Echinococcus multilocularis: the parasite-host interplay

Alveolar echinococcosis (AE) is a severe chronic helminthic disease caused by the intrahepatic tumor-like growth of the metacestode of Echinococcus multilocularis. Metacestodes are fluid-filled, asexually proliferating vesicles, which are entirely covered by the laminated layer, an acellular carbohydrate-rich surface structure that protects the parasite from immunological and physiological reactions on part of the host. The E. multilocularis metacestode has acquired specific means of manipulating and using the immunological host response to its own advantage. These include the expression of distinct immunoregulatory parasite molecules that manipulate and interfere in the functional activity of macrophages and T cells. Recent research findings have led to a better understanding of the protein- and glycoprotein composition of the laminated layer and the E/S fraction of the metacestode, including Em2- and Em492-antigens, two metacestode antigen fractions that exhibit immunosuppressive or -modulatory properties. Understanding of the events taking place at the host-parasite interface is the key for development of novel immuno-therapeutical and/or chemotherapeutical tools.     

Echinococcus multilocularis in north Italy

Alveolar echinococcosis is a zoonotic infection caused by the metacestode of the tapeworm Echinococcus multilocularis. Fox populations living in the Alpine regions of Italy had been considered free from this parasite until 2002, when two infected foxes were detected in Bolzano province (Trentino Alto Adige region) near Austrian border. A modified nested PCR analysis was used to detect E. multilocularis DNA in faecal samples belonging to red fox populations from five Italian regions. A total of 522 faecal samples were analysed from foxes shot in Valle d'Aosta (N = 65), Liguria (N = 44), Lombardy (N = 105), Veneto (N = 67), and Trentino Alto Adige (N = 241) regions. Among these, 24 samples, all from the Trentino Alto Adige region, were found positive. Moreoever, 1406 faecal samples of red foxes were analyzed by CA-ELISAs commercial test kit. This paper provides an update of the epidemiological knowledge of this parasite in north Italy.     

Observations on Echinococcus multilocularis in the definitive host

Six dogs were found to be susceptible to experimental infections with a European isolate of Echinococcus multilocularis from southern Germany. Two cats were only poorly susceptible. Adult worms were not evenly distributed throughout the small intestine and the majority of parasites were found in the posterior region. The mode of attachment of E. multilocularis in the dog was similar to that for E. granulosus with the adult worm extending its rostellum deep within a crypt of Lieberkühn. In cats only few worms were found to have penetrated deeply between the villi. E. multilocularis was found to possess a modified group of rostellar tegumental cells, morphologically and functionally identical to those described in E. granulosus and previously referred to as the "rostellar gland". By studying development in vivo and in vitro, the time required for the production of shelled eggs was demonstrated to be only 28 days. Concurrent experimental infections in dogs with E. multilocularis and E. granulosus revealed that both species will develop together in the same host. Their development was not retarded in any way by the presence of the other and both species were able to coexist in the same area of the intestine.     

Echinococcus multilocularis: responses to infection in Mongolian gerbils

Mongolian gerbils (Meriones unguiculatus) inoculated intraperitoneally with three acephalic cysts of Echinococcus multilocularis were very susceptible to infection. Aspects of the responses of gerbils to this infection were examined to determine if they could be related to the progress of the infection. Hematologic changes observed during the infection included anemia, reticulocytosis, lymphocytopenia, neutrophilia, monocytosis, and eosinopenia; these changes were related to the size of the infection. Infected gerbils also produced specific protein-A binding antibodies to E. multilocularis. At 14 weeks after inoculation, infected gerbils showed splenomegaly and somewhat elevated serum transaminase levels, although serum 5'-nucleotidase levels were normal.     

Observations on the development of Echinococcus multilocularis in cats

The development of a European isolate of Echinococcus multilocularis was compared in cats and dogs at the end of the prepatent period. Echinococcus multilocularis established in all dogs and cats, but worm recovery was significantly greater from dogs than from cats. Overall, worms in cats were not as advanced as those in dogs in terms of development and maturation, but there was no evidence of retarded development or stunted forms. These results confirm that dogs are highly susceptible to E. multilocularis, whereas cats have lower and more variable recovery rates. However, because cats produce thick-shelled eggs of E. multilocularis after experimental and natural infections, they have to be regarded as potential sources of infection both for intermediate and accidental hosts, including humans. However, their general role in the epidemiology of the infection has yet to be determined.     

Ecology and epidemiology of Echinococcus multilocularis in Europe

Human alveolar echinococcosis (AE), caused by the larval stage of Echinococcus multilocularis has a high mortality rate in untreated patients. The life-cycle of E. multilocularis in Europe predominantly involves foxes as definitive hosts. However, experimental studies demonstrated a comparable biotic potential of E. multilocularis in dogs and raccoon dogs but an insignificant potential in cats. AE occurs in central and eastern Europe at low incidence rates. Recent studies in foxes have shown that E. multilocularis has a wider geographic range (including Italy) than previously thought. In recent years, increases in fox populations have been observed in many European countries, especially in urban areas. As a result, the E. multilocularis cycle is now established in the urban environment. This presents an increased risk of infection for a large human population. Based on these facts and new epidemiological data, possible intervention strategies are presented.     

Echinococcus multilocularis: a rare cestode of the domestic cat in France

A cat living in the city of Annemasse (Haute-Savoie) was parasitized by a single minute specimen of the cestode E. multilocularis. The main characteristics of the parasite are described and illustrated. The cat has not previously been reported as one of the definitive hosts of this cestode in France. A potentially serious epidemiological problem is raised by the presence of an infected cat in an urban estate.     

