THE TRYPANOSOME OF NAGANA 



811 



after the first swelling has disappeared, a second swelling occurs at the site 

 of inoculation, in which the parasites multiply and soon cause a fresh infection 

 of the blood. The disease runs a distinctly intermittent course and the 

 parasite only multiplies at the site of inoculation. 



Dogs. Dogs in Europe are highly susceptible. The initial swelling lasts 

 a long time and the trypanosome only infects the blood stream after an 

 interval of 15 or 16 days. It is probable that subsequently multiplication 

 takes place in all the organs of the body. The most pronounced symptoms 

 are conjunctivitis, keratitis, and hypopyon, oedema of the external genitalia, 

 and paralyses. 



Indian dogs are highly immune to the dourine of India (Pease, Lingard). 



Immunity. Rouget has shown that the blood of infected rabbits and dogs 

 collected in the last stages of the disease has immunizing properties. Such 

 blood, injected as a prophylactic either alone or mixed with the virus, protects 

 mice against infection. It has no therapeutic properties. 



3. Trypanosoma brucei. 



The trypanosome of Nagana. 



Sir David Bruce has shown that Nagana or " Tsetse-fly disease " (Glossina 

 morsitans) is due to a trypanosome. 



Nagana is a disease affecting horses, asses, mules, oxen, dogs etc. in South 

 East and Central Africa. 



The disease is transmitted by the Tse-tse fly (Glossina morsitans). [It can also be 

 conveyed from infected to non-infected animals under experimental conditions by 

 Glossina palpalis]. It is probable that the fly often infects itself by biting wild 

 animals (buffaloes, etc.) whose blood not infrequently contains trypanosomes 

 although the animals themselves show no signs of disease (Bruce). 



Carnivora (dogs, etc.) appear to contract the disease by feeding upon the flesh 

 of animals dead of Nagana. It seems also to be proved that animals infected with 

 the disease may transmit the infection by biting healthy animals : such transmission 

 may possibly in the cases observed have been due to the presence in the saliva of 

 infected blood from erosions of the gums. 



Morphology. Trypanosoma brucei is found in varying numbers in the 

 blood of infected animals. 



In the fresh condition the parasite occurs as a motile vermicule having an 

 undulating membrane and an anterior flagellum : the posterior end is some- 

 times filiform, sometimes rounded or like 

 a section of a fir cone. The movements 

 though very active are prolonged, and 

 darting movements like those seen in T. 

 leivisi are never observed. All the para- 

 sites are much of the same size ; some 

 are broader than others and have two 

 undulating membranes (a stage of multi- 

 plication). 



In fixed and stained preparations, the 

 parasites measure, including the flagel- 

 lum, 26-27/n in length and 1'5-2'5/x in 

 breadth. In horses' and asses' blood 



the length generally reaches 2S-33/*. left, an adult trypanosome ; on the right, a 



The protoplasm is stained rather deeply S s p ^e s s t a ^ s) undergoing division (three 

 by Laveran's method and has a number 



of large, deeply-staining granules in its anterior part. The nucleus is 

 centrally situated, oval in shape, and stains rather less deeply than the 



FIG. 393. Trypanosome of Nagana (Tr. 

 brucei). (After Laveran and Mesnil.) On the 



