1948 Onderstepoort Journal of Veterinary Science and Animal Industry, Volume 23, 1948

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Contentes Pages: Onderstepoort Journal of Veterinary Research, Vol ??, 19??

CONTENTS

Volume 23: Numbers 1 & 2

Dr P.J. du Toit : an appreciation	De Kock, G & Robinson, EM	3

Professional staff, Onderstepoort laboratory	Anonymous	14

Section I: Protozoology

The campaign against East Coast fever in South Africa	Diesel, AM	19

Notes on serological tests carried out on equine species infected with dourine	Robinson, EM	33

Dourine infection in young equines	Robinson, EM	39

The demonstration and transmission of the South African strain of Trypanosoma equiperdum of horses	Parkin, BS	41

Transmission of the South African strain of dourine to laboratory animals	Haig, DA & Lund, AS	59

Cytauxzoon sylvicaprae gen. nov., spec. nov., a protozoon responsible for a hitherto undescribed disease in the duiker, Sylvicapra grimmia (Linne)	Neitz, WO & Thomas, AD	63

Section II: Virus Diseases

The 1944 epizootic of horsesickness in the Middle East	Alexander, RA	77

Immunological studies on bluetongue in sheep	Neitz, WO	93

The particle size of bluetongue virus as determined by ultrafiltration and ultracentrifugation	Polson, A	137

Preliminary note on the cultivation of Green's distemperoid virus in fertile hen eggs	Haig, DA	149

Section III: Bacteriology

The effect of inflammation on the survival of guinea pigs infected with anthrax	Sterne, M	157

The effect of inflammation on the development of immunity to anthrax in guinea pigs	Sterne, M	165

Bacillary white diarrhoea of poultry and its eradication in the Union of South Africa	Canham, AS	171

Section IV: Parasitology

Zoological Survey of the Union of South Africa. Tick Survey. Part I. Distribution of Amblyomma hebraeum, the Heartwater Tick	Theiler, G	217

Section V: Toxicology

Lantadene A, the active principle of Lantana camara L. Part II. Isolation of lantadene B, and the oxygen functions of lantadene A and lantadene B	Louw, PGJ	233

Section VI: Nutrition

The digestibility, for sheep, of the cellulose in a poor veld hay, as affected by supplements of a mixture of concentrates and green feed	Louw, JG & Bodenstein, SI & Quin, JI	239

On the availability of phosphorus in bonemeal, bonemeal supplemented with red oxide of iron, and bone ash to white rats	Louw, PGJ	261

Section VII: Sex Physiology

Researches into sterility of cows in South Africa. The influence of dry rations, lack of exercise, and lack of sunlight on reproduction of beef heifers and cows	Quinlan, J, Roux, LL, De Lange, M & Van Aswegen, WG	269

Section VIII: Pathology

Bioclimatological studies on white rats in South Africa. No 1. Skin cancer in rats following continued exposure to sunlight	De Kock, G & Quin, JI	349

Section IX: Physiology

Studies on the alimentary tract of Merino sheep in South Africa. XI. Digestion and synthesis of starch by ruminal bacteria	Van der Wath, JG	367

Studies on the alimentary tract of the Merino sheep in South Africa. XII. A technique for the counting of ruminal bacteria	Van der Wath, JG	385

Studies on the alimentary tract of Merino sheep in South Africa. XIV. The effect of some commonly used antifermentatives in the in vitro formation of gas in ruminal ingesta and its bearing on the pathogenesis of bloat	Clark, R	389

Studies on the alimentary tract of Merino sheep in South Africa. XV. The influence of different factors on the rate of cellulose digestion in the rumen and in ruminal ingesta as studied in vitro	Hoflund, S, Quin, JI & Clark, R	395

