Echinococcus Research Articles

Spatial spreading of Echinococcus multilocularis in Red foxes ( Vulpes vulpes) across nation borders in Western Europe

The occurrence of the fox tapeworm Echinococcus multilocularis in Red foxes was studied in Belgium and a neighbouring region in The Netherlands. A total number of 1202 foxes were analysed (1018 in Belgium and 184 in The Netherlands) of which 179 were infected with E. multilocularis (164 in Belgium and 15 in The Netherlands). Further, the spatial distribution of infection among sampled foxes was analysed with an ellipsoidal gradient, demonstrating a decreasing prevalence in northwestern direction. Using this gradient, we showed that the spatial patterns of infection in Belgium and the neighbouring region in The Netherlands correspond, indicating a continuous distribution of E. multilocularis across the nation borders. Part of the Belgian data allowed investigating temporal changes in the spatial distribution of E. multilocularis. This revealed a northwestern spread of E. multilocularis.

Echinococcus multilocularis – a zoonosis of anthropogenic environments?

Transmission of the fox tapeworm Echinococcus multilocularis, the causative agent of human alveolar echinococcosis, is known to depend on various environmental factors which are subject to human influence. Epidemiological data suggest that in most endemic regions anthropogenic landscape changes (e.g. deforestation and agricultural practices) have led to more favourable conditions for the parasite's animal hosts, especially arvicolid rodents, thereby increasing the risk for parasite transmission and human disease. Examples are the conversion of forests or crop fields into meadows and pastures in Europe, China and North America, and overgrazing of natural grassland in central Asia. Other anthropogenic factors include interference with host population densities by wildlife disease control, changing hunting pressure and provision of new habitats, e.g. in urban areas. Domestic dogs may, under certain conditions, get involved in the otherwise largely wildlife-based transmission, and thereby greatly increase the infection pressure to humans. The introduction of neozootic host species may increase transmission, or even initiate the parasite's life-cycle in previously non-endemic regions. Lastly, the parasite itself may be accidentally introduced into non-endemic areas, if suitable host populations are present (e.g. in northern Japan).

Imported disease of dogs and cats exotic to Ireland: Echinococcus multilocularis

Changes in legislation that facilitate the movement of animals within the European Union may increase the risk that some microbial and parasitic organisms, currently exotic to Ireland, will be introduced by travelled pet animals. It is possible that the fox tapeworm, Echinococcus multilocularis, might be introduced in that manner from any of the several member states in which it is endemic. Red foxes are the principal definitive hosts of E. multilocularis but dogs and cats can also be infected. Infection in the definitive host is of little clinical significance, but aberrant infection of humans results in alveolar echinococcosis, a debilitating disease that has a high mortality rate. Humans acquire the organism by ingestion of Echinococcus multilocularis eggs excreted by definitive hosts; the larval metacestodes develop primarily in the liver, in the initial asymptomatic phase as small, well-encapsulated cysts. Over time, perhaps five to 15 years, progressive local infiltration and secondary cyst development at distant sites occur with resultant clinical signs. Patients with infiltrative liver disease present with cholestatic jaundice, epigastric pain, fatigue, weight loss and hepatomegaly. If left untreated, the disease can be fatal.This paper recounts the life cycle of the parasite, and discusses the control measures on which its exclusion from Ireland depend. Strict adherence to the routine worming of travelled dogs with praziquantel, at appropriate doses, 24 to 48 hours prior to entry into the country will minimise the likelihood of introduction of this zoonosis.

