REPORT.

The parasite was found on the dry hard scab and on the skin where the scab had been rubbed off, and not in the sticky mucus - like exudate at the periphery of the scabs, where the slow moving psoroptes always abounds.

Not knowing the parasite, I submitted some micro-photographs of it to Mr A. D. Michael, the great authority on acarina, and he informed me it was" glyciphagus domesticus." He says, " It is found practically everywhere; it will thrive on dried fruit, cantharides, flour, or almost any dried animal and vegetable matter which is not too hard."

Being such a common parasite, it is not surprising to find it occasionally on dirty sheep; and as under a low magnification it presents many points in common with the psoroptes it is possible to mistake the one for the other. The distinguishing features between glyciphagus domesticus and the psoropt of sheep readily noted are, in the former the quicker movement, the equal size and similarity of the legs in both anterior and posterior pairs, all of which terminate with ambulacral suckers (the posterior legs of the hexapod larva terminating in a similar manner), and the long hairs which cover its Ii'dy. An examination of its mandibles will at once set any doubt which may remain at rest.

The illustrations (Plate II.) are reproduced from micro-photographs, the magnification being the same. It must be borne in mind that in any one stage the size of the parasite differs considerably, the difference being due to the number of ecdyses through which it has passed. The measurement I have given is that of the adult male. I have grown the parasite now for nearly twelve months on dried sheep skin.

DESCRIPTION OF PLATE II.

Glyciphagus domesticus x 70.

Fig.!. Hexapod larva. Fig. 2. Nympha. Fig. 3. Male. Fig. 4. Pubescent female. Fig. s. Ovigerous female with ova.

TEXAS FEVER OR REDWATER IN RHODESIA.

THE following is taken from a report by Mr Charles E. Gray, M.R.eV.S., Chief Cattle Inspector, Rhodesia, and Mr William Robertson, M.R.eV.S., Bacteriologist to the Veterinary Department, Cape Colony.

History of the disease in Rhodesia.-Although the mortality amongst stock in Rho,desia from this disease did not rise to epidemic proportions until the present season (190I-I902), localised outbreaks of Texas fever have been recorded from time to time for the past ten years, and there is no doubt that of late the gradual infection of the country generally, and of the transport

Journal of Comparative Pathology and Therapeutics. Plate II.

1\' ~

Fig . 1.

Fig. 2.

Fig. 3.

.. /" . . , .. .. j '

"J

Fig. 4.

Fig. 5.

REPORT.

routes and town lands in particular, had become so far established that all that was necessary to give the disease an impetus was the occurrence of a season which should be particularly favourable for the propagation of that tick (rhipicephalus decoloratus) which is responsible in South Africa for the dissemination of redwater infection. Given local conditions in any part of Rhodesia which might promote the mUltiplication of these pests, in whatever locality these insects might appear in excessive numbers, there an outbreak might be looked for, and in effect this is exactly what has happened during the present year.

How the infection was first established it is difficult to demonstrate conclusively, but looking back at the early records of redwater outbreaks in Rhodesia, it may be surmised that transport cattle coming from districts where the disease is endemic, like Natal and the Transkei, are probably responsible.

Ever since the occupation of Rhodesia, animals of this class, carrying in the blood the germs of the disease in its resting stage have moved and grazed along the transport roads, and as the progeny of ticks maturing upon such animals are infective, and can communicate the disease to susceptible stock, it may easily be seen how the seeds of redwater were sown widely throughout the territory. Against this theory one might argue that if such be the case, it is strange that the disease has not attracted the attention of the public before this, but it must be borne in mind that Rhodesia, unlike the proverbial happy country, has had a rather eventful history. First there was war and locusts, then came rinderpest which practically denuded the country of stock, and this was followed by a rebellion which at one time threatened to send the white settlers after the cattle. Taking these facts into consideration, and in addition to these the fact that those men to whose stock the loss from redwater could be chiefly confined were transport riders whose nomenclature of diseases of animals is generally based on the observation of the most notable appearance on post-mortem presented by the animal which is the subject thereof, it is no t difficult to see how a disease of this description might be fairly prevalent and yet pass unnoticed by the general public, so long as only one or two oxen dropped out of a span, many such cases being doubtless attributed to poison. There is no doubt that the appearance of redwater in what might be called an epidemic form was materially retarded by the ravages of rinderpest, as the absence of stock deprived the ticks of their only possible source of infection.