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Zoological Survey of the Union of South Africa. Tick Survey. Part I. Distribution of Amblyomma hebraeum, the Heartwater Tick
(Pretoria : The Government Printer, 1948) Theiler, Gertrud; Du Toit, P.J.
1. The distribution of A. hebraeum has been given in terms of political divisions as well as in terms of vegetational coverage. 2. A. hebraeum is seen to be present in the parklands and in the bushveld of the summer rainfall areas, where the bush coverage offers adequate shelter; it is absent, however, from the more arid bushveld regions even though the hush shelter would be adequate. 3. It is concluded that where farming conditions are favourable the tick could be controlled by dipping.
Bioclimatological studies on white rats in South Africa. No 1. Skin cancer in rats following continued exposure to sunlight
(Pretoria : The Government Printer, 1948) De Kock, G.; Quin, J.I.; Du Toit, P.J.
1. Skin cancer in rats (and in mice) can be produced by exposing them daily for definite periods to ultraviolet light. 2. Roffo produced identical neoplasms in rats by exposing them daily for 5 hours to sunlight. This was confirmed in the experiments at Onderstepoort, where rats were daily exposed for 4.5 hours to sunlight. In one instance a new growth developed in a rat exposed daily for only 2.5 hours. 3. So far no spontaneous skin cancer have been observed in the rats at Onderstepoort when kept under sheltered conditions but in one rat in these experiments, a fibroblastic sarcoma was found in the liver, lung, and omentum. 4. The skin cancers occurred on the hairless parts of the skin, and in the majority of rats new growths appeared in more than one place on the body. The ears were most frequently affected. 5. There was no definite occurrence of metastasis into other organs. 6. The earliest appearance of a new growth, to which attention is drawn, was ±10 months after exposure of the rats to sunlight. 7. In all the new growths a microscopical diagnosis of an epidermoid carcinoma was made. The statement by Roffo that some of these neoplasms were of the nature of sarcoma could not be confirmed at Onderstepoort. 8. The earlier lesions revealed the usual characteristics of an acanthoma associated in some cases with hyperkeratosis, while in the large actively growing neoplasms there was much evidence of anaplasia.
Researches into sterility of cows in South Africa. The influence of dry rations, lack of exercise, and lack of sunlight on reproduction of beef heifers and cows
(Pretoria : The Government Printer, 1948) Quinlan, J.; Roux, L.L.; De Lange, M.; Van Aswegen, W.G.; Du Toit, P.J.
1. The effects of a dry ration, high condition, and the restriction of sunlight, and exercise upon sexual activity and reproduction of beef females have been studied. The observations were conducted on 30 grade (mostly half-bred) Sussex-Afrikander females. The experiment was commenced when the heifers were 15 months old and its duration extended over a continuous period of approximately 13 years. A small number of the animals was eliminated soon after the commencement of the experiment, but 60 per cent. remained under observations for 9 to 13 years. The period of the experiment includes 12 calvings. 2. When a dry ration consisting of maize, wheaten bran and teff hay was fed for nine months of each year and maize silage of good quality was added during the remaining three months of each year, very satisfactory results of growth and reproduction were obtained. Beef heifers from the age of 15 months attained a satisfactory mean weight of approximately 900 lb. at maturity or when about 24 months of age. Mature animals maintained good condition on the ration and they were able to acquire considerable weight during the pregnancy periods in most cases resulting in very high condition. Sexual maturity was reached before the age of 24 mouths and sexual activity and reproduction cannot be said to have been affected adversely by the treatment. 3. High condition caused no ill-effects upon general health or the reproduction processes. 