Ultrastructure of Sarcocystis tenella (Sarcocystis ovicanis)

Morphometric Study of Microscopic Cysts of Sarcocystis Sp. in Sheep Carcasses

Muscular samples of the oesophagus and diaphragm of 335 sheep collected from the slaughterhouse of El Harrach were analyzed by the histopathological method to describe the morphology of two species of Sarcocystis: S. arieticanis and S. tenella. The cysts were counted and measured with a micrometer for their dimensions. A total of 895 cysts were measured. The width, length, shape index (length/width), the thickness of the wall and the length of the projections were recorded. The thick-walled cysts of S. tenella were 10—450 μm long (the mean ± SD value was 50.35 μm ± 1.380) and 1—110 μm (the mean ± SD value was 27.51 μm ± 0.533) wide. The cyst walls were 0.5—4 μm thick (the mean ± SD value was 1.547 μm ± 0.020) and provided with radial striations. The shape index was 1—14 μm (the mean ± SD value was 1.93 ± 0.045). While in the S. arieticanis, the cyst wall was thin and had long hair-like protrusions, the cysts measured 8—780 μm (the mean ± SD value was 123.13 μm ± 12.799) in length and 5—100 μm (the mean ± SD value was 37.00 μm ± 1.68) in width. The hair-like protrusions reached a length of 3—14 μm (the mean ± SD value was 5.428 ± 0.353) and the shape index was 1—17 μm (the mean ± SD value was 3.10 ± 0.281). For the length, the width and the shape index, the differences were statistically significant between thin-walled cysts and thick-walled cysts. The general structural features of the cysts, previously described by other authors, were confirmed.

Ultrastructural and Molecular Identification of the sarcocysts of Sarcocystis tenella and Sarcocystis arieticanis Infecting Domestic Sheep (Ovis aries) from Egypt

BACKGROUND

In spite of the global economic significance of sheep production, little is known about the prevalence of various Sarcocystis spp. infecting the domestic sheep (Ovis aries) in Egypt.

MATERIALS AND METHODS

Muscle samples were collected from 175 sheep (> 2 years) slaughtered at El-Mahalla El-Kubra abattoir, Gharbia governorate, Egypt. Samples were initially examined by naked eye for the existence of macrosarcocysts. The microscopic sarcocysts were detected and identified using the light microscopy and the Transmission electron microscopy (TEM). Different microscopic species of ovine Sarcocystis were molecularly confirmed by PCR, sequence analyses and phylogeny.

RESULTS

Preliminary light microscopic inspection of the muscle specimens revealed the existence of only the microscopic sarcocysts of Sarcocystis tenella and Sarcocystis arieticanis in 152 (86.8%) out of the175 examined animals. Sarcoysts of S.tenella had striated thick cyst wall that amounted from 3.5-5.5 μm in thickness whereas, S.arieticanis sarcocysts had a thin cyst wall that ranged from 1-3 μm in thickness. S.tenella sarcocysts were detected in 115 sheep (65.7%), and were more prevalent than those of S.arieticanis, observed only in 68 sheep (38.8%). No macroscopic sarcocysts were observed in any of the examined carcasses. Transmission electron microscopy (TEM) of the cyst wall of S.tenella revealed the existence of the short stubby villar protrusions (VP) with the characteristic disk-like structures at the tips of the (VP). While, TEM of S.arieticanis showed that the cyst wall had elongated tubular protrusions that measured approximately 5-7 μm in length. Each (VP) consisted of a dome-shaped base (0.3-0.9 μm in diameter), a relatively thick middle portion (0.1-0.3 μm) in width, and a thin hair-like distal portion that measured about (0.03 x 1-4.5 μm).

CONCLUSION

Comparative analyses of the sequences of the four genetic markers (18S rRNA, 28S rRNA, mitochondrial cox1 and ITS-1) for S.tenella and S.arieticanis isolates detected herein, revealed genetic variations of 95% and 95- 96% among the different isolates on the level of the 18S rRNA and 28S rRNA, respectively. Whereas, the cox1 and ITS-1 shared sequence identities of 76-78% and 70-73%, respectively. S.tenella was strongly related to S.capracanis infecting goats (Capra hircus). Sequence identity of 98% on the level of 18S rRNA, 28S rRNA genes was observed between the currently identified isolates of S.tenella and the formerly GenBank deposited isolates of S.capracanis. While, cox1 sequences shared identities of 92-93%. Furthermore, S.arieticanis isolates identified here were closely related to the formerly published sequences of S.hircicanis. The 18S rRNA and 28S rRNA sequences of S.arieticanis shared 98% and 94-95% identities with those of S.hircicanis, respectively. However, 87-88% homologies were observed between the cox1 sequences of S.arieticanis and S.hircicanis. Consequently, cox1 and ITS-1 gene sequences act as better genetic markers than 18S rRNA and 28S rRNA sequences for the characterization of ovine Sarcocystis spp. Maximum parsimony analyses based on the sequences of three genetic markers, (18S rRNA, 28S rRNA and mitochondrial cox1), yielded the same placement of the currently identified isolates of the two taxa (S.tenella and S.arieticanis) within a clade of Sarcocystis species with carnivorous animals as known, or assumed, final hosts.

