assessment for recrudescence of avian influenza in caged layer houses following depopulation : the effect of cleansing, disinfection and dismantling of equipment

Following an outbreak of highly pathogenic avian influenza virus (HPAIV) in a poultry house, control measures are put in place to prevent further spread. An essential part of the control measures based on the European Commission Avian Influenza Directive 2005/94/EC is the cleansing and disinfection (C&D) of infected premises. Cleansing and disinfection includes both preliminary and secondary C&D, and the dismantling of complex equipment during secondary C&D is also required, which is costly to the owner and also delays the secondary cleansing process, hence increasing the risk for onward spread. In this study, a quantitative risk assessment is presented to assess the risk of re-infection (recrudescence) occurring in an enriched colony-caged layer poultry house on restocking with chickens after different C&D scenarios. The risk is expressed as the number of restocked poultry houses expected before recrudescence occurs. Three C&D scenarios were considered, namely (i) preliminary C&D alone, (ii) preliminary C&D plus secondary C&D without dismantling and (iii) preliminary C&D plus secondary C&D with dismantling. The source-pathway-receptor framework was used to construct the model, and parameterisation was based on the three C&D scenarios. Two key operational variables in the model are (i) the time between depopulation of infected birds and restocking with new birds (TbDR) and (ii) the proportion of infected material that bypasses C&D, enabling virus to survive the process. Probability distributions were used to describe these two parameters for which there was recognised variability between premises in TbDR or uncertainty due to lack of information in the fraction of bypass. The risk assessment estimates that the median (95% credible intervals) number of repopulated poultry houses before recrudescence are 1.2 × 104 (50 to 2.8 × 106), 1.9 × 105 (780 to 5.7 × 107) and 1.1 × 106 (4.2 × 103 to 2.9 × 108) under C&D scenarios (i), (ii) and (iii), respectively. Thus for HPAIV in caged layers, undertaking secondary C&D without dismantling reduces the risk by 16-fold compared to preliminary C&D alone. Dismantling has an additional, although smaller, impact, reducing the risk by a further 6-fold and thus around 90-fold compared to preliminary C&D alone. On the basis of the 95% credible intervals, the model demonstrates the importance of secondary C&D (with or without dismantling) over preliminary C&D alone. However, the extra protection afforded by dismantling may not be cost beneficial in the context of reduced risk of onward spread

Assessing the quality of data for drivers of disease emergence

Drivers are factors that have the potential to directly or indirectly influence the likelihood of infectious diseases emerging or re-emerging. It is likely that an emerging infectious disease (EID) rarely occurs as the result of only one driver; rather, a network of sub-drivers (factors that can influence a driver) are likely to provide conditions that allow a pathogen to (re-)emerge and become established. Data on sub-drivers have therefore been used by modellers to identify hotspots where EIDs may next occur, or to estimate which sub-drivers have the greatest influence on the likelihood of their occurrence. To minimise error and bias when modelling how sub-drivers interact, and thus aid in predicting the likelihood of infectious disease emergence, researchers need good-quality data to describe these sub-drivers. This study assesses the quality of the available data on sub-drivers of West Nile virus against various criteria as a case study. The data were found to be of varying quality with regard to fulfilling the criteria. The characteristic with the lowest score was completeness, i.e. where sufficient data are available to fulfil all the requirements for the model. This is an important characteristic as an incomplete data set could lead to erroneous conclusions being drawn from modelling studies. Thus, the availability of good-quality data is essential to reduce uncertainty when estimating the likelihood of where EID outbreaks may occur and identifying the points on the risk pathway where preventive measures may be taken.</p

Assessing the probability of introduction and transmission of lumpy skin disease virus within the United Kingdom

Several emerging exotic diseases are currently oscillating on the eastern borders of the European Union (EU) including the bovine pathogen Lumpy skin disease virus (LSDV). Given the recent transboundary spread of LSDV into the EU, assessing the probability of further expansion is an important part of EU surveillance and can inform policy regarding risk mitigation priorities. This qualitative assessment focuses on the probability of introduction and onward transmission of LSDV into the United Kingdom (UK) for the time period June 2017 to June 2018. Overall the probability of introduction was considered, at most, to be very low. The probability of onward transmission was considered highest for vector mediated routes either via contact of an infected vector with susceptible cattle or contact of a competent native vector with an infected cattle. Factors with high uncertainty were identified to emphasise their impact on the assessment conclusions and for future research requirements. Medium to high uncertainty surrounds the probability of introduction to the UK via several of the routes assessed, in particular, the species of vectors involved and the illegal/legal import of meat and milk products; all estimates made consequential to these probabilities are therefore underpinned by high uncertainty. Whilst the assessment was UK centric the knowledge gaps are relevant to the probability of introduction and spread of LSDV in any geographical region. The value of estimating uncertainty lies in the identification of research required to make conclusions more robust

