They gave 6 people with chronic IBD a drink with eggs from intestinal worms that don't normally affect people. Five went into complete remission. A larger study is planned. It also makes me wonder about the effect of monthly worming our dogs. Stress is important, whether it is environmental, psychological or physiological.
Pregnancy is a stress, as is lactation.
Reproductive abnormalities may point to an underlying autoimmune problem or prime the dog's immune system so that it is more susceptible to other stresses. The same is true of many diseases - viral diseases, lymphoma and bone marrow problems as well as failure of immunity seem to be particularly dangerous, however. Food can also be a source of chemicals which have been implicated in the acquisition of autoimmune disease. Processing resulting in the loss of protective agents from the diet as well, may also be a contributing factor. Running a complete thyroid panel every year or two on all dogs used for breeding is at present still our best defense.