E-Coli can be a harmless resident of the gut and yet is also capable of causing serious illnesses. The majority of E-Coli strains reside permanently and usually harmlessly in the pigeon's intestinal system. At times, the E-Coli can grow wildly, leading to illness. This wild growth may be the result of over-crowding, nest area being dirty with droppings, humidity and lack of vitamins (especially vitamin A). The greatest danger is infection within the eggs or when the young is a few days old. The slightly older pigeons may suffer severe inflammation of spleen and of the liver and a large proportion may die. Symptoms may include loss of appetite, ruffled up feathers, drinking large amounts of water, vomiting and "going light". It is difficult to diagnose based on symptoms only, as E-Coli may also, like Paratyphoid, attack the joints and cause swollen joints, limpness, one or both wings drooping, etc. E-Coli can lead to infertility in males and infection of the ovaries, which may cause embryos to die (called "black eggs"). Young may be more severely affected and a higher proportion will become ill. Diarrhea is very common and treatment should include electrolytes to replace the lost fluids. All antibiotic treatments should be followed by pro-biotics. Drinking water should NOT be alkaline and these conditions are produced by the use of lime and disinfectants with substances like bleach. Wash or sprinkle a clean, dry surface with water containing apple cider vinegar which will create an acidic environment which resists E-Coli. The long-term use of pro-biotics will greatly contribute to the prevention of damage caused by E-Coli.