US Scientists uncover clue to fight swine virus
A team of scientists working together with the
Agricultural Research Service (USDA) in the US have discovered a vital clue to
counteract porcine reproductive and respiratory syndrome virus
The virus costs US swine producers around US$560m yearly. It causes pneumonia
and reproductive losses in pigs and infected sows to give birth to weak piglets.
Pigs require weeks or months to recover from the virus, which is not very
responsive to medications or vaccines.
Scientists evaluated two lines of swine for their genetic
resistance to PRRSV. They chose the Hampshire by Duroc cross (H.D.) for its high
growth rates and the Nebraska Index Line (I) for its improved reproductive
After exposure to PRRSV, all pigs became infected. However, the I line pigs
generally recovered more quickly.
Samples of blood, lung and bronchial lymph node tissue indicated that the
virus cleared up more quickly in I and H.D. pigs, who were resistant to
A study of
the tissue expression of 11 genes and one 'housekeeping' gene in the immune
response to PRRSV was carried out. The results showed that both swine lines had
significant activity in 11 of the 12 genes, but the type differed greatly
between the two.
The above findings are highly significant as they support existing research
that maintains that animal breeds with high growth rates devote less energy to
immune and disease traits.
â€¢ Agricultural Research
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