30 per cent. of the cows lived to the age of 14.4 years. The total pregnancies were 206, 191 calves were born, 15 abortions occurred. The mean calf production of all groups was 6.4 per cow. 4. The restriction of sunlight and exercise in no way detrimentally affected the health, growth and vigour of heifers and cows; being fed dry rations. There was no significant difference in the body weights of the comparative Groups A and C which attained 957.8 and 995.9 lb. at the age of 31 months respectively. The onset of maturity was not delayed. Up to the age of 31 months, or prior to being bred, a large number of dioestrous cycles were seen to have been experienced by the heifers receiving restricted sunlight and exercise. The mean number of dioestrous cycles experienced by the restricted groups was 15.5 as opposed to 12.2 in the unrestricted group. Considering all groups, the mode of the period of dioestrus was 20 days, and, although cycles as short as 10 days and as long as 123 days were experienced, approximately 75 per cent. of the dioestrous cycles fell between 18 and 23 days. It appears that as the age of the animals advanced under the treatment enforced the percentage of dioestrous cycles between 18 to 23 days decreased. Considering all groups for all periods, during which time 881 dioestrous cycles were observed, the mode was 20 days, 21.1 per cent. being of that duration. In 69.5 per cent. of cases the periodicity of oestrus was 18 to 24 days. 5. A restriction of sunlight and exercise did not affect the period between calvings. In all groups for the entire experimental period in 44.5 per cent. of cases, the period between calvings was 12 months. In the restricted exercise group in 51.1 per cent. of eases the period exceeded 12 months whereas in the group receiving exercise the equivalent figure is 50 per cent. Generally oestrus was observed to occur 15 to 21 days after calving. Although, in the majority of cases the period of absence of oestrus was in the vicinity of 60 days, many cases of over 100 days occurred and cases of even over 200 days were encountered. 6. Restricted sunlight and exercise had no effect upon conception rate. In the restricted group, 72.1 per cent. of cows were impregnated by one service, and the equivalent figure for the unrestricted group was 81.1 per cent. The percentages impregnated by 1 and 2 services is 80.9 per cent. and 90.5 per cent. respectively. Considering all groups only 5.8 per cent. required more than four services to establish pregnancy. 7. The lengths of gestation was unaffected by limiting sunlight and exercise. The mean gestation period up to the age of 6 years was 280.5 days; gestation periods during later periods or in older cows was 277.4 days, the difference being significant. 8. Unrestricted exercise and sunlight did not reflect any advantage upon the weight of calves produced. A suspicion exists that the use of different bulls during the course of the experiment influenced the birth weight of the calves during different periods. Considering all groups, few calves born weighed under the 60 lb. at birth, while weights up to 99 lb. were recorded. There is a tendency for lighter calves to be horn with advancing age of cows. 9. High-conditioned heifers, under conditions of restricted sunlight and exercise, showed no tendency towards abnormal sexual activity when breeding was delayed until the heifers were 35 months of age, that is, they calved down at 44 months of age. The reproductive functions and regularity of calving were unaffected by such delayed breeding. The disadvantage was that, over the lifetime of the cows, only 59 calves were obtained as compared to 66 in each of the groups bred six months earlier. 10. The environment enforced appears to improve the expectation of life and reproduction of beef cattle on the high veld of the Transvaal. This is, no doubt, due to protection from cold and ticks, as well as from diseases, such as contagious abortion and trichomoniasis, affecting the genital tract. 11. There is a predisposition to the development of cystic degeneration of the Graafian follicle during advancing age in cattle maintained under the environmental conditions enforced even when they are protected from genital infection by suitable hygiene.
Dr P.J. du Toit : an appreciation
(Pretoria : The Government Printer, 1948) De Kock, G.; Robinson, E.M.; Du Toit, P.J.
Retirement of Dr. P.J. du Toit as Director of Veterinary Services, Department of Agriculture, and as Dean of the Faculty of Veterinary Science, University of Pretoria, Union of South Africa.
Studies on the alimentary tract of Merino sheep in South Africa. XV. The influence of different factors on the rate of cellulose digestion in the rumen and in ruminal ingesta as studied in vitro
(Pretoria : The Government Printer, 1948) Hoflund, S.; Quin, J.I.; Clark, R.; Du Toit, P.J.
(1) The rate of cellulose digestion in ruminal ingesta was studied both in vivo and in vitro by a new technique in which cotton threads were used as test material. (2) It was found that the rate of cellulose digestion was markedly influenced by the diet. (3) The appetite for either lucerne or grass hay was directly affected by the rate of cellulose digestion. (4) On a basic diet of poor quality grass hay both cellulose digestion and appetite were stimulated by small amounts of sugar but markedly depressed by excessive amounts. More sugar could be tolerated if protein was also given. Optimal cellulose digestion necessitated a balance between readily available carbohydrate and protein. (5) Excess protein suddenly introduced after a period on a diet low in both protein and carbohydrate caused marked inhibition of cellulose digestion and inappetence. One case of sudden death was possibly associated with ammonia poisoning.
