222 REVIEW — TROPICAL MKniCTNE, ETC. 



Veterinary insects, especially mosquitoes. This view certainly receives some support, from the 



Diseases— following facts associated with the disease. Horse-sickness is mostly contracted after 



coiitliiKcd sunset, when insects begin to fly and become troublesome, the disease may travel from 



the low veldt to the high veldt in certain rainy seasons which are favourable for the 



breeding of insects; further, stable-kept horses are less likely to be infected than others; 



and, lastly, the disease tends to disappear suddenly, as a rule, after the first frosts. 



Theiler' elucidated an interesting fact, namely, that horse-sickness can be transmitted 

 to dogs and that the virus can be transmitted from dog to dog. The post mortem lesions 

 found in dogs are identical with those in the hoi'se. Some difficulty was experienced in 

 explaining the fact that horse-sickness may be contracted in parts of the veldt where an 

 equine had not been for some years, but in view of the fact that other animals besides 

 equines can suffer, this difficulty has now been overcome. 



Theiler and Simpson undertook a series of experiments with mosquitoes, Gnlex, 

 Sfetjomyia and Anopheles, in order to see whether they would act as hosts for the horse- 

 sickness virus. The experiments, unfortunately, were not a success, as the stable atmosphere 

 was inimical to the well-being of the mosquito. This observation is of interest, as it is 

 quite in accordance with the theory of the transmission of horse-sickness by mosquitoes. 

 Stable horses do not as a rule contract the disease. 



It still, however, remains to be proved whether the mosquito is the host of horse- 

 sickness, and, if so, to discover the particular species. 



The question of the identity of horse-sickness with heart-water, a view brought forward 

 by Edington, was disproved by Theiler in a series of experiments on goats and 

 horses. Theiler conducted some further experiments with the immunisation of mules 

 against horse-sickness, and found that the previous method of injecting the virus into the 

 jugular vein can be abolished with safety and replaced by a subcutaneous injection, 

 and that mules whilst undergoing horse-sickness reaction need not necessarily be stabled. 

 There was no difference in the character of the reaction between stabled and non-stabled 

 mules. 



Watkins Pitchford,-' in an interesting monograph on observations on the morbid 

 anatomy of South African horse-sickness, concludes that the cause of death in horse- 

 sickness is due to capillary embolism or its results, the emboli consisting of certain cells and 

 masses of semi-crystalline pigmented material in great abundance. 



He found that the medullary cavity of the thigh bones, and also sometimes of 

 the arm bones, contain these cells and pigmented material in great abundance. The 

 overgrowth of red marrow is probably the primary lesion of the disease. Further, 

 he considers that the disease horse-sickness belongs to an entirely new class, to which 

 some such name as critical myelaemic or myelocytic embolism might appropriately be given. 



Horse-sickness occurs in the Sudan and has caused loss amongst cavalry horses at 

 Shendi. I recall an epidemic in Kordofan. 



Epizootic Lymphangitis is a virulent inoculable disease which is characterised by 

 suppuration of the superficial lymphatic vessels, and is due to a specific organism. Owing 

 to the scanty amount of literature relating to this disease, the references to it have been 

 chiefly taken from a monograph on the subject by Pallin.'' 



This disease occurs in horses, mules and cattle, and is caused by a cryplococcus which is 

 present in the morbid tissues and products, partly free in the plasma and partly enclosed in 

 pus corpuscles, phagocytosis being marked. It is slightly ovoid, with one extremity pointed 

 and the other rounded. It measures about 3-4 ^u in diameter, and is characterised 

 by having a clearly-defined contour with a refractile double outline. Tokishige, in 

 Japan, places it in the class of Saccharomyces. 



Theiler* describes it as a Saccharomyces farciminosus, belonging to the group of yeast 

 fungi. There is often a small strongly refringent nucleus seen in the transparent cell body, 

 which is frequently active, moving from pole to pole of the yeast cell. It is stained with 

 difficulty, but can be coloured by the Gram-Weigert-Kuhne method or by the modification of 

 Gram's method as used by Claudius. Ziehl's Solution of carbol fuchsine, composed of 



Theiler, A. (1905-6), Report of Government Veterinary Bacteriologist, Transvaal Dept. of Agriculture. 

 Watkinf Pitchford, E. (1904), "Observations on the Morbid Anatomy of South African Horse-Sickness." 

 Pallin, W.A., "Epizootic Lymphangitis." 

 Theiler, A., " Epizootic Lymphangitis." Transvaal Department of Agriculture, Bulletin No, 4, 190G. 



