Part 76

Butter, cheese, whey, and other dairy products have been proved virulent in different cases (Galtier, Heim, Lasar, Bang, Obermüller, Roth, Groëning, Gasperimi, Petri, Rabinowitsch). This was true for butter 120 days old, and cheese 330 days. In a number of cases Rabinowitsch found a bacillus, similar to the tubercle bacillus and producing tubercle-like lesions, but differing in its staining, morphology and culture, and she supposed that other observers had mistaken this for the tubercle bacillus. Petri, Morgenroth and Hormann, found the bacillus of Rabinowitsch in company with the real tubercle bacillus in butter, and Rabinowitsch, later, in fifteen samples of butter found the bacillus tuberculosis in two.

Bacilli coming from the mouth, bowels, or lungs, are also liable to get into the milk, through the floating dust of the stable, or from the teats, udder, tail, etc., (Gaffky).

Oleomargarine cannot be considered as free from this indictment, for though the tuberculous glands, etc., from the mesentery, may be sterilized in the preliminary heating process, yet the subsequent mixing with milk is liable to convey the infection.

The ideal course with milk, if the herds cannot be purified from tuberculosis, would be to compulsorily remove from the herd every cow that shows objective symptoms of tuberculosis, or any internal disease of the udder, and to subject all the milk of the remainder to Pasteurization at a temperature of 155° F. for twenty to thirty minutes. This, however, requires skilled and faithful management to avoid renewed contamination from the lips of the vessel which may have escaped the heat, or from hands, vessels and objects that were in contact with the milk before. The boiling temperature for fifteen minutes would be a safer resort, as requiring less careful handling, yet even this may be contaminated afterward under poor management. It has the further drawback of the boiled milk taste and the coagulation of the albumen. But the outlay for such careful sterilization will soon amount to more than will the tuberculin test.

Meat. For various reasons meat must be held less virulent than milk, but mainly because it is less frequently the seat of tubercle than the udder, and because it is usually cooked before being eaten. The muscular tissue of the ox appears to be unfavorable to colonization by the bacillus, and although the intermuscular lymph glands do not partake of this inherent resistance, yet as the glands are very frequently affected from the tissues which they drain, they necessarily partake in some degree of the comparative immunity of the muscles. This immunity is, however, far from complete, as the frequent implication of the intermuscular glands (prescapular, axillary, prefemoral, etc.), sufficiently show. Again in estimating the virulence of meat we must never forget that in the great majority of cases, in ordinary infected herds, the tubercle is still essentially local; no generalization has taken place. The muscle is vascular throughout, and in cases of generalized tuberculosis is infecting, yet a single transient escape of tubercle bacilli into the blood does not ensure permanent infection of that fluid, which can usually purify itself in six days or less (Nocard). On the contrary, when the escape of bacilli into the blood is constant, so becomes of necessity the virulence of the blood and a rapid generalization ensues. Such continuous escape may occur in actively advancing tuberculosis at any point, but it is more certain if the degenerating tubercle has opened through the walls of the vessels (capillaries), so that the infecting bacilli can pass into the blood in a continuous stream. The pus and other microbes, in complex infections, hasten this degeneration and contribute to generalization of the tubercle and emaciation. The transient infection of the blood with the pure tubercle bacillus does not, however, lead to emaciation and marasmus, and hence the frequency of high condition in spite of extensive tuberculosis.

Ostertag gives the following as indicating blood infection: “When with emaciation there is evidence of recent blood infection, enlargement of spleen and all lymph glands, miliary tubercles of the lungs, liver, spleen and kidneys.” In the absence of these indications, though there may be numerous old standing tubercles, caseated, calcified or sclerosed, he considers that there is no reason to dread infection of the blood and carcass. Even a tuberculous intermuscular gland does not, in his opinion, condemn the adjacent muscle. When vomicæ (caverns) are present in the lungs and internal organs the flesh may still be used “if embolic tubercles of different ages, indicating repeated eruptions of tubercle bacilli into the blood stream are absent from the spleen and kidneys.” This meat is, however, to be sterilized before marketing (Ostertag).