Studies on the alimentary tract of Merino sheep in South Africa. XIV. The effect of some commonly used antifermentatives in the in vitro formation of gas in ruminal ingesta and its bearing on the pathogenesis of bloat
(Pretoria : The Government Printer, 1948) Clark, R.; Du Toit, P.J.
1. It has been shown that turpentine and two proprietary coal-tar preparations have little or no inhibitory action on gas formation in ruminal ingesta incubated in vitro when added in therapeutic concentrations. 2. Very small concentrations of these substances have a marked effect on the physical consistency of the ingesta, raising surface tension and breaking down foam. 3. This affords evidence that it is by their physical action on surface tension that these drugs exert their undoubted beneficial effect in acute bloat. 4. The "foam theory" of the pathogenesis of bloat is discussed. 5. Formalin and copper sulphate may have some inhibitory action on gas formation but the use of ruminal disinfectants cannot be recommended.
Studies on the alimentary tract of the Merino sheep in South Africa. XII. A technique for the counting of ruminal bacteria
(Pretoria : The Government Printer, 1948) Van der Wath, J.G.; Du Toit, P.J.
Studies on the alimentary tract of Merino sheep in South Africa. XI. Digestion and synthesis of starch by ruminal bacteria
(Pretoria : The Government Printer, 1948) Van der Wath, J.G.; Du Toit, P.J.
1. The only diastases present in the rumen seem to be those secreted by ruminal bacteria, which would then be responsible for the entire starch disintegration seen there. 2. In the rumen of sheep receiving a regular supply of starch in the diet, the bacterial disintegration of starch granules commenced after 5 hours and was completed within 18-20 hours. In the case of sheep not receiving starch in the diet, disintegration of the starch administered through the fistula commenced after 7 hours and took 8-10 hours to complete. 3. Starch granules of the various cereals differ in size and shape. The diameter of starch granules influences their rate of disintegration within the rumen. 4. Some of the products of starch degradation are resynthesized into glycogen and starch-like polysaccharines within certain ruminal bacteria and pseudo-yeasts. 5. The iodophilic micro-organisms encountered in the rumen and associated with the disintegration and digestion of starch, are described. 6. An iodophilic streptococcus closely associated with the disintegration of starch was isolated in pure culture and some of its characteristics described.
On the availability of phosphorus in bonemeal, bonemeal supplemented with red oxide of iron, and bone ash to white rats
(Pretoria : The Government Printer, 1948) Louw, P.G.J.; Du Toit, P.J.
Two experiments have been carried out with albino rats in which the availability of phosphorus in bonemeal , bonemeal supplemented with red oxide of iron and boneash have been tested out. In the preliminary experiment the P was supplied at a level of 0.23 per cent., the Ca/P ratio being 2:1. From this experiment no significant differences between the ash percentages of the femurs of the rats and the phosphorus retentions could be shown. Low phosphorus retentions indicated that the P was supplied in excess of the minimal requirements of the animals. In the second experiment P was supplied at a level of 0.16 per cent., the Ca/P ratio being 1.87. The percentage P retentions were considerably higher than in the preliminary experiment, the average percentage retentions being 76.07, 73.36 and 71.52. Again no significant differences could be shown by applying statistical analysis to the ash percentages of the femurs and the P retentions, which implies that under the conditions of the experiment the availability to white rats of the P in the three supplements, are similar.
The digestibility, for sheep, of the cellulose in a poor veld hay, as affected by supplements of a mixture of concentrates and green feed
(Pretoria : The Government Printer, 1948) Louw, J.G.; Bodenstein, S.I.; Quin, J.I.; Du Toit, P.J.
