Pigeon fancier's lung

Antigen avoidance and respiratory protection are the mainstays of management

Pigeon racing is based on the remarkable homing instinct of pigeons, which enables them to return to their loft over distances of many hundreds of miles. British pigeon fanciers are particularly proud of their role in the second world war, when highly trained pigeons were used for communication.1 Pigeons were parachuted in small containers into occupied Europe with instructions for the finder to attach espionage messages to the birds, which were then released to fly silently and undetected back to lofts in Britain.

There are now about 83 000 registered pigeon fanciers in Britain. When racing, the birds are transported to a liberation point; a ring is placed on one leg; and, when released, the bird returns to its loft, where the ring is removed and placed in a special clock which registers the exact “timing in” of the bird. The location of each loft has been registered so that the distance travelled by each pigeon can be calculated. Racing pigeons have been bred and trained for speed and endurance. The official British duration record is 1173 miles in 15 days, and the highest race speed is 110.07 miles per hour.2 Although a typical pigeon fancier keeps pigeons as a hobby, pigeon fancying is a multimillion pound business, and top class birds have been sold for as much as £110 800.2

Pigeon fancier's lung is a form of extrinsic allergic alveolitis in which the repeated inhalation of avian antigens provokes a hypersensitivity reaction in susceptible subjects.3 4 5 The acute form manifests as recurrent episodes of breathlessness and cough, with fever, shivering, and malaise, occurring four to eight hours after exposure to antigen. Lung function tests and chest radiographs may be abnormal after exposure but usually return to normal between episodes. The chronic form is characterised by the insidious development of breathlessness and pulmonary fibrosis.4

Classification into acute and chronic forms has caused confusion by implying an inevitable progression from acute to chronic disease if the fancier continues to keep pigeons. However, the interaction of antigen exposure and host response in the initiation and progression of the disease is considerably more complex than this, and an alternate classification system has been proposed that recognises three main patterns of disease,: “acute progressive,” “acute intermittent non-progressive,” and “recurrent non-acute” disease.6

Some patients present for the first time with established lung fibrosis without having experienced acute episodes,7 whereas others continue to have intermittent acute episodes for many years without progressing to permanent lung damage.4 5 Fanciers who develop the disease have often remained in a state of equilibrium with the antigen for many years before the onset of symptoms, and in some patients established disease may regress despite continued exposure to antigen.3 5

The clinical course of the disease is unpredictable. Progressive deterioration in lung function occurs in some fanciers with continued exposure to antigen, and, rarely, the disease may progress even after contact with pigeons has ceased.8 9 The variable clinical course of the disease is reflected in current concepts of its pathogenesis, which 1 factors that modulate the basic interaction of antigen and immune response, either enhancing or suppressing the inflammatory process.10 When treating patients with the disease, doctors should realise that it is not a uniform disease but rather a complex dynamic clinical syndrome.

Ideally, treatment of extrinsic allergic alveolitis consists mainly of avoiding contact with the inciting antigen, and complete cessation of exposure to pigeons is the safest advice for patients with pigeon fancier's lung. However, this may not be necessary in all cases, and fanciers are usually highly committed to their sport.5 Under these circumstances it is reasonable to recommend a combination of respiratory protection and antigen avoidance. Respiratory protection masks have been shown to improve symptoms, to prevent a reaction to antigen challenge, and to reduce the level of circulating antibodies.11 12 The protection provided by masks is not complete, however, since most masks permit penetration of particles less than 1 μm in diameter, and leakage through defects in the fit of the mask to the face allows particles to bypass the filter. In general simple masks complying with European Standard EN149 FFP2S provide a reasonable degree of protection, but it is essential that fanciers who use masks have adequate medical follow up to ensure that there is no progression of the disease.

Sensitised fanciers should wear a loft coat and hat that are removed on leaving the pigeon loft, to avoid continuing contact with pigeon derived antigens carried on clothing or hair. Time spent in the loft should be kept to a minimum, and whenever possible the fancier should avoid activities associated with high levels of antigen exposure such as “scraping out” or cleaning the loft. Fanciers should be advised not to transport pigeons on the back seat of a car since this can result in very high levels of airborne antigen in an enclosed space. Antigen avoidance and respiratory protection should be continued at pigeon shows. When highly sensitised patients have given up pigeons completely, they will still face a risk of residual antigen exposure in their home and, more likely, continued exposure through their social circle if they remain in close contact with other pigeon fanciers. Some fanciers find it helpful to increase the level of ventilation in their loft, but Edwards et al showed that this did not reduce particle and antigen counts in the loft, possibly because air turbulence generates as many airborne particles as are eliminated to the outside by ventilation.13

Although there is often an apparent beneficial response to corticosteroids, it is difficult to distinguish between the effects of treatment, the natural course of the disease, and the effect of antigen avoidance. There have been no controlled trials of corticosteroids in patients with pigeon fancier's lung, but studies of patients with farmer's lung provide insight into their effects on extrinsic allergic alveolitis. A randomised double blind placebo controlled study of corticosteroids in 36 patients with acute farmer's lung found that the patients given prednisolone showed more rapid improvement in lung function with a significantly higher diffusing capacity at one month compared with the control group.14 However, there was no difference in long term outcome between the two groups.

Treating patients with pigeon fancier's lung requires an appreciation of both the fascination of the sport to fanciers and the complexity of the disease. Antigen avoidance and respiratory protection are the main aspects of treatment, and corticosteroids have only a small role in the long term. It may not be necessary for the fancier to give up his pigeons, but ongoing supervision of symptoms, lung function, and chest radiographs is advisable. Sequential monitoring of the level of circulating antibody to pigeon derived antigen is a useful guide to the effectiveness of avoidance measures.12