The view herein expressed, that the disease has existed in sporadic form almost ever since the settlement of the country, is confirmed by information furnished by Colonel Napier of Bulawayo, who has recorded an outbreak in the Hartl~y and Salisbury districts in 1891, which was undoubtedly one of redwater, describing the disease in the following terms :-

"14th April.-Colonel Napier reporting re sickness amongst cattle at Salisbury and Umtali and enquiring if there is any resemblance or even if the diseases are not synonymous. At Hartley Hills 1891 and also Salisbury. Lost five spans out of six. Appearances, hanging look, general depression, feverish look about the eyes, eats until close on death, bowels loose, some­times the reverse, .in most cases passing blood in urine, in several instances cattle mad and violent and . charging people just before death, invariably covered with ticks. Post-mortem, yellowish watery fluid under skin of abdomen, gall discoloured, liver and spleen enlarged and affected, coagulated fluid attached to diaphragm. At the time Napier was under the impression that disease resembled blackwater fever in man, and found that in removing cattle to sand veldt past Charter there were no more deaths."

After this a blank occurs in the history of redwater which is filled in by war, rinderpest, and rebellion, but the thread is again taken up directly after

REPORT.

re-stocking began in 1897, when redwater appeared at Bulawayo amongst a lot of cattle which had been subjected to pwtec.tive inoculation against rinder­pest, many of which died. From this time onward sporadic cases of redwater appeared in various parts of Rhodesia, and the Umtali district in particular acquired the reputation of being one in which the occurrence of the disease was far from uncommon. It was only in the year 1901 that the disease began to excite particular comment, and the circumstances which gave rise thereto was the shipment to Beira, at the instance of Mr Rhodes, of a cargo of cattle from New South Wales intended for re-stocking purposes.

On account of railway washaways and other unavoidable accidents, these animals were detained in Beira for between two or three weeks, and during their detention redwater, contracted while grazing upon the Beira flats, appeared amongst them. The Veterinary Staff, then called in consultation, recommended that the survivors, to the number of about 800, sho'uld be sent forward to Umtali with all possible despatch, as the death of the' whole ship­ment appeared inevitable if they remained longer at Beira, while it was hoped that a proportion might survive if shipped to the higher veldt of Umtali. This was accordingly done, but the mortality was practically unchecked by the movement of the animals, and while confined to a portion of the Umtali Commonage and an adjoining farm they melted away until but three were left alive out of the whole shipment.

The deaths of so many highly susceptible cattle within a comparatively small area did much to heighten the general infection of the town lands at Umtali, and ro pave the way for the serious epidemic which occurred there during the next season, and it is worthy of note that as the disease spread through the Australian herd it exhibited the following characteristics. First, the most susceptible animals which fell victims shortly after the disease appeared presented all the usual clinical and post·mortem appearances found in redwater, as described by Smith and Kilbourne, Hunt, Lignieres, and other writers. These animals died .at the height of the disease, and most suffered from hremoglobinuria, but as time went on, and those of the herd which possessed a higher degree of immunity ultimately fell victims to the infection, the symptoms displayed and the lesions found on post· mortem were not so distinctly characteristic of redwater, and presented deviations from the normal type, many being considered by the veterinary surgeon in attendance to be cases of gall sickness (a vague term commonly applied to any disease in South Africa where there is marked derangement of the liver). During the outbreak amongst the Australian animals they were kept rigidly confined to certain grazing grounds, none. of the local cattle being allowed to mix with them, and no particular mortality amongst animals belonging to private owners was recorded.