The influence of varying amounts of a supplement consisting of starch, casein, brewers yeast and minerals, alone and in conjunction with one of green feed, on the digestibility of the cellulose in a basal ration of poor veld hay, containing only 2.2 per cent. protein, has been tested in a series of digestion trials with sheep. It is concluded that: (1) The ability of sheep to digest cellulose was impaired when kept for any length of time on the basal diet of veld hay only. (2) Daily supplements of 20, 50 or 85 grams of the concentrate mixture per sheep did not improve the digestion of the cellulose of the basal ration. Unlike the lowest one, the two higher supplements had, however, the effect of preventing deterioration of the digestive powers and appetites of the sheep. (3) The highest supplement of concentrate, 170 grams per animal per day, more than compensated for the energy deficiency of the basal ration but depressed the digestion of its cellulose. (4) Ability to digest cellulose, which had been temporarily weakened, as under (1) and (3) above, was restored by an additional supplement of green feed.
Lantadene A, the active principle of Lantana camara L. Part II. Isolation of lantadene B, and the oxygen functions of lantadene A and lantadene B
(Pretoria : The Government Printer, 1948) Louw, P.G.J.; Du Toit, P.J.
1. The active principle of Lantana camara L. has been renamed “Lantadene A”. 2. An inactive cogener of Lantadene A has been isolated and named “Lantadene B”. 3. The functions of the oxygen atoms in Lantadene A and B are discussed.
Bacillary white diarrhoea of poultry and its eradication in the Union of South Africa
(Pretoria : The Government Printer, 1948) Canham, A.S.; Du Toit, P.J.
(1) Standardization should be carried out with all strains of organisms and antigens prior to utilization for testing purposes. Single strains of organisms should be submitted to low dilution testing before use as antigens. (2) Known negative fowl serum should be used for negative control tests. (3) The water of condensation should be poured or siphoned out of flasks of growing cultures before washing off the growths for the preparation of antigen. (4) S. pullorum antigen appears to be a much more stable product than S. gallinarum antigen. Reliable results can be expected from S. pullorum antigens for at least two years after preparation, but S. gallinarum antigens over a year old should be checked prior to use for testing purposes. (5) The highest titred antigens are obtained by using single strains of S. pullorum or S. gallinarum for antigen production. (6) In most cases more positive reactors are picked out in badly infected flocks when single strain antigens are used, in preference to antigens made up of a number of strains. (7) The higher the titre of the single strain antigen the more positive reactors that are picked out, but one must be careful of so-called supersensitive strains. In a small number of cases a lower titred antigen may pick out more reactors than an antigen with a high titre. (8) To expedite the eradication of positive reactors from an infected flock it is advisable to use single strain antigens with high values. (9) The addition of small amounts of phenol has some effect in influencing the phenomena of "cloudy reactions" and flocculation in the tube test. The amount of normal NaOH solution added to antigens to prevent these two phenomena should be regulated by the pH of the antigen. Both S. pullorum and S. gallinarum antigens are made slightly more sensitive when adjusted to a pH of 8.2 to 8.5 by the addition of normal NaOH solution. The addition of the normal NaOH solution to the antigen should take place just prior to its use for testing and, bearing in mind that the density of the antigens is affected by this addition, due allowance should be made for this effect. (10) In South Africa complete agglutination in a dilution of 1:10 of a serum and antigen is regarded as indicative of a positive bacillary white diarrhoea or fowl typhoid carrier. (11) Titrations of sera of different fowls show how marked the variations are in the end points of agglutination. Marked fluctuations are shown in the positive titre of individual fowls tested over a period of time. (12) The intermittent reactor should not be regarded entirely as a fowl that produces agglutinins intermittently. Other factors such as the use of antigens of a low standard titre, and the dilution that is considered to indicate a positive reactor, must be borne in mind. (13) It does not always follow that an antigen having a high standard titre will always give a higher positive titre with any one known positive fowl serum, than an antigen of a lower standard titre. (14) There is little, if any, difference in test results when using either a S. pullorum or a S. gallinarum antigen provided the S. gallinarum antigen is only a few weeks old. Both S. pullorum or S. gallinarum antigens will