Female in house during heat - Page 7

They were unrelated and one was a different breed. The link aakay posted said that about 25% of all older unspayed females will develop pyo and about 4% (I think ) will die from it. Given I've had so many dogs for so many years the odds were about what I would expect. Those who have owned let's say less than 25  unspayed females in their lifetime, may never end up with a female with pyo.

Having said that, IMO there is a genetic component involved in the development of pyo. Were my dogs related, I'd have certainly had to consider that a factor.

I have read somewhere that bitches prone to hormonal troubles (often hard to breed, or have whelping complications, etc.) seem to be more prone to it, though not sure why at the time of the study. Since progesterone and estrogen are the key players, it would make sense that some will be more apt to develop abnormalities leading to infection than others, just as some women have hormonal difficulties all their lives and some never do.  It also seemed that bitches who were bred less often were more prone to it, though that doesn't seem to be a unanimous conclusion from what I can find. I, too, would suspect some sort of heritability or at least heritability of some trait leading to increased incidence of it. As with anything else, trying to keep the overall health of the dog as strong as possible including the immune system would seem to be beneficial and provide at least some protection, at least through middle age. I'm sure this becomes more difficult in advanced age. The median age among Beagles, I think it was, was over 9 years old. So, a conservative approach that would still allow for maximum ovarian exposure over their lifetime (increasing longevity in many breeds) would be to spay around age 8-9??? 

Something I've considered w/Pri is a partial spay. I would never deprive her of all her hormones, but when she is older, removing just her uterus might be something I would consider. It would depend on the circumstances in my home at the time. At the very least, my poor Pit Bull would be allowed more freedom when she is in season! And that randy Chihuahua, too.