Penetration of host IgG molecules into hydatid cysts.

Host IgG was detected in 15 out of 18 peritoneal hydatid cysts obtained from experimentally infected gerbils and in 18 out of 61 mouse hydatid cysts which had been implanted into the peritoneal cavity of gerbils for periods ranging from one day to two years. A wide variation in host IgG concentration was observed among the different cysts in which these immunoglobulins were found. These findings are discussed in terms of the possible manner by which macromolecules may enter into the hydatid cysts.     

Comparative cytotoxicity of secondary hydatid cysts, protoscoleces, and in vitro developed microcysts of Echinococcus granulosus.

Infection with the metacestode of Echinococcus granulosus is characterized by a concomitant immunity. Survival of established and developing hydatid cysts in the intermediate host implies a mechanism to modulate its immunological reactions. In order to investigate this mechanism, secondary hydatid cysts were isolated from intraperitoneally infected laboratory white mice (strain NMRI) 12 months p.i. A number of hydatid cysts were freed from the surrounding host adventitial tissue. Monolayer cultures of non-stimulated peritoneal macrophages of NMRI mice were prepared and incubated in the presence of the hydatid cysts. By means of a trypan blue exclusion test and by measuring the incorporation of tritium labelled uridine, it was found that the presence of hydatid cysts reduced the viability of the macrophages in vitro. Toxic substances are probably secreted since the medium of cultured hydatid cysts also displayed cytotoxic activity. Hydatid cysts with adventitia, as well as culture medium of those cysts, were less toxic. When toxins, partially purified from hydatid cyst fluid, were previously incubated on a collagen coated surface, a reduced level of toxicity was found, suggesting that collagen of the host adventitia may play a role in controlling the liberation of toxins by the hydatid cyst. Virtually no toxicity was exerted by protoscoleces or by the medium of cultured protoscoleces, in contrast to in vitro vesiculated protoscoleces (so called microcysts). The results reveal a novel feature of hydatid cysts that may play a role in the survival of the parasite in the immunized host.     

Comparative electrophoretic study of phosphoglucose isomerase,phosphoglucose mutase and tetrazolium oxidase in some hydatid cysts of Echinococcus granulosus collected from different mammal hosts

Hydatid cyst scolexes of lung and liver from sheep and water buffalo were electrophoreticaily examined for phosphoglucose isomerase (PGI), phosphoglucose mutase (PGM) and tetrazolium oxidase (Te) activity. One each of phosphoglucose isomerase, phosphoglucose mutase and tetrazolium oxidase activities were found in all of the hydatid cysts studied. PGI and PM in ail hydatid cysts studied appeared te be controlled by two codominant alleles. PGI and PGM proved to be a good taxonomic criterion to differentiate the hydatid cysts of the water buffalo from those from sheep. On the other hand, TO failed to differentiate between the sheep and water buffalo hydatid cysts. The hydatid cysts that parasitise the sheep's organs can be considered as arising from a different strain from the cysts that parasitise the water buffalo organs, while lung and liver hydatid cysts of the sheep appeared to be a similar strain.     

Free amino acid concentration in hydatid cyst fluids from fertile and infertile human and animal Echinococcus granulosus.

The aim of this study was to search and compare free amino acid composition of fertile and infertile cyst fluids obtained from humans and animals infected naturally with Echinococcus granulosus, by using automated analysis based on cation-exchange chromatography with post-column ninhydrin derivatization system. 11 free amino acids from fertile (sheep origin), nine from infertile (cattle origin), 13 from infertile (human origin) hydatid cyst fluids and 19 amino acids from sera of patients with hydatid infection were detected. The levels of glycine, alanine, valine and lyrosine in fertile and infertile hydatid cysts fluids were significantly higher than in sera from patients with hydatid cysts. Glycine level in the fertile hydatid cyst fluids (sheep origin) was significantly higher than those of infertile cysts fluids (cattle and human origin) and sera with hydatid patients. Glycine level in fertile hydatid cyst fluids was about two times more concentrated in infertile cattle cyst fluids, 10 times more concentrated in infertile human hydatid cyst fluids and 13 times more concentrated in sera with hydatid patients. On the other hand, alanine and valine concentration in the fertile and infertile cyst fluids were at similar level with the exception that valine level in fertile cyst fluids was 12 times more concentrated in infertile human cyst fluids. The levels of tyrosine, citrulline, leucine, isoleucine and lysine amino acids in fertile and infertile hydatid cyst fluids were similar. Our findings with respect to fertile and infertile cysts fluids showed that free amino acids concentrations in cyst fluids were significantly, higher in sera from patients with hydatid cyst. Total amount of free amino acids content in fertile and infertile cyst fluids was three to eight times higher from that of human sera with hydatid patients.     