Almost simultaneously with the outbreak at Umtali a number of sporadic cases of redwater appeared at Salisbury, 180 miles distant, on the Town Commonage, in the Makabusi Valley, and about the same time redwater was reported ~t Charter, some sixty miles farther on, amongst stock brought from Bulawayo.

This time last 'year at Bulawayo another outbreak also occurred amongst cattle introduced from the Cape Colony by rail, in the course of which some eighty-five head perished.

This closes the record of redwater outbreaks until the appearance of the disease in what might be called its present epidemic form. This outbreak dates from about the beginning of last wet season (i.e., November), which was characterised in Umtali and Salisbury both by the appearance of ticks in abnormal numbers; and shortly after its commencement a severe outbreak of typical cases of r.edwater broke out at Salisbury, at first mainly affecting cattle recently introduced from the Cape Colony, but afterwards extending to ani-

REPORT. 37 1

mals which had been in the district for years, and which grazecl in the Maka­busi Valley, where cases ,had occurred the previous season.

Somewhat earlier than the Salisbury outbreak a still more severe one began in Umtali amongst animals pastured on the commonage, and through their agency it extended along the mads to Melsetter (eighty miles) and Penhalonga (twelve miles). The line of medicinal treatment suggested by Dr Hutcheon, Chief Veterinary Surgeon, Cape Colony-the administration of calomel, quinine, carbolic acid, and linseed oil-was adopted generally throughout the district, and it was reported that at Melsetter this treatment was conspicuously successful, though only indifferent results were obtained in Salisbury. Ai time went on, what had been noticed in the outbreak amongst the Australian cattle the previous season was again observed; cases at Salisbury and Umtali which seemed to deviate considerably from the normal type began to appear, and when the attention of the public was drawn to the existence of this class of cases considerable uneasiness was manifested, many Umtali stockowners, who were unable to understand the reason of their occurrence, expressin~ an opinion that" a new disease," as they called it, had been imported from Australia.

Post-mortem appearances not placed upon record in any literature on the subject of redwater were also observed, and subsequently public agitation became so pronounced and emphatic, in spite of the repeated expressions by the Veterinary Department that the whole train of symptoms might be attri­buted to redwater infection of a severe type, that the Colonial Government, who were then approached, agreed to co-operate with the Rhodesian authorities in making a thorough investigation into the whole matter.

Clinical Symptoms.-The cases to be considered may be divided roughly into two classes, in much the same way as is done by M. Lignieres -a class of typical cases, such as were most commonly observed at the commencement of the present outbreak, and a class of atypical cases whose numbers increased as the epidemic progressed.

In a typical case of redwater, after an interval of two or three days in which the only evidence of systemic disturbance is an elevation of temperature, in many cases rising to 1060 F. or Iof F., a train of symptoms are presented, of which the following are the most characteristic.

The animal is dull and the appetite capricious, although the act of rumina­tion may be performed at intervals; in milch cattle there is a sudden falling off in the quantity of milk, while pregnant animals frequently abort. There is marked salivation and grinding of the teeth, with occasionally a slight flow of tears from the eyes, which have a somewhat glassy appearance; the bowels are generally extremely constipated, although in some cases diarrhcea is present, and when it is the discharges are dark in colour, assuming a reddish­brown tinge when dry. When made to move the animal does so unsteadily, the hind quarters swaying as if it had not complete control of its limbs, the swaying being most noticeable when the animal is turned sharply round. As the disease progresses the animal becomes greatly depressed, refuses all food, is disinclined to move, salivation is profuse, tremors of the muscles of the shoulders and flank are frequent, and the urine is often but by no means invariably discoloured, bearing at first a pinkish tinge, which later becomes red, and finally porter-coloured and highly albuminous, frothing up when voided. At this stage brain symptoms may appear, the animal charging reck­lessly at any moving object coming within range of its vision, and expiring in apparent delirium; on the other hand, the animal may die quietly without a struggle, death occurring in from five to ten days after the visible onset of the disease, or it may rally from the acute stage, the urine may clear off and become normal in colour, while the appetite remains in abeyance, and the animal die in the course of a few weeks from anremia.

