Chapter V: Diseases of the Blood (2)

=Nature and Symptoms of the disease.= The disease known usually as louping-ill or trembling has long been of annual and sometimes of biennial recurrence in certain parts of Great Britain. In these places sheep farmers look for the appearance about the middle of April, to its continuation during May, and to its gradual disappearance early in June. Lambs are most liable, but sheep are also quite susceptible to the disease, and in both the symptoms are the same. The disease under consideration is rendered quite distinct by certain well-known symptoms. Though these have been described in various ways, the disease can be recognised by the more or less complete paralysis of the body and limbs. Symptoms may succeed one another very rapidly, or may be spread over some length of time. The animal at first loses control over the muscles, which are seen to twitch convulsively. It may fall down and struggle on the ground, sometimes jumping up again, often to some height. Between the fits it is often seen to stand trembling. These symptoms are frequently accompanied by frothing at the mouth. Some such appearances are the usual onset to the disease, and are followed by a paralysis which usually affects the hind limbs, but may also include more or less of the body and the head and neck. The fore limbs are often similarly paralysed. The affected limb or limbs become cold to the touch. The paralysis necessarily brings the animal to the ground, though it may be able to crawl about by the aid of the unaffected legs. When the head and neck are affected the former is usually drawn to one side, and the eyes often become oblique. Excitement is greatly increased when the animal is disturbed. The symptoms, then, in a few words are more or less complete paralysis, preceded as a rule by fits and trembling.

The small number which recover present “a wry neck, stiff joint, high back, or other deformity.” During recovery swellings occur at the joints; these may be pierced with good results, giving a large discharge of pus. According to Fair, in the _Veterinarian_, Vol. VIII., “these abscesses usually appear in the neighbourhood of the joints, but sometimes above the arms, the brisket, or any neighbouring part of the body.”

While the disease is characteristically a sheep ailment, other animals are also liable. Swine fed with the carcases or blood of sheep which have succumbed to louping-ill die with every characteristic of the disease in a short time. If the carcase has been boiled this does not occur. Swine will also frequently take the malady if allowed access to the grass of affected fields. Cattle are said to take the disease, and in the North Tyne district it is said that if a cow takes louping-ill, the milk will give the illness to a calf or lamb. One or two cases of horses being attacked are also reported.

Regarding the infectious character of louping-ill, the following is very well known. Sheep bred on diseased places are not nearly so liable to the disease as sheep which have been introduced from unaffected places. Louping-ill may be introduced into a new place, but in such cases, unless the importation from affected farms be continued, the malady may disappear.

=Distribution of the disease.= In Great Britain it is confined to the North Tyne district of Northumberland and to the contiguous border counties of Scotland, extending into Kirkcudbrightshire and certain valleys of Dumfriesshire. It is rare in Berwickshire, common in the north and west of Roxburghshire and the similar hilly districts of Selkirkshire and Peeblesshire. It occurs in Ayrshire, to a slight extent in Lanarkshire, and is found in the western parts and islands of Argyleshire and Inverness-shire.

Not only is the disease very circumscribed in its distribution as a whole, but locally in the places mentioned infected and non-infected spots are pointed out. These may be quite contiguous. The flocks in the North Tyne district feed up and down the hills in limited “cuts,” and it is one of the features of the illness that certain “cuts” are very liable to it, while others, even on the same farm, are just as free. In many cases the nature of the pasture is such as to suggest to an experienced man the probability of its being subject to the disease. A dry and foggy pasture seems best suited for harbouring the cause of the malady. These infected places have remained wonderfully constant, but a peculiar feature about them is that some may be very bad for louping-ill one year, and others bad another year. Of two adjoining farms, one may be badly attacked and the other mildly, while in the following year the conditions may be reversed. Districts may present the same peculiarities. Thus, though the disease is essentially endemic, it is not absolutely constant in its recurrence. There seem to be certain circumstances capable of favouring or retarding it.

