ReviewEchinococcosis – an international public health challenge
Introduction
The genus Echinococcus is of great importance because it contains a number of zoonotic species that can cause serious ill health in man. There are at least 4 species in the genus, but recent molecular evidence suggests that there should be a taxonomic revision to at least 5 species (Table 1) or even possibly 6 (Le et al., 2002; McManus, 2002; Thompson and McManus, 2002). There is also significant strain variation in the species Echinococcus granulosus. With each species the definitive host is a carnivore, whilst the intermediate host can be one of a large number of mammalian species. The parasite is of pathogenic and economic significance in intermediate and aberrant intermediate hosts, where the larval parasite develops into a hydatid cyst. The genus is found throughout the world although a number of species have a limited geographical distribution.
Section snippets
Species and distribution
Cystic echinococcosis (CE) caused by the larval stage of E. granulosus is the most widespread of these parasites (Fig. 1). Dogs are the usual definitive hosts whilst a large number of mammalian species can be intermediate hosts, including domestic ungulates and man. In the UK, the parasite has a restricted distribution, being found mainly in mid and southern Wales. In Europe, zoonotic strains of E. granulosus are present in every country with the exceptions of Ireland, Iceland and Denmark. It
Clinical aspects
In the definitive host, adult Echinococcus penetrate deeply between the villi into the crypts of Lieberkuhn. Despite this intimate host parasite relationship there are few if any lesions. Consequently, there appears to be no ill effect on the definitive host even in the presence of very heavy infections.
In the intermediate host, hydatid cysts have been found in a large variety of mammalian species and often grow slowly, sometimes taking several years to develop. Cysts most frequently affect the
Human echinococcosis
Human echinococcosis results when man ingests eggs, which have been shed in the faeces of the definitive host. The initial phase of CE is asymptomatic with small well-encapsulated cysts. After an undefined period of several months to years, the infection may become symptomatic as a space-occupying lesion. However, 60% of infections will remain asymptomatic (Pawlowski et al., 2001). The liver is the most common organ involved, usually with over two thirds of cysts. The lungs are infected in
Epidemiology and transmission to man
Echinococcus granulosus has both sylvatic cycles, often involving wild carnivores and ungulates; and domestic cycles, usually involving dogs and farm livestock. It is the latter transmission cycle that is the most common and poses the greatest threat to human health. The highest incidence rates in man are often seen in areas where there is a close association with man and domestic livestock, often using dogs as working dogs. A common source of infection for dogs is offal from infected sheep,
Diagnosis
In the intermediate host, the presence of E. granulosus has usually been detected at post-mortem by examination of the viscera. This can provide important epidemiological data, which can be used to define the likely infection pressure (Cabrera et al., 1996; Ming et al., 1992; Torgerson et al., 1998). The main disadvantage of this approach is that a slaughterhouse sample is potentially biased. In Kenya ultrasound detected hydatid cysts in sheep and goats with a sensitivity and specificity of 54%
Control
Control of CE has always involved a combination of routine anthelmintic treatment of dogs, control and reduction of stray dog populations, supervision of the slaughter of livestock and subsequent disposal of offal, and education of the public. The prepatent period of E. granulosus is approximately 6 weeks and hence this has usually been the recommended treatment interval. Praziquantel is currently the most effective anthelmintic available for this purpose. Mathematical models have been
Conclusions
Despite the large efforts that have been put into the research and control of echinococcosis, it still remains a disease of worldwide significance. In some areas of the world, CE caused by E. granulosus is a re-emerging disease in places where it was previously at low levels. There are also disturbing trends in the distribution of E. multilocularis with an increased detection rate in Europe and a number of intensely infected communities in China. If this deteriorating trend is to be stopped
Acknowledgments
The authors would like to thank INTAS, the National Institutes of Health (USA), and The National Science Foundation (USA) for their financial support.
References (78)
- et al.
Identification of Echinococcus granulosus eggs
Diagnostic Microbiology and Infectious Disease
(2002) - et al.
Control of Echinococcus granulosus in Uruguay: evaluation of different treatment intervals for dogs
Veterinary Parasitology
(2002) - et al.
Screening of dogs for Echinococcus granulosus coproantigen in a low endemic situation in Cyprus
Veterinary Parasitology
(2002) - et al.
A large focus of alveolar echinococcosis in central China
The Lancet
(1992) - et al.
Detection, screening, and community epidemiology of taeniid cestode zoonosis: cystic echinococcosis, alveolar ecinococcosis, and neurocystercercosis
Advances in Parasitology
(1996) Polycystic echinococcosis in tropical America: Echinococcus vogeli and E. oligarthus
Acta Tropica
(1997)- et al.
