Control of hydatid disease in Wales

Cystic Echinococcosis in Turkana, Kenya: The Role of Cross-Sectional Screening Surveys in Assessing the Prevalence of Human Infection

Cystic echinococcosis (CE) is a neglected zoonotic disease caused by Echinococcus granulosus. Infection leads to formation of cysts within the viscera of the human host. In the 1980s, the transhumant population of northwest Turkana, Kenya, was found to have the highest prevalence of CE in the world. In 1983, AMREF Health Africa and the Kenya Medical and Research Institute launched a CE Control Program in northwest Turkana, screening and treating the local people. This epidemiological study of CE in Turkana analyses approximately 30 years of surveillance and surgical data. Cyst data were categorized using the World Health Organization CE ultrasound classification system before being analyzed for cyst, patient, and population characteristics, and surveillance data from 1985 are compared with more recent surveillance data to assess changes in prevalence in the control region since the commencement of control activities. In 1985, the prevalence of CE among the Turkana was 5.6%. In 2010-2011 and 2011-2012, calculated CE prevalence rates were 1.9% and 3.8%, respectively. Since the 1980s, the age distribution of people with CE in Turkana has shifted: initially, cases of CE appeared predominantly within younger age groups, but recent data reveal a higher prevalence within older age groups. The frequency of infection in females also significantly decreased. The reduction in CE prevalence from 5.6% in the 1980s to 1.9-3.8% in 2010-2012 and the shift in age distribution of CE-infected individuals over time indicate that the prevalence of CE in Turkana has decreased since the control program began.

Global Distribution of Alveolar and Cystic Echinococcosis

Alveolar echinococcosis (AE) and cystic echinococcosis (CE) are severe helminthic zoonoses. Echinococcus multilocularis (causative agent of AE) is widely distributed in the northern hemisphere where it is typically maintained in a wild animal cycle including canids as definitive hosts and rodents as intermediate hosts. The species Echinococcus granulosus, Echinococcus ortleppi, Echinococcus canadensis and Echinococcus intermedius are the causative agents of CE with a worldwide distribution and a highly variable human disease burden in the different endemic areas depending upon human behavioural risk factors, the diversity and ecology of animal host assemblages and the genetic diversity within Echinococcus species which differ in their zoonotic potential and pathogenicity. Both AE and CE are regarded as neglected zoonoses, with a higher overall burden of disease for CE due to its global distribution and high regional prevalence, but a higher pathogenicity and case fatality rate for AE, especially in Asia. Over the past two decades, numerous studies have addressed the epidemiology and distribution of these Echinococcus species worldwide, resulting in better-defined boundaries of the endemic areas. This chapter presents the global distribution of Echinococcus species and human AE and CE in maps and summarizes the global data on host assemblages, transmission, prevalence in animal definitive hosts, incidence in people and molecular epidemiology.

Echinococcosis: Control and Prevention

Human cystic echinococcosis (CE) has been eliminated or significantly reduced as a public health problem in several previously highly endemic regions. This has been achieved by the long-term application of prevention and control measures primarily targeted to deworming dogs, health education, meat inspection, and effective surveillance in livestock and human populations. Human CE, however, remains a serious neglected zoonotic disease in many resource-poor pastoral regions. The incidence of human alveolar echinococcosis (AE) has increased in continental Europe and is a major public health problem in parts of Eurasia. Better understanding of wildlife ecology for fox and small mammal hosts has enabled targeted anthelmintic baiting of fox populations and development of spatially explicit models to predict population dynamics for key intermediate host species and human AE risk in endemic landscapes. Challenges that remain for echinococcosis control include effective intervention in resource-poor communities, better availability of surveillance tools, optimal application of livestock vaccination, and management and ecology of dog and wildlife host populations.

Cystic echinococcosis in a fox-hound hunt worker, UK

A male resident in Vanuatu with prior history of employment as a hunt kennel-man in England (1980-2001) was surgically treated for the removal of a hydatid cyst subsequently confirmed as Echinococcus granulosus (G1 genotype). This is the first human molecularly identified CE case reported from the UK and a first in a fox-hound handler and indicates a general neglected occupational risk.