Imaging aspects and non-surgical interventional treatment in human alveolar echinococcosis

Alveolar echinococcosis (AE) of the liver caused by the metacestode of the fox tapeworm Echinococcus multilocularis is characterized by a multivesicular structure surrounded by an extensive fibro-inflammatory host reaction. The lesions behave like a slow-growing liver cancer, without sharp limits between the parasitic tissue and the liver parenchyma. Invasion of biliary and vascular walls is another hallmark of this severe disease. Moreover, the poor vascularization of the parasitic mass often leads to necrosis in the central part of the lesion. This explains why liver abscess due to superimposed bacterial infection of the necrotic area may occur in this disease. Currently, a range of imaging techniques can be used at the different stages of management of AE. For diagnosis, ultrasonography remains the first line examination. For a more accurate disease evaluation, aiming to guide the surgical strategy, computerized tomography, Magnetic Resonance (MR) imaging, including cholangio-MR imaging are of importance, providing useful complementary information. More recently, Positive-Emission Tomography using [18F] fluoro-deoxyglucose has been developed for the follow-up of inoperable AE patients under long-term benzimidazoles therapy. This approach seems very promising to assess inflammatory activity and thereby to indirectly depict parasitic activity. Non-surgical interventional procedures, mainly percutaneous biliary and/or centro-parasitic abscesses drainages, are currently a major aspect in the care of incurable AE patients and have largely contributed to the improvement of survival in this situation during the past 20 years. They may also be used as a bridge before a curative surgical procedure in symptomatic patients presenting a life-threatening bacterial and/or fungal infection. It is also very useful in inoperable patients to overcome similar infectious episodes.

WHO classification of alveolar echinococcosis: Principles and application

Alveolar echinococcosis is caused by the larval stage of the fox tapeworm ( Echinococcus multilocularis) and is frequently diagnosed as a space occupying lesion in the liver. The growth pattern resembles that of a malignant tumor with infiltration throughout the liver, spreading into neighbouring organs and metastases formation in distant organs. Thus, one of the prevailing differential diagnoses is liver cancer. Guided by the Tumor–Node–Metastasis (TNM) system of liver cancer, the European Network for Concerted Surveillance of Alveolar Echinococcosis and the WHO Informal Working Group on Echinococcosis proposed a clinical classification for alveolar echinococcosis. It was designated as PNM system (P = parasitic mass in the liver, N = involvement of neighbouring organs, and M = metastasis). As for TNM in oncology, single PNM categories were combined into four stages, I to IV. The system was developed by a retrospective analysis of 97 patients' records from two treatment centers (Besançon/France and Ulm/Germany). Recently, this WHO classification was applied to 222 patients in 4 clinical centers around the world (Besançon/France, n = 26; Urumqi/China, n = 46; Sapporo/Japan, n = 58; and Ulm/Germany, n = 92). All patients could be classified who had been diagnosed in the period from January 1998 to June 2005. The stage grouping indicated center differences, but appeared to segregate patients according to various treatment regimens. The WHO classification not only serves as a tool for the international standardization of disease manifestation but also aids to evaluate the outcome of a chosen diagnostic and treatment procedure in different treatment centers in Europe and Asia.

Exploratory spatial relative risk mapping

The many faces of disease mapping include maps of disease case locations, regional counts of cases, and disease risk. Another approach is that of mapping the relative risk. Previous methods to map the relative risk were based on regression models of relative risk, given information about geographical locations and established risk factors. However, spatial epidemiological investigations are often exploratory with limited knowledge about the putative risk factors. Indeed, often the primary motivation for the analysis is to identify unknown geographically varying risk factors. An exploratory approach to mapping the spatial relative risk is to scale the risk map using the background risk in the unexposed (or less-exposed) population. Exposure to unknown spatial risk factors is defined via specific cluster analysis. Identification of spatial disease clusters separates the population into those inside and those outside high risk areas (the exposed and unexposed populations). This exploratory approach to relative risk mapping gives the investigator an impression about the importance and geographical distribution of the unknown spatial risk factors. Two examples illustrate the exploratory relative risk mapping approach using a spatial point data set on pseudorabies in pig-herds and a regional count data set on small fox tapeworm infections in red foxes.

