from reading the first post Op says the other "2 litters' they had over the past 6 years were healthy ...
Anyways, brucellosis as mentioned is a possibility.
Also the virus that cause unexplained abortion of the puppies just about 2 weeks prior the due date should be considered , the same virus that may cause "fading puppy syndrome" can also cause abortions of otherwise perfect litters.
No explanation to how it is transmitted , not that i have found anyways. The female may deliver a perfect healthy litter afterwords as she will develop immunity . Unfortunatelly that is nothing one can do if it is indeed the virus.
Someone else mentioned the rise on Brucellosis... well, we are seeing more and more BYB cutting corners and lots of people taking chances ... people laugh when i say dogs can get STD's ... not everyone is as informed as we are here on YT .
Anyways, look into that virus possibility, it may explain the situation.
XOXO
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