Granulosus Infection Research Articles

Echinococcus granulosus infection of farm dogs of Iran.

The prevalence and distribution of Echinococcus granulosus in sheepdogs was studied in 13 provinces of Iran, where 90% of the Iranian sheep and goat populations and, thus, sheepdogs are found. Worms were found in 27.17% of 390 dogs successfully purged with 4 mg/kg arecoline hydrobromide. The highest prevalence was detected in dogs from the rural areas of Isfahan (central part of Iran) and the lowest, in dogs from those of Sistan (Southeast Iran). The frequency distribution of E. granulosus was overdispersed, with only a few animals harboring heavy infections.

Fine needle aspiration biopsy in the differential diagnosis of the liver cystic echinococcosis

Liver cystic echinococcosis (CE) in non-endemic areas poses several problems in the differential diagnosis of various space occupying lesions detected by US examination. Fine needle aspiration biopsy (FNAB) using teflon covered needles with a US visible marker may be very useful for the definitive diagnosis. In the Clinic of Parasitic and Tropical Diseases in Poznan, FNAB were performed in 121 patients with liver space occupying lesions, with an addition of an anthelmintic cover of albendazole. The biopsy material was examined parasitologically, cytologically, bacteriologically and immunologically. E. granulosus infection has been confirmed in 25 patients (20.6%), in 16 cases by finding parasite protoscoleces or hooks and in nine cases by detection of an antigen specific for E. granulosus, antigen 5 (Ag5). Additionally nine cases of malignancy (7.4%), four of angioma (3.3%) and three bacterial abscesses (2.5%) were diagnosed. There were no complications related to FNAB puncture. The algorithm of the clinical management of space occupying lesions suspected for CE was proposed. FNAB is a very important technique in the differential diagnosis of cystic echinococcosis.

Albendazole in treatment of human cystic echinococcosis: 12 years of experience

This review paper examines the evidence from published and previously unpublished sources for the efficacy and safety of albendazole (ABZ) obtained in the last 12 years. Benzimidazole treatment alone is not ideal, requiring prolonged administration over many weeks, with an unpredictable outcome in terms of response rates in individuals. However, studies have shown that treatment with albendazole in E. granulosus infection can result in an apparent cure in up to 30% of cases, with a further 40–50% showing objective evidence of response when followed in the short term. Some studies have demonstrated that even patients who do not show obvious initial evidence of response may be found to be cured when followed up over several years. Duration of therapy and dose are also important, and with ABZ, efficacy seems to increase with exposure up to 3 months in the commoner cyst sites. Formal dose ranging and minimal effective dose studies have not been performed, but the current dose of 800 mg daily appears to be adequate. The issue of cyclical versus continuous treatment still has to be resolved. Data on ABZ safety has been accumulated over the past 12 years of marketing. The profile shows that liver function abnormalities are common although rarely treatment limiting, while occasional hematological changes affecting the white cells may be more serious. The safety data supplies the rationale for monitoring of patients during treatment. On balance ABZ has been shown to be a useful advance in the management of cystic echinococcosis both when used as sole treatment or as an adjunct to surgery or other treatments.

Echinococcosis.

Echinococcosis is a human disease caused by the larval form of Taenia echinococcus, which lives in the gut of the dog, wild canides and other carnivorous animals which represent the definitive hosts and involves as intermediate hosts both domestic and wild animals. Humans become accidental intermediate hosts by ingesting Taenia eggs. The main species pathogenic for man are E granulosus causing cystic echinococcosis with worldwide distribution and endemic in sheep and cattle breeding countries, and E multilocularis causing alveolar echinococcosis, with preferential distribution in the northern hemisphere. After ingestion of contaminated food, hexacanth embryos migrate by the portal system to liver and later lung, brain and other tissues. Symptoms are related to both cyst location and size. E granulosus infection of the central nervous system (CNS) may be primary or secondary and has been estimated to be low (2%). Sharply demarcated, spherical and intraparenchymal, cysts may reach a large size causing neurological symptoms. Spilling of cyst fluid due to trauma or surgery may trigger anaphylaxis as well as disseminated infection. Host reaction is minimal in the brain but a foreign giant cell reaction may develop. E multilocularis develops within the liver as a rapid invasive pseudomalignant growth and may metastasize to the CNS, where estimated incidence reaches 5%. Hydatid antigens induce an immune reaction in the host which is helpful for the diagnosis. DNA probes and PCR may be applied to differentiate between Echinococcus spp. Although the host develops an immunological protection from reinfection, the parasite evades host immune attack. A wide range of evasion mechanisms have been advanced, including a barrier for host cells due to hydatid cyst laminated cuticle, polyclonal activation of lymphocytes by parasite soluble antigens, and depression of host cell immune responses. Chronic stimulation of the host by cyst fluid antigens leads to increased specific IgG4 production, which might act as blocking antibodies against anaphlaxis suggestive of host response immunomodulation.

