Predicting environmental suitability and geographical distribution of Dicrocoelium dendriticum at littoral of Caspian Sea: An ecological niche-based modeling

Validation of deep amplicon sequencing of Dicrocoelium in small ruminants from Northern regions of Pakistan

Dicrocoelium lancet flukes cause significant production loss in ruminant livestock. Although co-infection with multiple Dicrocoelium species within a host is common, techniques for studying the composition of these complex parasite communities are lacking. The pathogenicity, epidemiology, and therapeutic susceptibility of different helminth species vary, and little is known about the interactions that take place between co-infecting species and their hosts. Here, we describe the first applicationof metabarcoding deep amplicon sequencing method to studythe Dicrocoelium species in sheep and goats. First, rDNA ITS-2 sequences of four Dicrocoelium species (Dicrocoelium dendriticum, Dicrocoelium hospes, Dicrocoelium orientalis, and Dicrocoelium chinensis) were extracted from the NCBI public database. Phylogenetic analysis revealed separate clades of Dicrocoelium species; hence, molecular differentiation between each species is possible in co-infections. Second, 202 flukes belonging to seventeen host populations (morphologically verified as belonging to the Dicrocoelium genus) were evaluated to determine the deep amplicon sequencing read threshold of an individual fluke for each of the four species. The accuracy of the method in proportional quantification of samples collected from single hosts was further assessed. Overall, 198 (98.01%) flukes were confirmed as D. dendriticum and 1.98% produced no reads. The comparison of genetic distances between rDNA ITS-2 revealed 86% to 98% identity between the Dicrocoelium species. Phylogenetic analysis demonstrated a distinct clustering of species, apart from D. orientalis and D. chinensis, which sit very close to each other in a single large clade whereas D. hospes and D. dendriticum are separated into their own clade. In conclusion each sample was identified as D. dendriticum based on the proportion of MiSeq reads and validated the presence of this group of parasites in the Gilgit Baltistan and Khyber Pakhtunkhwa provinces of Pakistan. The metabarcoding deep amplicon sequencing technology and bioinformatics pathway have several potential applications, including species interactions during co-infections, identifying the host and geographical distribution of Dicrocoelium in livestock, drug therapy response evaluation and understanding of the emergence and spread of drug resistance.

Spatial Distribution of Dicrocoelium in the Himalayan Ranges: Potential Impacts of Ecological Niches and Climatic Variables

PURPOSE

Dicrocoeliosis can be an important cause of production loss in ruminants due to the cost of liver condemnation at slaughter. The aim of the present study was to determine the prevalence of Dicrocoelium infection and to predict the ecological niches and climatic variables that support dicrocoeliosis in the Himalayan ranges of Pakistan.

METHODS AND RESULTS

Dicrocoelium was detected in 33 of 381 liver samples and 238 of 6060 blood samples taken from sheep and goat herds in the area. The prevalence of dicrocoeliosis was higher in sheep than in goats and highest in females aged more than 3 years. An environmental risk map was created to predict active zones of transmission and showed the highest probability values in central parts of the Chitral district in the northwest of Pakistan. Climatic variables of the mean monthly diurnal temperature range (Bio2), annual precipitation (Bio12), and normalised difference vegetation index (NDVI) were found to be significantly (p < 0.05) associated with the presence of Dicrocoelium infection.

CONCLUSION

Together, the findings of this study demonstrate the most suitable ecological niches and climatic variables influencing the risk of dicrocoeliosis in the Himalayan ranges of Pakistan. The methods and results could be used as a reference to inform the control of dicrocoeliosis in the region.

Molecular analysis of internal transcribed spacer 2 of Dicrocoelium dendriticum isolated from cattle, sheep, and goat in Iran

Background

Dicrocoelium dendriticum is a broadly distributed zoonotic helminth, which is mainly reported from domesticated and wild ruminants. There is little data covering the molecular features of this trematode; therefore, current study aimed to molecularly analyze D. dendriticum in livestock.

Methods

Totally, 23 samples of D. dendriticum were collected from cattle, sheep, and goat from Ilam, Lorestan, and Khuzestan, three west and south-west provinces of Iran from February to August 2018. After genomic DNA extraction, the internal transcribed spacer (ITS) 2 fragment was amplified and sequenced in samples. To investigate genetic variations through the ITS 2 fragment of obtained D. dendriticum, phylogenetic tree and network analysis were employed.

Results

All 23 samples were successfully amplified and sequenced. Phylogenetic tree showed that our samples were clearly grouped in a clade together with reference sequences. There was no grouping based on either geographical regions or hosts. Network analysis confirmed the phylogenetic findings and showed the presence of nine distinct haplotypes, while our samples together most of sequences, which were previously submitted to the GenBank, were grouped in the Hap1.

Conclusions

Our findings indicated that although ITS 2 fragment discriminate D. dendriticum, this fragment is not suitable to study intra-species genetic variations. Therefore, exploring and describing new genetic markers could be more appropriate to provide new data about the genetic distribution of this trematode.

