Food stored in warehouses and producing plants may be eaten or contaminated and machinery & equipment fouled by their droppings. They can also transmit disease, a high proportion of feral pigeons are infected with ORNITHOSIS ( a mild form of PSITTACOSIS). Some carry SALMONELLA. Ornithosis is an acute infectious disease. The bacteria lives in the gut of the infected bird and is passed out in the faeces, eye and nasal secretions. It first appeared in pigeons in 1941. Ornithosis symptoms initially resemble those of the flu. If allowed to develop and remain untreated it can become serious leading to hospitalisation and even death in certain cases.
Fouling of buildings and monuments by nesting or roosting birds which is not only unsightly but may also have a destructive effect as the acidic droppings can erode and stain stonework. Pigeon droppings also known as guano can block gutters and drain pipes and can cause slip hazards particularly when walking on wet walkways, stairways or fire escapes.