37 2 REPORT.

In atypical cases the symptoms are by no means so diagnostic. In these there is in the early stage marked elevation of temperature, 106

0 F. or over, with at first comparatively little indication of systemic disturbance. The sali· vary secretion is slightly in excess. The animal continues to eat and the: bowels are practically normal, although close observation will show that the dung is frequently somewhat glazed in appearance and streaked from excess in the amount of mucus. The urine has sometimes a somewhat milky appearance at the onset, but frequently remains normal throughout the course of the disease, and the gait, although somewhat rather unsteady, is not markedly so. In cases of this class animals frequently survive the febrile stage and apparently become convalescent, but suddenly collapse and are found dead with a heap of albuminous froth exuding from the nostrils. Occasionally this preliminary stage of illness is quite overlooked and the animal is found dead, having apparently died suddenly from pulmonary effusion.

Not unfrequen~ly lung disturbance supervenes before the temperature sub­sides, nasal hremorrhages occur with discharge of bloody froth from the nostrils, and the animal manifests great distress, coughing in a manner which might lead to the supposition that lung-sickness was also present. So extreme does the difficulty of breathing become that not only does emphysema of the lungs result, but on more than one occasion there was observed extensive emphy­sema of the subcutaneous tissue, not as a post-mortem appearance, but during the life of the animal, possibly as a secondary corollary to pulmonary emphy­sema, the subcutaneous swelling crackling upon pressure like those of quarter­evil. If death does not occur at this stage, a type of broncho-pneumonia, associated with pleurisy, generally supervenes, and the animal may die from this cause, or may ultimately recover, although cases of recovery when lung complications make their appearance are extremely rare.

Instances in which no visible indisposition has been observed, and in which the animal is found dead with a frothy discharge from the nostrils are, pro­bably, cases of some standing which have passed unnoticed through the febrile stage, and collapsed subsequently, when secondary pulmonary redema sets in.

In some atypical cases the duty undertaken by the kidneys in typical cases, of excreting the blood pigment derived from the broken down blood corpuscles, seems to be undertaken by the bowels, and in such the dung becomes black and tarry in colour; and when bowel lesions are severe, extensive hremorrhage sometimes results, apparently from perforation of the walls of the internal blood vessels by an ulcerative process, enormous clots of coagulated blood being passed off in the dung, or found on post-mortem in the lumen of the intestine. The anremia induced by these bowel hremorrhages may, and often does, lead to death from exhaustion pure and simple.

Post-mortem Appearanct!s.-These vary in deta,l, but it is possible to have almost every organ of the body affected, more or less, and in general it is one set which shows the lesions in the most marked tlegree thus. The intestinal tract may be mainly involved, and the spleen and liver enormously congested. The kidney lesion is extremely constant, and the lymphatic glands are almost invariably affe~ted. Just as there are typical and atypical cases seen during life, so typical and atypical post-mortems are to be met with.

The lesions on post-mortem all tend to the impression that this is a much more severe type of the disease than the redwater met with in Cape Colony, and one lesion, viz., that in the lungs, was not met with before in anything like so marked a degree.

Typical Case.-Great pallor of subcutaneous tissues and of the visible mucous membranes. If the carcase is well nourished the fat has generally a yellowish or brownish-yellow tinge.

REPORT. 373

Spleen. Much enlarged, pulp diffiuent and soft in appearance; it has been aptly compared to black currant jam, its colour being darker than normal, and the white points or Malpighian bodies met with in a healthy organ obliterated by swelling of surrounding pulp. The organ may weigh from 10 to J SIbs. (normal weight It to 2 Ibs.).

Liver. Enlarged, more friable than normal, and of a mahogany colour on section, sometimes showing infarcts (hremcrrhagic spots) due to blocking of the fine capilla,y blood vessels with organisms, or debris and disintegrated matter, as the result of their attack.

Gall bladder. Has wall much thickened and cedematous, and frequently extravasations of blood, and even ulcers upon its internal mucous lining.