Ecological epidemiology: the role of landscape structure in the transmission risk of the fox tapeworm Echinococcus multilocularis (Leukart 1863) (Cestoda: Cyclophyllidea: Taeniidae)

The larval form of the fox tapeworm Echinococcus multilocularis causes a fatal liver infection in humans and has high prevalence in western China. The tapeworm lifecycle involves small mammal populations and canids, such as foxes and dogs. Human contact with infected canids may lead to the transmission of the worm to humans, causing the disease human alveolar echinococcosis. This paper introduces the tapeworm and reviews the current understanding of its transmission ecology in relation to each component of its lifecycle. Recent research indicates that landscape plays an important role in creating the necessary habitat conditions for natural transmission. Defining the landscape involves the use of satellite imagery, land cover classification and spatial analysis. The link between disease, remote sensing and landscape ecology is an expanding research area and potentially an important one in relation to Echinococcus multilocularis and alveolar echinococcosis.

Ovarian echinococcosis in a 4-year old girl - case report

Hydatid disease of the genital organs is very rare with an incidence of 0.2%. This disease has no specific symptoms and findings. It is usually diagnosed intraoperatively. We present a case of a four-year old girl with ovarian echinococcosis, who had earlier been operated on in the Clinic of Pediatric Surgery University Hospital “St. George” Plovdiv, Bulgaria because of intestinal obstruction after laparotomy for liver echinococcosis. Keywords : ovarium, echinococcus, girl African Journal of Paediatric Surgery Vol. 2(1) 2005: 24-26

Copro-diagnosis of Echinococcus multilocularis by a nested PCR in red foxes (Vulpes vulpes) from northern Italy.

Copro-diagnosis of Echinococcus multilocularis by a nested PCR in red foxes (Vulpes vulpes) from northern Italy.

Modelling the spatial distribution of Echinococcus multilocularis infection in foxes

Alveolar echinococcosis is a rare but fatal disease in humans and is caused by the fox tapeworm Echinococcus multilocularis. The densities of fox and grassland rodent populations and the interactions between them influence E. multilocularis transmission rates in Europe. Successful rabies control has caused fox populations and E. multilocularis prevalence rates to increase in many European countries. The potential increase of the infection pressure on the human population motivates the monitoring of the infection status of foxes over space and time. Detection of E. multilocularis antigen levels in fox faecal samples collected in the field might provide a pragmatic methodology for epidemiological surveillance of the infection status in wildlife hosts across large areas, as well as providing an indication of the spatial distribution of infected faeces contaminating the environment. In this paper, a spatial analysis of antigen levels detected in faeces collected in the Franche-Comté region of eastern France is presented. In Franche-Comté, rodent outbreaks have been observed to originate in areas rich in grassland. Spatial trends in fox infection levels were modelled here as a function of the composition ratio of grassland in the landscape derived from the CORINE land-cover map. Kriging models incorporating the grassland trend term were compared to a variety of models in which five alternative trend expressions were used: the alternative trend expressions included linear and quadratic polynomials on the x and y coordinates with and without a grassland term, and a constant mean model. Leave-one-out cross-validation indicated that the estimation errors of kriging with a trend models were significantly lower when the trend expression contained the grassland index term only. The relationship between observed and predicted antigen levels was strongest when the estimated range of autocorrelation was within the home range size of a single fox. The over-dispersion of E. multilocularis in foxes may therefore account for the majority of spatial autocorrelation locally, while regional trends can be successfully modelled as a function of habitat availability for intermediate hosts.

Ecological epidemiology: landscape metrics and human alveolar echinococossis

The larval form of the fox tapeworm Echinococcus multilocularis can cause a potentially fatal liver infection in human hosts. Globally rare, the disease has a high prevalence focus in western China. Recent research has linked landscape to the presence and prevalence of the disease. This paper discusses the epidemiology of E. multilocularis in terms of landscape and disease transmission ecology. Landscape form was defined using satellite imagery to create a land cover classification for a study site in Zhang County (Gansu Province, China). Following the analysis of many landscape metrics, mean shape index was found to be related to the prevalence of infection for 31 villages in 1975 and 1997, at two spatial intervals, suggesting that habitat form is a correlate of disease. A temporal difference shows that the landscape is no longer suitable for transmission. These results indicate the possibility of identifying future hotspots which could aid the management of the disease.

Wilderness in the city: the urbanization of Echinococcus multilocularis.

