Swine influenza is a respiratory disease induced by influenza A virus infection. (IAV). It is extremely infectious and primarily affects swine. The disease is characterized by fever, wheezing, sneezing, lethargy, and nasal discharge. Due to the fever brought on by the disease, pregnant sows may also undergo abortions. The diagnosis of swine influenza can be made using PCR or virus isolation. The disease is predominantly controlled by vaccination, but secondary bacterial infections can be treated with antibiotics.
It is essential to note that swine IAV strains do not typically spread readily among humans. As they can replicate influenza viruses of both avian and human origin, pigs can contribute to the emergence of zoonotic strains with pandemic potential. In 2009, a swine-origin H1N1 IAV strain spread worldwide, infecting humans, swine, and other animals. Human seasonal influenza viruses can also become established in swine, contributing to the genetic diversity of IAVs identified in swine. Globally, swine influenza is prevalent in regions that produce pigs.
Swine Influenza Management in Pigs/Swine
Causes of Swine Influenza Disease in Swine
The influenza A virus (IAV), a segmented, negative-stranded RNA virus with a sheath, causes swine influenza. Hemagglutinin and neuraminidase, the two primary antigenic proteins of IAV, define the virus subtype and are in charge of viral attachment to cells and viron release from infected cells.
H1N1, H1N2, and H3N2 are the three major subtypes of the swine IAV virus, and there are various strains of each subtype. Pigs frequently contract other viruses and germs, which puts them at risk of contracting swine influenza. These include Mycoplasma hyopneumoniae, Glaesserella parasuis, Actinobacillus pleuropneumoniae, and pig reproductive and respiratory syndrome virus. Disinfectants make it simple to inactivate the infection.
Disease Cycle of Swine Influenza Disease
Outbreaks of swine influenza occur year-round in warmer regions of the globe. Still, they are most prevalent in autumn and winter in North America. Aerosolization, direct pig-to-pig contact, and fomite transfer accelerate the spread of the disease within a herd. Swine influenza is endemic globally and pervasive in the global swine population.
Before weaning, piglets are a reservoir of influenza infection capable of transmitting the virus to other farms. Often, pigs act as vectors to spread IAV to herds and countries that have never had it before. The spread of new flu infections is helped by the fact that pigs move between crates and enclosures and that there are no all-in/all-out rules. As immunity in antibody-positive livestock declines, recurrent outbreaks may occur.
What are the Symptoms of Swine Influenza Disease?
- Symptoms include wheezing, sneezing, nasal discharge, elevated rectal temperatures, lethargy, difficulty breathing, and decreased appetite. Reproductive disorders such as abortion are rarely associated with these symptoms.
- The initial clinical symptoms include fever, puffy eyes, anorexia resulting in weight loss, depression, prostration, and huddling resulting in weakness.
- The sudden onset of acute respiratory symptoms, including paroxysmal coughing, wheezing, abdominal breathing irregularity, and ocular and nasal discharges, follows.
- Abortions, infertility, the production of small, feeble litters, and an increase in stillbirths may occur in breeding stock.
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Diagnosis of Swine Influenza Disease
Swine influenza can be diagnosed based on clinical symptoms. Still, confirmation necessitates the detection of the influenza virus through RT-PCR, virus isolation, or antibody detection. The virus can be isolated from nasal and oral discharge, infected lung tissue, and udder swabs. In acute and convalescent serum samples, the hemagglutination inhibition test can be used to demonstrate an increase in virus-specific antibody titers.
Before diagnos