Swine Influenza Virus (SI), Flu
Swine influenza is caused by a number of closely related influenza A viruses that are noted for their ability to change their antigenic structure and create new strains.Each serotype is identified by surface proteins referred to as "H" and "N". The three common strains that affect the pig are described as H1 N1, H1 N2 and H3 N2. There are also different strains within these serotypes with differing pathogenicity (capacity to produce disease).
The incubation period of the disease is very short, as little as 12-48 hours and the onset is usually rapid and dramatic.
It is virtually impossible to maintain a population of pigs that is influenza virus free.
The incubation period of the disease is very short, as little as 12-48 hours and the onset is usually rapid and dramatic.
It is virtually impossible to maintain a population of pigs that is influenza virus free.
SI in large herds may become endemic with intermittent bouts of disease and infertility and different strains may also sequentially infect the herd. Immunity to influenza viruses is often short lived (6 months) and the immunity profile in the breeding herd varies considerably with time.
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