pick out either bacillary white diarrhoea or fowl typhoid carriers; therefore there does not appear to be anything gained by using an antigen made up of a mixture of strains of S. pullorum and S. gallinarum (15) Differences in the positive titre, in some cases marked, will be observed when the same sample of serum is submitted to a group of S. pullorum or S. gallinarum antigens. (16) All carriers of either bacillary white diarrhoea or fowl typhoid will not be picked out by every antigen used, and therefore all positives are unlikely to be detected by one round of testing. (17) False positive reactions may be caused by the use of dirty glassware, but the more common cause is the presence of organisms, not belonging to the Salmonella group, isolated from the ovaries or from the heart blood. Most of these false positive reactions are found in the low test dilutions. Not all the organisms that set up these false positive reactions give rise to acid with lactose, and some ferment saccharose. These organisms give rise to no symptoms in the carriers, which appear to be healthy birds. (18) Young stock should be tested only after egg-laying has commenced, or at five or six months of age. Young birds from badly infected farms frequently give doubtful positive reactions to the agglutination test.
The effect of inflammation on the development of immunity to anthrax in guinea pigs
(Pretoria : The Government Printer, 1948) Sterne, Max; Du Toit, P.J.
1. An acute inflammation has the same general inhibitory effect on immunizing power that it has on the virulence of anthrax strains. 2. Irritant excipients have the same local stimulating effect on small immunizing doses of anthrax that they have on small virulent doses. 3. The apparent difference in the effect of irritants on small and on large immunizing doses of spores is because the raising of a sub-immunizing dose to a full immunizing is far more perceptible than the same order of increase of a large dose. 4. The probable advantages of using 20 per cent. NaCl solution as an excipient are pointed out. The bearing of these findings on earlier reports is discussed.
The effect of inflammation on the survival of guinea pigs infected with anthrax
(Pretoria : The Government Printer, 1948) Sterne, Max; Du Toit, P.J.
(1) The development of anthrax in guinea pigs is slowed down if an acute inflammation accompanied by an oedema is provoked elsewhere in the body. Thus the injection of saponin into a fore-limb or into the peritoneal cavity retards an anthrax inoculum in the hind-limb. Tissue destruction with inconsiderable oedema, as caused by concentrated salt solution, does not have this effect. (2) Large doses of anthrax injected into inflamed areas are retarded and often completely inhibited. However, the killing power of fractions of a lethal dose are enhanced if injected into early inflammatory, oedematous lesions, although the onset of deaths may be delayed. The effects of injecting large inocula into necrosed non-oedematous areas are neither increased nor diminished, while the killing power of small inocula is markedly increased. (3) Excipients such as saponin which cause tissue destruction accompanied by considerable oedema may slow down the development of large doses of anthrax. Small doses, fractions of a lethal dose, are, however, stimulated and their killing power greatly increased, although the onset of deaths is somewhat delayed. Excipients such as concentrated salt, which cause necrosis with little oedema, have no apparent effect on large anthrax inocula, but increase the killing power of fractions of a lethal dose, without delaying the onset of deaths. (4) The apparently anomalous action of inflammation on small and on large inocula is explained by the fact that if stimulation raises say a fifth of a lethal dose to a full lethal dose, the effect is very obvious, whereas the raising of a hundred lethal doses an equivalent amount will be virtually undetectable.
Professional staff, Onderstepoort laboratory
(Pretoria : The Government Printer, 1948) Anonymous; Du Toit, P.J.
Preliminary note on the cultivation of Green's distemperoid virus in fertile hen eggs
(Pretoria : The Government Printer, 1948) Haig, D.A.; Du Toit, P.J.