A distinct increase in fox populations, particularly in urban areas, has been observed in Europe. This is of particular concern in endemic regions of the small fox tapeworm Echinococcus multilocularis, the aetiological agent of human alveolar echinococcosis. Novel tools have facilitated the investigation of the ecology of urban foxes and have demonstrated the urban wildlife cycle of E. multilocularis. Such studies are essential for estimating the risk of transmission to humans and to determine the basics for the development of control strategies.

Processes leading to a spatial aggregation of Echinococcus multilocularis in its natural intermediate host Microtus arvalis

The small fox tapeworm ( Echinococcus multilocularis) shows a heterogeneous spatial distribution in the intermediate host ( Microtus arvalis). To identify the ecological processes responsible for this heterogeneity, we developed a spatially explicit simulation model. The model combines individual-based (foxes, Vulpes vulpes) and grid-based (voles) techniques to simulate the infections in both intermediate and definite host. If host populations are homogeneously mixed, the model reproduces field data for parasite prevalence only for a limited number of parameter combinations. As ecological parameters inevitably vary to a certain degree, we discarded the homogeneous mixing model as insufficient to gain insight into the ecology of the fox tapeworm cycle. We analysed five different model scenarios, each focussing on an ecological process that might be responsible for the heterogeneous spatial distribution of E. mulitlocularis in the intermediate host. Field studies revealed that the prevalence ratio between intermediate and definite host remains stable over a wide range of ecological conditions. Thus, by varying the parameters in simulation experiments, we used the robustness of the agreement between field data and model output as quality criterion for the five scenarios. Only one of the five scenarios was found to reproduce the prevalence ratio over a sufficient range of parameter combinations. In the accentuated scenario most tapeworm eggs die due to bad environmental conditions before they cause infections in the intermediate host. This scenario is supported by the known sensitivity of tapeworm eggs to high temperatures and dry conditions. The identified process is likely to lead to a heterogeneous availability of infective eggs and thus to a clumped distribution of infected intermediate hosts. In conclusion, areas with humid conditions and low temperatures must be pointed out as high risk areas for human exposure to E. multilocularis eggs as well.

Epidemiology of echinococcosis.

Various species and infraspecific forms of the cestode genus Echinococcus are causative agents of human echinococcosis. Pathology, epidemiology and geographical occurrence vary widely between the different Echinococcus taxa. As a general rule, those forms of echinococcosis that are transmitted mainly by wild animals are rather rare, due to limited contact between humans and wildlife. This is the case with alveolar echinococcosis (AE) caused by Echinococcus multilocularis, the 'fox tapeworm' (except in regions where domestic dogs are heavily involved in the lifecycle), and for the South American endemic species E. oligarthrus and E. vogeli. On the other hand, most forms of cystic echinococcosis (CE) are transmitted in domestic lifecycles involving dogs and livestock and constitute an emerging public health problem, especially in regions with extensive livestock husbandry and non-supervised slaughter. This review focuses on two fields where a wealth of new information became available in recent years. New data demonstrate that ' E. granulosus', the causative agent of CE, is an assembly of several, rather diverse, species and genotypes that show fundamental differences, not only in their epidemiology, but also in their pathogenicity to humans. This fact may explain the unequal distribution of high-endemicity areas for human CE on regional scales, which previously, has been attributed to differences in human behaviour. In addition, new data suggest that E. multilocularis is expanding its geographical range in the northern hemisphere, and its transmission is intensifying, e.g. in central Europe. Moreover, the lifecycle (involving wild foxes and rodents) is rapidly becoming 'urbanised' due to the recent establishment of fox populations in cities and towns. This shift from sylvatic to synanthropic occurrence is likely to result in an increased pressure on the human population of infection from AE.

Indications and results of liver transplantation for Echinococcus alveolar infection: an overview.