Control of hydatid disease in Wales.

OBJECTIVES--To evaluate the success of the south Powys hydatid control programme by analysis of trends in cystic disease in humans and sheep and dog infestation. DESIGN--A review of hospital admissions for human hydatid disease in 1984-90, abattoir prevalence surveys of hydatid cysts in adult sheep, arecoline acetarsol and coproantigen surveys of prevalence of Echinococcus infestation in dogs. SETTING--All hospitals in England and Wales, three abattoirs, and dog populations in mid ands south east Wales. SUBJECTS--Residents of England and Wales admitted to hospital between 1984 and 1990 with a new diagnosis of human hydatid disease (International Classification of Diseases (ICD), ninth revision, code 122) acquired in the United Kingdom. RESULTS--The average annual incidence of human hydatid disease in Powys, mid-Wales, fell from 3.9x10(-5) in 1974-83 to 2.3x10(-5) in 1984-90. Age specific incidence rates in Wales declined over this period only in children, and no cases occurred in children (<15 years) in Powys. Two Welsh children who lived in Gwent and mid-Glamorgan were infected. Prevalence of hydatid cysts in old sheep from south Wales declined during the control period, but in 1993 prevalence of cysts was 13%. Prevalence of E granulosus infestation was zero in the control area in 1993, but it was 2.4% in Powys dogs outside the control area in 1989 and 9.2% in dogs in Gwent in 1991. CONCLUSIONS--Human hydatid disease has been successfully controlled in south Powys but cystic echinococcosis is still endemic in sheep in mid-Wales, and there is a focus of infection in humans, sheep, and dogs in the bordering areas of Gwent and mid-Glamorgan. There is considerable potential for an upsurge in human cases if control measures are relaxed.     

Multiple unusual locations of hydatid cysts including bladder, psoas muscle and liver

Our case concerns 66-year-old female with a multiple unusual locations of hydatid cysts including bladder, psoas muscle and liver. Coexistence of hydatid cysts in these localizations has not been previously reported. The diagnosis of vesical hydatid cyst was facilitated by the coexistence of other echinococcosis locations. Treatment consists of the excision of the cysts in the same session without any postoperative anthelmintic drugs. In a two-year follow-up no recurrence has occurred.     

DNA damage, RAD9 and fertility/infertility of Echinococcus granulosus hydatid cysts

Hydatidosis, caused by the larval stage of the platyhelminth parasite Echinococcus granulosus, affects human and animal health. Hydatid fertile cysts are formed in intermediate hosts (human and herbivores) producing protoscoleces, the infective form to canines, at their germinal layers. Infertile cysts are also formed, but they are unable to produce protoscoleces. The molecular mechanisms involved in hydatid cysts fertility/infertility are unknown. Nevertheless, previous work from our laboratory has suggested that apoptosis is involved in hydatid cyst infertility and death. On the other hand, fertile hydatid cysts can resist oxidative damage due to reactive oxygen and nitrogen species. On these foundations, we have postulated that when oxidative damage of DNA in the germinal layers exceeds the capability of DNA repair mechanisms, apoptosis is triggered and hydatid cysts infertility occurs. We describe a much higher percentage of nuclei with oxidative DNA damage in dead protoscoleces and in the germinal layer of infertile cysts than in fertile cysts, suggesting that DNA repair mechanisms are active in fertile cysts. rad9, a conserved gene, plays a key role in cell cycle checkpoint modulation and DNA repair. We found that RAD9 of E. granulosus (EgRAD9) is expressed at the mRNA and protein levels. As it was found in other eukaryotes, EgRAD9 is hyperphosphorylated in response to DNA damage. Our results suggest that molecules involved in DNA repair in the germinal layer of fertile hydatid cysts and in protoscoleces, such as EgRAD9, may allow preserving the fertility of hydatid cysts in the presence of ROS and RNS.     

Prevalence of Echinococcosis in Reindeer (Rangifer Tarandus) in Sweden

In Sweden echinococcosis is uncommon in domestic animals. In reindeer in the most northern part of the country echinococcosis was found. Of 1453 pairs of lungs, 23 pairs (1.6 %) were infected with hydatid cysts. These were of two types: typical well-developed hydatid cysts, which were found in nine of the 23 infected lungs, and collapsed hydatid cysts, which were found in 13 of the lungs. In only one lung pair both types of cysts were seen.     

Ultrasonic diagnosis of liver hydatidosis

The paper is concerned with a study of an ultrasound picture of verified hydatidosis in 62 patients. The symptoms of hydatid cysts are the presence of daughter cysts and "hydatid sand", cuticular membrane desquamation, local cyst wall thickening and parietal layers, a necrotic zone in a preparasitic space and cyst calcification. The detection of these symptoms helps to estimate not only the type of a hydatid cyst but also the state and character of parasite activity permitting a choice of therapeutic tactics.     