Seroprevalence ofEchinococcus granulosusinfection in Croatian patients with cystic liver disease

Cystic liver disease (CLD), presenting with solitary or multiple cysts in the liver, is a common diagnosis today, primarily due to the frequent application of modern radiological methods. There is a wide range of possible causes. CLD of infective origin is usually caused by an echinococcal species. During the past three decades a number of cystic echinococcosis (CE) control programmes have led to a significant decrease in the incidence of human hydatidosis in some endemic areas. The aim of this study was to determine the seroprevalence ofE. granulosusinfection in Croatian patients with CLD. A total of 540 serum samples from patients with hepatic cysts detected by imaging methods were screened for the presence ofE. granulosusIgG antibodies using semiquantitative enzyme-linked immunosorbent assay. The Western blot technique was used as a confirmatory test for the CE diagnosis. The overallE. granulosusseroprevalence rate in patients with CLD was 3.9%. There was no significant difference in seroprevalence rate between male and female patients (P = 0.541). According to age groups, there was a significant difference in seropositivity among age groups (P = 0.002). The highest seroprevalence rate was detected in the youngest age group (up to 18 years), both in males and females (20% and 13%, respectively). This study indicates that CE still represents a public health problem in Croatia. Preventive measures should be used to controlEchinococcusinfections, including avoidance of contact with infected dogs, egg-contaminated soil or plants; control and treatment of dogs with antihelmintics; hand washing, improved sanitation and health education.

Control of cystic echinococcosis/hydatidosis: 1863-2002

Echinococcosis/hydatidosis, caused by Echinococcus granulosus, is a chronic and debilitating zoonotic larval cestode infection in humans, which is principally transmitted between dogs and domestic livestock, particularly sheep. Human hydatid disease occurs in almost all pastoral communities and rangeland areas of the underdeveloped and developed world. Control programmes against hydatidosis have been implemented in several endemic countries, states, provinces, districts or regions to reduce or eliminate cystic echinococcosis (CE) as a public health problem. This review assesses the impact of 13 of the hydatid control programmes implemented, since the first was introduced in Iceland in 1863. Five island-based control programmes (Iceland, New Zealand, Tasmania, Falklands and Cyprus) resulted, over various intervention periods (from <15 to >50 years), in successful control of transmission as evidenced by major reduction in incidence rates of human CE, and prevalence levels in sheep and dogs. By 2002, two countries, Iceland and New Zealand, and one island-state, Tasmania, had already declared that hydatid disease had been eliminated from their territories. Other hydatid programmes implemented in South America (Argentina, Chile, Uruguay), in Europe (mid-Wales, Sardinia) and in East Africa (northwest Kenya), showed varying degrees of success, but some were considered as having failed. Reasons for the eventual success of certain hydatid control programmes and the problems encountered in others are analysed and discussed, and recommendations for likely optimal approaches considered. The application of new control tools, including use of a hydatid vaccine, are also considered.

Dog echinococcosis in northern Spain: comparison of coproantigen and serum antibody assays with coprological exam

A large sheep-dog population from the province of Alava (northern Spain) has been investigated in order to determine the prevalence of the cestode parasite Echinococcus granulosus. Worms were detected in 14.0% of 721 dog faecal supernatants by coproantigen ELISA, and in 9.1% of 754 dog serum samples by serum antibody ELISA. A weak but statistically significant correlation (Spearman's rho=0.103, 95% CI: 0.023-0.178) between the two immunoassay results was found. In addition, eggs of the family Taeniidae were detected in 10.3% of 726 faecal samples examined by coproparasitological (flotation and sedimentation) tests. The overall E. granulosus infection rate, based on a Bayesian latent class model that accounts for the imperfect sensitivities and specificities of all diagnostic tests used, was estimated to be 8.0% (95% credible interval: 5.4-11.4%), corroborating that sheep-dog is the dog class most vulnerable to acquiring the infection. Dog sex did not influence the prevalence of E. granulosus, independently of the diagnostic test used or the dog region of origin. No significant linear correlation was found between the coproantigen ELISA OD values and the dog age (Spearman's rho=-0.049, 95% CI: -0.234 to 0.135), suggesting that there were no differences in prevalence of E. granulosus between old and young dogs. The obtained results highlight the importance of initiating a control program based on regular treatment of the sheep-dogs with praziquantel in the province of Alava.

Canine echinococcosis in northwest Libya: assessment of coproantigen ELISA, and a survey of infection with analysis of risk-factors

