agree there needs to be some sort of differentiator unless I’m missing something, AMBOSS article (https://next.amboss.com/us/article/P70WNh?q=ehrlichiosis#Zbb8143ef176ead7b35eebdf1cf5240fe) there’s barely an difference other than ehrlichiosis MIGHT present with a rash but anaplasmosis does not have a rash (and location ofc but there is no indication in question stem here)
Ehrlichia chaffeensis is harbored in white-tailed deer and transmitted to humans by tick bite. It replicates in vacuoles within monocytes and forms mulberry-shaped, intraleukocytic inclusions (morulae). Manifestations usually include nonspecific symptoms (eg, fever, chills, myalgia), maculopapular rash, and significant laboratory abnormalities, particularly lymphopenia. 
I think the only differentiation that can be possible is MEGA (Monocyte inclusion = Ehrlichia, Granulocyte inclusion = Anaplasmosis)
It’s probably tested in UWorld as amicro question, image based.
Also see NID: 1506276691066
Yeah, I would add either geography or blood smear findings, dealer’s choice… also, the QID tagged only asks about tx which is the same for both I believe