Vaccination trials in Australia and Argentina confirm the effectiveness of the EG95 hydatid vaccine in sheep.

Experimental vaccine trials against hydatid disease have been undertaken in sheep using the EG95 recombinant vaccine. Challenge infection was with viable Echinococcus granulosus eggs obtained from a New Zealand isolate (dog/sheep cycle), an Australian isolate (dingo/wallaby cycle) and an Argentine isolate (dog/sheep cycle). Vaccination with EG95 conferred a high degree of protection against challenge with all three parasite isolates (protection range 96-100%). Taken together, the trials demonstrated that 86% of vaccinated sheep were completely free of viable hydatid cysts when examined approximately 1 year after challenge infection. Vaccination reduced the number of viable cysts by 99.3% compared with unvaccinated controls. These results suggest that the EG95 vaccine could have wide applicability as a new tool for use in hydatid control campaigns.     

Apoptosis as a possible mechanism of infertility in Echinococcus granulosus hydatid cysts

Echinococcus granulosus is a parasitic cestode causing hydatidosis in intermediate hosts (human and herbivorous). Most symptoms of the disease occur by the pressure exerted on viscera by cysts that are formed upon ingestion of the parasite eggs excreted by definitive hosts (canines). Protoscoleces, the developmental form of the parasite infective to definitive hosts, are formed in the germinal nucleated layer of fertile hydatid cysts. For unknown reasons, some cysts are unable to produce protoscoleces (infertile hydatid cysts). In this study, analysis of DNA fragmentation using TUNEL and agarose gel electrophoresis showed higher levels of apoptosis in infertile cysts as compared to fertile cysts. Additionally, caspase 3 was detected both in fertile and infertile cysts; the activity of this enzyme was found to be higher in infertile cysts. We conclude that apoptosis may be involved in hydatid cyst infertility. This is the first report on the presence of programmed cell death in E. granulosus.     

Echinococcus granulosus protoscolex formation in natural infections

Echinococcus granulosus is a parasitic platyhelminth that is responsible for cystic hydatid disease. From the inner, germinal layer of hydatid cysts protoscoleces are generated, which are are the infective forms to the dog. Systematic studies on the cell biology of E. granulosus protoscolex formation in natural infections are scarce and incomplete. In the present report we describe seven steps in the development of protoscoleces. Cellular buds formed by a clustering of cells emerge from the germinal layer of hydatid cysts. The buds elongate and the cells at their bases seem to diminish in number. Very early on a furrow appears in the elongated buds, delimiting anterior (scolex) and caudal (body) regions. Hooks are the first fully-differentiated structures formed at the apical region of the nascent scolex. In a more advanced stage, the scolex shows circular projections and depressions that develop into suckers. A cone can later be seen at the center of the hooks, the body is expanded and a structured neck is evident between the scolex and the body. During protoscolex development this parasitic form remains attached to the germinative layer through a stalk. When fully differentiated, the stalk is cut off and the infective protoscolex is now free in the hydatid fluid.     

Treatment of hepatic hydatid cysts by percutaneous aspiration and hypertonic saline injection: results of a cooperative work

Percutaneous puncture-aspiration-injection-reaspiration (PAIR) of hydatid liver cysts, was performed in 38 patients 14-80 years old, with a total of 60 liver hydatid cysts. After aspiration under computed tomography guidance, hypertonic saline was injected into the cystic cavities of patients as a scolecidal agent. No major complications were associated with the procedures. In the follow-up period of 18 months, control CT scans of 35 cysts revealed a gradual decrease in cyst size with a mean volume reduction of 66%. Complications included two cases of urticaria, one case of anaphylaxis and one subcapsular hematoma. No mortality occurred. It is concluded that percutaneous aspiration and hypertonic saline injection for liver hydatid cysts appears to be an effective form of treatment and may eventually prove to be an alternative to surgical intervention.     

Echinococcus granulosus: DNA extraction from germinal layers allows strain determination in fertile and nonfertile hydatid cysts

A method for the isolation of Echinococcus granulosus DNA from germinal layers of hydatid cysts is described. The method includes a hexadecyltrimethylammonium bromide/chloroform extraction and an adsorption to diatomaceous earth suspension. DNA suitable for polymerase chain reaction was obtained and used for parasite strain determination by mitochondrial cytochrome c oxidase I gene sequencing. Fertile and nonfertile cyst isolates from sheep, cattle, pigs, and humans were characterized. Hitherto, no direct parasite strain characterization has been made on nonfertile hydatid cysts, whereas here we report that nonfertile hydatid cysts were produced by sheep strain (G1 genotype) in sheep, cattle, and humans and by pig strain (G7 genotype) in pigs.     