Alveolar echinococcosis (AE) of the liver, caused by the larval stage of the fox tapeworm Echinococcus multilocularis, has the characteristics of a slow-growing liver cancer. It is one of the rare parasitic diseases for which a parasitolytic drug is not yet available, and AE is lethal in the absence of appropriate therapeutic management. Complete surgical resection of the parasite at an early stage of infection provides favourable prospects for cure, but, due to a long clinical latency, many cases are diagnosed at an advanced stage, so that partial liver resection can be performed in only 35% of patients. Benzimidazole (BZM) treatment is given in inoperable cases but these compounds are only parasitostatic, and lifelong therapy is required. During the past 20 years some centres have considered liver transplantation (LT) for the treatment of incurable AE. Our review summarizes the results of this experience based on a series of 47 European patients who received transplants between 1985 and 2002, tries to specify the real place of LT for AE, and underlines the measures that could be undertaken in the future to improve the results. Five-year survival was 71%. Five-year survival without recurrence was 58%. Major technical difficulties related either to previous laparotomies or to the loco-regional involvement were observed. The nine early deaths concerned AE patients with a long past-history of symptomatic AE (iterative cholangitis, secondary biliary cirrhosis). Five late deaths were directly related to ongoing AE, located in the brain in three cases, a very rare AE location that was not investigated before LT in these patients. In general, the pre-LT screening for distant AE metastases appeared insufficient in this series. Heavy immunosuppressive schemes, absence or delayed re-introduction of BZM after LT have clearly played a role in this unfavourable course. This unique experience indicates that, despite major technical difficulties, LT for incurable AE is feasible and could be discussed in very symptomatic cases. Before LT, interventional radiology should be preferred to repeated laparotomies. Pre-LT and post-LT BZM treatment is mandatory. A careful evaluation of possible distant metastases should be done before the decision for LT is made. After LT, the possibility of an ongoing AE must be permanently kept in mind. This could be reduced by lightening the immunosuppressants, carefully following the specific circulating antibodies, and applying a systematic radiological evaluation, not only to the graft but also to the lungs and the brain.

Controlling Echinococcus multilocularis—ecological implications of field trials

Two field trials to reduce the prevalence of Echinococcus multilocularis in foxes have been conducted in recent years. Although both trials reduced prevalence considerably, they failed to eradicate the parasite in the study region. Following the control trial in northern Germany, prevalence recovered unexpectedly and rapidly, reaching pre-control levels five quarters (15 months) after the end of control. To understand the internal dynamics of the parasite–host system’s reaction to control, we developed a spatially explicit simulation model, Echi. The simulation model incorporates the information available concerning fox tapeworm population dynamics. Using epidemiological parameters to adjust pre-control prevalence, the model predicts the temporal evolution of the prevalence of E. multilocularis in controlled foxes without departing from the range of uncertainty of the field data. However, the model does not predict the rapid pre-control recovery observed in the field trial. The deviation of the model’s prediction from field data indicates the involvement of processes not yet taken into account. We modified the model step by step to mimic processes with the potential to cause the rapid post-control recovery of the prevalence of E. multilocularis in foxes. Neither the longevity of tapeworm eggs nor the migratory behaviour of foxes showed any influence on the post-control reaction of the parasite–host system. However, landscape structures leading to a heterogeneous distribution of infected foxes have the potential to alter the system’s reaction to control. If infected foxes are concentrated in multiple clusters in the landscape, the model prediction tallied with the range of uncertainty of the field data. Such spatial distribution of infected foxes may be caused by differential abiotic conditions influencing the survival of tapeworm eggs. The model was found to comply best with field data if the foxes acquire partial immunity by being exposed to the fox tapeworm. Both hypotheses explaining the rapid post-control recovery of the prevalence of E. multilocularis observed in the fox population were supported by field data. Both hypotheses have far-reaching consequences for future control trials. The spatial aggregation of infected foxes would enable control efforts to be concentrated on these highly infected areas. However, the acquisition of immunity acts as a buffer to control, necessitating intensified control measures.

Human hydatidosis in Mar del Plata, Buenos Aires Province, Argentina, (1992-1995): A preliminary study

Fil: Elissondo, Maria Celina. Consejo Nacional de Investigaciones Cientificas y Tecnicas; Argentina. Universidad Nacional de Mar del Plata. Facultad de Ciencias Exactas y Naturales. Departamento de Biologia; Argentina

Echinococcus multilocularis alkaline phosphatase as a marker for metacestode damage induced by in vitro drug treatment with albendazole sulfoxide and albendazole sulfone.