Maximising data to optimise animal disease early warning systems and risk assessment tools within Europe

Timely and reliable data and information availability and sharing is essential for early warning, prevention and control of transboundary diseases. While there are a growing number of global datasets capable of providing information for use in early warning systems and risk assessment (RA) tools, there are currently time-consuming data cleansing and harmonisation activities which need to be carried out before they can be reliably used and combined. Thus, using global datasets as they stand can lead to errors in RA parameterisation and results due to inherent biases in the data, e.g. missing disease prevalence data treated as a zero may inadvertently penalise those countries which do report disease outbreaks as opposed to those countries which are affected by a pathogen but do not report outbreak data. It is therefore of great importance that data are clearly provided and easy to understand and that data providers strive for greater harmonisation of database standards. In this paper the datasets utilised in the SPARE (’Spatial risk assessment framework for assessing exotic disease incursion and spread through Europe’) project are described and discussed in terms of key criteria: accessibility, availability, completeness, consistency and quality. It is evident that most databases exist as information portals and not exclusively for RA purposes. Another striking issue from this assessment is the need for enhanced data sharing specifically with regards to data on illegal seizures, arthropod vector/wildlife abundance, intra-country livestock movement and national animal disease surveillance. It is hoped that the outcomes of this work will promote discussion and exchange between data providers, including the development of standardised data exchange protocols. The transformation of datasets to a common format is a considerable challenge but recommendations could and should be made on the standardisation of datasets and reporting in order to achieve a unified approach across Europe

Using multi-criteria risk ranking methodology to select case studies for a generic risk assessment framework for exotic disease incursion and spread through Europe

We present a novel approach of using the multi-criteria pathogen prioritisation methodology as a basis for selecting the most appropriate case studies for a generic risk assessment framework. The approach uses selective criteria to rank exotic animal health pathogens according to the likelihood of introduction and the impact of an outbreak if it occurred in the European Union (EU). Pathogens were evaluated based on their impact on production at the EU level and international trade. A subsequent analysis included criteria of relevance to quantitative risk assessment case study selection, such as the availability of data for parameterisation, the need for further research and the desire for the case studies to cover different routes of transmission. The framework demonstrated is flexible with the ability to adjust both the criteria and their weightings to the user's requirements. A web based tool has been developed using the RStudio shiny apps software, to facilitate this

A qualitative risk assessment for visual-only post-mortem meat inspection of cattle, sheep, goats and farmed/wild deer

The UK Food Standards Agency is currently funding research to build the evidence base for the modernisation of meat inspection. This includes an assessment of the risks to public health and animal health/welfare of moving to a visual-only post-mortem meat inspection (PMMI), where routine mandatory palpation and incision procedures are omitted. In this paper we present the results of a risk assessment for a change from current to visual-only PMMI for cattle, sheep/goats and farmed/wild deer. A large list of hazard/species pairings were assessed and prioritised by a process of hazard identification. Twelve hazard/species pairings were selected for full consideration within the final risk assessment. The results of the public health risk assessment indicated that all hazard/species pairings were Negligible with the exception of Cysticercus bovis in cattle, which was judged to be of low-medium increased risk for systems not conforming to criteria as laid down by EC Regulation 1244/2007, compared to systems that do conform to Regulations for visual-only PMMI. Most hazard/species pairings were concluded to pose a potential increased risk to animal health/welfare, including Mycobacterium bovis (very low – low increase in risk, but with considerable uncertainty), Fasciola hepatica (negligible – very low) and Cysticercus bovis (very low – low). Due to low feedback rates to farmers, the real risk to animal health/welfare for F. hepatica and C. bovis, including animals in non-conforming systems under visual-only PMMI, is probably negligible. That then leaves M. bovis as the only confirmed non-negligible animal health and welfare risk

A qualitative risk assessment of the microbiological risks to consumers from the production and consumption of uneviscerated and eviscerated small game birds in the UK

