Cattle-men recognise the disease chiefly by the diarrhœa and loss of appetite.
Lastly, a third and rarer form occurs during which appetite is maintained in spite of the diarrhœa. The animals remain thin, develop poorly, but survive for a month, six weeks or two months. The diarrhœa diminishes or disappears, but its disappearance is followed by complications such as broncho-pneumonia, pleuro-pneumonia, endocarditis, acute arthritis, etc., a fact which led Prof. Galtier to give the disease the name of “septic pleuro-pneumonia in calves.” These complications, again, are extremely grave, and generally prove fatal after a period of varying length. They are due to local development of microorganisms of the kind which produce septicæmia, and similar to those described under the name of broncho-pneumonia of intestinal origin in sucking calves.
They differ, however, as regards their cause, from the primary affection, and may be due to very varied organisms, the commonest being those of suppuration. These organisms, in fact, are alien to the primary disease, and obtain entrance from without, very probably by the tracheobronchial tract.
In young pigs septicæmia assumes the same forms as in the calf. In lambs the chronic form seems more frequent than the peracute and the ordinary forms.
Causation. The septicæmia of calves, and possibly of all new-born animals, of whatever species, is produced by a microbe which flourishes in the manure and litter of stables, and which Nocard included in the group of Pasteurella. It can be found in the blood from the moment the first external symptoms appear until the time of death. During the last hours, however, the bacterium Coli communis also invades the circulation in many instances, and if cultures are not made until some hours after death, the colon bacillus and bacteria of putrefaction are more particularly discovered.
The microbe of calf septicæmia can be readily cultivated in jelly or in ordinary liquid media. Injected into the veins of experimental animals, it reproduces the clinical symptoms, and causes death more or less rapidly, according to the dose injected.
The virulence of cultures grown in defibrinated calf’s blood seems more intense, and Moussu has been able to reproduce the clinical form of the disease by applying to the umbilical cord of a new-born animal a pledget of cotton wool saturated with such a culture, and covering it with a dressing. The germs of the disease are spread throughout the byres through the medium of fæces. When the umbilical cord has become dry, that is, after the third day, the application of virulent cultures to the stump no longer causes infection.
Pathogeny. The pathogeny of this septicæmia of calves and of new-born animals is easy to explain.
At birth the young animals fall on the litter, and the umbilical cord becomes contaminated. The infective agent, finding an excellent culture medium in the tissues of the cord, at once begins to develop, increases in enormous numbers, steadily ascends along the cord, and sets up septicæmia. It grows in the gelatinous Wharton’s jelly and in the fibrinous plug closing the arteries and umbilical vein, and soon enters the true circulation. Septicæmia is then fully established, general disturbance sets in, and with it the diarrhœa by which it is externally indicated.
It is important to remember, however, that infection occurs most readily through the medium of the cord, and during the first few days after birth: it may occasionally be brought about towards the eighth or tenth day, when the shrivelled portion of the cord falls; in this case its entrance is effected through the little umbilical wound.