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.