Transmission of hydatid disease to sheep from wild dogs in Victoria, Australia

Adult tapeworms and metacestodes of Echinococcus granulosus were found commonly in wildlife on Crown Land (Alpine National Park or State Forest) in the area around Mansfield, Victoria. A total of 756 sheep from 32 farms in the area were examined at slaughter. Seventeen of the farms (Group A) adjoined Crown Land and wild dogs commonly entered these farms and killed sheep. A high prevalence of hydatid infection was found in sheep from 15 of these farms. Serology and arecoline purging failed to identify infection with E. granulosus in any domestic dogs on these farms, despite some farmers sometimes feeding their dogs with offal of sheep and/or kangaroos. The remaining 15 farms (Group B) were in an area where wild dogs did not occur. Sheep infected with hydatid cysts were present on 2 farms in Group B, but E. granulosus infection was not evident in wildlife species examined from this area. The only sheepdog to have detectable serum antibodies against E. granulosus was a dog from a farm separating the 2 Group B farms where infected sheep were found. Echinococcus granulosus were not found when this dog was purged. The implications of the results of this study are discussed in terms of transmission and control.

Antigenic polypeptides of Echinococcus granulosus oncospheres and definition of protective molecules.

Immunoblotting and in vitro oncosphere-killing were used to identify a putative protective molecule in Echinococcus granulosus mature oncospheres. A range of sera from sheep that had been shown to be protected against E. granulosus, and from those that were not, were tested. The sera used were obtained from sheep hyperimmunized with E. granulosus oncospheres, or immunized with oncosphere non-denatured extract, with immature oncosphere extract or with denatured extracts of oncospheres. Results indicated the involvement of native antigens of 23, 25, 30, 34 and 40 kDa in the protective response to E. granulosus infection. The rapid appearance of antibodies to the 23, 25 kDa antigens, their association with early onset of protection and in vitro oncosphere lysis by affinity-purified antibodies obtained from these fractions, indicated that these antigens contained protective epitopes. Final confirmation was provided by immunization of sheep with fractions prepared by preparative SDS/PAGE, and challenge infection. Only the fraction containing the 23 and 25 kDa molecules was able to stimulate protection. Antisera against this pair of molecules should provide a useful probe for screening an E. granulosus oncosphere cDNA library to identify clones expressing protective molecules.

Transmission dynamics of Echinococcus granulosus, Taenia hydatigena and Taenia ovis in sheep in uruguay

A base-line survey was carried out on the transmission dynamics of Echinococcus granulosus, Taenia hydatigena and Taenia ovis in sheep in the Department of Florida, Uruguay. Mean life expectancy at birth of the sheep population in this Department was estimated at 3.5 and 4.8 years for male and female sheep, respectively. Both intensity and prevalence of E. granulosus infection increased with age providing no evidence that immunity was acquired in the population. This revealed that E. granulosus was only relatively stable and in an equilibrium endemic steady state with an estimate of the basic reproduction ratio ( R 0) of about 1.2. The mature larval pepulation in sheep was over-dispersed with parameter k, from fitting a negative binomial, being 0.199 and 0.556 in 42- and 54-month-old sheep, respectively. The mean number of cysts increased by 1.05 cysts per year and the infection pressure was calculated as 0.174 infections per year, implying that each infection consisted of 693.6 eggs to produce 6.03 cysts. Neither intensity nor prevalence of infection with T. hydatigena or T. ovis increased with age. This indicated that immunity was acquired to reinfection by both parasites and they were in an equilibrium hyperendemic steady state with an estimated R 0 of 4.2–5.8. Viability and fertility of E. granulosus, and viability of T. hydatigena cysts in the older age groups were low. The effects of the different transmission levels of the parasites on potential control strategies are discussed.

