1 Wilkinson, Jour. of Roy. Agr. Soc., No. 50.
But while the essential cause of glanders is the specific bacillus, an individual susceptibility is no less requisite to an attack. This may be innate or acquired. As we have seen, it varies according to the genus, being greatest in the solipede. But many solipedes show a strong power of resistance. Of 138 horses similarly exposed by cohabitation with glandered horses, but 29 (21 per cent.) suffered. Of 28 inoculated with glanders virus, but 9 (32 per cent.) succumbed (Lamirault, Bagge, Tscherning). The accessory causes which predispose the system to the reception of glanders may be included under one general term—low condition and ill health. Three of these causes, however, deserve especial mention: 1st. Impure and rebreathed air. Prior to 1836 the yearly losses per 1000 of the French army horses were from 180 to 197. At the date named the ventilation of the stables was greatly improved, and the mortality fell to 68 per 1000 per annum, one-half from glanders. Later improvements have reduced the 34 cases to 2. During the Italian War, in 1859, 10,000 of these horses were kept for nine months in open sheds, with but one case of glanders.2 In the expedition to Quibéron during the Napoleonic wars, a cavalry contingent, believed to be healthy, shipped on new transports, encountered a storm, and had the hatches fastened down, so that several horses were suffocated. Among the survivors, landed at Southampton and placed in stables hitherto unchallenged, many soon developed glanders in its worst form. Similar results followed the English expeditions to Varna in 1854, and that to Abyssinia in 1867. In badly-ventilated mines and stables, especially cellar stables, glanders, once started, is always most virulent.
2 Larrey, Hyg. des Hop. Mil., 1862, p. 63.
2d. Cold, damp, draughty stables greatly favor the progress of glanders. Leblanc reports the case of a stud of 240 horses that had had no glanders for eight years, but which lost half their number in three months after removal into a new stable, very lofty, but dark and damp, and subject to cold draughts. It is worthy of notice that they had also been subjected to double work, and were consequently emaciated, but there was not known to be any unusual exposure to contagion. In a Boston street-car stable, where glanders had long prevailed, Thayer cut it short by destroying the infected animals and by improving the ventilation by windows hung at the bottom and opening inward, so that the air entered in an upward direction, and cold draughts on the horses were avoided.
3d. Debility from ill-health, low feeding, or overwork.—The nervous and nutritive debility consequent on chronic disease, overwork, and exhaustion lessens the power of resistance to specific poisons, but in such circumstances there is always the added predisposition of an excess of waste material in the blood, a specially abundant food for the disease-germ. So notorious is this that it used to be held that the specific poison of glanders was generated in connection with the excess of creatine, creatinine, and lactic acid resulting from muscular action. Of the effect of low diet we have a striking example, furnished by Bouley, of a stud of 120 horses, 60 of which were attacked within a year after they had been placed on a food insufficient to repair the body-waste, and from which the disease disappeared after the slaughter of the infected and improvement of the ration. So long as glandered horses were preserved for work, the then nearly ubiquitous germ attacked nearly all that were run down by chronic diseases; hence glanders was looked upon as the natural winding up of exhausting diseases in the horse, as tuberculosis was thought to be in the human subject. Modern discovery shows that without the germ all such debilitating causes are impotent, but it can never disprove the great potency of these in laying the system open to attack, nor the value of vigorous health and sound hygiene in fortifying the system against it.
The channel of infection manifestly varies in different cases. In direct inoculations the morbid process develops first at the point of insertion, and secondly in the nearest lymphatic glands and internal organs. When contracted in the ordinary way, the lesions are usually first seen in the posterior nasal passages, the larynx or the lungs, or in the superficial lymphatics, especially of the hind limbs. This susceptibility of the deeper portions of the air-passages seems to imply that the bacillus, borne on the air, is lodged on different parts of the respiratory mucous membrane, and first sets up the morbid process in the thinnest or most susceptible portion. That it can be thus borne on the air is shown by the experiments of Viborg and Gerlach, who separately collected the particulate elements from the exhalations of glandered horses and successfully inoculated them. That the virus is not usually carried far on the air in a virulent form is attested by the many instances in which horses have stood for months in the same stable with a glandered animal without becoming infected. That infection may also take place through the ingestion of infected matters is undoubted, as glanderous products mixed with food, or even made into balls and enclosed in paper and administered to horses in this form, have produced the disease. The virulence is said to be lost by passing through the digestive canal of man (Decroix), dog, pig, and fowl (Renault), but even to Carnivora the infection may be conveyed in the food.
