Recent insights into the morphology, molecular characterization and tissue localization of the caprine Sarcocystis species infecting domestic goats (Capra hiricus); Sarcocystis moulei, Sarcocystis capracanis, and Sarcocystis hircicanis
Authors: El-Morsey Ahmed , Abdo Walied 
Published: August 2023

Abstract
Species of the Sarcocystis are getting more attention within the previous 20 years as a result of, recent discoveries of many novel species parasitizing both avian and mammalian intermediate hosts, high economic losses resulting from the condemnation of meat due to the existence of macroscopic cysts of some Sarcocystis species in several muscular organs. Macroscopic lesions associated with eosinophilic myositis as a consequence of bovine or ovine Sarcocystis spp. encystation in cattle, sheep, and goat musculature. Or even merogony stages associated with granulomatous reactions might appear grossly as yellowish-white spots or cyst-like lesions, in some cases on the external surfaces of the internal organs such as the liver, kidney, lung, or spleen of the animal during carcass inspection in abattoirs. Additionally, the adverse pathogenic effects on the intermediate host as, abortion, fever, anaemia, anorexia, and even deaths, more specifically due to infection by some of the canine-transmitted Sarcocystis spp. Domestic goats (Capra hiricus) play an important role as a good source of meat, leather industries, milk, and milk products. Goats are excellent converters of low-quality feed that are not preferred by other meat-producing animal species into very valuable sources of human nutrition and economic income. The global goat population continues to grow and is now more than 1 billion. Sarcocystis spp. infecting domestic goats (Capra hiricus) were surveyed in El-Mahalla El-Kobra City slaughterhouse, El-Gharbia province, Egypt, for one year and a half that extended from June 2021 to January 2023. One hundred and fifty domestic goat carcasses (Capra hiricus) including one hundred and eleven males and 39 females were examined for the existence of both macroscopic and microscopic sarcocyst forming Sarcocystis spp. Sarcocysts of S. moulei, S. capracanis, and S. hircicanis were identified in the current investigation. Ninety seven (64.67%) out of a total of 150 slaughtered goat carcasses were found to be infected. S. moulei macrosarcocysts were detected in 7 goat carcasses (4.67%) out of the 150 examined animals. While both S. capracanis and S. hircicanis microcysts were found in 90 (60%) out of the 150 inspected goat carcasses. Goat carcasses harboring only S. capracanis cysts were 51 out of 150 (34%). S. hircicanis microsarcocysts were found in 28 of 150 (18.67%). Dual microscopic Sarcocystis spp. infection by the two species was (11/150 = 7.33%). S. moulei macrosarcocysts were found in the oesophageal, cardiac, lingual, skeletal, and diaphragmatic muscles of 7 goats. Two morphotypes of S. moulei were observed. Morphotype (I) appeared as large-sized oval, ovoid or spherical cysts those measured 2–15 mm in length x 2–6 mm in width (n = 50) and were mainly localized in the oesophageal, skeletal, diaphragmatic, and lingual to little extent in the cardiac muscles. S. moulei morphotype (II) macrosarcocysts were spindle-shaped to a little extent spheroid, sometimes elongated, smaller in size, and measured 1.8‒6 x 0.5‒2 mm (n = 50). These macrosarcocysts were predominantly localized in the cardiac, oesophageal, lingual, and skeletal to a little extent in the diaphragmatic muscles. By TEM, S. moulei sarcocysts belonging to the two morphotypes were morphologically the same. S. moulei macrosarcocysts identified herein, had a cyst wall that was characterized by highly branched or sometimes cauliflower-like villar protrusions (VP) which had dumbbell-like structures (dbs) on the outer surface of the parasitophorous vacuolar membrane (PVM). The interior of the VP was packed with well-developed microtubules in longitudinal and cross arrangements. Two rows of spherical vesicular structures were located on the PVM in the interspaces between the VP. S. moulei cyst wall was 3‒6 µm thick. S. capracanis microsarcocysts detected herein, had a cyst wall that ranged from 4‒8 µm in thickness. The VP was upright finger-like or cylindrical. The PVM had many electron-dense corrugations in the region of the VP. Deeply stained or electron dense oval or rounded structures (eds) were localized in between the VP on the surface of the sarcocyst. The ground substance (GS) contained electron-dense granules (edg), which were variable in their distribution as they were crowded toward the bases of the VP and few in other regions of the (GS). The (edg) in the core of the VP were variable in size and included small and large-sized granules. Few amounts of microfilaments were detected inside the cores of VP. The microsarcocysts of S. hircicanis had a thinner cyst wall (~ 1‒3 µm) with long hairy VP. Their VP could be divided into three portions. The first or the proximal third is wider than both the second and the third one that tapers distally for a long distance. The distal portions were in the form of electron-dense tips (edt). Tips of the VP were electron-dense or osmiophilic and appeared dense black. The hairy long VP ranged from 1 to 7.5 µm in length. Microtubules were missing inside the cores of the VP. Electron-dense projections were observed in the interspaces between the VP on the outer surface of the PVM. Prominent electron-dense particles (edp) of variable dimensions, ranging from (~ 100–200nm), were dispersed within the GS. Eventually, the three caprine Sarcocystis species were molecularly characterized through PCR, sequencing, sequence, and phylogenic analyses of the 18S rRNA, 28S rRNA, and Cox1 genes.