Critical Reasoning (CR) | Re: Humans get Lyme disease from infected ticks. Ticks get infected by fee

Hi ExpertsGMATNinja VeritasPrepKarishma

Can you please help to understand last line of the argument. Although I got to OA with a pinch of guess, I want to validate my understanding.

Argument:
(I)T ___ (LD) ____> Humans
T____(LD)____> feeding on animals

How easily the LD gets transmitted varies on animals on which ticks feed.
Typically the transmission is easier if host animal is WF mice.

Now I got stuck in last sentence seeing the word- bio-diversity.

Is my understanding