Green's distemper vaccine virus has been propagated 30 generations in developing hen eggs. Injections were made onto the chorio-allantoic membranes of eggs that had received a preliminary incubation of 8 days. Re-incubation was done at 35°C., and passage of the membranes was made at approximately 4 day intervals. The egg-adapted strain produced markedly oedematous changes with some necrosis in the membranes, but only occasionally killed the embryo. The titre of infected chorio-allantoic membranes, measured by ferret injection was between 10⁻³ and 10⁻⁵. That of the embryos and extra-enbryonic fluids of the same eggs was 10⁻³. The reactions produced by the egg-adapted strain when injected into ferrets were similar to those produced by the parent strain. Five c.c. of anti-distemper serum neutralized the egg-cultured virus. Thirteen dogs were inoculated with suspensions of chorio-allantoic membranes. In nine there was no reaction. In one there was a slight reaction, but in three the reactions were very severe and one died after showing typical distemper symptoms. The egg-adapted virus did not agglutinate chicken or guinea pig red cells and failed to infect mice when instilled intra-nasally.
The particle size of bluetongue virus as determined by ultrafiltration and ultracentrifugation
(Pretoria : The Government Printer, 1948) Polson, A.; Du Toit, P.J.
1. The particle diameter of bluetongue virus (sheep virulent and egg adapted virus) was determined by gradocol membrane filtration. 2. Details of the technique for clarifying infective emulsions by aluminium hydroxide adsorption and trypsin digestion are given. 3. The density of the egg adapted virus was calculated from data obtained from centrifugation in media of low and high specific gravity and was found to be 1.147.gm./cm.³ in strong cane sugar and 1.106 gm/cm.³ in serum albumin. 4. The particle diameter of the sheep virulent virus was determined approximately, and of the egg adapted virus accurately by centrifugation.
Immunological studies on bluetongue in sheep
(Pretoria : The Government Printer, 1948) Neitz, W.O.; Du Toit, P.J.
1. Complaints that the present method of immunization against bluetongue is not safe and that it produces an inadequate immunity have been justified. 2. A plurality of antigenically different virus strains has been established. 3. There appears to be an antigenic component common to all strains investigated and in addition an unknown number of different specific components. 4. There is a wide variation in the virulence of different strains. 5. The virus is not attenuated by serial passage through sheep. 6. The significance of these findings is discussed.
The 1944 epizootic of horsesickness in the Middle East
(Pretoria : The Government Printer, 1948) Alexander, R.A.; Du Toit, P.J.
(1) The history of horsesickness in Egypt and Palestine is traced. (2) It is believed that the 1944 epizootic was started in Egypt by the introduction of one or more infected equines into the Komombo area from the South and that it was not a recrudescence of the infection introduced the previous year. (3) The chief characteristics of the epizootic are described and figures are quoted to show the morbidity and mortality in horses, mules, and donkeys. (4) The manner in which infection was introduced in to Palestine remains obscure, and the various factors involved are discussed. The possibility that infected insect vectors were carried by aircraft, not only from Egypt, but from some other focus is discussed. (5) The great similarity but not complete identity between the Egyptian and Palestine strains of virus, as determined by in vitro and in vivo laboratory experiments, is reported. The chief point of resemblance is the similarity of antigenic structure; the chief points of difference are the period of incubation in horses and the virulence. (6) Attention is directed to the susceptibility of the donkey. (7) The general measures of control and their relative effectiveness are described. (8) Mass immunization is shown to be the only effective measure of control, and figures are given to indicate the rate of development of immunity. (9) The future of horsesickness in the Middle East and the measures necessary to prevent reinfection are discussed.
Cytauxzoon sylvicaprae gen. nov., spec. nov., a protozoon responsible for a hitherto undescribed disease in the duiker, Sylvicapra grimmia (Linne)
(Pretoria : The Government Printer, 1948) Neitz, W.O.; Thomas, A.D.; Du Toit, P.J.
1. A new genus and species of a protozoan parasite from the duiker (S. grimmia) is described. The name Cytauxzoon sylvicaprae is proposed for it and it is provisionally classed as a member of the family Theileridae, du Toit, 1918. 2. The symptomatology and the pathological changes of the disease produced by this parasite are detailed. 3. The attempt to transmit the disease to sheep was not successful. 4. The mode of transmission is unknown. 5. The importance of studying this and similar diseases in our wild animals is stressed, since valuable information may be brought to light on the life histories and the role played by such parasites in our stock diseases.

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