Distribution of Blastocystis subtypes isolated from various animal hosts in Thailand

Blastocystis in humans and domestic animals: Risk factors assessment and potential zoonotic transmission in a periurban and rural region of Northeastern Argentina

Blastocystis is a protist that infects both human and animal hosts worldwide. This study aimed to investigate the presence of Blastocystis in humans and domestic animals living in a periurban (PZ) and rural zone (RZ) in Northeastern Argentina and to assess their relation to socio-environmental conditions and hygiene practices as risk factors for human infection. In addition, we identified Blastocystis subtypes to evaluate the risk of zoonotic transmission. A total of 563 fecal specimens were collected from 289 humans, principally children, and 274 animals. Samples were examined by coprological examination and further analysis by real-time PCR and sequencing were performed. A semi-structured questionnaire was applied to obtain socio-environmental and hygiene practices data. The results showed an overall prevalence of 41.6 % in children and 10.2 % in animals. Non-schooled children (OR = 0.54) and children from urban area (OR = 0.55) showed a lower risk of infection. Molecular analyses revealed five subtypes (ST1, ST2, ST3, ST5, and ST7) present in humans and four subtypes (ST1, ST5, ST7 and ST10) in animals. The overlap of STs between humans and domestic animals in the same household (STs 1, 5 and 7) suggests potential zoonotic transmission, underscoring the role of infected animals as a potential risk factor for human infections. Our results can inform local health authorities to promote policies aimed at reducing transmission, emphasizing the need for direct molecular-level assessments of other common environmental sources, such as water and soil, highlighting the importance of adopting a One Health approach to better understand Blastocystis circulation.

Molecular Detection and Genotyping of Blastocystis in Farmed Minks and Raccoon Dogs in Northern China

Blastocystis is a common intestinal protozoan found in both humans and animals. However, research on Blastocystis infections in minks (Neovison vison) and raccoon dogs (Nyctereutes procyonoides) is limited. This study aimed to investigate the prevalence and subtypes of Blastocystis in these two species across northern provinces of China using small subunit rRNA gene sequence analysis. We examined 275 minks (89 from Hebei Province, 57 from Heilongjiang Province, 109 from Liaoning Province, and 20 from Shandong Province) and 235 raccoon dogs (114 from Hebei Province, 27 from Heilongjiang Province, 61 from Liaoning Province, and 33 from Jilin Province). The overall infection rate was 13.5% (69/510). Farmed minks had a prevalence of 1.5% (4/275), while raccoon dogs showed a significantly higher prevalence of 27.7% (65/235). We identified five distinct subtypes (ST1, ST2, ST3, ST5, and potentially novel subtype) across both species: ST1 (15 cases), ST2 (15 cases), ST3 (31 cases), ST5 (7 cases), and potentially novel subtype (1 case). This study is the first to report ST1 and ST3 in minks and ST1, ST2, ST5, and potentially novel subtype in raccoon dogs. As ST1, ST2, ST3, and ST5 subtypes are also found in humans, our findings suggest that minks and raccoon dogs may serve as potential reservoirs for human Blastocystis infections. Furthermore, the newly identified, potentially novel subtype might also be transmissible to humans or other animals. This research enhances our understanding of Blastocystis distribution among hosts in China and supports zoonotic disease prevention efforts related to farmed minks and raccoon dogs.

Molecular characterization and subtype analysis of Blastocystis sp. in captive wildlife in Henan, China

Blastocystis sp. is a zoonotic intestinal protozoan that is ubiquitous globally, residing in the gastrointestinal tracts of both humans and various animals. In the present study, a PCR-sequencing tool based on the SSU rRNA gene was employed to investigate the prevalence and subtypes of Blastocystis spp. in 204 fresh fecal samples collected from 20 captive wildlife species from a bird park in Henan Province, Central China. Overall, Blastocystis was present in 13.73% (28 out of 204) of the samples and 25% (5 out of 20) of the species. A total of four zoonotic subtypes of Blastocystis sp. were found: ST1, ST3, ST5, and ST27, with the latter being the most prevalent, accounting for 35.71% (10 out of 28) of the 5 species positive for Blastocystis sp. To the best of our knowledge, this is the first report of Blastocystis ST27 in birds in China, namely bar-headed goose (Anser indicus) and peafowl (Pavo muticus). The data suggest that captive wildlife, particularly those in bird parks, may frequently be infected with this zoonotic pathogen. Consequently, these animals may serve as potential reservoirs for zoonotic infections in humans.

