PLASMODIUM, HAEMOPROTEUS AND LEUCOCYTOZOON 



269 



PLASMODIUM RELICTUM 

 (GRASSI AND FELETTI, 1891) 



Synonyms : Plasmodium praecox 

 Grassi and Feletti, 1890. (Bray, 1957 

 considered the correct specific name to 

 be praecox, but he continued to use re- 

 lictum. ) 



Disease : Pigeon malaria. 



Hosts : Pigeon, mourning dove, pin- 

 tail, cinnamon teal, falcated duck, black 

 swan, and various passerine and other 

 wild birds. This species was first des- 

 cribed from the English sparrow. Exper- 

 imental infections have been studied in the 

 canary, duck, chicken and other birds. 



Location : Erythrocytes. The exo- 

 erythrocytic stages are in endothelial cells. 



Geographic Distribution : Worldwide. 



Prevalence : This species is common 

 in wild passerine birds. It occurs occa- 

 sionally in domestic pigeons, having been 

 found in them by Sergent and Sergent 

 (1904) in Algeria, Coatney (1938) in Ne- 

 braska, Herman et al. (1954), Mathey 

 (1955) and Graue (cited by Levi, 1957) in 

 California, Becker, Hollander and Pat- 

 tillo (1956) in Iowa, Pelaez et al. (1951) 

 in Mexico, Cassamagnaghi (1950) in 

 Uruguay, Haiba (1946, 1948) in Egypt, and 

 Rousselot (1943) in the French Sudan. 



Morphology : The gametocytes and 

 schizonts are round or irregular. The 

 host cell nucleus is displaced and often 

 expelled by the larger forms. The pig- 

 ment granules of the gametocytes are rel- 

 atively fine and dot-like. The schizonts 

 produce 8 to 32 merozoites, the number 

 depending on the particular strain. 



Life Cycle : The life cycle of this 

 species has been studied extensively 

 (Bray, 1957). The exoerythrocytic stages 

 occur in the endothelial cells. The asex- 

 ual cycle has been reported to take from 

 12 to 36 hours in different strains; some 

 have a very high and others a low degree 

 of synchronicity (Hewitt, 1940). Many 

 species of mosquitoes can act as vectors. 



Huff (1954) listed 12 of Culex, 4 of Ano- 

 pheles, 3 of Aedes and 2 of Culiseta, and 

 remarked that 93% of the species which had 

 been tested had been found susceptible. 



Pathogenesis : P. relic turn is highly 

 pathogenic for the pigeon but less so for 

 the mourning dove and canary. Affected 

 squabs become weak and anemic, with en- 

 larged and heavily pigmented spleens and 

 livers. Pigment may also be deposited in 

 the fat. Hill (1942) showed that anemia is 

 the principal cause of death. 



PLASMODIUM CIRCUMFLEXUM 

 KIKUTH, 1931 



Hosts : This species is quite common 

 in a wide variety of hosts. The type host 

 is a German thrush, Tiirdus pilaris. It 

 was found in the ruffed grouse in Canada by 

 Fallis (1945, 1946), and a similar form was 

 found in the Canada goose in Illinois by 

 Levine and Hanson (1953). 



Location: Erythrocytes. The exo- 

 erythrocytic stages are in endothelial cells. 



Morphology : The gametocytes and 

 trophozoites are elongate; they tend to en- 

 circle the host cell nucleus but are gener- 

 ally not in contact with it and do not displace 

 it. The schizonts produce 13 to 30 mero- 

 zoites (average 19). 



Life Cycle : The life cycle is similar 

 to that of other avian species of Plasmodium. 

 Exoerythrocytic stages occur in the endo- 

 thelial cells. The known vector mosquitoes 

 are Culex tarsalis, Culiseta annulata and 

 C. melaneura. Two other species of Culex 

 and 5 of Aedes have been found insuscepti- 

 ble (Huff, 1954). 



PLASMODIUM CATHEMERIUM 

 HARTMAN, 1927 



Disease: Canary malaria. 



Hosts: This species was first found 

 in the English sparrow. It is common in 

 passerine birds and has also been found in 

 canaries. 



