Montgomery to be the primary ball carrier.

蒙哥马利成为主要持球者。

It's believed that fruit bats are the primary carrier of the disease in nature and it was through direct contact with them that the disease first spread to humans.

据信，果蝠是自然界中该疾病的主要携带者，正是通过与果蝠的直接接触，该疾病首次传播给了人类。

Now, historians know that fleas were the main cause of the propagation of  the disease, even if debates persist over which animal was the primary carrier of fleas.

现在，历史学家知道跳蚤是疾病传播的主要原因，尽管关于哪种动物是跳蚤的主要携带者的争论仍在继续。