i also get herx reactions from Black Cumin Seed oil - i had assumed this is most likely due to it ramping up the immune response - in my case it results in increased fatigue mainly - but long term it may be helping.
most of the stuff i have read on it is focussed on its immune-stimulating properties - increasing things like autophagy etc - which can be very useful in intercellular infections as it causes infected cells to self destruct and exposes the bacteria to the immune system.
however, this study says it does have some incomplete inhibitory effect on babesia and Theileria species
https://parasitesandvectors.biomedcentral.com/articles/10.1186/s13071-019-3296-z#tab1it also references a number of other natural substances that can inhibit these piroplasms - again to some limited degree
-allicin
-NAC
-EGCG