Bile. Yellowish-red, or more commonly dark dirty green in colour, con­taining inspissated particles of bile pigment and much mucus (this bile has been likened to chewed grass in appearance.)

Kidneys. Softened and friable, structure is frequently hremorrhagic, cap­sule easily stripped off, infarcts present, either recent, appearing as dark red spots on outside and in structure of organ, or of longer standing and white in colour, roughly spherical in shape, standing up from the surface of organ, and softer than surrounding kidney substance.

Intestines. Frequently congested, Peyer's patches enlarged and inflamed, sometimes covered with a yellow croupous exudate, and gut contains bile-stained mucus, crecum often affected, diffuse congestion of lining membranes, ulcers may be found at the junction of the small and large intestines (ilio crecal valve), the last part of the gut (rectum) shows congestion in striated marking on the mucous membrane.

Bladder. May contain normal urine, high co!oured ditto, or water of the colour of claret or porter, owing to the presence of broken down blood which has been passed out by the kidneys and due to the destruction of the red blood corpuscles by the piroplasma.

Stomachs First, second, and third are normal, the fourth frequently shows general congestion, reddening and thickening Df the mucous membrane, ulcers may be present at the edges of the mucous folds, and at the pyloric opening of the stomach (t:e. , the opening into the intestine), the stomach frequently contains semi· fluid food mixed with blood, and it is the presence of this lesion and the ulcers on the mucous membrane which might cause a careless or incompetent observer, or one who only saw the fourth stomach, to confound the disease with rinderpest.

The existence of any rinderpest infection complicating 'these cases has, however, been disproved by the fact that, inoculation with rinderpest serum did not modify or prevent in any way the course of the disease, nor did cattle which had been salted to rinderpest during the 1897 outbreak, which were then highly fortified with virulent rinderpest blood for serum-producing purposes, possess any special immunity during the present outbreak.

Heart. Flabby and pale, fat around base of a yellow colour, and littl~ red spots (petechire) on outer serous covering (epicardium) and under ~nner serous lining (endocardium); there may be small quantity of clear flUId m heart sac (pericardium).

Blood. Generally paler in colour than normal, and in advanced stages of the disease much diminished in quantity, and often so watery that it scarcely stains the fingers.

Lymphatic Glands. Enlarged, friable, and in many cases hremorrhagic. Atypical Case.-In addition to the post-mortem appearances given abovr,

i.e, the lesions in spleen, liver, kidney, and heart (which are generally iJresent), the respiratory tract may be the seat of the disease. The lining membrane of the nose (schneiderian membrane) is purple, dusky red, or dull blue in hue, the pharynx ditto, the trachea or wind pipe filled with a thick

374 REPORT.

froth, and the lungs filled with a clear straw-coloured exudate, and showing much emphysema, so much in some cases as to dissect out the lobules of the lung.

The lungs are heavy, darker in colour than normal, and on cutting into the substance froth and this clear fluid exudes.

A clear, straw-coloured jelly-like exudate is present around the base of the heart and enveloping the bronchial lymphatic glands, which are much enlarged, and the exudate extends some distance up the neck in the jugular furrow.

Frequently there is a similar exudate around the lower end of the ,rectum and bladder, and the mesenteric and pelvic lymphatic glands are much enlarged, hremorrhagic, and friable.

In such a case as above one frequently notes froth issuing from the 'animal 's nostrils immediately after death, preceded by a clear reddish-yellow fluid.

The two modifications of the disease are quite mixed up, and it is generally impossible, except in last stages, when an animal is sick, and even dying, to say whether the lungs are affected or not, and in a span of oxen dying from the disease half only may show lung lesions on post-mortem, or the whole lot may die and not one show anything abnormal in the respiratory apparatus. The number of animals which succumb to the disease showing lung lesions on post-mortem is estimated at from 30 to 35 per cent.

Microscopical Examination oj Blood and Tissues.-In every case of the disease subjected to microscopical examination the authors were able to demonstrate in the blood and affected tissues the presence of the caus~ l parasite of Texas fever or redwater; all the forms and stages recorded by observers have been seen, and also one form at least which appears not to have been previously observed.

