Bioclimatic analysis and spatial distribution of fascioliasis causative agents by assessment of Lymnaeidae snails in northwestern provinces of Iran.

BACKGROUND: Snails of the Lymnaeidae family are the intermediate hosts of Fasciola species, the causative agents of fascioliasis. The purpose of this study was to determine the prevalence of Fasciola species in lymnaeid snails and to investigate the association of geoclimatic factors and Fasciola species distribution in northwestern provinces of Iran using geographical information system (GIS) data. METHODS: A total of 2000 lymnaeid snails were collected from 33 permanent and seasonal habitats in northwestern Iran during the period from June to November 2021. After identification by standard morphological keys, they were subjected to shedding and crushing methods. Different stages of Fasciola obtained from these snails were subjected to the ITS1 polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) method for species identification. The associations of weather temperature, rainfall, humidity, evaporation, air pressure, wind speed, elevation, and land cover with the distribution of Fasciola species were investigated. Geographical and statistical analysis was performed using ArcMap and SPSS software, respectively, to determine factors related to Fasciola species distribution. RESULTS: Of the 2000 snails collected, 19 were infected with Fasciola hepatica (0.09%), six with F. gigantica (0.03%), and 13 with other trematodes. Among geoclimatic and environmental factors, mean humidity, maximum humidity, and wind speed were significantly higher in areas where F. hepatica was more common than F. gigantica. The altitude of F. hepatica-prevalent areas was generally lower than F. gigantica areas. No significant relationship was observed between other investigated geoclimatic factors and the distribution of infected snails. CONCLUSIONS: The present study showed the relationship of humidity and wind speed with the distribution of snails infected with F. hepatica or F. gigantica in the northwestern regions of Iran. In contrast to F. gigantica, F. hepatica was more prevalent in low-altitude areas. Further research is recommended to elucidate the relationship between geoclimatic factors and the presence of intermediate hosts of the two Fasciola species.

Assessment of the genetic diversity of lymnaeid (Gastropoda: Pulmonata) snails and their infection status with trematode cercariae in different regions of Thailand.

Lymnaeid snails are some of the most widespread snails and are the first intermediate host of trematode parasites that affect human and livestock health. A full understanding of the genetic relationship of hosts and parasites is of paramount importance for effective parasite management. The present study assessed the prevalence of trematode larvae in lymnaeid snails and examined the genetic diversity of these snails collected across Thailand. We collected 672 lymnaeid snails from 39 locations in 22 provinces of six regions in Thailand. Subsequently, cercarial infection in the snails was observed by using the shedding method. Lymnaeid snails released 5 types of trematode cercariae, namely, xiphidiocercariae, echinostome cercariae I, echinostome cercariae II, furcocercous cercariae, and strigea cercariae. The phylogenetic analysis based on ITS2 and 28S rDNA sequences revealed 5 cercaria types assigned to four trematode families, of which two belong to the group of human intestinal flukes. Combination of shell morphology and sequence analysis of the mitochondrial COI and 16S rDNA genes, the lymnaeid snails were classified into two species, Radix rubiginosa and Orientogalba viridis. Moreover, the combined dataset of mtDNA genes (COI + 16S rDNA) from R. rubiginosa and O. viridis revealed 32 and 15 different haplotypes, respectively, of which only a few haplotypes were infected with cercariae. The genetic diversity and genetic structure revealed that R. rubiginosa and O. viridis experienced a bottleneck phenomenon, and showed limited gene flow between populations. Population demographic history analyses revealed that R. rubiginosa and O. viridis experienced population reductions followed by recent population expansion. These findings may improve our understanding of parasite-lymnaeid evolutionary relationships, as well as the underlying molecular genetic basis, which is information that can be used for further effective control of the spread of trematode disease.

Diversity of trematode cercariae among naturally infected lymnaeid snails from Phayao, Thailand.

