THE HEMOFLAGELLATES 



65 



which first appear in the blood 18 to 24 

 hours after infection. 



According to Baker, there is no mul- 

 tiplication in the avian host, the trypano- 

 somes simply becoming larger. This 

 would account for their sparse numbers in 

 the blood. They persist in the rook and 

 jackdaw over-winter, being more or less 

 restricted to the bone marrow, and re- 

 appear in the peripheral blood in the spring 

 Diamond and Herman (1954), too, found 

 that T. avium could be isolated from the 

 bone marrow of Canada geese much more 

 readily than from the blood. 



Nothing is known of the pathogenicity 

 of the avian trypanosomes. They are pre- 

 sumably non-pathogenic. 



Avian trypanosomes can be readily 

 cultivated on several media, including 

 NNN medium and the SNB-9 (saline-neo- 

 peptone-blood) medium described by 

 Diamond and Herman (1954). 



Genus LEISHMANIA Ross, 1903 



Members of this genus occur primar- 

 ily in mammals. They cause disease in 

 man, dogs and various rodents including 

 gerbils and guinea pigs. Leishiiiaiiia is 

 heteroxenous, being transmitted by sand- 

 flies of the genus Phlebotoiuiis. It is 

 found in the leishmanial stage in the cells 

 of its vertebrate hosts and in the lepto- 

 monad stage in the intestine of the sandfly 

 and in culture. 



Morphology : All species of Leish- 

 mania look alike, altho there are size dif- 

 ferences between different strains. The 

 leishmanial stage is ovoid or round, 

 usually 2. 5 to 5. by 1 . 5 to 2. p. , altho 

 smaller forms occur. Only the nucleus 

 and kinetoplast are ordinarily visible in 

 stained preparations, but a trace of an in- 

 ternal fibril representing the flagellum 

 can sometimes be seen. This flagellum 

 and the basal granule from which it arises 

 can also be seen in electron micrographs 

 (Chang, 1956; Pyne and Chakraborty, 

 1958). The leptomonad forms in culture 

 and in the invertebrate host are spindle- 



shaped, 14 to 20 |i long and 1. 5 to 3. 5(i 

 wide. 



Life Cycle : In the vertebrate host, 

 Leishmauia is found in the macrophages 

 and other cells of the reticulo-endothelial 

 system in the skin, spleen, liver, bone 

 marrow, lymph nodes, mucosa, etc. It 

 may also be found in the leucocytes, es- 

 pecially the large mononuclears, in the 

 blood stream. It multiplies by binary 

 fission in the leishmanial form. 



The invertebrate hosts of Leishmauia 

 are sandflies of the genus Phlebotomus . 

 When the sandflies suck blood they ingest 

 the leishmanial forms. These pass to the 

 midgut, where they assume the leptomonad 

 form and multiply by binary fission. They 

 may be either free in the lumen or attached 

 to the walls. 



Their further development varies with 

 the particular species of Pldebotomiis and 

 strain of Leislniiaitia. In good vectors like 

 P. argentipes, P. papatasii and P. sergenti, 

 they begin to extend their range forward to 

 the esophagus and pharynx by the fourth or 

 fifth day. They continue to multiply to 

 such an extent that they plug up the esopha- 

 gus and interfere with blood- sucking. When 

 an infected sandfly bites, it clears the pas- 

 sage by injecting some of the leishmanial 

 forms into its victim and thus transmits the 

 parasite. Leishmauia may also be transmit- 

 ted when sandflies are crushed on the skin. 



In other cases, the parasites remain 

 in the sandfly midgut and do not pass for- 

 ward into the pharynx. These can then be 

 transmitted only by crushing the sandflies. 

 A third type of development was described 

 by Shoshina (1953), who found leptomonads 

 in the hindgut of P. )nini(tiis var. arpark- 

 leiisis in Russia and suggested that feces 

 containing them might be rubbed into the 

 bite while scratching it. 



In addition to transmission by sand- 

 flies, it has been suggested that direct 

 infection by means of excretions of infected 

 individuals might occur in kala azar. 



Species of Leishmania : The specia- 

 tion of Leislimaiiia has been discussed by 



