814 THE FLAGELLATA 



Trypanosoma cazalboui (Laveran) is the cause of a disease of horses and cattle 

 in the Soudan known as Souma. 



Trypanosoma pecaudi (Laveran) is the infecting agent in Balri, a disease of 

 horses and other beasts in the Soudan. 



4. Trypanosoma evansi. 



The trypanosome of Surra. 



Evans described a disease, Surra, 1 affecting horses, elephants and camels in 

 India, which is due to a trypanosome other than that which causes Nagana. 



[But since it has been shown that Mbori, a disease of dromedaries in the Sudan, 

 is caused by a species of trypanosome similar to that of Surra this latter disease can 

 now no longer be regarded as limited to India, and Laveran is of the opinion that 

 other African epizootic diseases due to trypanosomes other than T. brucei may also 

 be varieties of Surra. ] 



T. evansi on inoculation will produce an infection in rats, mice, dogs, 

 monkeys, cattle, horses, asses and mules. 



Infected horses and mules invariably die of an acute disease, but bovine 

 animals and sheep and goats often recover after suffering from a sub-acute 

 or chronic infection. Animals which recover are immune to the disease. 

 In Bos indicus (the Indian sacred bull) the immunity does not appear to last 

 more than 2 years (Wryburg). 



Morphologically, T. evansi and T. brucei are identical, though perhaps the 

 former is more slender and more motile than the latter (p. 811) and contains 

 fewer chromatin granules. 



The two parasites are however specifically different, and the diseases to 

 which they give rise cannot be regarded as identical (Laveran and Mesnil). 

 Goats hyper-immunized against Nagana are as susceptible to Surra as non- 

 immunized goats (Laveran and Mesnil), and a Brittany cow which had 

 recovered from Nagana and was hyper-immunized against that disease proved 

 as susceptible to Surra as did a normal animal of the same race (Nocard). 



It is difficult to obtain cultures. Laveran and Mesnil only succeeded once 

 in six experiments : the organism died out after the first sub-culture. 



The disease appears to be transmitted by a fly of the genus Tabanus and 

 perhaps also by a Stomoxys. [Possibly by more than one species of each of 

 these genera. In any case Surra is, like Nagana, mainly propagated by 

 biting flies (Laveran and Mesnil).] 



5. Trypanosoma equinum. 



The trypanosome of Mai de Caderas. 



Mai de Caderas 2 is a fatal disease of Equidae in South America : it is charac- 

 terized by fever, progressive wasting, profound anaemia and paralysis of the 

 hind quarters. The disease is contagious, but the channels of infection are 

 absolutely unknown, so that it is not even agreed whether biting insects 

 play any part in the spread of the disease or not. 



[Sexual intercourse does not give rise to infection as it does in the case of dourine 

 (Lignieres). The only fact upon which all observers are agreed is that the Capybara 

 (Hydrochcerus capybara) is the source from which the carrier of the disease probably 

 obtains its supply of the virus. When the farmers in Paraguay find dead Capy- 

 baras on their farms, they know that caderas will soon break out among the horses. 

 There is a striking analogy between this mortality among the Capybaras which 



1 [Surra is the word which has been used from time immemorial by the natives of certain 

 parts of India to denote a disease of horses, characterized by profound cachexia without 

 any lesion being found post mortem to account for it (Laveran and Mesnil). ] 



2 [Mai de caderas denotes disease of the hind-quarters and is so called from the paralysis 

 of that part of the body which is so characteristic a symptom of the disease. ] 