In order to determine the prevalence and risk factors for canine echinococcosis in different endemic localities in the Tripoli area of northwest Libya, stray dogs were examined post-mortem, and owned dogs screened for Echinococcus granulosus infection using a standardised genus specific coproantigen ELISA. The prevalence of E. granulosus infection at necropsy in stray-dogs was 25.8% (15/58, 95% CI 15.3-39.0%), and 21.6% (72/334, 95% CI 17.3-26.4%) of owned dogs tested were positive by coproantigen ELISA. Sheepdogs appeared to have a significantly higher copro-positive prevalence (19/19 positive, p=0.003), compared to 23.6% of other dog classes (e.g. 52/220 guard dogs and household pets). Worm burdens in necropsied dogs ranged from 29 to 2900 (mean 1064) and were positively correlated to coproantigen ELISA OD values (r(s)=0.87, p<0.001), but negatively correlated with dog age (r(s)=-0.69, p=0.001). Dog age was a significant factor in copro-prevalence as there was an increasing coproantigen-positive tendency in younger dogs (< or =5 years, p=0.04). A total of 45/132 (34%, 95% CI 25.9-42.1%) of farms/homestead had at least one dog that was coproantigen positive. Overall copro-prevalence in dogs by locality varied, with Alkhums (Leptis-Magna) district having the highest copro-prevalence at 38.7% (24/62, 95% CI 26.6-50.8%) (p=0.001). Coproantigen testing of a cohort of owned dogs before and approximately 15 months after praziquantel treatment showed a significant decrease in the coproantigen positive rate from 21.6% (72/334) to 9% (21/233) post-treatment. The overall E. granulosus coproantigen positive rate ('re-infection rate') within the same cohort of dogs was 22 % (10/45) by 15 months post-treatment. Significant risk factors for a copro-positive owned dog were associated with non-restraint of dogs, and owners that did not de-worm their dogs. Home slaughtering of livestock and lack of knowledge about E. granulosus transmission were also significant risk factors for a canine coproantigen positive result.

Double-antibody sandwich ELISA using biotinylated antibodies for the detection of Echinococcus granulosus coproantigens in dogs

Here we present the diagnostic evaluation of an improved double-antibody sandwich ELISA for detecting Echinococcus granulosus antigens in dog faecal samples (coproantigens). A purified rabbit IgG fraction against protoscolex excretory-secretory products was used as primary antibody, and the same fraction conjugated with biotin as secondary antibody. In order to validate the sandwich ELISA, intra- and inter-assay precision, linearity, and recovery percentages were calculated. The diagnostic evaluation of the method was carried out by investigating faecal samples from 37 dogs naturally infected with E. granulosus, 15 Echinococcus-free dogs infected with Taenia spp., 82 dogs with non-taeniid helminths and 66 dogs free of helminth infections. An overall sensitivity of 78.4% and specificity of 93.3% were determined. Positive and negative predictive values were 72 and 95%, respectively, and the diagnostic efficiency was 90.5%. In addition, the sandwich ELISA detection limit was estimated in 5.12 ng ml(-1). These results are highly satisfactory, allowing the use of this methodology in surveillance and control programs for intestinal echinococcosis in dogs.

Reemergence of canine Echinococcus granulosus infection, Wales

As a consequence of large-scale outdoor slaughter of sheep during the 2001 foot and mouth disease (FMD) outbreak in the United Kingdom and the possibility of increased risk for transmission of Echinococcus granulosus between sheep and dogs, a large survey of canine echinococcosis was undertaken in mid-Wales in 2002. An Echinococcus coproantigen-positive rate of 8.1% (94/1,164) was recorded on 22% of farms surveyed, which compares to a rate of 3.4% obtained in the same region in 1993. Positivity rates between FMD-affected properties and unaffected ones did not differ significantly. Significant risk factors for positive results in farm dogs were allowing dogs to roam free and the infrequent dosing (>4-month intervals) of dogs with praziquantel. When these data are compared to those of a previous pilot hydatid control program in the area (1983-1989), an increase in transmission to humans appears probable.

Hydatid control in Australia: where it began, what we have achieved and where to from here

Echinococcus granulosus was imported into Australia with domestic livestock about 200 years ago. It spread rapidly through domestic animals and quickly became a public health problem in the new colony. Control was hampered by ignorance of the transmission pattern. The association between metacestodes and tapeworms was not elucidated until 63 years after the arrival of the First Fleet. Australian wildlife were highly susceptible to infection with E. granulosus and wildlife/domestic animal interaction facilated rapid infiltration of wildlife by E. granulosus. The wildlife reservoir has hampered hydatid control campaigns on mainland Australia but successful eradication has been achieved in the island state of Tasmania where there was no wildlife reservoir. The application of a new recombinant vaccine for sheep in control campaigns and the use of praziquantel baits for controlling infection in dingoes around bush campsites and picnic areas is discussed.

Echinococcosis: disease, detection and transmission

Echinococcosis is one of the world's most geographically widespread parasitic zoonoses, with transmission occurring in tropical, temperate and arctic biomes. Most human infections are due to Echinococcus granulosus transmitted between domestic dogs and livestock, but this cosmopolitan species also cycles between wild carnivores (principally canids) and wild ungulates. The other species with significant zoonotic potential is E. multilocularis that occurs naturally in fox definitive hosts and small mammal intermediate hosts. These two species cause human cystic or alveolar echinococcosis respectively, which may be considered serious public health problems in several regions including developed countries. This review provides an introductory overview to the Supplement and summarises the biology and epidemiology of these two related cestodes with an emphasis on applied aspects relating to detection, diagnosis and surveillance in animal and human populations, and includes aspects of transmission ecology, and also considers aspects of community epidemiology and potential for control.