=Lesions.= The chief lesions are localised in the membranes of the brain and spinal cord, which are congested or inflamed, and contain an increased amount of cerebro-spinal fluid or a jelly-like, sometimes blood-stained exudation. Softening and hardening of the spinal cord have both been observed. Inflammation of the pleura and pericardium, with fluid or jelly-like exudation, are common; lobar congestion of the lungs, endocarditis, gastritis, and enteritis have all been described; some observers have mentioned congestion of the kidneys and liver and swelling of the spleen. Lesions of the nerve-centres are the most constant and reliable.

=Etiology.= Depressing and weakening influences of all kinds have been blamed for producing the disease, but the general consensus of opinion points in the direction of infection with microorganisms carried and introduced into the sheep’s system by the common sheep tick or “grass tick” (_Ixodes redurius_). The following remarks on, and illustrations of, this parasite are from an article by Mr. Wheeler, of Alnwick (_Veterinarian_, Vol. LXXIII., No. 867, p. 141).

=Life History of the Grass Tick.= Sheep ticks (which must not be confused with the sheep-ked, or keb, a wingless six-legged fly, universal on sheep everywhere) are allied to the spiders. They pass through four stages of existence: the egg—the six-legged larva—the eight-legged pupa—and, finally, the eight-legged adult male or female.

In each of the three stages of larva, pupa, and adult female, all species of ticks attack some “host” or animal, either beast, bird, or reptile, to which they attach themselves by the “rostrum” or beak, and become greatly distended by suction of the host’s blood. When replete they fall to the ground—if a larva or pupa, in order to undergo its metamorphosis to the next stage of its existence, and afterwards seek a fresh host; if an adult female, to lay its eggs amongst herbage. The adult male is not capable of distension by suction, though it equally attaches itself to a host.

After undergoing metamorphoses, grass ticks, with the exception of males, are light in colour, soft and lethargic, and remain concealed for some time while recovering strength before seeking a fresh host.

Professor Neumann alludes to the fact that a fresh host is sought by ticks three several times during their existence.

=The Larva.= When first hatched out from the eggs, which are supposed to be laid at the roots of coarse herbage, the young ticks are white and soft, but soon gain strength. Provided the weather is favourable, they climb up the stems, and, holding by their two posterior pairs of legs, await the passing of a host, employing their two front legs as insects use their antennæ.

In this, as in other “free living” stages of their existence, the young larvæ show great activity, attaching themselves and clinging tenaciously to any moving object. They appear to be more numerous on the rank rushes growing in damp, undrained places.

On finding a host, larvæ attach themselves by the rostrum, and remain there for about two days, by which time they are distended, black and globular. At this time they are easily detached from the host, and have lost their activity and clinging habits.

=The Pupa.= The possession of eight legs distinguishes the pupa easily from the larva. The extra pair are placed behind the others. After the metamorphosis, the pupa takes up its position on the stalks of herbage, just as the larva had done, for another chance of attachment to a host. But whereas adult grass ticks seem to confine themselves mostly to sheep, cattle, and deer, the larvæ and pupæ attach themselves very readily to various hosts, such as horses, dogs, and even human beings. After about four days the pupa is again replete with blood, black and opaque, and again drops to the ground to undergo its second and final change.

=Adults.= On reaching the adult age, both males and females again wait on herbage for a passing host. At this time, as well as after distension of the female on the host, an action which appears to be sexual intercourse freely takes place, even in confinement. On the host the females gradually distend (Fig. 202), and in the course of so doing vary much in colour and appearance. When fully replete, the female _Ixodes reduvius_ becomes globular and black. One taken in this condition on April 15th commenced to lay on May 12th, and a few others taken at the same time commenced shortly afterwards.

Grass ticks never remain on the host to undergo metamorphosis or to lay eggs. They must therefore during their cycle of existence contrive to find a fresh host no fewer than three times.

In an article published in the Transactions of the Highland and Ag. Soc. for 1902 Mr. Wheeler draws attention to the close points of resemblance between louping-ill, Texas fever, tsetse fly disease, surra, heart-water, yellow fever, and malaria.

In the article previously referred to he summarises his conclusions as follows:—

One species only of tick, _Ixodes reduvius_, commonly known as the grass tick, has been found to carry the louping-ill bacillus to the sheep. It is easily recognised by the red body of the young females, the legs, shield, etc., being dark brown.

It lays its eggs, and undergoes its metamorphoses, in coarse herbage, and after each change seeks a fresh “host” on which to distend itself to a large size by suction of blood.

