330 PARASITES OF THE DOMESTIC ANIMALS 



healthy ones, the second of the latter will not usually contract the 

 disease. This is due to the fact that the proboscis of the fly, charged 

 with the trypanosomes from the blood of the sick animal, becomes 

 cleaned of the organisms in biting the first of the healthy ones. Any 

 biting arthropod may transmit by the direct method; the ability to 

 infect is usually Hmited to a few hours from the time of biting an in- 

 fected animal, though under experimental observation it has been re- 

 tained for a considerably longer time (see Glossina, p. 44). 



Nagana 



The fundamental work upon this disease was carried on in Zululand 

 by Bruce who, in 1895, discovered that nagana, or the so-called tsetse 

 fly disease, was caused by a trypanosome which, after its discoverer, 

 has been named Trypanosoma brucei. 



"Nagana, or fly disease," Bruce writes, "is a specific disease which 

 occurs in the horse, mule, donkey, ox, dog, cat, and many other animals, 

 and varies in duration from a few days or weeks to many months. It 

 is invariably fatal in the horse, donkey, and dog, but a small percentage 

 of cattle recover. It is characterized by fever, infiltration of coagulable 

 l5miph into the subcutaneous tissue of the neck, abdomen, or extrem- 

 ities, giving rise to swelling in these regions, by a more or less rapid 

 destruction of the red blood corpuscles, extreme emaciation, often- 

 blindness, and the constant occurrence in the blood of an infusorial 

 parasite." 



Nagana is a Zulu word which, according to Bruce, refers to the state 

 of depression and weakness characteristic of the disease. 



Nagana exists, particularly in low and humid regions, throughout 

 Africa with the exception of Tunis, Algeria, and Morocco, and most of 

 the country south of the Tropic of Capricorn. The disease is supposed 

 to be transmitted mainly the by the tsetse fly Glossina morsitans, though 

 other species probably play an equal part in this respect. Etiologic 

 reference to nagana has already been made in the review of the work of 

 Bruce under the subject of Glossina (p. 44) and need not be repeated 

 here. 



Plate V. — -VARfons Species op Thypanosoma. 1. Trypanosoma lewisi, of the rat. 

 2. Trypanosoma lewisi, multiplication rosette. 3. Trypanosoma lewisi, small form re- 

 sulting from the disintegration of a rosette. 4. Trypanosoma brucei, of nagana. 5. 

 Trypanosoma equinum, of caderas. 6. Trypanosoma gambiense, of sleeping sickness. 

 7. Trypanosoma gambiense, undergoing division. 8. Trypanosoma theileri, a harmless 

 trypanosome of cattle. 9. Trypanosoma transvaliense, a variation of T. theileri. 10. 

 Trypanosoma avium, a bird trypanosome. 11. Trypanosoma damonise, of a tortoise. 

 12. Trypanosoma solese, of the flat fish. 13. Trypanosoma granulosum, of the eel. 14. 

 Trypanosoma rajae, of the skate. 15. Trypanosoma rotatorium, of frogs. 16. Cryptobia 

 borreli, of the red-eye (a fish). (After Crawlej', from Laveran and Mesnil; Cir. No. 194, 

 Bu. An. Ind., U. S. Dept, Agr.) 