Genetic diversity of single-celled microorganism Blastocystis sp. and its associated gut microbiome in free-ranging marine mammals from North-Western Mediterranean Sea

Blastocystis sp. is frequently identified in humans and several animal hosts exhibiting a wide genetic diversity. Within One Health perspective, data on Blastocystis sp. distribution and its circulating subtypes (STs) from the terrestrial environment are available, while those from the marine environment remain still scare. A genetic and 16S rRNA gene sequencing analysis were conducted over the period 2022-2024 by screening fecal samples from four different species of free-ranging marine mammals (sperm, fin, long-finned pilot and Cuvier's beaked whales) circulating within North-Western Mediterranean Sea. 10 out of 43 fecal samples (23.2 %) were found positive to Blastocystis sp. using molecular tools. A predominance of zoonotic subtype ST3 among different species of marine mammals as well as the presence of ST1 allele 4 subtype and even untypable subtype within the fin whale specimen was reported. Moreover, Firmicutes, Bacteroidetes and Proteobacteria within the different Blastocystis-carrier marine mammal species as well the identification of Archaebacteria from Methanomethylophilaceae family within the fin whale isolate were detected by Illumina V3-V4 generated data. The present survey presents new insights regarding Blastocystis sp. prevalence and its circulating zoonotic ST1-ST3 subtypes from the marine environment, as well as its associated gut microbiome, providing hence baseline data for a better understanding of the associated risk and to prevent human and marine ecosystem exposure to these anthropogenic microorganisms.

First Report on the Frequency and Subtype Distribution of Blastocystis sp. in Extensively Reared Holstein-Friesian Cattle from Terceira Island, Azores Archipelago, Portugal

This study is the first to report Blastocystis sp. in dairy cattle from Terceira Island, part of the Azores Archipelago. Blastocystis sp. is an enteric protozoan with high genetic diversity and is associated with both zoonotic and non-zoonotic subtypes (STs). The present survey aimed to fill the gap in knowledge regarding the occurrence and genetic characterization of Blastocystis sp. isolates in Holstein-Friesian cattle in this geographical area. A total of 116 stool samples were thus collected from dairy cows, and Blastocystis sp. DNA was detected using qPCR. The results revealed a 14.7% occurrence rate (17/116), with seven STs identified including ST3, ST5, ST7, ST10, ST14, ST25, and ST42, with variable frequency. Some of these STs (ST5, ST7, ST10, and ST14) are potentially zoonotic, underscoring their potential public health significance. However, the low frequency of Blastocystis sp. in this animal cohort possibly attributed to the extensive grazing system practiced on Terceira Island and the limited presence of zoonotic isolates, suggests a minimal risk of transmission from cattle to humans. This study highlights the importance of further research on the transmission dynamics of Blastocystis sp., particularly in regions with varying farming practices, to better understand its epidemiology and zoonotic potential.

Global Prevalence and Subtype Distribution of Blastocystis sp. in Rodent Populations: A Systematic Review and Meta-Analysis

BACKGROUND

The present systematic review and meta-analysis aimed to gather and analyse global data on the prevalence, subtypes (STs) distribution and zoonotic potential of Blastocystis sp. in rodents.

METHODS

A systematic literature search was performed across multiple databases (PubMed, Scopus, Web of Science and ProQuest) for studies published by 23 July 2024. The analysis included 34 studies/78 datasets, comprising 5661 samples from various rodent species across 15 countries. Statistical analyses were performed using comprehensive meta-analysis (CMA) software, employing a random-effects model to estimate pooled prevalence and 95% confidence intervals (CIs) and the I2 index for assessing heterogeneity.