In all stages grass ticks abstain from all food except when on a host, and they are endowed with extraordinary powers of fasting until a host is found.

Ticks soon die of drought where there is no good harbourage among rank vegetation.

Judging from analogy, it is probable—

That the bacillus can only be obtained from a diseased sheep, and inserted by the tick into another sheep.

That ticks convey the bacillus through their eggs to their offspring, as well as retain it through their metamorphoses.

That there is no danger in removing sheep from foul ground to cultivated lowlands, but that the disease is easily imported from one hill farm to another.

Strong and fat animals are nearly as susceptible to attack as weakly ones.

If the land is once free of disease, it can only be re-imported by diseased sheep, or ticks taken from them.

SUGGESTED MEASURES FOR PREVENTION.

Burning and cutting of long grasses, bracken, rushes, etc.

Salt and sulphur given to the sheep.

Inoculation.

Removal of all diseased sheep to a separate inclosure, where hand-picking and dipping are carefully attended to, the pasture is kept short, and damp places are drained. The sheep to be confined to this inclosure so long as the tick season lasts.

Immediate slaughter and burial of all affected sheep.

BRAXY.

[The following is a very condensed account of a paper published by C. O. Jensen on the above disease. It first appeared in English in the _Veterinarian_, Vol. LXIX., No. 825, p. 621, along with the original illustrations.]

The name Braxy is applied to a disease in some respects resembling anthrax, which appears as an epizootic, and is best known in Iceland, the Faroe Islands, and parts of Norway, though it also occurs in Scotland and Cornwall. Krabbe describes the disease as infectious, very acute in its course, and as proving fatal within a few hours of the appearance of certain characteristic swellings about the posterior parts of the body. Post-mortem reveals extensive dark purplish staining of the abomasum and distension of the digestive canal with gas, while decomposition of the cadaver occurs with excessive rapidity, the liver and kidneys undergoing softening, the skin assuming a bluish tint, the wool becoming loose, and the entire carcase giving off a most offensive stench. Krabbe states that the disease was regarded as a form of anthrax—a view, however, in which he does not coincide. Somewhat later Messrs. J. Sigurosson, S. Jönsson, and Einarsson, all natives of Iceland, and the Norwegian State Veterinary Surgeon, Ivar Nielsen, carefully described the disease, throwing considerable light both on the conditions in which it appears and on its etiology.

According to them, braxy is an acute, or even exceedingly acute, infectious disorder, which begins as a hæmorrhagic inflammation of the mucous membrane of the abomasum, is accompanied by excessive development of gas in the digestive canal, especially in the stomachs, and proves fatal in some cases by a kind of general infection, in others by a specific intoxication, or by dyspnœa due to tympanites.

Braxy commits its chief ravages during the winter months: appearing first in autumn, the cases increase as winter approaches, to diminish again in spring; in summer they are exceedingly rare. This fact explains why the disease was so long regarded as due to climatic influences. Even at the present day, when it is known to be due to a specific organism, the action of temperature, etc., must still be regarded as probably playing an important part in infection. The disease is said not to occur in mild weather; but whether or not this be true, every one is agreed that it is principally seen during frost, especially when frost is unaccompanied by snow.

From experience gained both in Iceland and Norway, the disease appears to be often localised in certain districts and fields—a fact largely accounted for when we learn that up to the present little or no attempt has been made to prevent the spread of infection from the dead bodies.

Braxy chiefly attacks young animals, and is rare in those over three years of age. Hjaltelin estimates the number of deaths in a single district during the years 1849–1854 at approximately 6,000, made up as follows:—

Yearling lambs 2,440
Two-year sheep 2,460
Three-year sheep 1,020
Animals older than three years 80

The younger animals suffer most, and in Norway Nielsen directs attention to the heavy fatalities amongst lambs.

=Symptoms.= The sheep suddenly appears ill, is dull, lies about, and cannot be induced to rise; all movement seems to give pain, and from time to time the animal groans; the posterior parts of the body become swollen, and a little froth often escapes from the mouth. The pulse varies between thirty and thirty-five per minute, and is often imperceptible in the extremities; the temperature may rise to 105° or even 108° Fahr. This condition may last some hours, and always ends with the animal’s death; sheep, which overnight had shown no signs of illness, are often found dead in the morning. The incubation period is from forty-eight to sixty hours, but ordinary cases seldom live longer than from five to eight hours after the symptoms declare themselves.