Since the beginning of the 21st century, consumption of wild game birds has been increasing, concurrent with a rise in consumer interest in free-range and 'healthy-eating' foodstuffs. Game birds can carry zoonotic pathogens, predominantly within the viscera. Whilst removal of the viscera is normal practice during the dressing of game birds, there is a specialised market in the UK for certain small game birds that are consumed uneviscerated. This qualitative risk assessment evaluates the risks to the consumer from the production and consumption of both uneviscerated and eviscerated small game birds for Salmonella spp., Escherichia coli (verotoxigenic), E. coli (antimicrobial resistant), Campylobacter spp., Toxoplasma gondii, Chlamydophila psittaci and Listeria monocytogenes. Whilst most pathogen/bird combinations were considered to have a very low risk, results suggest that Campylobacter spp. and T. gondii can pose an increased risk to consumers for some species of wild game birds. There was no greater risk associated with the consumption of uneviscerated game birds than for eviscerated birds. In some cases, the risk from eviscerated birds may even be slightly higher, as the risk of cross-contamination during evisceration can outweigh the reduction in pathogenic organisms due to removal of the viscera. Additionally, the current low frequency of consumption of uneviscerated game birds of most species reduced the overall risk estimate for these birds. If there is an increased frequency of consumption in the future, then this risk should be re-examined. Assuming a general level of compliance with regulations and basic hygiene practices, the results suggested that large outbreaks of infection among UK consumers are unlikely, but sporadic, infectious events could occur due to combinations of 'rare-event, hygiene-related issues' in the 'field-to-fork' chain and/or inadequate cooking of the bird

A qualitative risk assessment of cleansing and disinfection requirements after an avian influenza outbreak in commercial poultry

1. During an avian influenza (AI) outbreak in the United Kingdom, the joint aim of the poultry industry and the Government is to eliminate and prevent the spread of infection, through control measures based on the current European Union (EU) Council Directive (2005/94/EC). An essential part of these measures is the cleansing and disinfection (C&D) of infected premises.2. This risk assessment assessed the differences in re-infection in a repopulated flock if the EU Directive is interpreted to permit secondary C&D to be undertaken either with or without dismantling complex equipment. The assessment estimated the probability of virus survival on different types of equipment in a depopulated contaminated poultry house before and after preliminary and secondary C&D procedures. A risk matrix spreadsheet tool was used to carry out the assessment and concluded that, provided secondary C&D is carried out with due diligence (i.e. carried out to a defined code of practice as agreed by both industry and policymakers), the risk of re-infection from equipment is negligible, both with and without dismantling complex equipment in all farm types considered.3. By considering the equipment types individually, the assessment identified those areas of the house which may still contain viable virus post-preliminary C&D and on which attention should be focussed during secondary C&D. The generic risk pathway and matrix spreadsheet tool have the potential to be used for other pathogens and species, given appropriate data

A qualitative risk assessment for visual-only post-mortem meat inspection of cattle, sheep, goats and farmed/wild deer

The UK Food Standards Agency is currently funding research to build the evidence base for the modernisation of meat inspection. This includes an assessment of the risks to public health and animal health/welfare of moving to a visual-only post-mortem meat inspection (PMMI), where routine mandatory palpation and incision procedures are omitted. In this paper we present the results of a risk assessment for a change from current to visual-only PMMI for cattle, sheep/goats and farmed/wild deer.A large list of hazard/species pairings were assessed and prioritised by a process of hazard identification. Twelve hazard/species pairings were selected for full consideration within the final risk assessment. The results of the public health risk assessment indicated that all hazard/species pairings were Negligible with the exception of Cysticercus bovis in cattle, which was judged to be of low-medium increased risk for systems not conforming to criteria as laid down by EC Regulation 1244/2007, compared to systems that do conform to Regulations for visual-only PMMI.Most hazard/species pairings were concluded to pose a potential increased risk to animal health/welfare, including Mycobacterium bovis (very low - low increase in risk, but with considerable uncertainty), Fasciola hepatica (negligible - very low) and Cysticercus bovis (very low - low). Due to low feedback rates to farmers, the real risk to animal health/welfare for F.hepatica and C.bovis, including animals in non-conforming systems under visual-only PMMI, is probably negligible. That then leaves M.bovis as the only confirmed non-negligible animal health and welfare risk