Flock dying of mysterious infection

[AmyThomson1]

I have a mixed breed flock, and a mysterious internal infection is killing my hens. Back in June, my 3 year old French black Marans started acting off. It soon became apparent that she was severely ill. I took her to a vet who diagnosed her with a severe abdominal infection. Her abdomen was distended and filled with fluid. Then in August my 9-1/2 yo Australorp showed similar symptoms. I took her to a vet that dealt with chickens, and he said salpingitis, gave me some antibiotics and pain meds. I did what I could for her, and the antibiotics appeared to help. But a few weeks later she was sick again, and died before I could get her to the vet. Then, while I was traveling my 3 yo red laced Wyandotte died. Now my flock is down to three pullets, one last 3 year old hen and a rooster. I don’t know what is killing them.
Any advice would be welcome.

 

[Eggcessive]

Welcome to BYC. Have you had the chickens all of their lives? Chicken can suffer from reproductive disorders, cancer, water belly, worms, crops problems, and intestinal infections among other problems. These problems may not be related at all, but a necropsy after one dies, either by your state vet or done by you, may shed some light on what killed a hen. The oldest hen may have been at the end of her days. Have they ever suffered from an unknown illness, sneezing, or respiratory issues? My hens had infectious bronchitis, which can cause reproductive disorders later on, and led to some early premature deaths in my flock.