RESULTS

This review found that 16% (95% CI: 12.6%-20.2%) of rodents worldwide were infected with Blastocystis sp. Voles and squirrels exhibited the highest infection rates at 29.8% (95% CI: 14.7%-51%) and 28.8% (95% CI: 14.4%-49.2%), whereas civets and porcupines had the lowest rates at 9.5% (95% CI: 6.6%-13.6%) and 7.1% (95% CI: 3.3%-14.7%), respectively. The findings indicated that rodents can host various Blastocystis sp. STs (ST1-ST8, ST10, ST13, ST15, ST17), with several (ST1-ST8 and ST10) having zoonotic potential. Globally, ST4, ST5, ST1 and ST3 were the most commonly reported STs in rodents. China and the UK showed the highest ST diversity in rodents, with 10 (ST1-ST7, ST10, ST13, ST17) and 7 (ST1-ST5, ST10, ST15) distinct STs, respectively. ST6, ST7 and ST13 were unique to China, whereas ST15 was found only in the United Kingdom. Squirrels, rats, mice and voles had the highest ST diversity of Blastocystis sp., with 8, 7, 5 and 5 distinct STs, respectively. Notably, ST6 and ST13 were unique to squirrels, ST7 only appeared in rats, and ST15 was found only in voles. Most ST1, ST3-ST5 and ST17 came from Asia. ST6, ST7 and ST13 were also isolated there, whereas ST15 was only found in Europe. ST17 was reported in Africa, ST4 and ST17 in North America, and ST1-ST3 and ST8 in South America.

CONCLUSIONS

This review emphasizes the widespread presence of Blastocystis sp. in rodent populations globally, underscoring the need for continued surveillance and research into its zoonotic potential.

Cats and dogs as hosts of Blastocystis - What is the evidence?

Blastocystis is one of the most common intestinal parasites observed in human and non-human hosts. Recent meta-analyses have indicated a potential role for pets such as dogs and cats as reservoir hosts of Blastocystis, but the data underpinning this hypothesis are of mixed quality. Reviewing data for 45,894 samples tested for Blastocystis by DNA-based methods and 11,908 subtype observations, a model was developed for calculating indices that could be used for evaluating individual species as natural hosts of Blastocystis, based on weighted products of positivity rates and subtype distributions. Data from cats and dogs were analysed, using other well-sampled hosts (pig, cattle, sheep, goat, and human) as references. Data from cats and dogs meeting the inclusion criteria were entered into the model. The overall positivity rates for pigs, cattle, sheep, goats, humans, dogs, and cats were 40 %, 40 %, 35 %, 28 %, 25 %, 6 %, and 5 %, respectively, with statistically significant lower positivity rates in cats and dogs (p < 0.0001). Indices indicating Blastocystis specificity to host ranged between 0.16 (humans) and 0.49 (cattle) for the reference hosts, whereas indices for cats and dogs were only 0.01 and 0.02, respectively. Finally, indices for ST specificity to host were higher for reference hosts (range, 0.66-0.93) than for cats (0.62) and dogs (0.56). Taken together, the analyses indicate that cats and dogs are not natural or reservoir hosts of Blastocystis and that the sporadic subtype pattern observed in these hosts might indicate exposure to Blastocystis through contaminated water/feed, including Blastocystis colonizing prey animals.

Accelerating the paradigm shift in Blastocystis research

Blastocystis, once targeted as a harmful intestinal parasite, is now seen as potentially beneficial. Piperni et al. link its presence to improved gut health, higher microbial diversity, and favorable cardiometabolic outcomes, which suggests that Blastocystis might indicate a healthy diet and gut, possibly serving as a symbiont rather than a pathogen.

New Haplotypes of Blastocystis sp. Identified in Faeces from Various Animal Groups in Algeria

PURPOSE

Blastocystis sp. is a single-celled, anaerobic, parasitic protozoan commonly found in the intestinal tract of animals and humans globally. Genetic analysis has revealed significant diversity within its species, leading to the identification of at least 40 subtypes (ST1-ST40). This study aimed to identify and differentiate Blastocystis in faeces samples from various animal hosts in Algeria.

METHODS

A total of 403 fecal samples, collected from both domestic and zoo animals, were subjected to PCR amplification and sequencing of Blastocystis-specific small subunit ribosomal RNA (SSU-RNA) gene.

RESULTS

The overall prevalence of Blastocystis in animals was found to be 38.9%. Through comprehensive phylogenetic and phylogeographic analyses, we identified four distinct subtypes (ST1 in both domestic and zoo animals, and ST3, ST4, and ST5 exclusively in zoo animals), encompassing nine different haplotypes, including five that appear original to Algeria.

CONCLUSION

This study represents the first epidemiological molecular investigation of Blastocystis sp. in animals in Algeria.