Immunology and molecular biology of Echinococcus infections

Echinococcus spp. are the etiological agents of hydatid disease in man and other intermediate hosts. Many questions regarding the factors which determine susceptibility/resistance to hydatid disease, and the factors which influence the viability and fertility of hydatid cysts, remain to be answered. Recent research into the effects of hydatid infection on the immune system of the host has provided some insights into the host-parasite relationships. Immunochemical and recombinant DNA techniques are being applied to improve diagnosis of hydatidosis in man and E. granulosus infection in dogs, and also in the development of vaccines against infection with taeniid cestode larvae. The successes which have been achieved in these areas are likely to provide valuable tools for the control of cystic hydatidosis in man. These recent studies in the areas of immunobiology, serological diagnosis and vaccination are reviewed.     

Prevalence of hydatid in buffaloes in India and report of a severe liver infection

Of 3200 buffaloes examined at Bareilly abattoir 915 (28.6%) were positive for hydatidosis. The hydatid infected organs were lungs (60%), liver (32%), spleen (4%), kidneys (2%), heart (0.9%) and brain (0.1%). The number of hydatid cysts encountered in lungs of an individual buffalo was 1-9 and 1-7 in liver. One buffalo liver showed severe hepatomegaly, cirrhosis and had an exceptionally high number of hydatid cysts. Infectivity studies in pups showed 16-29 per cent worm establishment with the presence of shelled eggs within the uterus of the parasite on day 45 post-infection.     

Epidemiology of hydatid disease in Sardinia: a study of fertility of cysts in sheep

Hydatidosis, caused by Echinococcus granulosus, is a cyclozoonotic disease of economic significance in Sardinia. The life-cycle involves stray and sheep dogs as definitive hosts and sheep, pigs, goats and cattle as intermediate hosts. The most important intermediate host is sheep, due to home slaughtering with ready access of the viscera to dogs. This survey was undertaken in 1987 to ascertain the epidemiological significance of sheep in maintaining the life-cycle. A total of 700 (91.3%) of 767 sheep harboured hydatid cysts. The frequency distribution of the number of hydatid cysts was over-dispersed. Of 497 infected sheep, 7.6% had fertile cysts, 75.7% sterile cysts and 16.7% fertile + sterile cysts.     

Viability of Echinococcus granulosus cysts in mice following cultivation in vitro.

The viability of hydatid cysts developed in vitro for 90 days was assessed by implantation into mice. Cysts removed from mice at 270 days post-infection (p.i.) increased their size 13.5-fold and contained several brood capsules containing protoscoleces. Thus, cysts remain viable after prolonged in vitro culture. The implantation in mice of 15 cysts developed in vitro yielded an average of 10 cysts per mouse, which is indicative of a high survival rate in these experimental infections. The ultrastructural study of cysts recovered from mice 270 days p.i. showed that the germinal membrane was more compact than before implantation and several layers of tegumental cells had developed. Observations of cysts removed from mice indicated that the plasma membrane surrounding microtriches had prolongations opening into the laminated layer.     

Fine structure of the germinal membrane of Echinococcus granulosus cysts.

The ultrastructure of the hydatid cyst germinal membrane was studied. It was divided into 3 regions, the tegument, the tegumental cell region, and the innermost area bordering the cyst cavity. The morphology of tegumental, muscular, flame, duct, and glycogen-containing cells and cells containing lysosomal-like bodies is described. The significance of these findings is discussed in terms of the possible function of these structures and present knowledge on the penetration of macromolecules into hydatid cysts.     

Medical treatment of pulmonary hydatid disease: for which child?

There have been many encouraging studies on medical treatment of pulmonary hydatid disease due to Echinococcus granulosus infection. Our aims were to demonstrate the safety and efficacy of medical treatment in pulmonary hydatid disease and to describe a pediatric population who would benefit from medical treatment, especially in respect to the diameter of the hydatid cyst. All patients were treated with mebendazole or albendazole. Treatment outcome was defined as cure, improvement or failure. Among 82 patients, 34.1% were cured, 34.1% improved and 31.8% failed. When 102 cysts were individually evaluated, 36.31% were cured, 32.4% improved and 31.3% failed. The cure and the failure rates were statistically insignificant in cysts treated with mebendazole and albendazole; however statistically significantly more cysts were improved with albendazole. The results were statistically insignificant between continuous and cyclic albendazole treatment. The mean size of successfully treated cysts was 5.3+/-3.4 cm, but "failed" for cyst with a mean size of 7.3+/-4.3 cm. There was a positive, weak and statistically significant correlation between the cyst size and treatment results. The major complication was infection. We suggest that selected pediatric patients with uncomplicated pulmonary hydatid cysts sized less than 5 cm should have a trial of medical treatment with a very close follow up.