Echinococcus multilocularis in a European beaver from Switzerland

Infection with the larval stage of the cestode parasite Echinococcus multilocularis was diagnosed in a European beaver (Castor fiber) in central Switzerland. The animal was hit, run over by a car, and died of trauma. It was in normal body condition and no signs of disease were seen. At necropsy, multiple cystic structures up to 1 cm in diameter were found in the liver adjacent to the hilus. Within the parasite vesicles, multiple protoscolices were visible. The species was determined to be Echinococcus multilocularis by upon polymerase chain reaction and direct immunofluorescence with MAbG11-FITC. This is the first report of Echinococcus multilocularis in European beaver.     

Investigation on the occurrence of Echinococcus multilocularis in Central Italy

Background  

Feed contaminated with Salmonella spp. constitutes a risk of Salmonella infections in animals, and subsequently in the consumers of animal products. Salmonella are occasionally isolated from the feed factory environment and some clones of Salmonella persist in the factory environment for several years. One hypothesis is that biofilm formation facilitates persistence by protecting bacteria against environmental stress, e.g. disinfection. The aim of this study was to investigate the biofilm forming potential of Salmonella strains from feed- and fishmeal factories. The study included 111 Salmonella strains isolated from Norwegian feed and fish meal factories in the period 1991–2006 of serovar Agona, serovar Montevideo, serovar Senftenberg and serovar Typhimurium.     

Protective immune mechanisms against the metacestode of Echinococcus multilocularis

Infection with the larval stage of the fox tapeworm Echinococcus multilocularis results in a life-threatening hepatic disease concerning humans and intermediate rodent hosts. Immunoepidemiological surveys provided information that a large proportion of infected individuals may demonstrate either constitutional resistance to early post-oncospheral development of the parasite or late resistance to disease by exhibiting an intrahepatic died-out parasite lesion. Similar events have been found in secondary infections of laboratory rodents. Dissection of humoral and cell-mediated immune responses in susceptible versus resistant individuals provides insight into immunological pathways associated with the different outcome of infection. Survival strategy of the metacestode obviously focuses on the crucial role played by the parasite laminated layer. This layer protects the metacestode from host effector mechanisms which can potentially kill the proliferating germinative compartments in case of resistant hosts. Bruno Gottstein and Richard Felleisen here discuss the need to search for more parameters discriminating between the different immune pathways in order to find out (immunogenetic?) predispositions responsible for the respective phenomena.     

Echinococcus multilocularis: inhibition of murine neutrophil and macrophage chemotaxis

Resident peritoneal neutrophils and macrophages from mice infected with 50 +/- 5 cysts of Echinococcus multilocularis were collected at 2, 4, 6, 8, 10, and 16 weeks postinfection. Their ability to respond and migrate to purified parasite larval antigens or endotoxin-activated mouse serum (EAMS) in comparison to normal peritoneal cells from uninfected mice was tested in vitro using Boyden chambers. Early in the infection, both cell types responded to the specific and nonspecific chemoattractants as the control group. However, at 8 and 10 weeks postinfection, the neutrophils and macrophages lost their response to parasite antigens but retained their ability to migrate to EAMS. Toward the 12th and 16th week postinfection, both cell types lost their ability to migrate to the specific as well as the nonspecific factors. The data presented suggest that the cellular mechanisms of recognition and chemotaxis in mice infected with alveolar hydatid cysts are impaired.     

Echinococcus multilocularis: susceptibility and responses to infection in inbred mice

Kroeze W. K. and Tanner C. E. 1987. Echinococcus multilocularis: susceptibility and responses to infection in inbred mice. International Journal for Parasitology17: 873–883. Of six strains of mice examined, C57L/J mice were the most susceptible to intraperitoneal infections with Echinococcus multilocularis. Five of the six strains developed splenomegaly during the infection. Changes in leukocyte levels in infected mice were most pronounced in the C57L/J and BALB/cJ strains. Two of the six strains of mice, C57BL/6J and C57BL/6J (bg^J), showed low specific IgG responses to E. multilocularis when measured using an ELISA. Many of the responses observed were directly correlated with the parasite burden in infected animals. It is concluded that susceptibility or resistance to E. multilocularis in mice is probably controlled by non-H-2 gene(s); additionally, hematological and immunological responses to infection, although correlated to parasite burden, varied among strains of mice, suggesting some degree of host genetic control of these responses.     

Rapid technique for cryopreservation of Echinococcus multilocularis metacestodes

Cysts of E. multilocularis were minced to prepare a crude homogenate and after addition of glycerol at a final concentration of 10%, cryopreservation was performed at a rate of 1 degree C min-1 in a controlled-rate freezer. The aliquots were subsequently stored in liquid nitrogen. All 22 isolates tested were successfully cryopreserved and their viability maintained.     

The impact of globalisation on the distribution of Echinococcus multilocularis

In the past three decades, Echinococcus multilocularis, the cause of human alveolar echinococcosis, has been reported in several new countries both in definitive hosts (canids) as well as in people. Unless treated, infection with this cestode in people is fatal. In previously endemic countries throughout the Northern Hemisphere, geographic ranges and human and animal prevalence levels seem to be increasing. Anthropogenic influences, including increased globalisation of animals and animal products, and altered human/animal interfaces are thought to play a vital role in the global emergence of this pathogenic cestode. Molecular epidemiological techniques are a useful tool for detecting and tracing introductions, and differentiating these from range expansions.