In practice the best plan is to recommend slaughter as soon as the diagnosis becomes certain, provided that the meat can still be utilised.
PNEUMO-MYCOSIS DUE TO ASPERGILLI.
The term pneumo-mycosis, or pulmonary aspergillosis, is used to denote a condition due to the growth in the respiratory apparatus of a fungus of the order aspergillus (family, Perisporiæ; sub-order, Perisporiaceæ; order, Ascomycetes).
In ruminants, as in all other animals, pulmonary aspergillosis occurs accidentally, and may often pass unperceived, in spite of the indications given by Lucet and Bournay regarding its development and symptoms.
It seems most frequently to be caused by Aspergillus niger and Aspergillus fumigatus, particularly by the latter, which, according to Rénon’s work, also appears to be the most pathogenic. It only develops in animals whose respiratory apparatus is injured and is the seat of such lesions as those of chronic bronchitis, bronchi-ectasis, and of parasitic lesions or those containing cavernous spaces resulting from abscess formation, etc., etc.
The fungi, or more properly the spores, which have accidentally penetrated into the respiratory channels germinate and develop in the pathological dilatations, causing disseminated areas of pneumonia and some mechanical disturbance, but not producing intoxication by liberating toxins.
Causation. Infection occurs through the air passages, in consequence of the inspiratory current carrying spores of the fungi into the ramifications of the bronchi, where they develop if the soil is favourable. Development is favoured if the animals exposed to contamination are in bad condition, or if, as sometimes happens, the walls of the stables are not kept clean, and are covered with various forms of fungi.
Prolonged feeding on musty fodder may also favour respiratory infection; but it seems highly improbable that under ordinary conditions infection can occur through the digestive tract. Infection of the lung must also be regarded as exceptional, if one bears in mind the frequency with which oxen are fed on musty or mildewed fodder and the small number of accidents recorded.
Symptoms. The symptoms are obscure, and pulmonary aspergillosis is often only discovered on post-mortem examination. A cough is the chief symptom. It is dry at first. Afterwards it becomes spasmodic and frequent.
Respiration is difficult, dyspnœic, effected only with effort, and sometimes even discordant. Expiration is sighing.