While the virus is concentrated in the material of the special glanderous deposits and the discharges from these, yet no part of the body can be considered as free from the poison. Viborg, Coleman, Hering, and Chauveau have communicated the disease by transfusion of blood from a glandered horse to a healthy one; hence every vascular organ must be liable to infect. The secretions of the diseased body (tears, saliva, mucus, sweat, urine, and milk) have each been successfully inoculated, and the conveyance of the disease to the foetus in utero and to the female by coition imply that even the generative secretions are virulent. Failures to convey the disease by inoculation with the blood and secretions have often occurred, however, and they must be held as less virulent than the products of the local disease-processes.
The claims that inoculation with pus, ichor, and other irritants have produced glanders must be entirely discredited. The deposits and ulcers in the lungs and elsewhere resulting from such inoculations have been either septicæmia, mistaken for glanders in the earlier days of pathological anatomy; or the septic and other inflammations set up by these inoculations have merely served as fertile spots for the planting and growth of the glanders bacillus accidentally present, and which to a healthy system might have proved harmless.
In 1882, Chauveau had demonstrated the particulate nature of the glander germ by his unsuccessful inoculations with the liquids filtered from dilutions of pus taken from a pulmonary glanderous ulcer. The filtrate and the liquid mixture formed by mixing the pus with five hundred times its own weight of water retained their virulence undiminished. In 1868, Christol and Kiener discovered in glanderous products a bacillus which they figured as made up of a chain of nearly globular elements apparently enclosed in a common sheath. In 1881-82, Bouchard, Capitan, and Charrin cultivated these microphytes in a neutralized extract of meat through five successive cultures, using in each case a milligramme of the previous culture, or less than 1/1000 part of the culture-liquid. Counting that the milligramme of pus would give to each centigramme of the first culture-liquid 1,000,000,000 bacilli, it follows that the second culture would, on the principle of dilution, contain 1,000,000, the third 1000, the fourth 1, while for the fifth it was as 999 to 1 that it would receive nothing unless the germ were multiplied in the culture-liquid. Inoculation of a cat with this fifth culture, started originally from a nasal ulcer of a glandered horse, led to a fatal result in twenty-five days, with suppurating tumor of the left testicle and inguinal glands. The products of the first cat were inoculated on a second, those of the last on a third, those of the third on a guinea-pig, and those of the guinea-pig on an ass, producing in every case specific lesions of glanders, including miliary nodules and abscesses, and death respectively on the following days: 16, 7, 31, and 10.
In September, 1882, and the two succeeding months, a similar course of experiments was conducted by Schütz and Löfler at Berlin. The virulent matter used for starting the culture was procured from a pulmonary deposit and spleen of a glandered horse; the cultivation was continued through eight successive culture-fluids. One horse was successfully inoculated with the product of the eighth culture, and a second with both the fifth and eighth. The first died on the fifty-eighth day, and the second, now very weak, was sacrificed on the fifty-ninth. Both showed the most extensive lesions of glanders alike in the skin, the lymphatic glands, the pituitary and laryngeal mucous membrane, and the lungs. To demonstrate the bacillus they take a thin layer of the infecting liquid on a cover glass, dry it, stain with methyl violet, wash with dilute acetic acid, dehydrated by absolute alcohol, and clear by oil of cedar. Like other pathogenic microphytes this may be preserved for months or years if thoroughly dried, but in the moist condition it is easily destroyed by heat (133° F.; Viborg, Hofacker, Renault), chlorine, and the disinfectant chlorides and sulphites.