Diseases of cattle, sheep, goats and swine

by G. Moussu; Jno. A. W. Dollar

Causation. The causes of lymphadenitis and of lympho-cythæmia are unknown in veterinary as in human medicine. Apparently these diseases are more common in adults than in young animals. Some regard them as infectious in character, but this can hardly be the case, as all experimental attempts to transmit the diseases have failed. It is more plausible to compare the development of these morbid conditions with that of malignant tumours, and although some doubt still exists, simple lymphadenitis may be described as an aleucæmic lymphoma or lympho-cytoma, which has gradually become generalised, spreading by way of the lymphatic channels from the gland first affected through the surrounding glandular system. Lympho-cythæmia, on the other hand, may be said to be a leucæmic lympho-cytoma, which spreads both by the blood circulation and by the lymphatic paths (spleen, hæmatopoietic glands and organs).

This view of the development of the lesions enables us to class lympho-sarcomata with lymphomata and lympho-cytomata. The malignant character and extremely rapid development of lympho-sarcomata appear due to its extending by contiguity of tissue, and simultaneously by the lymphatic paths.

This new grouping would consequently place on one side myelogenic leucæmia, also called myelo-cythæmia, which is perhaps a different morbid species. This would destroy the unity implied in Jaccoud’s theory of the lymphogenic diathesis; but for all that this method of grouping might be justified by reference to specific cellular characteristics. In myelo-cythæmia the disease appears to commence as a lympho-cythæmia, i.e., it is unaccompanied by enlargement of lymphatic glands or hypertrophy of the spleen or liver, though the blood appears leucæmic. The condition is not a leucæmia due to lymphocytes, but rather a leucæmia produced by mono- and poly-nuclear eosinophile leucocytes, i.e., leucocytes derived from the bone marrow.

The patients are carried off rapidly after persistent wasting, decline and cachexia, whilst on post-mortem examination the puriform aspect of the bone marrow is an extremely striking characteristic.

Diagnosis. There is rarely much difficulty as regards the diagnosis. The enlargement of the lymphatic glands, for instance, can readily be detected, and the only disease with which this can possibly be confounded is tubercular enlargement.

With the means at present available for diagnosing tuberculosis, such as microscopic examination of the discharge, inoculation with discharge, examination of material from the glands, injection of tuberculin, etc., the nature of the disease can always be placed beyond doubt.

In lympho-cythæmia and in myelo-cythæmia, the whitish-violet lactescent appearance of the blood is of unmistakable significance, particularly when the manifest progressive wasting of the whole system is taken into account.

Histological examination of the blood after fixation and staining will in the former cases reveal the presence of very large numbers of lymphocytes, and in the latter an absolute increase in the number of the mono- and poly-nuclear lymphocytes. It should be easy, therefore, to distinguish the two diseases, especially as other symptoms vary.

In the early stages leucæmia may be mistaken for the leucocytosis seen in infectious diseases. These forms of leucocytosis are very common in animals of the bovine species. They occur in certain forms of tuberculosis, in uterine infections, in cases of internal suppuration, in tumour of the heart, the rumen, etc., and vary in so far as one style or another of white blood corpuscle predominates. The diagnosis, therefore, necessitates that the white blood corpuscles should be counted, and whenever it is found that their variations in number are no more than between 5,000 and 15,000 per cubic millimètre, the case may be regarded as one of temporary leucocytosis.

If, on the other hand, those corpuscles number more than from 15,000 to 20,000, or, as may sometimes happen, they attain to from 200,000 to 300,000 per cubic millimètre (one white to two or three red blood corpuscles), the case is one of leucæmia, and, according to the predominance of the particular type of cell, it is a lympho-cythæmia or a myelo-cythæmia.