The prevalence of foodborne parasites in raw vegetables in Iran: a comprehensive systematic review and meta-analysis

Foodborne parasites in raw vegetables could cause parasitic infections in humans. An effective approach to the reduction of pathogenic microorganisms in vegetables involves identifying the main sources of contamination and the ecology of the involved microorganisms. This review aimed to evaluate the prevalence of foodborne parasites in raw vegetables in Iran. According to the reviewed studies, the prevalence rate of Ascaris spp., Giardia spp., Toxocara spp., Fasciola, Trichuris, Cryptosporidium, Dicrocoeliasis, Taenia spp., and Entamoeba histolytica was 6 % (95 % CI: 5-8 %), 6 % (95 % CI: 5-7 %), 6 % (95 % CI: 4-7 %), 2 % (95 % CI: 1-2 %), 1 % (95 % CI: 1-2 %), 10 % (95 % CI: 6-15 %), 2 % (95 % CI: 1-3 %), 5 % (95 % CI: 4-6 %), and 3 % (95 % CI: 2-4 %), respectively. According to the standard deviation map, Ilam province was one of the high-risk areas in terms of food-borne parasites in raw vegetables (3 SD < prevalence < 4 SD). Given the key role of raw vegetables in human parasitic contamination, governments must implement more stringent programs for effective wastewater treatment, preventing domestic and wild animals from entering farms, not using human and animal manure on farms, using ready-to-eat packaged vegetables, food safety training for households, implementation of GMP and HACCP in the factory vegetable packaging are required in this regard, especially in the high-risk areas of Iran, such as Ilam province.

SUPPLEMENTARY INFORMATION

The online version contains supplementary material available at 10.1007/s40201-021-00714-w.

Constraints of using historical data for modelling the spatial distribution of helminth parasites in ruminants

Dicrocoelium dendriticum is a trematode that infects ruminant livestock and requires two different intermediate hosts to complete its lifecycle. Modelling the spatial distribution of this parasite can help to improve its management in higher risk regions. The aim of this research was to assess the constraints of using historical data sets when modelling the spatial distribution of helminth parasites in ruminants. A parasitological data set provided by CREMOPAR (Napoli, Italy) and covering most of Italy was used in this paper. A baseline model (Random Forest, VECMAP^®) using the entire data set was first used to determine the minimal number of data points needed to build a stable model. Then, annual distribution models were computed and compared with the baseline model. The best prediction rate and statistical output were obtained for 2012 and the worst for 2016, even though the sample size of the former was significantly smaller than the latter. We discuss how this may be explained by the fact that in 2012, the samples were more evenly geographically distributed, whilst in 2016 most of the data were strongly clustered. It is concluded that the spatial distribution of the input data appears to be more important than the actual sample size when computing species distribution models. This is often a major issue when using historical data to develop spatial models. Such data sets often include sampling biases and large geographical gaps. If this bias is not corrected, the spatial distribution model outputs may display the sampling effort rather than the real species distribution.

Evaluation of zoonotic platyhelminthe infections identified in slaughtered livestock in Iran, 2015-2019

Background

Platyhelminth infections of livestock can result in considerable economic losses. This study aims to evaluate the spatial frequency of cystic echinococcosis (CE), dicrocoeliasis, and fascioliasis in livestock slaughtered in Iran during the years 2015–2019 and estimate direct costs associated with organ condemnation due to these parasites.

Methods

Abattoir data from 413 abattoirs representing all 31 Iranian provinces were collected from the Iran Veterinary Organization. Infection prevalence was calculated per year at the province level. The Local Moran’s I statistic was performed to evaluate spatial autocorrelation of animals positive at slaughter for the years 2015–2019. Direct costs associated with condemned livers were calculated for each parasitic condition, with costs associated with condemned lungs also included for CE.

Results

Overall prevalence values for the study timeframe were as follows: sheep and goat fascioliasis 1.56% (95% CI: 1.56–1.56%), cattle fascioliasis 3.86% (95% CI: 3.85–3.88%), sheep and goat dicrocoeliasis 4.63% (95% CI: 4.62–4.63%), cattle dicrocoeliasis 3.08% (95% CI: 3.07–3.09%), sheep and goat CE 5.32% (95% CI: 5.32–5.33%), and cattle CE 7.26% (95% CI: 7.24–7.28%). Northwest Iran had the highest prevalence of CE and fascioliasis. High infection areas for Dicrocoelium spp. included the provinces of Zanjan, Gilan, Qazvin, and Tehran, which are located in northern Iran. Direct economic losses for sheep and goat fascioliasis, dicrocoeliasis, and CE for the study period were US$13,842,759, US$41,771,377, and US$22,801,054, respectively. Direct economic losses for cattle fascioliasis, dicrocoeliasis, and CE for the study period were US$1,989,200, US$1,668,986, and US$2,656,568, respectively.

Conclusion

Our findings provide valuable data for future monitoring of these important parasitic diseases in Iranian livestock. Disease control strategies are required to reduce the economic and public health impact of these platyhelminths.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12917-021-02888-9.

Molecular confirmation of Dicrocoelium dendriticum in the Himalayan ranges of Pakistan

Lancet liver flukes of the genus Dicrocoelium (Trematoda: Digenea) are recognised parasites of domestic and wild herbivores. The aim of the present study was to confirm the species identity of Dicrocoeliid flukes collected from the Chitral valley in the Himalayan ranges of Pakistan. The morphology of 48 flukes belonging to eight host populations was examined; but overlapping traits prevented accurate species designation. Phylogenetic comparison of published D. dendriticum ribosomal cistron DNA, and cytochrome oxidase-1 (COX-1) mitochondrial DNA sequences with those from D. chinensis was performed to assess within and between species variation and re-affirm the use of species-specific single nucleotide polymorphism markers. PCR and sequencing of 34 corresponding fragments of ribosomal DNA and 14 corresponding fragments of mitochondrial DNA from the Chitral valley flukes, revealed 10 and 4 unique haplotypes, respectively. These confirmed for the first time the molecular species identity of Pakistani lancet liver flukes as D. dendriticum. This work provides a preliminary illustration of a phylogenetic approach that could be developed to study the ecology, biological diversity, and epidemiology of Dicrocoeliid lancet flukes when they are identified in new settings.