Sonographic findings in hydatid disease of the liver: comparison with other imaging methods

Patients with hepatic hydatid disease were examined by sonography (N = 62), plain radiography (N = 62), computerized tomography (CT; N = 25) and/or isotope scans (N = 31). The clinical presentation ranged from asymptomatic to right upper quadrant complaints and, rarely, remote symptoms. Plain radiology showed liver calcifications in 26% of the cases tested; half of the calcifications were in collapsed, flattened cysts. Sonography, the investigation of choice, since it is cheap, non-invasive and accurate, is particularly useful during the active stage of cyst development, when plain X-rays appear normal or show non-specific hepatomegaly. Sonography was used to categorize cysts as 'solitary univesicular' (23% of cases, echo-free, with sand or split wall), 'solitary multivesicular' (31%), 'solid echogenic mass' (10%), 'multiple' (21%); either uni- or multi-vesicular) or 'collapsed, flattened and calcified' (16%). Sonography was superior to CT in the investigation of the cyst wall, hydatid 'sand', daughter cysts, and the relationship of the cyst to the diaphragm. However, CT was superior to sonography in detecting gas within the cysts and minute calcifications and in anatomical mapping. The majority of the hydatid cases had multivesicular cysts. In Jordan, as in all endemic areas, a univesicular cyst of the liver should be considered a possible Echinococcus granulosus infection until proven otherwise.

Maternal transfer of protection from Echinococcus granulosus infection in sheep

Although passive immunity against larval metacestodes of the genus Taenia is well established, the transfer of immunity against Echinococcus granulosus infection has not been demonstrated convincingly. The immune status of newborn lambs born to ewes that had been infected or immunised with E granulosus eggs or oncospheres was investigated. The ewes and their six- to eight-day-old lambs were subsequently challenged. Lambs born to triply infected ewes were 80 per cent protected from a challenge infection whereas lambs born to singly infected ewes were only 45 per cent protected. Lambs born to ewes that had been immunised with preparations of sonicated oncospheres had the lowest levels of immunity. The infected ewes were challenged intramuscularly with activated oncospheres and showed some degree of immunity. Ewes which had received oncospheres solubilised in sodium dodecylsulphate or sonicated oncospheres were protected from subsequent oral challenge by 60 to 66 per cent. Radial immunodiffusion revealed that lambs with statistically significantly lower levels of IgG were more susceptible to challenge. However, the degree of protection did not show a simple relationship to the titre of antibody, as determined by an elisa using a solubilised antigen.

Lack of an association between hydatid disease and autoimmunity

The prolonged survival of Echinococcus granulosus within the human host indicates that some mechanism is operating to permit parasite evasion of the host immune response. Several publications have described autoimmune phenomena in patients infected with hydatid cysts. The aim of this study was to test the postulate that there is a higher prevalence of autoantibodies in serum from patients with hydatid disease than in control samples, and this may provide some evidence of an association between autoimmunity and E. granulosus infection. Sera from 70 patients with hydatid disease and 45 control subjects were assayed for the presence of antinuclear antibodies (ANA), tissue specific autoantibodies and rheumatoid factor. All patients were aged between 20 and 80 years of age with no known history of autoimmune disease. Hydatid patients were surgically confirmed cases. Control subjects were chosen on the basis that they were age and sex matched to the test sera and had no known illness at the time blood samples were obtained. On the basis of an ANA autoantibody titre of > 1:40 being regarded as positive, 19 (27%) of the hydatid patients, 13 (28%) of the controls were positive. Low levels of tissue specific autoantibodies and rheumatoid factor were detected in sera from 5 (7%) and 2 (11%) hydatid patients and 4 (8%) and 3 (16%) of control subjects respectively. No significant differences (P > 0.05) were found between autoantibody levels in the hydatid patient sera and the controls. These findings suggest that there is no association between hydatid infection and the level of autoantibodies to a broad range of self antigens.

Diagnosis of canine echinococcosis: comparison of coproantigen and serum antibody tests with arecoline purgation in Uruguay

Echinococcus granulosus is one of the most important and widespread of the helminth zoonoses. Diagnosis of E. granulosus infection in dogs currently relies on arecoline dosing and detailed examination of the purge for adult worms. Two immunodiagnostic tests (ELISA) based on genus specific coproantigen detection or serum antibody (IgG, IgA and IgE) detection were compared against arecoline purgation for the detection of Echinococcus in naturally infected dogs in Uruguay. The coproantigen ELISA had a sensitivity of 76.9% compared with 34.6% for the serum IgG ELISA when assessed against 26 purge positive dogs (purge worm count range 1–4331). Coproantigen reactivity was positively correlated ( r=0.65) to purge worm count, with a threshold at over 20 worms. There was no positive correlation of antibody levels with worm counts. In 26 matched Echinococcus positive dog samples, the overall sensitivity of serological detection increased to 69.2% when seroreactivity for IgA and IgE antibodies were included and to 96.2% for both coproantigen and antibody assays combined. The detection of current infection of individual dogs with E. granulosus by coproantigen ELISA has the potential to replace arecoline purgation, while specific serum antibody detection should be useful in assessing Echinococcus exposure in dog populations.