The United States Bureau of Animal Industry orders the destruction of all cases of “extensive or generalized tuberculosis;” “any disease or injury causing elevation of temperature or affecting the system of the animal to a degree which would make the flesh unfit for human food;” also “any organ or part of a carcass which is * * * affected by tuberculosis * *.”

In most countries of Europe even emaciated animals are used for food for animals or even man, provided the wasting is not too extreme. The carcass must, however, first be subjected to a temperature of 230° F. for a period of three hours. This is sold in a special market as low priced meat and labelled as such. Ordinary cooking does not always sterilize, as Martin and Woodhead, like Vilemin, found living bacilli in the centre of a cooked six-pound roast.

TREMBLING IN SHEEP. LOUPING-ILL. INFECTIVE MYELO-MENINGITIS. IXODIC TOXÆMIA.

Definition: infective, tick-borne disease, characterized by meningo-myelitis. Animals susceptible: sheep, and possibly swine (Meek, Greig-Smith) and cattle (Williams). Known in North Britain only in spring (in Skye also in autumn), on rough pasture with much brush, and wood ticks, (Ixodes ricinus, erinaceous, marginatus or other). Experimental infection. Bacteriology: Bacterium fluorescens β and γ found in exudate and infecting. Accessory causes: dried grass of previous year, brush, low condition, cold, youth. Symptoms: incubation 10 to 30 days; impaired innervation, hyperæsthesia, timidity, excitability, trembling, jerking, lack of coördination and balance, falling, convulsive struggling, jumping, rolling of eyes, stiffness, opisthotonos, paresis, paralysis of hind—later of fore limbs, apathy. Wry neck, arched back, stiff joints. Diagnosis from myelo-meningitis by its enzoötic appearance, in spring, on tick infested ground: from paralytic rabies, also by absence of that disease locally; from tetanus by its general prevalence, the absence of tonic spasm, and presence of palsy; from braxy by the lack of emphysematous swellings, and of speedy sepsis; from anthrax by usually healthy spleen and its confinement to sheep. Lesions: cerebral meningitis with encrease of subarachnoid fluid, of myelon, reddened, softened, also of other serosæ, stomach, bowels, liver and kidneys. Prevention: destroy ticks in winter by burning grass and brush, by ploughing and cropping; or fence off ½ the pasture one year and the other half next; or lime soil; or dip repeatedly in April, May and June to keep off ticks; avoid moving sheep in these months: Give liberal feeding. Mortality 10 to 20 per cent.

Definition. All infective disease of sheep, inoculated by ticks, and producing a meningo-myelitis, with drowsiness, hyperæsthesia, irritability, paresis and other nervous disorders.

Animals susceptible. This is almost exclusively a disease of sheep, yet Meek and Greig-Smith claim to have seen it in swine that have eaten the raw carcasses of louping-ill sheep, or that have ranged the tick infested pastures, and in rabbits inoculated with the microbe from the wound caused by the tick. W. Williams claims to have seen well marked cases in cattle, and heard of cases in horses and swine. He speaks, however, rather obscurely of “the tick disease” and seemingly includes in this all affections inoculated by ticks.

Geographical Distribution. This disease has been hitherto described as existing in the northern part of Great Britain only, but given the presence of the tick, and of the infection which it carries and the malady might easily be extended indefinitely. It is known to prevail in Northumberland north of the Tyne, in Kirkcudbright, Dumfries, Ayrshire, Lanark, Peebles, Roxburgh, Berwick, Argyle, Inverness, and Ross. In Berwick it is less prevalent than in the other countries named, while in the Western Isles it is not only widely spread rising on the hills 2000 feet or as high as the sheep range, but in Skye there are two distinct outbreaks, in spring and autumn respectively, apparently coinciding with the appearance of two successive generations of ticks. This may be due to the prevalence of warm winds from the Gulf Stream. Further investigation will doubtless show a much wider distribution—the author has seen an affection bearing the same general characters on the spurs of the Lammermoors in East Lothian, and the supposed adaptation of the Norse word hloupa (staggering) suggests that it is probably not unknown in Scandinavia. W. Williams notes its prevalence on the Silurian formation, but ticks confine themselves to no geologic stratum, and the tick is the main agent in carrying infection.

