Here in western KY, with that presentation, Neospora would be Candidate #1, 2, and maybe #3. Lots of coyotes and roaming dogs.
Over 25 years in the diagnostic lab here, I could count on one hand the number of confirmed Lepto abortions I saw. But... feral hogs are not (yet) a significant issue here in the western half of the state. In 30 years, I only saw one IBR abortion that was not vaccine-related. Have only seen photos of fungal abortion due to consumption of moldy hay - never saw one in person - and I'm sure that there's plenty of moldy hay fed here.
If you're going to pursue diagnostics, fetus, PLACENTA, and paired (acute & convalescent) maternal serum samples can be helpful. If I had to choose only one, I prefer placenta.
But... over time, definitive diagnosis rate on most abortion/stillbirth cases is distressingly low - 25% or less... but we can 'rule out' the things that the producer can do something about.
A positive Lepto titer to one or more serovars in a vaccinated cow is to be expected. A single (acute) sample is of little significance in a vaccinated cow - but if you pull a convalescent sample 3 weeks or so later, antibody levels may be higher or lower, giving a better inclination as to whether a particular Lepto serovar was actually involved. If titer levels stay the same... it's probably just a vaccine-induced titer.
Lepto hardjo-bovis (HB on your vaccine/bacterin bottle), which is the 'cattle-adapted' strain (cattle are the source/carriers) primarily causes early embryonic death... cows go through 3, 4 or more cycles, conceiving and then aborting the embryo, before they finally 'stick'. Mid-to-late term Lepto abortions will generally be due to one of the other Lepto strains, and infected cows will not be persistently infected 'carriers' like those infected with hardjo-bovis.