Glioma after cerebral hydatid disease

BACKGROUND

The authors present the case of a 31-year-old man with a malignant glioma. He had been treated for cerebral hydatid as a child, and 22 years later he developed a glioma at the site of his previous disease.

DISCUSSION

Could chronic inflammatory change following intracranial hydatid disease have induced neoplastic transformation of glial cells?

Pulmonary cystic hydatid disease in Ireland

BACKGROUND

Hydatid disease is rare in Ireland and its incidence and prevalence are unknown. Most cases are diagnosed by a combination of clinical findings, morphological features on imaging and by serological testing.

AIMS

We describe an Irish case of pulmonary hydatid disease detected at bronchoscopy by bronchoalveolar lavage, and discuss the diagnosis and treatment of the disorder.

CONCLUSION

The diagnosis of this rare disease requires a high index of suspicion. Treatment is primarily surgical, with a role for antihelminthic agents.

Pulmonary echinococcosis with chest wall involvement in a patient with no apparent risk factors

Pulmonary hydatid disease is rare in the U.K., and chest wall involvement has to our knowledge not previously been described in this country. We report the case of a 72-year-old man who was found to have a left upper lobe opacity on his chest radiograph. He declined further investigation at the time, but 2 years later developed a palpable mass over his left lateral chest wall. Fine-needle aspiration-biopsy of this mass revealed the diagnosis of pulmonary hydatid disease. Despite thorough questioning, no risk factor could be identified for the development of the disease. Hydatid disease should be remembered as a rare cause of mass lesions identified on chest radiographs even in non-endemic regions. Spread to the chest wall may mimic malignancy.

Canine echinococcosis: an alternative for surveillance epidemiology

The essential activities for programmes of cystic echinococcosis control are the census of all dogs from the program and identification of parasitised animals. Currently, in South America evaluations and epidemiological surveillance are based on the administration of arecoline hydrobromide. This method has the disadvantage of increasing environmental pollution and risk for operators and owners of treated dogs. A genus-specific ELISA capture method has been employed for recently issued faeces and the confirmation of positive examination was performed by dog autopsies. Our work presents an alternative method based on collection of dry field-dispersed faeces, followed by serological diagnosis by Copro-ELISA and confirmation by Copro-Western blot. If Copro-ELISA were used to define positive samples of dry faeces, the Copro-Western blot assay would provide 70% sensitivity and 100% specificity. Global efficiency of the system using dry faeces would reach 76%, allowing epidemiological surveillance to be oriented to analysis of surface units instead of dog as measurement unit.

Use of sentinel lambs to survey the effect of an education programme on control of transmission of Echinococcus granulosus in South Powys, Wales

In this article the effects of an education programme (area II) on transmission of Echinococcus granulosus from dogs to sheep in Wales and of substitution of the education programme by a 6-weekly anthelmintic control programme (area I) are compared with the situation in an area where no control interventions had occurred (area III). The education programme failed to prevent transmission of E. granulosus to sentinel lambs examined at 15 months of age, 6%, 4%, and 10% of which were infected in areas I, II, and III, respectively. Educational efforts did, however, show some positive effects; for example, significantly more farmers (87-98%) in areas I, II, and III used praziquantel to treat their dogs compared with 39% of farmers in a lowland area in the east of England where E. granulosus is absent. In particular, the interval between treatments of dogs was significantly shorter in areas targeted with education programmes, and 38% of farmers in area I treated dogs at a 4-6 week interval, as did 17% in area II and 10% in area III, compared with only 3% in the lowland area. Also, more dogs in Wales (65-88%) were treated at an interval of < or = 3 months, whereas most of the dogs in the lowland area (64%) were treated at intervals of > or = 6 months. The shorter treatment intervals with praziquantel may account for the significantly fewer positive coproantigen tests among dogs in area I (6.3%) and area II (5.6%) compared with area III (23.9%).

Detection of gastrointestinal helminth infections using coproantigen and molecular diagnostic approaches

Intestinal helminth parasites are responsible for a significant amount of pathology in both humans and farmed animals, resulting in a reduction in the quality of life, and occasionally lethal infection as well as causing decreases in livestock productivity. The importance of these parasites globally has resulted in efforts to understand the mechanisms of the host–parasite interaction epidemiology, and to develop methods for diagnosis and control.