Detection of Blastocystis sp. and Dientamoeba fragilis using conventional and molecular methods in patients with celiac disease

Blastocystis sp. and Dientamoeba fragilis are intestinal protists, which are common worldwide, but the pathogenic role of these organisms in gastrointestinal diseases is still controversial. This study aimed to investigate the frequency of Blastocystis sp. and D. fragilis in stool samples from adult patients with celiac disease (CD) by using conventional and molecular methods. A total of 75 patients with CD and 75 healthy individuals were included in this study. Fresh stool specimens collected from each individual were analyzed by conventional and molecular methods. The overall prevalence of Blastocystis sp. and D. fragilis was 41.3% (31/75) and 24% (18/75) in patients with CD, and 46.7% (35/75) and 13.3% (10/75) in healthy controls, respectively. There was no statistically significant difference in the prevalence of Blastocystis sp. and D. fragilis between CD patients and healthy individuals. Blastocystis sp. subtypes were identified in 20 CD and 16 control patients and the overall subtype distribution was observed as ST1 13.9%, ST2 30.6%, and ST3 55.6%. The prevalence of Blastocystis sp. and D. fragilis in adults with CD is similar to the prevalence of protozoa in healthy adults. In this study, the most prevalent Blastocystis subtype was ST3 and the most frequent allele was a34 in both CD patients and healthy individuals. No significant difference was found between the two groups in terms of the detection rates of Blastocystis sp. and D. fragilis, and it is thought that both protists may be colonisers of the intestinal microbiome.

Blastocystis colonization and associations with population parameters in Thai adults

BACKGROUND

Blastocystis is a unicellular eukaryote commonly found in the intestinal tract of humans and other animals. The prevalence of Blastocystis has been investigated in both developed and developing countries, yet its occurrence and distribution in rural locations has been less studied. Herein, we aimed to examine the distribution of Blastocystis colonization in Thai adults representing background populations along a rural/peri-urban gradient, as well as associations between colonization and personal characteristics.

METHODOLOGY

A total of 238 participants were recruited from rural and peri-urban areas situated in three provinces. The presence of Blastocystis in feces was evaluated using PCR and qPCR. Information on gender, age, region (province), rural/peri-urban location, and body mass index (BMI) was collected.

PRINCIPAL FINDINGS

The overall rate of Blastocystis carriage was 67.2%. Univariate analysis revealed significant associations between Blastocystis carriage and region (p<0.05), location (p<0.001) and age group (p<0.05). Logistic regression analysis revealed that rural/peri-urban location and BMI were significantly associated with Blastocystis carriage. Nine subtypes (ST1-ST7, ST10 and ST23) were identified with ST3, ST7 and ST1 as the most abundant ones, in this order. The greatest diversity of subtypes, in terms of numbers, was found in the middle aged group (nine subtypes), while the least diversity was found in the young adult and obese (three subtypes each) groups.

CONCLUSIONS

This study increases the understanding of the epidemiology of Blastocystis colonization and its association with population parameters and characteristics in middle-income countries.

Large-Scale Molecular Epidemiological Survey of Blastocystis sp. among Herbivores in Egypt and Assessment of Potential Zoonotic Risk

Given the proven zoonotic potential of the intestinal protozoan Blastocystis sp., a fast-growing number of surveys are being conducted to identify potential animal reservoirs for transmission of the parasite. Nevertheless, few epidemiological studies have been conducted on farmed animals in Egypt. Therefore, a total of 1089 fecal samples were collected from herbivores (sheep, goats, camels, horses, and rabbits) in six Egyptian governorates (Dakahlia, Gharbia, Kafr El Sheikh, Giza, Aswan, and Sharqia). Samples were screened for the presence of Blastocystis sp. by real-time PCR followed by sequencing of positive PCR products and phylogenetic analysis for subtyping of the isolates. Overall, Blastocystis sp. was identified in 37.6% of the samples, with significant differences in frequency between animal groups (sheep, 65.5%; camels, 62.2%; goats, 36.0%; rabbits, 10.1%; horses, 3.3%). Mixed infections were reported in 35.7% of the Blastocystis sp.-positive samples. A wide range of subtypes (STs) with varying frequency were identified from single infections in ruminants including sheep (ST1-ST3, ST5, ST10, ST14, ST21, ST24, ST26, and ST40), goats (ST1, ST3, ST5, ST10, ST26, ST40, ST43, and ST44), and camels (ST3, ST10, ST21, ST24-ST26, ST30, and ST44). Most of them overlapped across these animal groups, highlighting their adaptation to ruminant hosts. In other herbivores, only three and two STs were evidenced in rabbits (ST1-ST3) and horses (ST3 and ST44), respectively. The greater occurrence and wider genetic diversity of parasite isolates among ruminants, in contrast to other herbivores, strongly suggested that dietary habits likely played a significant role in influencing both the colonization rates of Blastocystis sp. and ST preference. Of all the isolates subtyped herein, 66.3% were reported as potentially zoonotic, emphasizing the significant role these animal groups may play in transmitting the parasite to humans. These findings also expand our knowledge on the prevalence, genetic diversity, host specificity, and zoonotic potential of Blastocystis sp. in herbivores.