Causes. 1st, Sheep Ticks. The sheep tick is not the ked (Melophagus ovinus) which is common on long wooled sheep everywhere and is an example of a wingless, degraded dipterous insect.

The sheep ticks, on the other hand, are true ixodes, and of the same family with our common wood tick and of the cattle tick (boöphilus bovis) of the Southern States and the West Indies. The ticks collected from the sheep by W. Williams were identified by Mr. Moore, of the British Museum, as ixodes ricinus, ixodes erinaceous and ixodes marginatus. Those obtained by Meek and Greig-Smith showed the following characters: The male is 2.48 mm. long, by 1.30 mm. broad; the female is 5 to 5.5 mm. long, by 3 mm. broad, or when gorged with blood, 10 mm. long, by 7 mm. broad. The fasting female is yellowish green, and when full of blood, blue. Following the rule of their genus, the mature tick has eight legs, the larva but six. The fasting larva has head, legs and dorsal plate (scutellum) brown, the remainder of the body yellow. Scattered hairs appear on the body, legs and maxillæ.

In all ticks the rostrum is a characteristic feature. It consists centrally and interiorly of a dart covered below and on each side by rows of teeth turned backward, which, when imbedded in the skin, hold so firmly that the parasite may be pulled in two in any attempt to pull it out. Above this dart and on the two sides lie the cheliferæ (horns), each furnished with three or four teeth turned outwardly and more or less recurved, by which the dart is worked into the skin. Finally, on the lateral sides of this central apparatus, are the two maxillary palpi, which are not inserted into the skin, but applied against it and operate as feelers prior to and during the insertion of the dart and cheliferæ. The maxillary palpi are club-shaped and soft.

Ticks pass through three moultings before they attain to the sexually mature eight-legged form, and though the hexapod larvæ attach themselves to animals and irritate the skin by their bites, it is only the mature, impregnated egg-bearing female that lives exclusively on blood and sucks this to excess.

While given species of ticks show a preference for particular genera of animals, yet ticks generally in their vagabond life will leave the long grass and brush where they have been hatched to become temporarily the guests of any passing animal. It is, therefore, premature to seek to identify any single species of tick as the only bearer of the infection, and it is quite possible that any one of several species may contribute to its propagation.

Experimental Infection by the Tick. W. Williams muzzled four sheep from a healthy district and turned them for several hours a day on a tick-infested field, and two sickened—one on the eighth day and one on the sixteenth. Twelve ticks sent out of the district and put on a healthy sheep caused illness on the tenth day. In a second experiment with ten sheep, during a colder spring, when there were fewer ticks, no deaths occurred.

Meek and Greig-Smith turned twenty sheep on a tick-infested louping-ill pasture, six of the number wearing muzzles to prevent grazing, seven having been dressed with a mixture of sweet oil, 2 quarts; castor oil, 1 quart; train oil, 1 quart; pitch oil, 3 gills, and cade oil, 1 gill, while the remaining seven were unmuzzled and undressed. The muzzled sheep were regularly taken out and fed on food from a healthy locality. At the end of a fortnight oils were reapplied on the second lot (seven sheep). No ticks appeared on these sheep, while many were found on the undressed ones. On the fifteenth one of the unmuzzled and untreated sheep sickened and died with lesions of louping-ill. On the twenty-second day one of the muzzled sheep sickened, and died of louping-ill next morning. On the thirty-first day another of the muzzled sheep took ill and on the thirty-eighth was killed. It showed characteristic symptoms and lesions. The seven salved sheep, on which no ticks could at any time be found, remained healthy throughout.

Bacteriology. W. Williams describes a bacillus which he figures as forming filaments of very uneven breadth, with frequent branching (contrary to the habit of bacilli), and forming spores in clusters. These were obtained from the coagulum of the cerebro-spinal fluid and Meek and Greig-Smith conclude that the alleged mycelium was but the filaments of fibrin.

