On a Haemogregarine sp. [protozoa, apicomplexa, adeleina] naturally infecting the viper Bitis arientans in Saudi Arabia with reference to the host-parasite relationship

ABSTRACT

The study described the developmental stages of a haemogregarine species in the blood and tissues of the viper Bitis arientans. Two out of 9 [22.2%] snakes from the south western region of Saudi Arabia, and recorded for the first time in such locality. The erythrocytic parasites were differentiated into three forms the youngest form [trophozoite] measuring 7.34 +/- 0.16 x 3.38 +/- 0.07 micro m; the intermediate form [developing gametocyte] measuring 13.36 +/- 0.20 x 5.11 +/- 0.11 micro m and the largest form [mature gametocyte] measuring 18.69 +/- 0.32 x 4.32 +/- 0.16 micro m. None of the leucocytes seemed to be parasitized. Also, two types of meronts were detected in lung endothelial cells of infected vipers. Small meronts [micromeronts] measured 21.86 +/- 0.28 x 16.13 +/- 0.25 micro m and yielded about 12 merozoites. The large meronts [macromeronts] measured 38.09 +/- 0.33 x 21.52 +/- 0.32 micro m and yielded 28-42 merozoites. Random distribution of nuclei was observed in early meronts of both sizes, meanwhile peripheral arrangement of nuclei characterizing the subsequent developing events of meronts [ectomerogony]. Histopatho-logical studies showed that the infected erythrocytes were hypertrophied, mechanically stretched and their cytoplasm was faintly stained due to dehaemoglobinization. The host cell nucleus was elongated and laterally displaced. Trabeculae of the infected lung exhibited marked thickening and alveoli were collapsed in various degrees. Haemorrhagic foci and spongy structures were detected in some infected lung tissues. Formation of fibrous tissues around the meronts was seen in some foci