First report of molecular characterization and phylogenetic analysis of Sarcocystis tenella from India

Molecular Identification of Sarcocystis Species in Sheep from Lithuania

Data on the distribution of different Sarcocystis species in various muscles of sheep are scarce. In the present study, 190 diaphragm, oesophagus, and heart muscle samples of 69 sheep raised in Lithuania were examined for the presence of Sarcocystis spp. Under a light microscope, two morphological types of microcysts corresponding to S. arieticanis and S. tenella were detected. Eight and 12 sarcocysts of S. arieticanis and S. tenella, respectively, were isolated and characterised by the sequencing of a portion of cox1. The sequence comparisons revealed the highest similarity between European and Asian isolates of S. arieticanis and S. tenella obtained from domestic sheep and other wild Caprinae hosts. Based on peptic digestion, nested PCR targeting cox1, and sequencing, a 100% infection prevalence of S. arieticanis and S. tenella was observed in the 69 studied animals. The occurrence of S. tenella was significantly higher in the diaphragm than in the oesophagus (χ2 = 13.14, p < 0.001), whereas differences in the prevalence of S. arieticanis in the studied muscle types were insignificant (χ2 = 1.28, p > 0.05). Further molecularly based epidemiological studies are needed to compare the prevalence of Sarcocystis species in various muscles of sheep raised in different geographic regions.

Sequence phylogenetic analysis and associative genetic diversity of Sarcocystis hirsuta based on 18S rRNA gene

Background

Sarcocystis hirsuta, a tissue cyst-forming coccidian parasite of cattle, is worldwide in distribution. In spite of its global presence, limited literature is available on its characterization studies. No literature is available from India on molecular aspects of S. hirsuta. The present study was designed to characterize the isolates of S. hirsuta on the 18S gene locus. A total of five isolates of S. hirsuta were characterized. PCR products were cloned, sequenced, and compared with other sequences across the world. A phylogenetic tree was constructed based on the maximum parsimony (MP) method with the tree–bisection–regrafting (TBR) algorithm.

Results

An appreciable genetic variability was noticed between various S. hirsuta isolates at the 18S gene locus. Sequences generated from the present study (MN121567–MN121571) represented two haplotypes with 99.74–100.00% nucleotide homology within themselves. Alongside, a nucleotide homology of 97.82–99.92% was observed between Indian isolates and isolates across the globe. The two haplotypes were markedly distinct from each other with 3 nucleotide substitutions within themselves. Overall, Indian isolates of S. hirsuta were close to those from China and Vietnam than to those from New Zealand, Brazil, and Germany.

Conclusion

The present communication describes the first report of phylogenetic characterization of S. hirsuta from India. The findings are very much important in delineating the evolutionary phylogenetics of S. hirsuta.

Phylogenetics of Sarcocystis fusiformis isolates based on 18S rRNA and cox 1 genes

Sarcocystosis is a significant meat borne coccidian disease with immense zoonotic potential. Sarcocystis fusiformis is the most prevalent Sarcocystis spp. affecting buffaloes across the globe. Most of the molecular characterization works on S. fusiformis are from Egypt and there is no record of such work from India. In the present study, 21 isolates of S. fusiformis from Northern India were characterized for 18S rRNA (MF595821-MF595841) and cox 1 (MF423105-MF423119 and MH899162-MH899167) genes. S. fusiformis was seen as a monophyletic sister group to S. cafferi on the phylogenetic tree comprising of different Sarcocystis spp. Both genes placed S. fusiformis close to those Sarcocystis spp. which have felids as definitive hosts in comparison to those with canids as definitive host. A total of 15 and 7 haplotypes were noticed for both the genes, respectively. The studied Indian isolates showed 99.1-100.0% and 99.2-100.0% nucleotide homologies within themselves for both the respective gene loci. Over all, cox 1 gene was found to be better in delineating the evolutionary phylogenetics in comparison to 18S rRNA gene. The findings are important from evolutionary point of view.

First description of Sarcocystis species infecting Barbary sheep (Ammotragus lervia)

Barbary sheep (Ammotragus lervia) is a North African native wild Caprinae, introduced in the 1970s in new territories such as Spain, the USA, and Mexico. Here, we describe Sarcocystis species in Barbary sheep. Sarcocysts were found in 19 out of 56 adult A. lervia in Southern Spain and characterized morphologically and molecularly. By light microscopy, sarcocysts had thin (< 1 μm) or thick (> 2 μm) walls. By transmission electron microscopy, sarcocysts with thick walls had Type 14 villar protrusions corresponding to S. tenella/S. capracanis of domestic sheep (Ovis aries) or goats (Capra hircus). Sarcocysts with thin walls had Type 7b villar protrusions that corresponded to S. arieticanis/S. hircicanis of domestic sheep or goats. Molecular analyses allowed the identification of only thick-walled Sarcocystis species. Six sarcocysts were assigned to S. tenella (99.2-100% and 95.6-100% sequence similarity within 18S rRNA and COI, respectively) and 19 sarcocysts were assigned to S. capracanis (98.5-99.8% and 97.9-99.0% sequence similarity within 18S rRNA and COI, respectively). Further studies are needed for taxonomic identification of sarcocysts in Barbary sheep because Sarcocystis species in sheep and goats are not cross transmissible despite morphological similarities.

Phylogenetic characterization of Setaria equina and its association with other filarids

Molecular characterization studies on Setaria equina are limited. The present study aimed to characterize S. equina at the cytochrome c oxidase gene and to examine its phylogenetic relationships with other filarid species. Sequence analysis showed 100% nucleotide homology with an S. equina sequence from Italy (AJ544873). However, both sequences exhibited 7 nucleotide substitutions from a S. equina donkey isolate from Egypt (MK541847). Overall, S. equina formed a monophyletic sister group to Setaria tundra. All Setaria spp. examined formed a separate group on the phylogenetic tree that was related to corresponding Onchocerca spp. and Dirofilaria spp. clades. Human filarid worms-Brugia spp. and Wuchereria spp. grouped in a separate clade alongside Theilezia spp. Dipetalonema spp.-formed a separate group at the top of the tree.

First report of the isolation and phylogenetic characterization of equine Setaria digitata from India based on mitochondrial COI, 12S rDNA, and nuclear ITS2 sequence data

Equine ocular setariasis arising mainly from ectopic infestation of Setaria digitata is a common vision impairing ophthalmic disease in India, and the identification of this filarial nematode is based solely on morphology. However, morphological characters alone are inadequate to detect and differentiate S. digitata from its congeners. The present communication reports the first phylogenetic characterization of equine S. digitata from India based on sequences derived from the mitochondrial cytochrome c oxidase subunit 1 (COI), the mitochondrial small subunit ribosomal DNA (12S rDNA), and the nuclear internal transcribed spacer 2 (ITS2). Three isolates were characterized for each gene, and respective sequences were submitted to NCBI database (MN078131, MN078132, and MN095798). The sequences were also compared with the other related sequences available from PubMed around the globe, and phylogenetic analysis was carried out in conjunction with nucleotide homologies. There was no intraspecific variation among the Indian isolates. The phylogenetic analysis of S. digitata, inferred from these genes, showed that the isolate sequences obtained from different host species created a separate monophyletic clade within the genus Setaria with minor sequence variations revealing similar molecular characteristics of S. digitata isolates throughout the globe. In addition, the studied Indian isolates were found closer to Sri Lankan isolates. The S. digitata and S. labiatopapillosa appeared as sister species.