Life cycle of Hepatozoon mehlhorni sp. nov. in the viper Echis carinatus and the mosquito Culex pipiens.

Hepatozoon mehlhori sp. nov. and its developmental stages from the tissues of the Egyptian viper Echis carinatus and the mosquito Culex pipiens are described. The erythrocytic parasites were differentiated into the small form (trophozoite) measuring 14.5 +/- 0.6 x 4 +/- 0.12 micron and the mature form (gametocyte) measuring 17.2 +/- 1.6 x 5.4 +/- 0.5 micron. Merogony took place in the pulmonary endothelial cells and in the parenchyma cells of the liver and spleen of the infected vipers. Two types of meront were found. The large meronts (macromeronts) were 30.2 +/- 1.73 x 22.6 +/- 1.2 microns in size and yielded 16-40 (average, 28) micromerozoites measuring 17.2 +/- 0.7 x 5 +/- 0.15 microns. The small meronts (micromeronts) measured 18.2 +/- 0.6 x 13.5 +/- 0.5 microns and yielded 2-14 (average, 8) macromerozoites that were 15.1 +/- 0.12 x 6.2 +/- 0.8 microns in size. After syzygy in the haemocoel of the mosquito, the microgamont produced four uniflagellate microgametes (6.4 +/- 0.3 x 4.5 +/- 0.5 microns in size, with a short flagellum measuring 3.2 +/- 0.1 microns); on the 3rd day post-infection (p.i.)., one of these fertilized the macrogamete, giving rise to the zygote. The oocyst developed from the zygote on the 5th day p.i. and measured 135 +/- 2.6 x 120 +/- 1.8 microns. About 11-60 (average, 35) sporoblasts were formed by centripetal invaginations from each oocyst on the 8th day p.i. and developed into sporocysts on the 14th day p.i. Inside each sporocyst, 5-12 (average, 8) sporozoites, each measuring 12.6 +/- 1.2 x 4.1 +/- 0.3 microns, developed on the 16th day p.i. According to the above-mentioned characteristics the parasite was recorded as being a new species and was named Hepatozoon mehlhorni. Experimental transmission was accomplished by i.p. inoculation of the infectious stages (sporozoites) into uninfected vipers and led to the appearance of blood stages at 4-6 weeks p.i.