The striking post-mortem appearances, especially the hæmorrhagic inflammation of the abomasum, were early the subject of remark. This appearance is very characteristic.

If the animals are slaughtered, the most important change is found to be a purplish, dark, somewhat swollen patch in the abomasum; during the course of the disease this increases in size, and if the animal should be allowed to die of braxy the entire abomasum shows hæmorrhagic or sero-hæmorrhagic infiltration; the abomasum and the first part of the small intestine usually contain no food, but may often show a certain amount of bloody fluid. This hæmorrhagic inflammation may extend in a forward direction, implicating the other stomachs, or backward, invading the small or both small and large intestines. The other parts of the intestinal canal are congested. The pleural and peritoneal cavities contain a little serous fluid. The blood is dark in colour, but may be clotted; the spleen is at times somewhat swollen, at others normal. The liver is usually light-coloured, soft, and degenerated; occasionally this degenerative process is extremely marked, but due allowance should always be made for post-mortem change. The kidneys may appear degenerated; in many cases they are enlarged and soft, or almost fluid in consistence. The carcase decomposes very rapidly; within a short time of death the belly is distended with gas, the rectum protrudes at the anus; the skin assumes a bluish colour in places, and the wool falls out; sometimes the skin bursts, revealing the presence in the subcutaneous tissue of a sero-hæmorrhagic fluid.

Braxy is, then, a primary violent hæmorrhagic inflammation of the abomasum, with or without secondary general infection.

From careful study it seems quite certain that the Scottish “braxy” is identical with the Norwegian and Icelandic “bradsot”; it appears at the same season, and is intimately connected with climatic influences; it runs its course so rapidly that animals left healthy at night are found dead in the morning; and the pathological anatomy of braxy is the same as that of “bradsot.”

To Ivar Nielsen, of Bergen, must be ascribed the honour of elucidating the etiology of braxy. During the course of investigations, published in 1888, he found, partly in the local lesions of the intestinal track, partly in the capillaries of the internal organs, a special bacillus, easy to distinguish from that of anthrax, of which he gives the following description:

“The bacilli (_B. gastromycocis-ovis_) are oval, of a length varying from 2 to 6 micromillimètres, and a thickness of one micromillimètre. They are often in pairs, arranged in a straight line or meeting at an angle; in the former case, and especially if deeply stained, the pair may present the appearance of a single bacillus. Occasionally they form long chains. Near the centre of the bacillus, but not always centrally placed, may often be found a zone measuring more than half the total length of the bacillus, and exhibiting little or no colouration. It appears as though the stained portions gradually contracted, finally forming two deeply coloured masses at the poles of the lemon-shaped bacillus, which then somewhat resembles the bacillus of rabbit septicæmia, except that the unstained part of the braxy bacillus is larger and more rounded, appearing to be bulged out laterally. In dry preparations the bacillus is easily recognised on account of the highly refractile character of the colourless portion; but in sections careful search is often required, especially if the section be somewhat thick. Whether the colourless portion represents a spore cannot at present be said, though such appears probable. The bacillus is always found in the mucous membrane of the abomasum, and especially in the submucous and subserous connective tissue. In the other organs the bacillus may be present in considerable numbers, or, on the other hand, may be impossible to detect.”

The same bacillus has been found in the tissues of affected sheep both in Norway and in Iceland; the bacillus, when subcutaneously injected, produces a violent hæmorrhagic inflammation of the same character as one finds in the abomasum in cases of spontaneous braxy, and the local changes at the point of inoculation may, just as in spontaneous braxy, be accompanied by a general infection with degeneration of different organs, and with softening of the kidney substance.

The bacillus of braxy is anaërobic. In cultures it develops considerable quantities of gas, just as it does when inoculated into the tissues. It is closely related to the bacillus of symptomatic anthrax, which it somewhat resembles in general appearance, and of which it reminds one by its ability to produce hæmorrhagic inflammation in the muscular tissues. It is distinguished from the last named, however, by being pathogenic to swine, mice, pigeons, and poultry, which are not killed by the bacillus of symptomatic anthrax.

