Halteridium parasites are common in the blood of passerine birds, such as pigeons, finches, stone owls, Java sparrows, parrots, etc. The Halteridium embraces or grows around the nucleus of the host red cell without displacing the nucleus. Young forms and multiplicative stages of H. columbæ have been found in leucocytes in the lungs of the pigeon (fig. 76, 8-12). Male and female forms (gametocytes) are seen in the blood (fig. 76, 3a, 3b). The cytoplasm of the male gametocytes is pale-staining and the nucleus is elongate, while the cytoplasm of the females is darker and the nucleus is smaller and round. Formation of male gametes from male gametocytes (the so-called process of “exflagellation”) may occur on a slide of drawn infected blood, also fertilization, and formation of the oökinete, as first seen by MacCallum. The correct generic name for Halteridia is, apparently, Hæmoproteus. Wasielewski (1913), working on H. danilewskyi (var. falconis), in kestrels, finds that the halteridium may be pathogenic to nestlings. The cycle of H. noctuæ described by Schaudinn (1904) lacks confirmation. The account of the life-cycle of H. columbæ given by Aragão (1908) is illustrated in fig. 76. It agrees with the work of Sergent (1906–7) and Gonder (1915). Mrs. Adie (1915) states that the cycle in Lynchia is like that of a Plasmodium.
Fig. 76.—Hæmoproteus (Halteridium) columbæ. Life-cycle diagram: 1, 2, stages in red blood corpuscle of bird; 3, 4, gametocytes (3a ♂, 3b ♀); 5a, formation of microgametes; 6, fertilization (in fly’s gut); 7, oökinete; 8–12, stages in mononuclear leucocytes in lungs. (After Aragão.)
(3) The Leucocytozoön type. The trophozoites and gametocytes occur within mononuclear leucocytes and young red cells (erythroblasts) in the blood of birds. Laveran and França consider that the Leucocytozoa occur in erythrocytes. The host cells are often greatly altered by the parasites, becoming hypertrophied and the ends usually drawn into horn-like processes (fig. 77), though some remain rounded. Leucocytozoa are limited to birds, and very rarely produce pigment. Male and female forms (gametocytes) are distinguishable in the blood (fig. 77), and the formation of male gametes (“exflagellation”) may occur in drawn blood.
Fig. 77.—Leucocytozoön lovati. a, Male parasite (microgametocyte), within host cell, whose ends are drawn out; b, female parasite (macrogametocyte) from blood of grouse. × 1,800. (After Fantham.)
The Leucocytozoa were first seen by Danilewsky in 1884. They are usually oval or spherical. It is not easy sometimes to distinguish the altered host cell from the parasite, as the nucleus of the former is pushed to one side by the leucocytozoön. The cytoplasm of the female parasite stains deeply, and the nucleus is rather small, containing a karyosome. In the male the cytoplasm stains lightly and the nucleus is larger, with a loose, granular structure.
Many species of Leucocytozoa are recorded, but schizogony has only been described by Fantham (1910)[191] in L. lovati in the spleen of the grouse (Lagopus scoticus), and by Moldovan[192] (1913) in L. ziemanni in the internal organs of screech-owls.