Researchers with the Western College of Veterinary Medicine have identified genetic markers that might help identify genetic lines that are more resistant to PRRS. Porcine Reproductive and Respiratory Syndrome can result in early farrowing, birth of weak infected pigs or death of the fetus but some fetuses within a litter or entire litters will escape infection. To identify strategies to keep sows from infecting their offspring, researchers are examining the mechanisms of fetal compromise.

Dr. John Harding, a Professor with the Western College of Veterinary Medicine, says some fetuses resist infection better than others.

Clip-Dr. John Harding-Western College of Veterinary Medicine:

The infection tends to be heterogeneous or uneven in the endometrium and clusters spatially within a litter so resilience might simply be a chance event. If the level of virus is low in the endometrium adjacent to a given fetus, virus transmission may simply be delayed.

We also understand that fetuses with intrauterine growth restrictions are relatively resistant and have lower viral load than normal growth littermates. This might be because they have a smaller placenta, perhaps less efficient nutrient exchange or lower rates of cell division affecting the likelihood of infection, the amount of virus crossing the placenta or they have lower metabolic demands resulting in greater ability to withstand the adverse metabolic consequences of infection.

There might also be a genotypic affect. So, using a genomic approach, we have identified several genetic markers related to fetal resilience and are continuing to explore these in terms of specific genes that might be involved and how any specific mutation or variant might change fetal metabolism to result in greater resilience.

Source : Farmscape

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