Lymnaeids are aquatic snails playing an important role in the transmission of many parasitic trematode species of veterinary and medical importance. In this study, we assessed the presence of cercarial flukes in naturally infected lymnaeid snails from Phayao province, Thailand, and determined the species diversity of both the intermediate snail hosts and parasite larvae. A total of 3,185 lymnaeid snails were collected from paddy fields at 31 sites in eight districts of Phayao province between October 2021 and December 2022. Larval fluke infection was assessed using the cercarial shedding method. The collected snails as well as emerging cercariae were identified at the species level via morphological and molecular methods. The sequences of snail internal transcribed spacer region 2 (ITS2) and cercarial 28S ribosomal RNA gene (28S rDNA) and cytochrome C oxidase1 (Cox1) were determined by PCR amplification and sequencing. Three species of lymnaeid snails were detected in this study, including Radix (Lymnaea) rubiginosa (Michelin, 1831), Radix (Lymnaea) swinhoei (Adams, 1866) and Austropeplea viridis (Quoy & Gaimard, 1832), of which R. rubiginosa was the most abundant, followed by A. viridis and R. swinhoei. The overall rate of trematode cercarial infection in the lymnaeid snails was 2.8% (90/3,185); the cercarial infection rate in R. rubiginosa and A. viridis was 3.5% (60/1,735) and 3.1% (30/981), respectively. No larval fluke infection was observed in the studied R. swinhoei (0/469). Nine morphotypes of cercariae were detected at 15 sites from four districts. The emerging cercariae were molecularly identified as Clinostomum sp., Aporocotylidae sp., Apharyngostrigea sp., Trichobilharzia sp., Apatemon sp., Pegosomum sp., Petasiger sp., Echinostoma revolutum and Plagiorchis sp. These findings emphasize the occurrence and diversity of trematode cercariae among naturally infected lymnaeid snails in Phayao province and could contribute to broadening our understanding of the host-parasite relationships between trematodes and their first intermediate hosts as well as developing effective interventions to control trematode parasitic diseases.

Fasciolosis in the Mediterranean island of Corsica (France): Insights from epidemiological and malacological investigations.

Fasciolosis is a re-emergent parasitic disease of worldwide significance with a major global impact on livestock health and production. In the French Mediterranean island of Corsica, fasciolosis has been recognized for a long time but little is known about its dynamic as the main investigations are outdated. Three compartments - definitive domestic hosts, intermediate hosts and environment - involved in fasciolosis transmission were studied by applying an integrative and extensive approach: (1) farm and abattoir surveys, (2) snail sampling, identification and infection prospection, and (3) snail habitat analysis; and (4) a questionnaire-based survey to inquire about husbandry practices and environmental risks. Our results indicate a significant circulation of the liver flukes in Corsican livestock, with 90% (252/279) of the sampled farms testing positive for anti-F. hepatica antibodies. At the abattoir, 46% (67/149) of cattle were positive for F. hepatica antibodies and eggs were present in the bile of 19% (26/139) bovines. In addition, high prevalence of Dicrocoelium dendriticum (69%) was observed in slaughtered cattle. Malacological surveys registered the occurrence of several lymnaeid species in a variety of habitats throughout the island. In particular, we report for the first time the presence of the invasive lymnaeid snail Pseudosuccinea columella in Corsica, a potential intermediate host for F. hepatica. We also found that the presence of Galba truncatula and, to a lesser extent, that of Peregriana peregra, is associated with altitude. Fasciola hepatica DNA was detected in the latter species occurring at two different sites. Finally, a questionnaire-based study revealed risky management practices among Corsican farmers, low perception of transmission and a suboptimal use of flukicide treatments as main control strategy. Our results show that animal fasciolosis in Corsica is characterised by a significant circulation and a favourable epidemiological scenario for transmission to occur.

Genetic diversity and relationships of the liver fluke Fasciola hepatica (Trematoda) with native and introduced definitive and intermediate hosts.

Fasciolosis is a worldwide spread parasitosis mainly caused by the trematode Fasciola hepatica. This disease is particularly important for public health in tropical regions, but it can also affect the economies of many developed countries due to large infections in domestic animals. Although several studies have tried to understand the transmission by studying the prevalence of different host species, only a few have used population genetic approaches to understand the links between domestic and wildlife infections. Here, we present the results of such genetic approach combined with classical parasitological data (prevalence and intensity) by studying domestic and wild definitive hosts from Camargue (southern France) where fasciolosis is considered as a problem. We found 60% of domestic hosts (cattle) infected with F. hepatica but lower values in wild hosts (nutria, 19%; wild boars, 4.5%). We explored nine variable microsatellite loci for 1,148 adult flukes recovered from four different populations (non-treated cattle, treated cattle, nutria and wild boars). Populations from the four groups differed, though we found a number of migrants particularly non-treated cattle and nutria. Overall, we detected 729 different multilocus genotypes (from 783 completely genotyped individuals) and only 46 genotypes repeated across samples. Finally, we experimentally infected native and introduced intermediate snail hosts to explore their compatibility with F. hepatica and assess the risks of fasciolosis expansion in the region. The introduced species Galba truncatula and Pseudosuccinea columella attained the higher values of overall compatibility in relation to the European species. However, concerning the origin, sympatric combinations of G. truncatula were more compatible (higher prevalence, intensity and survival) than the allopatric tested. According to our results, we should note that the assessment of epidemiological risks cannot be limited to a single host-parasite system, but should focus on understanding the diversity of hosts in the heterogeneous environment through space and time.

Autochthonous Human Fascioliasis, Belgium.