McFadyean found pus microbes.

Meek and Greig-Smith (Veterinarian, 1896–7) found in the black bloody swellings under the skin, where the ticks had inserted their proboscides, a variety of microbes which in pure cultures did not provoke louping-ill. These included staphylococcus cereus albus, sarcina lutea, bacterium putridum, bacterium coli commune, micrococcus sulphurous, micrococcus bicolor, and micrococcus caudicans. He also found penicillium glaucum. Two organisms allied to the bacterium fluorescens and designated as β and γ (G) respectively, were found in these sores and produced in rabbits and sheep nervous disorders and lesions which could be fairly identified with louping-ill. These are about 1.5 to 1.7μ long by 0.7μ broad, and chromogenic with a special fluorescent appearance. Microbe β inoculated on a rabbit caused on the second day rhythmic movements of the head downward and to one side, the eyelids closing as the head dropped, as if the animal were constantly falling asleep. In another rabbit it caused stiffness of the legs only and in a third it had no effect. Microbe γ when cultivated ærobically was harmless to rabbits, but when grown anærobically on mutton bouillon to which a drop of blood had been added, it caused on the second day general paralysis of the neck and limbs, spasmodic twitching of the muscles, dyspnœa and feeble heart action. Two rabbits which survived the early effects developed large axillary and inguinal abscesses four months later.

A lamb inoculated with the bouillon culture of γ showed after thirteen days, lameness of one hind limb, with paresis, and a disposition to fall to one side or the other. Two months later, when it had greatly improved, a second inoculation of microbe γ grown anærobically in bouillon and blood, caused, on the third day, a severe aggravation of the lameness.

Accessory Causes. Much depends on the abundance of old dried grasses of the previous year in which the larval ticks may hibernate. Land that has been burnt over in winter, that is cleared of brush, or in which the aftermath has been killed by free salting or liming will be largely cleared of the ticks.

Whatever disturbs or undermines the general health lays the system open to the disease and many flockmasters in tick-infested districts have succeeded in greatly reducing the mortality by feeding sound hay and oats in winter. Sudden changes of weather have long been noticed to coincide with outbreaks of the disease. A change to cold and wet is especially dangerous as causing a chill and robbing the system of its tone and vigor. But a sudden access of warm spring weather, especially if at the same time moist, may have a decidedly predisposing effect by lowering the general tone. A fatal paresis common in the flocks of New York, in the absence of ticks, shows a similar tendency to select the atonic animal. This occurs mainly in spring, when the sheep have been shut up in close confinement for weeks or months, with flaccid muscles and fatty livers, and above all if they are in advanced pregnancy with twin lambs, and if their fleeces are extra heavy. In both affections the majority of the flock escape, while those that are specially predisposed succumb. Lambs suffer most, doubtless because of relative weakness, and on account of their innate and unexhausted susceptibility.

Symptoms. After an incubation varying from ten days to thirty some impairment or disorder of the innervation is shown, varying widely, however, in different cases.

The two names “trembling” and “louping-ill” long used by shepherds as characteristic of the disease indicate spasmodic disorder of a clonic kind, the paresis which is essentially passive having been very naturally overlooked, or held to be subordinate. There is hyperthermia the temperature rising at times to 105° or higher, and often marked hyperæsthesia and excitability at the outset. On approaching the patient it is very much frightened, and when caught, struggles and twitches in a remarkable manner or trembles violently. If merely raised or disturbed the trembling or clonic spasms are very marked, the nose is jerked forward and upward from the contraction of the muscles attached to the occiput; the legs may be lifted jerkingly as in stringhalt; when raised they are moved stiffly or sway uncertainly before the foot is once more planted; or the sheep loses its balance, falls to the ground and struggles convulsively in its efforts to get up and escape. As the result, it will in certain cases jump to its feet, rising meanwhile to an undue height in the air. In other cases there is squinting or rolling of the eyes, and movements of the jaws with frothing from the mouth. Or the spasms may be tonic affecting especially the muscles of the back and loins, and causing extreme stiffness or rigidity or even opisthotonos. Lambs are unable to suck.