Use of stronger live IBD vaccines are probably justified for this highly virulent form.

使用毒力强些的IBD活苗也许可以应对这种高致病型的IBD。

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All mice were challenged with highly virulent tachyzoites to observe the survival time.

用弓形虫速殖子腹腔攻击感染小鼠，观察小鼠的生存时间。

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The results indicated that the immunized chicken flocks were infected by highly virulent MDV.

结果表明：该免疫鸡群受到了MDV强毒攻击，发生了马立克氏病。

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Secondly, the 2009 H1N1 lacks a gene that is present in highly virulent flu viruses, such as the one in 1918.

CNN: Swine flu, part II: What's in store in the months to come

Estimates of the number of dead run to the hundreds of millions world-wide and scores of millions in the U.S. If nature fails to deliver an epidemic, it is unfortunately easy for a highly trained terrorist, by genetic manipulation, to create a super-virulent pathogen with a nearly 100% rate of mortality.

WSJ: Our Blindness