198 



BIRD MALARIA 



fCH. 



The Morphological Changes. 



Development in the mosquito. The experiments of Ross, 

 Sergent, Ruge and Neumann have shewn that at least four 

 species of CuHcinae are capable of transmitting P. prcecox, 

 viz. Culex pipiens, C. fatigans, C. nemorosus and Stegomyia 

 fasciata. In all these species the development of the parasite 

 is practically identical with that of P. vivax in Anopheles, 

 and therefore it is unnecessary to describe it in detail. 



The development, however, does not take place with equal 

 facility in all these species, even under the same conditions of 

 temperature and humidity. 



Thus Neumann found that out of 501 Stegomyia fasciata 

 which fed on an infected canary, only 57 (= 11-4 per cent.) 

 subsequently shewed the development of ripe cysts and the 

 sporozoites of the parasite. On the other hand out of 104 

 Culex pipiens fed under similar conditions, 85 (= 817 per cent.) 

 became infected. Moreover the time occupied in the develop- 

 ment of the parasite, from the ingestion of the gametocytes 

 to the appearance of sporozoites in the salivary gland of the 

 mosquito, was longer in the case of Stegomyia than in Culex. 



At a temperature of 27° C, with a relatively high humidity 

 of about 75 to 80 per cent., the times occupied by the various 

 stages of development were as follows : 



Formation of microgametes 

 Copulation . . 

 Formation of ookinete, 



commencement of 



majority formed 

 Disappearance of ookinetes from 



the stomach . . 

 Formation of sporocyst . . 



Development of sporozoites in the 

 cyst 



Total developmental period, from 

 the ingestion of the infected 

 blood to the appearance of 

 sporozoites in the salivary 

 glands of the infected mosquito 



In Culex 

 30 to 45 mins. 

 30 to 60 mins. 



About 10 to 12 hours 

 20 hours 



After 48 hours 

 About 30 hours 



6 to 7 days 



9 to II days 



In Stegomyia 

 30 to 60 mins. 

 39 to 90 mins. 



About 16 hours 

 26 hours 



After 72 hours 

 Not before the 

 3rd or 4th day 



8 to 10 days 



13 to 15 days 



