Mortality. Prognosis. The disease is very fatal to both pigeons and chickens, 50, 70 or even 100 per cent. perishing when a flock is attacked for the first time. In flocks that have previously suffered, on the other hand, a large number are practically immune, and even if they contract the disease it assumes a mild form, and they survive but may retain the germ and continue to communicate it to others. Even the young of such immune flocks suffer less severely, coming as they probably do from less susceptible and therefore surviving birds, or having already perhaps contracted a mild (non-fatal) type of the disease from their parents.
Differential Diagnosis. From psorospermosis (coccidiosis) it is distinguished by its origin on the mucous membranes, and not on the skin, the skin lesion being a secondary one. In psorospermosis the primary lesion is usually on the skin, from which it extends to the mouth and especially along its floor. In psorospermosis the morbid deposit assumes the form of rounded warty-like masses, on comb or wattles; is easily propagated by inoculation, is promptly checked by antiseptics, does not tend to produce internal extension nor generalization, and on microscopic examination shows numerous spheroidal coccidia intermingled with the epidermic cells and possessing amœboid movement. By virtue of this automatic movement they make their way between and into the epidermic cells in which they multiply.
From the croupous angina of Rivolta it is distinguished by the absence of the infusoria (monocercomonas gallinæ) to which he, Delprato and Pfeiffer attributed that affection. The monocercomonas is a flagellate organism 14 μ to 25 μ in length and 5 μ to 7 μ in breadth. Its rounded end bears one flagellum as long as the body, and its acute end three flagella which give it active motions. These are found in the yellowish white swellings of the mucosa, which vary in size from a millet seed to a pea, covering a hyperæmic spot and composed of epithelial cells, blood globules—white and red,—leucocytes, granules and the infusoria. The false membrane is remarkable for its lack of consistency and its tendency to invade the mouth and gullet rather than the air passages. These infusoria are not colored by picrocarminate of ammonia, but stain by methyl-violet and then appear as round or slightly irregular hyaline bodies.
From aspergillus disease of pigeons, by the absence of the characteristic, miliary, white nodule of that disease showing caseated contents intermixed with an abundant mycelium of aspergillus fumigatus. The aspergillus disease attacks especially the mouth but may also implicate the gullet, lungs, liver, intestine and kidneys. The microscopic examination of the exudate is conclusive, by reason of the presence of the bacillus diphtheriæ columbarum, and the comparative absence of the filamentous mycelium.
Treatment. This is mainly prophylactic. The first step must be to separate the sick and healthy, destroying the former, or shutting them up in a special enclosure apart from all other birds. In the case of valuable chickens, their eggs may be set under other hens and the young raised apart from the suspected flock. This may even be attempted in pigeons, the common eggs being removed and the valuable ones put in their place under a healthy sitting dove. In the case of pigeons that have been recently through the disease they should be kept strictly by themselves, even though they may appear to have regained perfect health. The dead bodies must be burned or deeply buried. Sparrows and even rabbits dying in the vicinity must be similarly disposed of, and where the disease prevails sparrows and small birds may be exterminated as probable bearers of infection.
The purchase of strange birds must be carefully guarded, none being taken that show weeping eyes, nasal discharge, labored or wheezing breathing, and all new birds should be placed by themselves in quarantine for ten to fifteen days. Finally a thorough disinfection of the place where the sick have been is of first importance. Thorough cleaning of the poultry house, followed by a coat of white-wash, every gallon of which contains four ounces of chloride of lime, or one drachm of mercuric chloride will usually prove effective. The poultry runs should be liberally sprinkled with a solution of sulphuric or hydrochloric acid, one part to 1000. The same may be used on the building, which may further be fumigated by burning sulphur.
Poultry shows should be kept under the most rigorous sanitary supervision.
Curative treatment is only profitable in the case of specially valuable birds, and even then only, as a rule, when the disease is confined to the nose, mouth, larynx and pharynx. The affected parts may be brushed with a solution of chloride of iron (1 dr. of the tincture to 1 oz. water), nitrate of silver (2 grs. to 1 oz. water), sulphide of calcium (½ dr. to 1 oz. water), tannin (10 grs. to 1 oz.). Tincture of iodine may be applied direct, or a solution of carbolic acid or of creosote or creolin (1 part to 50) will often succeed. Thomassen recommends the removal of the false membranes and the application of boric acid followed by dry sulphur. Benoist says the majority recover when made to inhale the fumes of oil of turpentine evaporated at a gentle heat twice a day.
As internal medication, or to correct the intestinal affection, sulphate of iron may be dissolved in the drinking water, or salicylic acid may be given in pill form with molasses.