Evaluation of molecular methods for the field study of the natural history of Dicrocoelium dendriticum

Dicrocoeliidae Family: Major Species Causing Veterinary Diseases

This chapter analyses the taxonomic position of the Dicrocoeliidae family and several of its genera and species. The chapter reviews the biology of major veterinary disease-causing species, including Dicrocoelium dendriticum, Dicrocoelium hospes, Dicrocoelium chinensis, Eurytrema pancreaticum and Platynosomum fastosum. All these species have indirect life cycles with two intermediate hosts: molluscs as the first host and ants, grasshoppers and lizards as the second host. Dicrocoelium dendriticum is a widespread liver fluke found in ruminants across Europe, Asia, North Africa and North America. It can also infect humans. Dicrocoelium hospes is widely distributed in the savanna areas of Africa south of the Sahara, while D. chinensis is mainly found in ruminants in East Asia and some European countries (probably imported from Asia). Eurytrema pancreaticum is a common parasite that lives in the bile ducts, gall bladder, pancreatic ducts and intestines of ruminants. It is found in Europe, Madagascar, Asia and South America. Adults of P. fastosum live in the liver, gall bladder and pancreas of birds and mammals in Europe, Africa, Asia, North, Central and South America. Information on the epidemiology, pathology, clinical aspects, diagnosis, treatment, control, prevention and economic impact of Dicrocoeliosis caused by D. dendriticum, Eurytrematodosis and Platynosomiosis have been included.

Case report: Infection with Dicrocoelium dendriticum in a Japanese Chin dog

Dicrocoelium dendriticum is a trematode colonising the bile ducts of herbivores. Coproscopic findings in dogs are usually considered gastrointestinal passages of eggs after ingestion of unheated liver tissue or infected ruminant faeces. Here, a Japanese Chin presented with diarrhoea and weight loss. Eggs comparable to D. dendriticum were detected in faeces and infection was confirmed via PCR and by ruling out differential diagnoses. Egg excretion continued for a period of 10 months. Praziquantel (50 mg/kg body weight [BW]) was administered orally for four consecutive days. Egg excretion 10 days after treatment entailed further treatments with 100 mg/kg BW, again for four days. Faecal samples were negative ten days and four weeks afterwards, diarrhoea resolved, and the dog gained weight. In cases of repeated coproscopic positivity for D. dendriticum, an infection with dogs acting as definitive hosts should be considered. Treatment with praziquantel at a higher dosage may be required.

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 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.

Dicrocoeliidae Family: Major Species Causing Veterinary Diseases

This chapter analyses the taxonomic position of Dicrocoeliidae family and several of its genus and species. The biology of the major species causing veterinary diseases such Dicrocoelium dendriticum, Dicrocoelium hospes, Dicrocoelium chinensis, Eurytrema pancreaticum and Platynosomum fastosum, has been reviewed. All these species have an indirect life cycle, involving two intermediate hosts (molluscs as first and ants, grasshoppers and lizards as second). Dicrocoelium dendriticum is a very widespread hepatic trematode in the ruminants of many countries in Europe, Asia, North Africa and North America, even affecting humans. Dicrocoelium hospes is widely distributed in the savanna areas of Africa south of the Sahara, whilst D. chinensis has mainly been found in ruminants in East Asia and some European countries (probably imported from Asia). Eurytrema pancreaticum is a common parasite whose adults live in ruminant bile ducts, gall bladder, pancreatic ducts and intestines in Europe, Madagascar, Asia and South America. Adult P. fastosum live in the liver, gall bladder and pancreas of birds and mammals in Europe, Africa, Asia, North, Central and South America. Information about the epidemiology, pathology, clinical aspect, diagnosis, treatment, control, prevention and economic impact mainly of Dicrocoeliosis produced by D. dendriticum, as well as of Eurytrematodosis and Platynosomiosis, has been included.