Molecular Characterization of Sarcocystis Species Isolated from Sheep and Goats in Riyadh, Saudi Arabia

Simple Summary

In this article, we investigated the occurrence of Sarcocystis species in samples of sheep and goats obtained from slaughterhouses in Riyadh, Saudi Arabia. We searched for tongue, heart, esophagus, diaphragm and skeletal muscle tissues. Fragments of these tissues were investigated by macroscopic evaluations, direct optical microscopy of tissue fragments, optical microscopy of digested fragment sediment, transmission electron microscopy and PCR followed by nucleotide sequencing. From the set of information obtained, we searched 230 sheep, and 84 goats; 91 and 36 were found to be infected, respectively. Transmission electron microscopy (TEM) revealed Sarcocystis tenella (S. tenella) in sheep and Sarcocystis capracanis (S. capracanis) in goats. Sarcocystis species were confirmed in Saudi Arabian sheep and goats by molecular testing. S. capracanis was most closely related to S. tenella, with the mitochondrial cytochrome c oxidase subunit I gene (COX1) sequences sharing a (91.7%) identity.

Abstract

Sarcocystosis is induced by species of Sarcocystis, which is an intracellular protozoan parasite in the phylum Apicomplexa. The diversity and importance of Sarcocystis species in sheep and goats in Saudi Arabia are poorly understood. In this study, the tongue, esophagus, heart, diaphragm, and skeletal muscles were collected from 230 sheep and 84 goats, and the tissues were examined for the presence of Sarcocystis species by macroscopic examination and light microscopy. Microscopic Sarcocystis species cysts were found in both sheep and goats. Transmission electron microscopy (TEM) revealed S. tenella in sheep and S. capracanis in goats. Sarcocystis species were confirmed for the first time in Saudi Arabian sheep and goats by molecular testing. S. capracanis was most closely related to S. tenella, with the COX1 sequences sharing 91.7% identity. A phylogenetic analysis produced similar results and indicated that the Sarcocystis isolates were within a group of Sarcocystis species in which dogs were the final host. Finally, the Sarcocystis species cysts from sheep and goats could be grouped together, indicating that they were strongly related.

Meningoencephalitis caused by pathogenic Sarcocystis species in a naturally infected sheep in Turkey

A 3-year-old sheep was examined after an acute onset of hind limb paralysis and ataxia. At necropsy, central nervous system, pulmonary and intestinal hyperaemia and ecchymoses in the aortic arch were observed. Main microscopic lesions were confined to the heart, cerebrum and cerebellum. There were a multifocal mild myocarditis and nonsuppurative meningoencephalitis together with protozoal cysts in the heart and the brain. Protozoal cystic structures were observed within many of the myocardial fibers as well as in the cerebrum and cerebellum. Using light microscopy it could not be morphologically determined whether these organisms were Toxoplasma (T.) gondii or Neospora (N.) caninum. Additional diagnostic methods like immunohistochemistry and polymerase chain reaction provided differentiation of Sarcocystis from T. gondii and N. caninum. Transmission electron microscopy demonstrated characteristic features of Sarcocystis sp. as previously described. This is the first confirmed diagnosis of Sarcocystis sp. in the central nervous system of a sheep from Turkey.

Prevalence, morphology, and molecular characteristics of Sarcocystis spp. in domestic goats (Capra hircus) from Kunming, China

Despite the importance of worldwide goat production, little is known about the prevalence of Sarcocystis spp. in domestic goats (Capra hircus) in China. The aims of the present study were to determine prevalence of Sarcocystis spp. in domestic goats in Kunming, China, as well as to identify parasite species based on morphological characteristics and DNA sequence analysis. Only microscopic sarcocysts of Sarcocystis spp. were detected in 174 of 225 goats (77.3 %). By light and transmission electron microscopy, two species, i.e., Sarcocystis capracanis and Sarcocystis hircicanis, were identified. Two sarcocysts from each of the two species were randomly selected for DNA extraction; the 18S rRNA gene (18S rRNA), the 28S rRNA gene (28S rRNA), and the mitochondrial cytochrome c oxidase subunit 1 (cox1) were amplified by the polymerase chain reaction (PCR) and subsequently sequenced. The results were compared with other previously sequenced Sarcocystis species retrieved from GenBank. There was little sequence variation between two isolates of the same species. S. capracanis was most closely related with Sarcocystis tenella; 18S rRNA, 28S rRNA, and mitochondrial cox1 sequences shared identities of 95.7-99.1, 95.3, and 92.3-93.2 % with those of S. tenella, respectively. Thus, mitochondrial cox1 sequences seem to perform better than 18S rRNA sequences or 28S rRNA sequences for identification of the two species. S. hircicanis was most closely related to Sarcocystis arieticanis, i.e., 18S rRNA and 28S rRNA sequences of the former species shared 97.2-97.4 and 95.6-96.1 % identities with those of latter, respectively. Phylogenetic analysis inferred from the three genetic markers yielded similar results and indicated the two species were within a group of Sarcocystis species with canines as known, or presumed, definitive hosts.

Crystalloid body, refractile body and virus-like particles in Apicomplexa: what is in there?

The phylum of Apicomplexa comprises parasitic protozoa that share distinctive features such as the apical complex, the apicoplast, specialized cytoskeletal components and secretory organelles. Other unique cytoplasmic inclusions sharing similar features have been described in some representatives of Apicomplexa, although under different denominations. These are the crystalloid body, present for example in Cryptosporidium, Plasmodium and Cystoisospora; the refractile body in Eimeria and Lankesterella; and virus-like particles, also present in Eimeria and Cryptosporidium. Yet, the specific role of these cytoplasmic inclusions in the cell cycle of these protozoa is still unknown. Here, we discuss their morphology, possible inter-relatedness and speculate upon their function to bring these organelles back to the attention of the scientific community and promote new interest towards original research on these elusive structures.