The bacilli of braxy, malignant œdema, symptomatic anthrax, together with Ivar Nielsen’s shortly described bacillus of whale’s septicæmia, and Thoma’s bacillus of malignant emphysema (found in extensive subcutaneous inflammation and emphysema in man), and certain others less well known, form a group of closely allied bacilli resembling one another in form, in being anaërobic, and in producing a sero-hæmorrhagic inflammation and emphysema, but differing in the manner of producing their effects.

Experience and analogy both seem to indicate that young animals occasionally suffer from mild attacks of braxy from which they recover. Such animals afterwards exhibit a well-marked immunity against the disease.

Ivar Nielsen attempted to vaccinate against braxy by a method resembling that used in black-quarter. He dried the diseased kidney tissue, and injected subcutaneously small quantities of the material thus obtained suspended in water. A slight local inflammation followed, which appeared to protect against later “spontaneous” infection. He has used this method in his own district, and states that it is also practised to some extent in Iceland. As far as one can judge—and of course a just opinion is very difficult to form—these inoculations appear of value.

The result of experiment, considered in conjunction with the good results of inoculation for black-quarter, would seem to indicate that Nielsen’s method of vaccination against braxy may yet prove of the greatest possible value, although the method will doubtless require modification in its details.

These modifications Jensen enumerates at some length.

(Mr. Dollar has been informed that Professor Hamilton and Dr. McCall have been engaged in an investigation regarding the possibility of conferring immunity against braxy, and that a Government report will be issued on the subject. Up to the present time however—April, 1905—he has not been able to obtain this report or any advance proof sheets of it.)

BILHARZIOSIS IN CATTLE AND SHEEP.

This disease is caused by the bovine blood fluke (_Schistosoma bovis_) of cattle and sheep. Synonyms: _Bilharzia bovis_; _Bilharzia crassa_; _Gynæcophorus crassus_; _Gynæcophorus bovis_; _Bilharzia hæmatobia crassa_; _Schistosomum bovis_.

=Geographical Distribution.= Egypt, Italy, Sicily, India (?).

This parasite was discovered by Sonsino (1876) in Egypt in the portal veins of the ox, and later he found it in sheep, while Grassi and Rovelli afterwards found it in about 75 per cent. of the sheep slaughtered at Catania, Sicily.

=Source of Infection.= Clinical observation and analogy point to unfiltered drinking water as the source of infection.

=Position of the Parasite.= The worms are found in the veins of the abdomen, the vena porta, vena linealis, vena renalis, and the venous plexus of the bladder and of the rectum.

=Symptoms.= The young parasites appear to do no injury; in fact, even the adult worms seem to be inoffensive in themselves. The eggs, on the other hand, armed with a sharp point, are the exciting cause of the disease. The position of the parasite in the venous system, and the consequent location of the agglomeration of eggs, determine the particular symptoms. Either the genito-urinary system is attacked, in which case hæmaturia is one of the first symptoms, or the large intestine is attacked and blood is noticed in the fæces.

If the parasites are lodged in the venous plexus of the genito-urinary system, the chief symptoms are: hæmaturia, pains in the lumbar region, the left iliac fossa, the thigh, or in the vulva, which may be spontaneous or may accompany micturition; cystitis, vesical calculus, urinary fistulæ, vaginal verminous tumours, nephritis.

The eggs accumulate in the capillaries, which they rupture; they traverse the mucosa and fall into the bladder, thus causing more or less hæmorrhage; in this way the _hæmaturia_ is established, which is often the initial symptom. At first the urine is quite bloody, but it gradually becomes clearer, and it is only at the end of micturition that muco-purulent flakes are expelled, in which numerous eggs and even embryos are found; the urine contains also epithelial cells, more or less pus, eggs, and occasionally embryos. On micturition sharp pains are felt at the base of the penis or at the gland, possibly due to the passage of eggs. The passage of eggs through the walls of the bladder gives rise to _cystitis_; blood becomes more abundant in the urine after fatigue or coitus; clots may form and cause retention of urine; chronic urethritis may develop, evidently due to the presence of the eggs. In Egypt 80 per cent. of the cases of vesical calculus in man coincide with bilharziosis; the formation of the calculi evidently results from the presence of the eggs, for the central nodule always contains one or more of these structures. Urinary fistulæ, opening on the perineum, more rarely into the rectum, occasionally form. The mucosa of the vagina, also of the uterus and bladder, becomes impregnated with calcareous salts. Nephritis develops in grave cases.