In a blood film taken from an ordinary case of the disease, at least 70 per cent. of the red blood corpuscles are seen to be invaded by the parasite, in one stage or another (this invasion may reach 90 per cent.). The forms most commonly met with were the bacillary and spherical types alluded to by Professor Koch in his report upon Texas fever in Daa-es-Salem under 1897 date, in which he states :-

"With regard to the forms of the pyrosoma and the relations of both it and the full grown parasite to mild and severe Texas fever, I have come to differ­ent conclusions from American investigators. I found, namely, in the red blood corpuscles of cases which took a severe form, and rapidly proved fatal, strange forms resembling miniature staves, so that one might take them to be small bacilli. These are frequently curved, and sometimes so strongly that they form rings and in that case resemble the parasite of tropical malaria. Between such forms and the pear-shaped form of the full grown pyrosoma there are a number of intermediate stages. In the severer cases they are found in extraordinary large numbers, 80 to 90 per cent. of all red corpuscles being invaded. As far as my experience goes in quite acute cases only the first forms are met with. "

Messrs Gray and Robertson completely corroborate this statement of Pro­fessor Koch, and as far as their experience goes in very acute cases the pyrosoma form of the parasite is generally absent, and the stave or bacillary form is almost invariably present. . Out of several hundred cases in which the blood was microscopically examined, in twenty cases only was the typical double pyrOsoma (alluded to by Smith and Kilbourne) met with, and then in conjunction with the bacillary and spherical stages. The parasites appear quite as numerous in covers lips from the peripheral circulation as in smears taken from the internal organs.

Briefly the forms of the parasite met with in this epidemic may be classed as follows :-

REPORT. 375

No. 1. The. typical pyrosoma, single or double, and its modifications. (I) The willow leaf form. (2) The clove or pin forms, and (3) the form where the head of the pyrosoma is much distended, seems vacuolated" and does not take stain.

NO.2. The bacillary or rod forms; two or more of these may approxi­mate themselves in such a manner as to take the form of a ring resem· bling one of the stages in the life history of the parasite of human malaria.

NO.3. The coccus or spherical form; as many as eleven of these may occupy one red blood corpuscle (the size ranging from a pin point up t9 a spherical body occupying one third of the space of a red blood corpuscie, clear in the centre, and taking the stain at four points in the margin). A very common appearance seen in blood films is two spherical bodies in each. red blood corpuscle.

Methods of Staining.-In microscopical examination of the films from the blood and smears from the organs of affected animals, the customary methods in regard to fixing and staining were employed. The films were air dried, fixed by immersion for · two minutes in equal parts absolute alcohol and ether, dried, stained with eosin (5% in 75% alcohol), washed, counterstained in a watery solution methylene blue for fifteen minutes, dried and mounted. When a quick diagnosis was required, Loefflers methylene blue was employed. A weak solution of gentian violet stains the organisms well, but such prepara­tions fade with great rapidity. In the case of sections, eosin and counter­staining with methylene blue gave good results. Coles' stain (eosin and haematoxylin) gave very indifferent results.

Tna/ment.-At the beginning of the present epidemic medicinal treatment in not a few cases gave encouraging results, the prescription recommended by Dr Hutcheon being extensively tried and favourably reported upon in some quarters.

Calomel 1 drachm. Corbolic Acid 1 drachm. Quinine 2 drachms. Raw Linseed Oil I pint.

This is a first dose. Mix well and administer with care, the last three ingredients only to be repeated every twelve hours as long as necessary. If this treatment is to have any value, it must be commenced as soon as the animal appears sick. This drench was employed with good results in the Melsetter district at the commencement of the present redwater outbreak, but as the disease assumed a severe form, proved of no value; and when certain remedies proved of value during the present epidemic, the success was probably due more to the fact that the drenched cattle had a mild dose of infection, than to any very great efficacy in the drenching material. Liberal intra-muscular doses of acid hydro bromate of quinine in some cases seemed to answer fairly well; intravenous injections of Baccelli's mercuric chloride solution were tried,. and combinations of various other drugs, but as the veldt infection increased medicines proved utterly unavailing .