Veterinary aspects of alveolar echinococcosis – a zoonoses of public health significance
Veterinary Parasitology
(2001) - et al.
Alveolar echinococcosis in humans: the current situation in central Europe and the need for countermeasures
Parasitology Today
(1999) - et al.
Echinococcosis: an emerging or re-emerging zoonosis?
International Journal for Parasitology
(2000) Australian contributions to an understanding of the epidemiology and control of hydatid disease caused by Echinococcus granulosus past, present and future
International Journal for Parasitology
(1990)
Vaccination trial in Australia and Argentina confirms the effectiveness of the EG95 vaccine in sheep
International Journal for Parasitology
Coproantigen detection in dogs experimentally infected with Echinococcus granulosus by a monoclonal antibody-based Enzyme-Linked Immunosorbant Assay
International Journal for Parasitology
Frequency distribution of Echinococcus granulosus hydatid cysts in sheep populations in the Xinjiang Uygur Autonomous region, China
Veterinary Parasitology
Echinococcus multilocularis in domestic cats in France: A potential risk factor for alveolar hydatid disease contamination in humans
Veterinary Parasitology
The longevity of hydatid cysts in horses
Veterinary Parasitology
Evaluation of diagnostic ultrasound as a mass screening technique for the detection of hydatid cysts in the liver and lungs of sheep and goats
International Journal for Parasitology
Equine hydatidosis. A review of the current status in Great Britain and the results of an epidemiological survey
Veterinary Parasitology
Towards a taxonomic revision of the genus Echinococcus
Trends in Parasitology
The use of mathematical models to simulate control options for echinococcosis
Acta Tropica
Economic aspects of echinococcosis
Acta Tropica
Cystic echinococcosis in humans in Kyrgystan: an epidemiological study
Acta Tropica
Further evidence for the long distance dispersal of taeniid eggs
International Journal for Parasitology
The emerging epidemic of echinococcosis in Kazakhstan
Transactions of the Royal Society of Tropical Medicine and Hygiene
Modelling the prevalence of Echinococcus and Taenia species in small ruminants of different ages in Northern Jordan
Veterinary Parasitology
Coproantigen for the detection for immunodiagnosis of echinococcosis and taeniasis in dogs and humans
Parasitology
Transmission dynamics of Echinococcus granulosus, Taenia Hydatigena and Taenia ovis in sheep in Uruguay
International Journal for Parasitology
Risk factors associated with human cystic echinococcosis in Florida, Uruguay: results of a mass screening study using ultrasound and serology
American Journal of Tropical Medicine and Hygiene
Detection of Echinococcus coproantigens by enzyme-linked immunoabsorbent assay in dogs, dingoes and foxes
Parasitology Research
Echinococcus multilocularis coproantigen detection by immunoabsorbant assay in fox, dog and cat populations
Journal of Parasitology
Urban transmission of Echinococcus multilocularis
Detection of Echinococcus multilocularis in the definitive host: coprodiagnosis by PCR as an alternative to necropsy
Journal of Clinical Microbiology
Risk factors associated with human cystic echinococcosis in Jordan: results of a case-control study
Annals of Tropical Medicine and Parasitology
Echinococcus multilocularis and alveolar echinococcosis in Europe (except parts of Eastern Europe)
Epidemiology of Echinococcus multilocularis and E. granulosus in central Europe
Parassitologia
Alveolar echinococcosis (Echinococcus multilocularis ) and other forms of echinococcosis (Echinococcus vogeli and Echinococcus oligarthrus)
Echinococcosis in animals: clinical aspects, diagnosis and treatment
Experience gained and evaluation of the echinococcosis/hydatidosis eradication programmes in Cyprus 1971–1999
Detection of cestode infections in the definitive hosts: present status and future advances
Cited by (163)
Assessing the role of individual foxes in environmental contamination with Echinococcus multilocularis through faecal samples
2024, International Journal for ParasitologyCystic, Alveolar and Neotropical Echinococcosis
2023, Manson's Tropical Diseases, Fourth EditionInsects dispersing taeniid eggs: Who and how?
2021, Veterinary ParasitologySeroprevalence of human cystic echinococcosis in South Kashmir, India
2020, Parasite Epidemiology and ControlCitation Excerpt :All serum samples were stored at −70 °C until antibody determination. Specific ELISA was used for detecting specific anti Echinococcus granulosus antibodies in the sera of participants as described earlier (Torgerson and Budke, 2003; Chiraga et al., 2014. Specific ELISA used was a commercially prepared kit (Echinococcus ELISA IgG- NovaTec, Germany –D-63128).