If the parasites lodge in the veins of the rectum the lesions caused are analogous to those described for the genito-urinary tract.

The heart, lungs, and liver generally remain normal.

=Pathology.= The bladder is reduced in size, while its wall is greatly thickened, due chiefly to hypertrophy of the muscularis; the mucosa is also thickened, and at certain points it is indurated by uric or calcareous deposits, but the principal lesion consists in ulcerations covered with sanious pus. Lesions analogous to those of the bladder are also observed in the lower third of the ureters, and may extend as high as the kidney; the ureter is enlarged and tortuous; the mucosa irregular; its lumen may remain nearly normal in size, but its wall becomes very thick: the flow of urine may be obstructed; in short, a veritable hydro-nephrosis obtains, which results in atrophic lesions of the kidney, and may finally end fatally.

The mesenteric lymphatic glands may hypertrophy, their substance becoming tumefied, presenting small hæmorrhagic centres, and containing eggs. The liver may contain eggs and become somewhat cirrhotic; the eggs accumulate in the branches of the portal veins, or after piercing the walls they lie in the hepatic parenchyma. The lungs may also contain eggs.

=Diagnosis.= The diagnosis may easily be made by a microscopic examination of the urine to determine the presence of the egg.

=Prognosis, etc.= The severity of the disease varies directly with the number of parasites (and hence the number of eggs) in the body. Fortunately, in the majority of cases, the number of parasites is small, though it may increase from repeated infections to 500 or more. In cases of comparatively light infection the disease is reduced to a slight chronic cystitis, with now and then exacerbations, in course of which a slight amount of blood and pus is passed in the urine. The disease may last for years without apparent increase. In the most severe cases death may occur from various causes, rupture of the bladder, ascending pyelo-nephritis, uræmia, albuminuria; the patient may die in marasmus, being exhausted by the dysentery or the anæmia.

Bilharziosis is accordingly not such a fatal disease as has sometimes been supposed.

HEAT STROKE—OVER-EXERTION.

In oxen and sheep heat stroke is rare as a primary accident, but it is frequently produced by over-exertion resulting from the combined action of the sun’s rays, heat, and fatigue due to work or travelling.

It is commonest during the hottest months of the year in oxen doing hard work or in flocks which have been travelled considerable distances. It may also be seen during cooler seasons as the result of exceptional fatigue.

The disease results from a general intoxication which reacts most markedly on the cerebro-spinal centres. It is in fact a complex intoxication resulting from failure of the natural excretory organs to perform their function completely, and from excessive central heat acting on the nervous centres.

Fat animals out of condition are more readily attacked than working animals or sheep reared in the open air.

=The symptoms= are very characteristic. Oxen when attacked first of all show extremely rapid respiration and dyspnœa, announcing progressive asphyxia. They move with the nostrils dilated, the eyes prominent and injected, the mouth open and the tongue lolling out. Then all of a sudden they come to a stop beside a wall, or, if at liberty, in a ditch, and refuse to move. They may die rapidly with symptoms of asphyxia if they are forced to move until completely exhausted. In others, after a rest of several hours, the breathing becomes slower, the anxiety less and normal conditions return.

In sheep the same general signs may be seen: panting respiration, cyanosed mucous membranes and extreme anxiety, while death follows rapidly in the same way, with symptoms of asphyxia.

The =diagnosis= is extremely easy. The =prognosis= is grave.

=Treatment= consists in prompt and free bleeding to prevent pulmonary congestion. The animals should be rested in a shady, sheltered spot. They should have cool drinks and be sprinkled over the head, neck, or entire surface of the body with cold water.

To prevent such attacks, fat animals should not be moved for long distances, or during the hottest hours of the day, while difficult and prolonged exertion should be avoided.