.Inoculation Experiments.-On January 6th, before the disease had excited much comment in Salisbury, steps were taken on a small scale to prepare for protective inoculation in the expectation that when the rains ceased and winter came on tick infection would then be diminished to an extent which would render inoculation practicable.

For this end, and with a view to ascertaining whether immunity could be produced by inoculation with the blood taken from the three Australian cows which had survived the disease at Umtali the previous seaSon, three calves were inoculated with blood drawn from the jugular of one of these animals, each calf receiving 5 cc. respectively. Although these three animals mani­fested no external evidence of constitutional disturbance, they experienced a

REPORT.

temperature reaction .which may be considered characteristic of redwater, their temperatures tending in an upward direction about the seventh day, reaching a maximum about the twelfth, becoming normal about the seventeenth, to rise again on the twenty-first, beginning to subside for a second time about the twenty-fifth day.

After being under observation fer over forty days and continuing in good health, with a view to testing their immunity one of them received an .injec­tion of 10 cc. subcutaneously and another 2 cc. intravenously of virulent blood taken from an animal at the height of the disease, and which displayed on subsequent post-mortem the peculiar <:edema and emphysema of the lungs to which reference has already been made, and at the same time a healthy un­protected calf was inoculated as a control with 2 cc. of the same blood given intravenously. While the immunised stock reacted, their temperature 'records displaying the same peculiarities noted upon their first inoculation with recovered blood, the reaction was not so marked as that of the control, which however, showed no external symptoms of illness in spite of his high tem ­perature. When it was found that no ill effect resulted from a primary inoculation of virulent blood, with a view to hastening the process of calf immunisation, as the winter was approaching when it was hoped to begin general inoculation, a series of calves were inoculated with doses of virulent blood varying from 2 to 25 cc., and none of these calves succumbed, nor were any noteable signs of indisposition displayed by any of them, as they were kept in a kraal to protect them from ticks, and stall Jed; although aU gave a characteristic reaction, while calves in infected herds, exposed to natural infection, in many cases died off with almost the same rapidity as adult cattle.

About this time experimental inoculation with glycerinated bile, injected subcutaneously and intravenously, in doses varying from 20 to 60 cc~ taken from animals dying of the disease, preserved by adding two parts of bile to one of glycerine, was tried extensively in the U mtali and Penhalonga Districts, and at first the result appeared so satisfactory that public confidence in the methoa seemed warranted. In herds in which the disease had appeared and which were subjected to bile inoculation, the disease ceased for four or five weeks ; such herds, while kept under close observation remained healthy and were pointed out by their owners as evidence that bile inoculation had come to stay. Unfortunately, however, as subsequent developments showed, the apparent arrest of the disease in these cases was not due to the protec­tive influence of glycerinated bile, but merely to the fact that the supply of pathogenic ticks having been exhausted by the cattle which succumbed at the first outbreak, a considerable interval varying with climatic conditions had to elapse before the progeny of the first brood of disease-producing ticks were hatched out and took part in the dissemination of the disease.

That this is the true explanation of the phenomenon observed in the case of bile-inoculated herds there is no reason to doubt, as the disease exhibited similar characteristics in herds on the margin of the invaded area which were not inoculated in any way, and both in bile inoculated herds and uninoculated herds the disease subsequently reappeared and finally cleaned them out.

Returning to the account of the work conducted in Salisbury, while the series of calves,were reacting to the inoculation with virulent blood which has been referred to, the disease extended with great rapidity in the Salisbury district, its extension being facilitated by the movements of hitherto unin­fected cattle which were taken through the highly infected commonage on their journey to and between the town and the comparatively clean farms outside. .

