Discussion on a Selection of Key Scientific Articles

By John Atkinson,
Associate Director, Intergovernmental Veterinary Health
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Protecting poultry from avian influenza. Youngs, E., Tasker, J., Hammond, P. Vet Rec. 2018;3 February:144-145. doi: 10.1136/vr. k463

Key Thoughts:
Viral diseases that spread between wild and domestic populations can cause devastating outbreaks that have a huge impact on the animals affected and the humans that depend on them. Whether people have one animal or thousands, everyone must take responsibility in preventing the spread of serious viral diseases such as avian influenza. Biosecurity should be a priority at all times, not only when the threat of a particular disease is near.

Article Summary:
H5N6 highly pathogenic avian influenza has been diagnosed in England in recent years, with backyard flocks being affected as well as commercial ones. This means that everyone who keeps poultry, regardless of the number of birds, must be well informed about this serious disease.

Avian influenza is caused by a virus that is often transmitted by the faeco-oral route, and so the chances of infection can be reduced by minimising the contact between domestic birds and wild birds and their faeces.

This can be achieved by implementing several measures, which were legally required following the declaration of a prevention zone in England and Wales in January 2018. These include feeding domestic birds in enclosed areas, restricting access of people to domestic bird enclosures, and cleaning and disinfecting key areas.

It is essential that everyone involved in poultry is aware of the disease and understands that clinical signs vary significantly, with some birds being severely affected whilst others hardly at all. Such vigilance should be combined with robust biosecurity and prompt reporting of suspected cases.

Relevant measures to prevent the spread of African swine fever in the European Union domestic pig sector Jurado, C., Martínez-Avilés, M., De La Torre, A., Štukelj, M., Cardoso de Carvalho Ferreira, H., Cerioli, M., Sánchez-Vizcaíno, J.M., Bellini, S. Front Vet Sci. 2018;5:77. doi: 10.3389/fvets.2018.00077

Key Thoughts:
The situation Europe is facing with African swine fever (ASF) is extremely serious, with the disease continuing to advance slowly. Everyone involved in keeping pigs or hunting wild boar in the region should be educated about the disease and what they can do to prevent it. Most preventative measures are applicable regardless of the pig farming system involved, and, in the absence of a vaccine, biosecurity has never been more important.

Article Summary:
ASF is a notifiable disease affecting domestic pigs and wild boar which is commonly spread by direct or indirect contact with infectious animals or their fluids, ingestion of contaminated feed, pork, or pig products, or contact with contaminated surfaces or fomites.

The disease entered the eastern European Union (EU) in 2007, and in the last 10 years has continued to spread despite the implementation of measures to prevent spread in domestic pigs and wild boar. These measures focus on early detection and strict sanitary measures, with no vaccine or treatment currently available.

The paper aimed to review the preventative measures to avoid the spread of ASF in the EU, and assess their importance according to the different pig farming systems: commercial, non-commercial, and outdoor. Searches of the Internet and Pubmed database were undertaken, relevant literature selected, and preventative measures identified. A list of preventative measures was reviewed, and then assessed by a group of 12 out of 20 invited ASF experts in terms of their importance to each type of pig farming system within the EU.

Thirty-seven preventative measures were identified from the final 52 documents reviewed. The measures were then grouped according to the applicable pig farming system. Many measures were applicable to all farm types, including identification of animals and farm records, no swill feeding, containment of pigs, education of pig farm workers, no contact between pig farm workers and external pigs, restrictions on pig farm workers during the wild boar hunting season, and appropriate disposal of carcasses, manure, and food waste. Increased veterinary input was important for non-commercial and outdoor farms.

Prevention is essential to avoid further spread of ASF in Europe, and measures should focus on controlling what enters pig farms, control of pig feed, and improving veterinary input and education.

Risk of introduction of lumpy skin disease in France by the import of vectors in animal trucks Saegerman, C., Bertagnoli, S., Meyer, G., Ganière, J.-P., Caufour, P., De Clercq, K., Jacquiet, P., Fournié, G., Hautefeuille, C., Etore, F., Casal, J. PLoS ONE. 2018:13(6): e0198506. https://doi.org/10.1371/journal.pone.0198506

Key Thoughts:
Earlier this year it was announced that the lumpy skin disease (LSD) outbreak in Europe has been very well controlled with vaccination, so it is important not to become complacent about this transboundary disease. Those involved in cattle production should understand the risks for LSD introduction and how to mitigate them. For herds that bring cattle onto the farm, attention should be given to where the animals are sourced and how they are transported.

Article Summary:
LSD appears to be mainly spread over short distances by vectors, and long distances by the movement of infected cattle. However, the movement of infected vectors in animal transport vehicles may also contribute to long-distance disease spread.

The risk of introducing LSD from Southeast Europe to France by moving vectors in cattle and horse trucks was assessed. More work is required to fully understand the vectors involved in the transmission of LSD; this study focused on Stomoxys calcitrans flies.

A quantitative import risk analysis (QIRA) model was developed with input from six LSD experts. The model included 10 probabilities as input variables, as well as estimates of numbers of flies transported and numbers of cattle and horse movements. These estimates were based on published literature and the EU movement database (TRACES), respectively.

The probability of an LSD outbreak occurring in France due to vectors being moved in cattle trucks was 6 x 10-5 and 5.93 x 10-3, with a median value of 89.9 x 10-5. It was noted that the animals being transported and associated vectors do not only pose a risk to the end destination country, but to any country in which they are unloaded for a rest during the journey.

Cleaning, disinfection, and disinsectisation of live animal transport vehicles before leaving at-risk areas is important to reduce the risk posed by infected insect vectors. This risk can also be reduced by reducing the spread and circulation of LSD virus in affected countries through early LSD detection and vaccination campaigns.

The model quantifies the risk of LSD introduction through insect vectors in trucks, which is important because the LSD situation in Europe is changing. The model is flexible and can be adapted to countries other than France, vectors other than Stomoxys calcitrans, and diseases other than LSD.



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