Even though direct contagion has not been proved, it is impossible to doubt that stables may become infected. This is sufficiently proved by the continued appearance of the disease when disinfection is neglected after the occurrence of the first case.
It is possible that the causes formerly assigned—viz., chills, the influence of draughts, and a morbid predisposition—may increase susceptibility in animals otherwise well cared for, but it is quite certain that infection of the stable is an important factor.
Lesions. The lesions vary with the complications, but those shown in the beginning are always identical. The mucous membrane of the nasal cavities is congested, inflamed, sphacelated, and ulcerated at different points. The turbinated bones and the ethmoid cells may become necrotic; in the larynx the region of the glottis is always most markedly affected; the mucous membrane becomes ulcerated in the neighbourhood of the vocal cords, and the tissues may become more deeply attacked.
In the trachea and bronchi the mucous membrane undergoes desquamation, and may become ulcerated at the points where false membranes have formed. The mucous membrane of the sinuses is always affected, but is rarely ulcerated.
Such complications as capillary bronchitis, broncho-pneumonia, and gangrene of the lung may be noted.
The mucous membrane of the mouth presents a violet-red or blackish-red colour; the tongue and gums are swollen, and ulcers as large as a lentil or a halfpenny may occur either singly or in a confluent form.
The genito-urinary apparatus reveals signs of croupal cystitis, submucous effusions of blood, vaginitis with the formation of false membranes, acute pyelitis, etc.
Diagnosis. When the symptoms are fully developed the diagnosis of gangrenous coryza is extremely simple, but the absence of some of these may justify hesitation in forming an opinion. If the examination is carefully carried out, it is always possible to distinguish this disease from simple coryza, which is only accompanied by trifling fever, and in which appetite is preserved; from foot-and-mouth disease, with its very characteristic buccal eruption and absence of lesions from the upper portions of the respiratory tract; and from contagious ophthalmia.
Prognosis. Up to the present time the prognosis has always been regarded as extremely grave, the mortality being sometimes as high as from 90 to 100 per cent., and moreover the cases which recover are invariably those of what is considered the chronic form. Sudden sinking of temperature during the disease is an unfavourable sign. From 1894 to 1900 Moussu never cured a single case, whatever his method of treatment; nevertheless, it now seems possible to regard the condition a little more hopefully, provided that no incurable complication occurs before the beginning of treatment.
Treatment. Of all the modes of treatment suggested—viz., anti-febrile agents, general stimulants, purgatives, diuretics, external stimulant applications, etc.—none have succeeded. Antiseptics injected into the nasal cavities, antiseptics given internally, milk diet, and all the methods hitherto suggested are equally useless.