The light microscopy and ultrastructural characteristics of Myxobolus naffari (Myxosporea, Myxobolidae) infecting the Nile carp Labeo niloticus (Cyprinidae) and its histological impact

During a survey of myxosporean parasites infecting freshwater fishes from the River Nile at Giza Governorates, Egypt between March and September 2016, nine out of 30 specimens of the Nile carp Labeo niloticus (Cyprinidae) were found to be naturally infected with Myxobolus naffari (Myxobolidae). Small macroscopic plasmodia appeared embedded in the host gill tissue accompanied with fusion of the gill epithelia, and atrophy was observed at the site of infection. The host reaction was manifested by the encapsulation of the plasmodia with a thick layer of connective tissue. The plasmodia appeared as white, elongated rods between gill filaments with an intensity ranging from three to eight cysts/fish. The average dimensions of plasmodia were 1.2­2.0 (1.8 ± 0.2) mm long × 0.4­0.7 (0.6 ± 0.2) mm wide. The spores were oval, reaching 9.56­11.2 (10.2 ± 0.2) µm long and 6.5­7.7 (7.0 ± 0.4) µm wide with two equal-sized polar capsules regularly arranged at the anterior pole of each spore. They were 4.51­5.5 (5.1 ± 0.4) µm in length and 1.5­2.0 (1.7 ± 0.2) µm in width. Histological, semi-thin sections were taken through parasite plasmodia and transmission electron microscopic examination of ultrathin sections was performed to describe the developmental stages of the recorded parasite within the host fish.

Developmental stages of Hepatozoon seurati (Laveran and Pettit 1911) comb. nov., a parasite of the corned viper Cerastes cerastes and the mosquito Culex pipiens from Egypt.

Developmental stages of Hepatozoon seurati (Laveran and Pettit 1911) comb. nov. are described from the tissues of the corned viper Cerastes cerastes, and from the vector Culex pipiens. The parasite described in the present study is firstly recorded as Haemogregarina seurati (Laveran and Pettit 1911) in the same host. After demonstration of the sporogonous development in the mosquito vector (C. pipiens) which showed all characteristics of the genus Hepatozoon (large oocysts containing many sporocysts producing numerous sporozoites), the parasite should be transferred into the genus Hepatozoon. The infected erythrocytes measured 20 ± 0.95 × 7.3 ± 0.85 µm; while uninfected cells measured 13.3 ± 1.04 × 7.5 ± 0.16 µm. Hypertrophy and faintly stained cytoplasm are mostly occurred in infected erythrocytes. Blood stages of the parasite were found exclusively in the erythrocytes in two forms: (1) small trophozoites (10.0 ± 0.52 × 3.0 ± 0.4 µm) and (2) long (mature) sausage-shaped (16.5 ± 1.5 × 3.5 ± 0.4 µm). Merogony occurred in the endothelial cells of the blood capillaries of lung, liver, and spleen. Mature meronts was 27.6 ± 0.7 × 17.5 ± 0.5 µm in diameter and contained 20-35 merozoites (averaged in 26). These merozoites measured 16.5 ± 1.5 × 3.5 ± 0.4 µm. Syzygy and gamogony occurred in the mosquito myxocoel till the 5th day post-infection (p.i.) while sporogony took place after 15 days p.i. On the third day p.i., a large spherical macrogamete of 29.0 ± 0.8 × 20.5 ± 0.6 µm containing a distinct nucleus in association with a single microgamete were observed. The microgamete was pyriform measured 8 ± 02 µm in length. It had a prominent nucleus and a long flagellum of at least 20.4 ± 1.3 µm in length. Fertilization occurred on the 3rd to the 4th days p.i. and the formed zygote developed into an oocyst in which repeated mitotic divisions with centripetal invaginations occurred producing sporoblasts. After sporulation, each sporoblast termed as sporocyst, and contained 18 banana-shaped sporozoites measured 14.0 ± 1.6 × 3.2 ± 0.6 µm. Experimental transmission was successful by intraperitoneal inoculation of the infective stages (sporozoites) to uninfected vipers and led to the appearance of blood stages after 5-6 weeks.

A new species of Oochoristica (Eucestoda: Cyclophyllidea) parasite of Agama mutabilis (Reptilia: Agamidae) from Egypt.

The morphological and morphometric characterization of Oochoristica mutabili, an anoplocephalid cestode infecting the small intestine of the Egyptian changeable lizard, Agama mutabilis (F: Agamidae) in South Sinai were described by light and scanning electron microscopy as a first description from this host in Egypt. Ten out of fifty six (17.9%) of the examined specimens were infected with Oochoristica. Strobila was 14.6 (11.5-22.3) mm long; composed of 34 (30-45) proglottids; 7 (6-11) undifferentiated, 8 (6-10) contained sexual primordia, 14 (13-20) mature and 5 (3-9) gravid. Scolex 324 (300-360) microm wide with four circular suckers measuring 100 (97-124) microm in diameter; neck region is evident. Genital pores irregularly alternating, situated in the anterior quarter of proglottid; testes in median mass situated in the posterior half of proglottid extending laterally to vitellarium; ovary bilobed and situated in the centre of proglottid, vitellaria entire, slightly wider than one lobe of the ovary. Gravid proglottids contained in a uterine capsule containing numerous oncospheres. The described parasite is compared with different species of the same genus from different hosts, it was found that morphometrically the present species was more or less different from the comparable species and the only morphologically similar species was O. parvovaria. Both species were similar in the presence of the cirrus sac, which lied anterior to the ovary, and the bilobed ovary situated in the center of proglottids. However, it can be differentiated by possessing more proglottids, fewer testes, and the lack of primordial development in immature proglottids of the comparable species.