![\"Testing_A_Virus\"](\"http:\/\/www.tomgrimshaw.com\/tomsblog\/wp-content\/uploads\/2018\/12\/Testing_A_Virus-300x200.jpg\")
<\/p>\n<\/p>\n
No matter your stand on vaccines, this is a worthwhile read.<\/p>\n
…Read and others, including researchers at the U.S. Department of Agriculture, posit that the virus that causes Marek\u2019s has been changing over time in ways that helped it evade its previous vaccines. The big question is whether the vaccines directly incited these changes or the evolution happened, coincidentally, for other reasons, but Read is pretty sure the vaccines have played a role.<\/p>\n
In a 2015 paper in PLOS Biology, Read explains how he and his colleagues vaccinated 100 chickens, leaving 100 others unvaccinated. They then infected all the birds with strains of Marek\u2019s that varied in how virulent \u2014 as in how dangerous and infectious \u2014 they were. The team found that, over the course of their lives, the unvaccinated birds shed far more of the least virulent strains into the environment, whereas the vaccinated birds shed far more of the most virulent strains. The findings suggest that the Marek\u2019s vaccine encourages more dangerous viruses to proliferate. This increased virulence might then give the viruses the means to overcome birds\u2019 vaccine-primed immune responses and sicken vaccinated flocks…<\/p>\n