Predominance of the Blastocystis subtype ST5 among free-living sympatric rodents within pig farms in China suggests a novel transmission route from farms

Blastocystis is a parasitic protist that can infect humans and various domestic and wild animals. However, there is limited research on the prevalence of this parasite among rodents, particularly those living in pig farm settings. Therefore, to investigate the occurrence, molecular characterization, and zoonotic potential of Blastocystis among rodents within pig farm environments, we conducted an investigation of 227 rodents and shrews from 34 pig farms located in Henan, Shaanxi, and Shanxi provinces of China using nested PCR of the SSU rRNA gene of Blastocystis. The potential transmission and public health implications were also assessed from a One Health perspective. Blastocystis was detected in 86 (37.9%) fecal samples. The highest infection rate was observed among Ruttus norvegicus (73.7%, 42/58), followed by Ruttus tanezumi (30.1%, 41/136), and Mus musculus (12.0%, 3/25). However, it was not detected among individuals with Apodemus agrarius (n = 1) and Crocidura shantungensis (n = 7). Five known zoonotic Blastocystis subtypes (ST1-ST5) were identified, with ST4 (51.2%, 44/86) and ST5 (40.7%, 35/86) being the predominant ones, followed by ST1 (3.5%, 3/86), ST3 (3.5%, 3/86), and ST2 (1.2%, 1/86). ST4 was prevalent among R. norvegicus (83.3%, 35/42), while ST5 dominated R. tanezumi (70.7%, 29/41). Furthermore, ST5 exhibited the widest distribution at pig farm level, accounting for 65.0% (13/20) of Blastocystis-positive pig farms. This investigation presents the first documented Blastocystis infection in R. tanezumi and M. musculus, highlighting the predominant presence of the zoonotic ST5 subtype in rodents for the first time. The results demonstrate that sympatric rodents can serve as natural reservoirs for Blastocystis and play a role in its transmission. These findings provide information on the dynamics of rodent transmission and emphasize the potential public health threat posed by zoonotic Blastocystis subtypes spillover from pig farms.

First molecular subtyping and zoonotic significance of Blastocystis sp. in Dromedary (C. dromedarius) and Bactrian (C. bactrianus) camels in Iran: A molecular epidemiology and review of available literature

BACKGROUND

Blastocystis sp. is a zoonotic protozoan parasite, and there is limited information about its molecular prevalence and subtypes (STs) distribution in camels globally, especially in Iran.

OBJECTIVES

This study aimed to examine the prevalence, STs distribution, and zoonotic potential of Blastocystis sp. in one-humped and two-humped camels in Ardabil province, northwestern Iran.

METHODS

A PCR-sequencing tool using the SSU rRNA gene was employed to examine the occurrence and genetic variation of Blastocystis sp. in 150 faecal samples from Bactrian (Camelus bactrianus, 50 samples) and Dromedary (Camelus dromedarius, 100 samples) camels in Ardabil province.