We report 2 cases of human fascioliasis (HF) in Belgium, likely caused by consumption of vegetables from a garden that was flooded by pasture runoff. Because autochthonous HF is rare and the route of transmission was unusual, HF was not diagnosed until 6 months after symptom onset in both cases.

Infección con Fasciola hepatica en el ganado y hospederos intermediarios en 10 vaquerías de un municipio occidental de Cuba / Natural Infection with Fasciola hepatica in Host-Snails and Cattle in Ten Dairy Farms from a Western Municipality in Cuba / Infecção com Fascíola hepática no gado e hospedeiros intermediários em 10 leiterias de um município ocidental de Cuba

Resumen La fasciolosis es una trematodosis que afecta fuertemente al ganado de Cuba. Se estudiaron 10 vaquerías del municipio más occidental de Cuba para determinar la prevalencia de esta parasitosis en el ganado y en los hospederos intermediarios. Se recolectaron y estudiaron muestras fecales de 455 vacas lecheras seleccionadas al azar. Las muestras fueron conservadas a -20 oC hasta su estudio. La detección de la infección por Fasciola hepatica fue realizada a partir de un método de Elisa denominado FasciDIG®. El análisis e interpretación de los resultados demostró que 146 muestras fueran positivas a F. hepatica (32,09 %). Todas las vaquerías presentaron animales infectados con rangos de prevalencia entre las vaquerías que oscilaron de 9,5 % al 84 %. También fue posible encontrar las dos especies de hospederos intermediarios de este parásito en Cuba, Galba cubensis y Pseudosuccinea columella. Debe prestarse atención a la prevalencia en bovinos encontrada en este estudio para prevenir la aparición de brotes humanos de esta enfermedad.

Abstract Fasciolosis is a foodborne trematodosis affecting many cattle farms in Cuba. Ten dairy farms in western Cuba were studied to assess the prevalence in both intermediate and definitive hosts. A single stool sample from 455 dairy cows was taken and studied. The animals were randomly selected and the samples were kept at -20oC until infection was determined. Detection of the Fasciola hepatica infection was carried out using a non-commercial sandwich-ELISA called FasciDIG®. Results showed that 146 samples were positive for F. hepatica (32.09%) with every farm testing positive for F. hepatica infection, while prevalence ranged from 9.5% to 84% among farms. It was also possible to detect the presence of the two species of intermediate hosts of this trematode in Cuba, Galba cubensis and Pseudosuccinea columella. Main attention must be given to bovine prevalence found in this study in order to prevent eventual human outbreaks of this disease.

Resumo A fasciolose é uma trematoda que afeta fortemente ao gado de Cuba. Foram estudadas 10 leiterias do município mais ocidental de Cuba para determinar a prevalência desta parasitose no gado e nos hospedeiros intermediários. Se coletaram e estudiaram amostras fecais de 455 vacas leiteiras selecionadas aleatoriamente. As amostras foram conservadas a −20 oC até seu estudo. A detecção da infecção por Fascíola hepática foi realizada a partir de um método de Elisa denominado FasciDIG®. A análise e interpretação dos resultados demonstrou que 146 amostras foram positivas à F. hepática (32,09 %). Todas as leiterias apresentaram animais infectados com rangos de prevalência entre as leiterias que oscilaram de 9,5 % a 84 %. Também foi possível encontrar a duas espécies de hospedeiros intermediários deste parasita em Cuba, Galba cubensis e Pseudosuccinea columella. Deve prestar-se atenção à prevalência em bovinos encontrada neste estudo para prevenir a aparição de surtos humanos desta enfermidade.

The Status of Human and Animal Fascioliasis in Iran: A Narrative Review Article.

BACKGROUND: The public health importance of human fascioliasis has increased during last few decades due to the appearance of new emerging and re-emerging foci in many countries. Iran, as the most important focus of human disease in Asia, has been included among six countries known to have a serious problem with fascioliasis by WHO. Various aspects of the disease in Iran are discussed in this review. METHODS: This narrative review covers all information about human and animal fascioliasis in Iran, which has been published in local and international journals from 1960 to 2014 using various databases including PubMed, SID, Google Scholar, Scopus, Science Direct. RESULTS: During the period of the study the infection rates of 0.1% to 91.4% was noted in various livestock. Despite the higher infection rates of livestock in southern areas in past decades, human disease has been mostly encountered in northern Provinces especially in Guilan. Recent studies indicate noticeable decrease in prevalence rates of veterinary fascioliasis in Iran, however the prevalence rates of fascioliasis in livestock in northern Provinces of Guilan and Mazandaran seem to remain at a higher level in comparison to other parts. New foci of the disease have also been reported recently. CONCLUSION: While the prevalence of animal fascioliasis has decreased during last decades, human fascioliasis emerged as a public health problem in the country. The validity of new foci of human fascioliasis needs complementary standard studies.