The state of affairs being serious, it was decided to put protective inocula­tion to the test on a more extensive scale among-st adult cattle belonging to the Government, as a preliminary to carrying out the work still more widely

REPORT. 377

if the results justified it, although the conditions were the reverse of favour­able, as, with the exception of two days of severe frost in June, the weather remained abnormally mild, and larval ticks were abundant. The dose of recovered blood injected subcutaneously in each case was from 3 to 5 ,cc., kept fluid by the addition of 10 cc. of a 5 per cent. solution of citrate of potash to every 100 cc. of blood. The result of inoculation within the in­fected area cannot be considered to have been satisfactory, as it was found practically impossible to keep stock free from ticks while undergoing the inoculation fever, and thereby protecting them from the possibility of further infection by pathogenic ticks, consequently a large proportion of the animals succumbed to the combined effect of artificial inoculation with recovered blood and natural infection by disease-bearing ticks. Without the highly infected area more hopeful results were obtained, but even here it was found that the blood of our immunised animals having become intensified through these cattle becoming infested with virulent ticks, which were now abundant in the kraals in which they were housed, either induced such a violent reaction that fatal results followed inoculation, or the immunity which was conferred by the inoculation afforded little protection when those resisting the inoculation were brought into thoroughly infected areas' after an interval of thirty days, the interval of repose recommended in Queensland after in· oculation, and even when kept outside these areas on comparatively clean ground they gradually succumbed to secondary infection communicated by the pathogenic larval ticks hatched out from those parasites which had matured upon their neighbours that had died from inoculation. This being the case, and the number of larval ticks being on the increase with the onset of milder weather, further progress with inoculation against disease of such abnormal virulence as is displayed during this outbreak was out of the question until some arrangements can be made to protect already immunised stock, which are now beginning to break down under constant tick infection, from further attacks, and also to protect inoculated cattle from tick infection while undergoing immunisation, if such a process be at all possible at this present stage of the epidemic, which in virulence seems unique. So deadly is it that the mortality amongst calves, which generally resist redwater infection, has been extreme, animals only a few weeks old developing the disease; while Madagascar cattle, which are usually highly resistant, also die, and the seven cattle sent up here by the Natal Government to see whether animals immune to coast infection would withstand the disease only lived three weeks. Further­more, the few animals which have recovered from a first attack in many in· stances developed a second attack about three months later which terminated fatally. Hence it is apparent that if a severe natural attack only confers immunity for a comparatively short space of time, there is but little likelihood of animals being effectually protected by the mild attack which is induced by inoculation unless they can be guarded against gross tick infection.

The severity of the present outbreak may be due to anyone or to a com­bination of the undermentioned causes :-'

First.-It may arise from infection with abnormal numbers of pathogenic ticks.

Second.-The disease may have become intensified by its passage through a large number of highly susceptible animals.

Third.-It may be due to climatic influences, and may persist as a constant characteristic of Rhodesian redwater.

Of these three causes the authors are inclined to ascribe the present virulence of Rhodesian redwater to the second in the main, although it may be somewhat influenced by the first, but this is a point which will be more easily settled when the dipping tanks, now in progress of construction in various stock· raising centres, are ready.

Summary.-The Rhodesian epizootic of redwater differs from that disease

REPORT.

!n Cape Colony and from the description of the worker6 in other countries m-

I. The severity of the infection and mortality amongst infected herds.-z. The fact that young animals (sucklings) bred and run on infected veldt

contract the disease and die. 3. The fact that one attack (and sometimes a second or third) o( the

disease does not confer any lengthy immunity. 4. The severity of the post-mortem lesions. 5. The presence of lung lesions in 30 per cent. and of kidney and: lung

lesions (infarcts) in the greater proportion of cases. 6. The uncertainty of conferring immunity upon clean stock by the m~thods

of inoculation practised in the Cape Colony and America. -From the experience gained during their work with the disease in Rhodesia

and the perusal of the literature upon the subject by workers with Tex~s (ever in other countries, the authors believe that the disease has behaved as it always does when invading a fresh area, and as it did on the first invasion of the Cape Colony, Queensland, and many parts of America, i.e., assumed the form of a severe epidemic, and has developed a virulence which will probably abate at a later stage.

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