RESULTS

The overall prevalence of Blastocystis sp. in camels was determined to be 12% (18/150) through microscopy and PCR analyses. Phylogenetically, this study identified three distinct zoonotic STs: ST7, ST10, and ST14. ST10 was the most prevalent, comprising 50% (9/18) of the isolated STs from camels. ST14 closely followed with 38.9% (7/18), while ST7 made up 11.1% (2/18) of the total STs. In brief, ST10, ST14, and ST7 represented 50% (7/14), 35.7% (5/14), and 14.3% (2/14) of the Blastocystis-positive cases in one-humped camels, respectively. Further, each of the ST10 and ST14 accounted for 50% (2/4) of the Blastocystis-positive samples in two-humped camels. An analysis of the available data reveals that out of the 37-44 identified Blastocystis STs, 15 (ST1-ST7, ST10, ST14, ST15, ST21, ST24, ST25, ST26, and ST30) have been reported in camels. The predominant STs observed are ST10 and ST14. Furthermore, among the 15 zoonotic STs (ST1-ST10, ST12-ST14, ST16, and ST23) of Blastocystis reported thus far, nine zoonotic STs (ST1-ST7, ST10, and ST14) have been found in camels.

CONCLUSIONS

These findings indicate that camels serve as a proper reservoir for a diverse array of Blastocystis STs and thereby can play a significant role in the transmission of this protozoan infection to humans, animals, and water reservoirs.

Subtype-host patterns and genetic differentiation of Blastocystis sp. in the Philippines

Blastocystis sp. is a gastrointestinal protozoan commonly encountered in humans and animals. Specificity to certain hosts may be associated with 38 known subtypes (STs) and 8 nonmammalian and avian STs (NMASTs). This can be determined by analyzing ST-host associations, ST-allele data, genetic variability analyses, and fixation index (FST) with sufficient data present. Thus, newly acquired and previously published data on Blastocystis sp. STs and NMASTs from the Philippines were compiled to determine the following: (1) ST-host associations, (2) ST-allele diversity per ST in certain hosts/sources, (3) intrasubtype diversity of certain STs found in different hosts using genetic variability analysis, and (4) comparison of similarities between specific ST populations to determine if these are the same circulating populations using FST. A total of 448 samples subtyped using both sequence-tagged site primers and the 600-bp barcoding region of the Blastocystis sp. SSU rRNA gene were analyzed in this study. Patterns of association for the Philippine samples were similar to those from neighboring Southeast Asian countries and around the world: ST1-ST4 were found in humans but ST3 was the most common, ST5 were found in pigs, and ST6 and ST7 were found in poultry. Blastocystis sp. from humans are mostly the same ST alleles (ST3 allele 34 and ST1 allele 4) while 3-5 ST alleles were found in the most common STs in pigs, macaques, and poultry. Also, ST1, ST3, ST5, and NMAST I are undergoing population expansion according to genetic variability analyses through possible addition of new alleles based on ST-allele diversity. Moreover, FST shows the same circulating population of ST1 in humans, pigs, and water indicating a possible waterborne route of cross-transmission. In contrast, ST3 found in humans possibly come from the same circulating population and is genetically distinct from those in nonhuman sources.

Identification of Blastocystis spp. in Urban Rodents of Different Districts in Southwestern Iran: Subtype Distribution and Possible Zoonotic Potential

PURPOSE

Rodents are one of the most abundant and diverse species of mammals and have recently been identified as carriers of numerous human pathogens. The current study was conducted to assess the prevalence, subtype (STs) distribution, and zoonotic potential of Blastocystis spp. in various species of rodents in Shiraz, southwestern Iran.

METHODS

For this aim, a total of 120 fresh fecal samples were collected from Mus musculus (n = 40), Rattus norvegicus (n = 40), and Rattus rattus (n = 40) in various municipality districts of Shiraz (6 out of 10 districts) between February and November 2020. Upon detecting parasites using light microscopy, a DNA fragment of the Blastocystis SSU rDNA gene was amplified using conventional PCR.

RESULTS

By employing direct wet mount examination, 8 out of 120 fecal samples (6.7%; 2 from house mice, 3 from black rats, and 3 from brown rats) tested positive. Similarly, 5% (2/40) of house mice, 7.5% (3/40) of black rats, and 7.5% (3/40) of brown rats tested positive using the molecular method. Phylogenetic analysis revealed that the Blastocystis infecting different rodent species in Shiraz belonged to two potentially zoonotic STs (ST1 and ST4). Accordingly, rodents should not be overlooked as potential reservoirs of zoonotic Blastocystis infections. Different sampled urban districts and their statistical association with reported prevalence rates were analyzed separately.

CONCLUSION

 Overall, the issue of the frequency and ST distribution of Blastocystis in urban rodents of Iran is still open to question and for a proper understanding, wider and more comprehensive studies are needed.