56 



THE HEMOFIAGELLATES 



used for prophylaxis. In actual use, a 

 mixture of 3 parts of the methyl sulfate 

 and 4 of the chloride, known as Antrycide 

 prosalt, is employed. The methyl sulfate 

 eliminates any trypanosomes that might 

 be present at the time of treatment, and 

 the chloride provides the prophylaxis. The 

 prosalt is injected subcutaneously in 

 amount sufficient to give 5 mg/kg of the 

 methyl sulfate. In areas where there are 

 relatively few tsetse flies (defined as an 

 apparent density (AD) of less than 10 flies 

 caught per 10,000 yards of patrol, using a 

 standardized catching technic), treatment 

 every 2 months is effective, but under 

 heavy challenge (defined as an AD of 40 or 

 more) this protection may break down. 



Prothidium (R.D. 2801), which con- 

 tains the pyrimidine moiety of Antrycide 

 linked to a phenanthridinium instead of a 

 quinoline nucleus, was introduced in 1956 

 as a prophylactic agent. According to 

 Robson and Cawdery (1958), it is better 

 than Antcycide prosalt, a single subcutan- 

 eous dose of 4 mg/kg protecting zebus 

 naturally exposed to T. congolense, T. 

 vivax and T. brucei injections for 110 or 

 more days. 



Complexes or salts of suramin with 

 Ethidium, Antrycide and other trypano- 

 cides were introduced by Williamson and 

 Desowitz (1956) for prophylactic use. 

 They obtained more than 7 months' pro- 

 tection against T. congolense and T. vivax 

 by subcutaneous injection of Ethidium sur- 

 aminate. However, Robson and Cawdery 

 (1958) considered that the local reactions 

 which it produced were so severe as to 

 preclude its use even tho at 5 mg/kg it 

 protected naturally exposed zebus for 113 

 days or more. Further work with such 

 complexes may be rewai'ding. 



Pentamidine has been used extensively 

 in prophylaxis of human trypanosomosis, 

 but is not used in domestic animals. 



Whenever a drug is used continuously 

 for prophylaxis, there is danger that drug- 

 fast strains of parasites may appear be- 

 cause the blood level becomes so low that 

 relatively resistant individuals can survive. 

 This has happened particularly with Antry- 



cide and also with the phenanthridinium 

 derivatives. Unfortunately, too, strains 

 which have become resistant to Antrycide 

 are also resistant to phenanthridinium 

 compounds. No drug resistance has ap- 

 peared so far to Berenil. 



Control: Same as for T. brucei. 



TRYPANOSOMA DIMORPHON 

 LAVERAN AND MESNIL, 1904 



This species was once thought to be a 

 synonym of T. congolense, but Hoare 

 (1959) restudied Laveran and Mesnil's 

 original slides, measuring 1200 individuals 

 and analyzing the data statistically, and 

 showed that it differs in length. T. di- 

 morphon is 11 to 24 jj, long with a mean of 

 16. 2 (i; the means of different populations 

 ranged from 15. 3 to 17. 6|n . Despite its 

 name, Hoare (1959) found that it is actually 

 monomorphic. It is slender, without a 

 free flagellum, and its undulating membrane 

 is not pronounced. The posterior end is 

 rounded (chiefly in the shorter forms) or 

 pointed (chiefly in the longer forms). The 

 nucleus is in the middle or posterior part 

 of the body. The kinetoplast is fairly large 

 and typically subterminal and marginal. 



T. dimorphon occurs in Gambia, French 

 Guinea, Ivory Coast, Belgian Congo, Sudan, 

 Somalia, Southern Rhodesia, Portuguese 

 East Africa, Zululand and possibly Nigeria, 

 and has been found in the horse, sheep, 

 goat, cattle, pig and dog. It is transmitted 

 by tsetse flies in the same way as T. con- 

 golense. 



TRYPANOSOMA SIMLAE 

 BRUCE ET AL. , 1912 



Synonyms : T. ignotum, T. rodhaini, 

 T. porci. 



T. simiae was first found in a monkey, 

 but its natural reservoir host is the wart- 

 hog {Phacophoerus aethiopiciis). It is 

 highly pathogenic for the pig and camel, 

 causing a peracute disease with death 

 usually in a few days. This is the most 

 important trypanosome of domestic swine. 



