Myxosporidian parasites infecting fish are very dangerous parasites causing severe damage to a large number of economically important fishes especially in aquaculture. A survey of myxosporean parasites infecting four species of fishes from the River Nile in Egypt is conducted. One hundred and ninety-five out of 316 fish specimens with a percentage of 61.7% were found to be naturally infected with these parasites. Light microscopic examination of different tissues revealed the presence of 12 myxosporean species belonging to the family Myxobolidae. Four of the identified species are novel and the other eight species are redescribed. Myxidium sp.nov. a coelozoic species inhabiting the gallbladder of Labeo niloticus with its mature spores float free in bile was detected. These spores possess a fusiform, straight, or slightly crescentic shape with less pointed ends and two equal polar capsules. Three novel histozoic Myxobolus species infecting Oreochromis niloticus were identified. Myxobolus sp(1).nov. is a species inhabiting kidney tissue with ovoid spores exhibiting a small intercapsular appendix. Myxobolus sp(2).nov. and Myxobolus sp(3).nov. recovered from kidney and intestinal tissues. Spores of Myxobolus sp(2).nov. are elliptical in shape with an anterior end wider than posterior one. Their two polar capsules are ovoid to pyriform occupied nearly the first third of the spore body. Spores of Myxobolus sp(3).nov. are broader than long with nearly rounded or ovoid two polar capsules. Eight species of the recovered myxosporean parasites are redescribed, Myxobolus niloticus Fahmy et al., 1971 from pectoral, dorsal, and tail fins of L. niloticus, Henneguya suprabranchiae Landsberg, 1987, and Henneguya branchialis Ashmawy et al., 1989 are recovered from the gills and suprabranchial organ of the catfish Clarias gariepinus, respectively, Myxobolus naffari Abdel-Ghaffar et al., 1998 and Myxobolus imami Ali et al., 2002 are found in the kidney of Barbus bynni and L. niloticus, Myxobolus caudatus Ali et al. & Parasitol Res (2002) from Tail fin of B. bynni, Myxobolus fomenai Abdel-Ghaffar et al., 2008 from kidney and intestinal tissues of O. niloticus, Thelohanellus niloticus Abdel-Ghaffar et al., 2012 are observed in the gills of L. niloticus.

In the present study, A cestode parasite was recovered from the intestine of the domestic sheep, Ovis aries (Bovidae) from the main slaughterhouse of Cairo, Egypt during the year of 2015. The parasite was observed attached to the wall of the host intestine by unarmed scolex with suckers only. Five out of 10 gastrointestinal tracts (50%) were found to be infected. Light microscopic examination showed that the adult worm of this species was whitish in color measured 421-492 (470±0.4) cm in length and 4.2-6.99 (5.6±0.7) mm in width. The scolex was with prominent four suckers measured 0.38-0.42mm in diameter. The scolex led into a long neck followed by segments. The mature segment was broader than longer, each proglottid measured 3.23-5.29 (4.6± 0.2) mm in width and 1.0-1.64 (1.4±0.02) mm in width and showed a two set of genital organs. The ovaries and the vitelline glands formed a ring on either side, median to the longitudinal excretory canals, while the testes were distributed throughout the central field or they may be concentrated toward the sides. Each ovary was of ovoid shape, measured about 0.16-0.19 (0.14±0.01) × 0.12-0.15 (0.13±0.02) mm and was located 0.8± 0.1 mm apart from the lateral side. The testes were concentrated on both sides. At the posterior border of each proglottid, a row of interproglotidal glands was arranged around small pits. Gravid segments measured 0.022-0.076 (0.048±0.2) mm in length and 2.10-5.02 (3.05±0.02) mm in width. The present parasite was compared with the previous species of the same host which showed that the parasite isolated is Monezia expansa.

In the present study, the morphology and morphometric characterization of Thelohanellus niloticus sp. nov., a new myxozoan belonging to genus Thelohanellus Kudo, 1933 (Myxosporea, Bivalvulida) infecting the gills of Labeo niloticus (Osteichthyes, Cyprinidae), were described for the first time from the River Nile at El-Minia Governorate, Egypt. Forty-one out of 78 (52.6 %) of the examined fish were infected. The infection was observed as irregular, milky whitish, cyst-like plasmodia (up to 0.8 mm in diameter) attached to the gill filaments of the host fish. These plasmodia contained tear-shaped myxospores with slightly tapering anterior and rounded posterior ends. Each spore has a single pyriform polar capsule. Spores measured about 23.3 ± 0.3 (20.4-27.1) μm long and 13.4 ± 0.4 (11.5-14.2) μm wide. The polar capsule was 11.7 ± 0.3 (9.2-12.5) μm long and 4.7 ± 0.3 (3.5-6.2) μm wide, containing a polar filament coiled perpendicular to the longitudinal axis of the spore body making eight turns. Occasionally, an oblong, irregular-shaped mass of protoplasm with a slightly oval nucleus (1.4 μm in diameter) and a small iodinophilous vacuole measured 0.85 ± 0.2 μm (0.73-1.2 μm) were observed in the spore. Due to the lack of the second polar capsule characterizing Myxobolus sp., the present parasite is placed within the genus Thelohanellus. Based on morphological differences (compared with other members of Thelohanellus Kudo, 1933) and the host specificity, this species is described as a new one of the genus Thelohanellus recorded for the first time in Egypt.

The Journal of Medical Entomology and Parasitology is one of the series issued quarterly by the Egyptian Academic Journal of Biological Sciences. It is an important specialist journal covering the latest advances in that subject. It publishes original research and review papers on all aspects of basic and applied medical entomology, parasitology and host-parasite relationships, including the latest discoveries in parasite biochemistry, molecular biology, genetics, ecology and epidemiology in the content of the biological, medical entomology and veterinary sciences. In addition to that, the journal promotes research on the impact of living organisms on their environment with emphasis on subjects such a resource, depletion, pollution, biodiversity, ecosystem…..etc. www.eajbs.eg.netProvided for non-commercial research and education use. Not for reproduction, distribution or commercial use. Keywords:Toxocara canis-Nematoda-Toxocaridae-Canis familiaris-Light and scanning electron microscopyToxocara canis is one of the most prevalent and pathogenic gastrointestinal nematodes infecting dogs. The present study aimed for the description of this nematode isolated from the dog, Canis familiaris (Canidae) based on light and scanning electron microscopy. The recovered worms were long and yellow by naked eyes. Light and SEM observations showed that the anterior ends of both sexes constitute mouth and buccal capsule, which were surrounded by three well-defined interlocked lips, distinctly offset from the anterior end, one dorsal, and two laterals, the dorsal lip swollen with narrowed dentigerous ridges bordered the outer margin of the internal surface. Two fine cuticular pits were seen on the apex of the external surface of the apical part of the lips with narrow cervical alae that tapered gradually, merged into the cuticle, giving the anterior end a lancet-like appearance. The cuticle is transversely annulated. Male worms 19-31 (24.2± 1) mm long x 0.48-0.62 (0.51± 0.3) mm wide. The posterior end equipped by 32 pairs of papillae. Females long measured 33-42 (35.1± 1) mm long x 0.55-1.33 (0.9±0.02) mm wide. Semicircular anal opening at conical posterior end with no anal lips nor papillae were observed.

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