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Pig

The impact of swine influenza and how to control it on farm

02 March 2020
Clinical
11 mins read
02 March 2020
Volume 25 · Issue 2
Figure 1. The structure of influenza virus, including the surface proteins haemagglutinin (HA) and neuraminidase (NA), and the RNA genome.
Figure 1. The structure of influenza virus, including the surface proteins haemagglutinin (HA) and neuraminidase (NA), and the RNA genome.

Abstract

Swine influenza (SIV) can reduce productivity on farm and therefore can have a large economic impact also. The virus has four common lineages in swine, H1avN1av, H1huN2, H3N2 and H1pdmN1pdm (the pandemic strain). The virus invades the respiratory tract and therefore the majority of clinical signs are of respiratory nature, including sneezing, coughing and nasal discharge, which can also be accompanied by fever and lethargy. Diagnosis of the disease is important to determine the strain on the farm and therefore implement a control plan which may include biosecurity and hygiene measures in combination with vaccination. Vaccination has been shown to be effective in reducing the clinical signs, lung lesions and the viral shedding. Vaccination of the breeding herd can result in an improvement in reproductive performance, such as a reduction in the return to oestrus rate and an increase in the number of piglets born alive. Control of SIV should be a combined approach to achieve the best results on farm.

Swine influenza A virus (SIV) can have a large economic impact on the pig industry, and the zoonotic threat also makes it a concern for public health. A study has shown that 56% of UK farms were positive for influenza, based on 146 samples from nine farms. The same study also showed Ireland to have a number of positive farms for pandemic SIV, H1pdmN1pdm (Henritzi, 2019). Biosecurity and hygiene protocols should be implemented on farm to reduce environmental contamination and therefore the risk of pathogen spread. Understanding of diagnostic testing is extremely important in implementing the correct vaccination protocol on farm and the various methods of testing and the vaccination options will be discussed in this article.

Swine influenza is caused by influenza A virus which is an orthomyxovirus 80–120 nm in diameter, comprising eight pieces of segmented RNA coding for 12 proteins, including haemagglutinin (HA), neuraminidase (NA) and matrix 2 proteins which form part of the virus envelope (Figure 1). The virus is classified by type A, B, C or D, which is based on the matrix and the nucleoprotein. The subtypes are then defined by the haemagglutinin (HA) and neuraminidase (NA) proteins (Sandbulte et al, 2015). New subtypes can develop by antigenic shift, antigenic drift or reassortment. Three reassortment porcine lineages circulate in swine in Europe, including H1avN1av, H1huN2 and H3N2. However, the human pandemic H1N1/2009 virus has established a fourth lineage in swine, H1pdmN1pdm (Henritzi et al, 2016).

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swine influenza
diagnosis
biosecurity and hygiene
vaccination