Alveolar echinococcosis (AE) is caused by the metacestode stage of the fox tapeworm Echinococcus multilocularis. The disease affects the human liver and occasionally other organs and is fatal if treatment is unsuccessful. The present chemotherapy of AE is based on the administration of benzimidazole carbamate derivatives, such as mebendazole and albendazole. Albendazole treatment has been found to be ineffective in some cases, parasitostatic rather than parasiticidal, and the recurrence rate is rather high. Therefore, chemotherapy usually involves the lifelong uptake of massive doses of albendazole and new treatment options are urgently needed. In order to avoid costly and time-consuming animal experimentation, a first step in searching for novel parasiticidal compounds could be the in vitro drug screening of novel compounds by employing metacestode cultivation. However, presently used techniques (e.g., transmission electron microscopy) for determination of parasite viability involve costly equipment and time-consuming preparation of rather large amounts of parasite material. We therefore searched for a parasite marker which can be easily traced and the presence or absence of which is indicative of parasite viability. In this study we show that the increase of E. multilocularis alkaline phosphatase activity in culture supernatants during in vitro drug treatment with albendazole derivatives correlates with the progressive degeneration and destruction of the metacestode tissue. The inexpensive and rapid assay presented here will serve as an ideal tool for performing first-round in vitro tests on the efficacy of a large number of antiparasitic compounds.

MCP-1 and MIP-2 levels during Echinococcus granulosus infections in mice.

Ten BALB/c mice were infected with the cestode Echinococcus granulosus. After the infection, serum was collected at different periods of time and monocyte chemotactic protein-1 (MCP-1) and macrophage inflammatory protein-2 (MIP-2) were determined. The level of MCP-1 increased from at day 20 post infection (p.i.), to a maximum of on day 60 p.i., then decreased to on day 130 p.i. A second peak was observed at day 150 p.i. In addition, MIP-2 was detectable in serum as late as day 100 p.i. The highest level was observed on day 130 p.i., and decreased thereafter. Serum from noninfected animals (controls) contained no detectable levels of either MCP-1 or MIP-2. However, MCP-1 and MIP-2 appear to be implicated in E. granulosus infections, but their exact role during the disease is under determination.

Efficacy of Droncit R Spot-on (praziquantel) 4% w/v against immature and mature Echinococcusmultilocularis in cats

The causative agent of alveolar hydatidosis in humans, the fox tapeworm Echinococcus multilocularis, is extending its geographical range in Europe and has been found in domestic cats in some areas. A dermally applied cestocidal treatment for domestic cats has been developed and the efficacy of this treatment is reported. Thirty purpose-bred cats were experimentally infected each with 10 000 protoscoleces of Echinococcus multilocularis. Ten days later one group of ten cats was treated with Droncit R Spot-on (Praziquantel) 4% w/v dermally in one place on the dorsal aspect of the neck at a dose of 8 mg/kg. Eleven days later (21 days p.i.) a second group of ten cats was also treated with Droncit R Spot-on the same way. One group of ten cats was left untreated as controls. Twenty three days after infection the cats were examined for the presence of E. multilocularis tapeworms. No E. multilocularis were recovered from any of the cats in either of the treated groups. Echinococcus multilocularis were recovered from eight of the ten cats left untreated as controls. The worm burdens in the untreated cats were 0, 0, 5, 15, 75, 110, 220, 815, 2635, and 3045 worms per cat. The worms ranged in development from the three to four segment stage. Many of the E. multilocularis with four segments contained unshelled eggs in the terminal segment. This study indicates that Droncit R Spot-on (Praziquantel) 4% w/v applied dermally at 8 mg/kg is highly effective in removing E. multilocularis from the small intestine of cats infected with immature and mature (prepatent) infections of E. multilocularis. In the cats with the mature infections all tapeworms were absent from the small intestine within 2 days of treatment.