Echinococcus granulosus: the mechanism of oncosphere lysis by sheep complement and antibody

A heat-labile component of normal sheep serum (56°C for 30 min but not 50°C for 30 min) was able to lyse oncospheres in vitro. The degree of effect, and the proportion of oncospheres lysed, was related to the concentration of normal unheated sheep serum complement, or other sources of complement (rabbit, mouse) in the culture. Lower concentrations were required for lysis if the culture serum was obtained from sheep immune to E. granulosus infection. Heat inactivation of normal or immune sheep serum removed any lytic ability. No lysis occurred in any concentration of unheated foetal lamb serum. However, unheated foetal lamb serum was able to restore the lytic effect to heated normal or immune serum. This suggests that lysis in both immune and normal serum is antibody-dependent and complement-mediated. The lysis in normal serum would appear to be due to natural cross-reacting antibodies that can fix complement at the oncosphere surface. The complement lesion resulted in damage to the plasma membrane. This then peeled back, predisposing the oncosphere to osmotic destruction. The use of bleach to dissolve the embryophore caused damage to the plasma membrane similar to that caused by complement. Developing metacestodes at 3 days of age in vitro in immune serum were susceptible to the addition of complement at that time.

Specific cellular and humoral immune responses induced by different antigen preparations of Echinococcus multilocularis metacestodes in patients with alveolar echinococcosis.

A specific proliferation of the peripheral blood mononuclear cells (PBMC) stimulated by antigens of Echinococcus sp. has been shown in patients with cystic as well as alveolar echinococcosis. However, the development of a major granulomatous reaction around the parasitic larvae is a characteristic feature of the local immune response to E. multilocularis while humoral immune responses seem to predominate in E. granulosus infection. The aim of this study was to analyse the specific proliferation of the PBMC from 36 patients with alveolar echinococcosis, and 23 controls, induced by a crude preparation of E. multilocularis (EmcAg) as well as by two E. multilocularis specific antigen preparations, the Em2 antigen and the protoscolex (ESAg) antigen. The significant correlation observed between the proliferation index either by Em2 and ES or by Emc suggests that both antigens account for an important part of the lymphocyte proliferative response. The strong effect of these species specific antigens on lymphocyte proliferation is confirmed by the comparison of the results obtained in this study to those obtained in a previous study of specific cellular immunity to E. granulosus antigens in patients with cystic echinococcosis. The proliferation indices were significantly elevated in all those 7 patients with a proven AE who were sero-negative using the Emc ELISA as well as in the 12 patients also seronegative, but using the Em2 ELISA. In 5 seronegative patients who had had a complete resection of the parasitic lesions two years before the lymphocyte proliferation evaluation, the PI was above the threshold value for two dilutions of EmcAg. PI under the threshold values were obtained only in patients with residual lesions. These results suggest that E. multilocularis specific antigens promote the proliferation of lymphocytes which could be TH1 cells, responsible for the intense periparasitic granulomatous reaction characteristic of alveolar echinococcosis.

Hyperendemic focus of echinococcosis in north‐eastern Victoria

To establish the prevalence of echinococcosis in feral canids in a region in the north-east of Victoria (Tallangatta) and assess its potential public health significance in this region. Dingoes and foxes were examined for Echinococcus granulosus worms at autopsy. All of the 17 canids that were examined harboured E. granulosus worms in their small intestine. The parasite burdens ranged from approximately 2000 to over 30,000 worms per canid. There is an endemic focus of canine echinococcosis in Tallangatta. Although the transmission appears to be between feral canid definitive hosts and macropodid (kangaroo) intermediate hosts, there is significant potential for E. granulosus infection to spill over into the human population. There is an urgent need to study the epidemiology of echinococcosis in this region to prevent transmission of the disease from feral to domestic life cycles.

The development of new foci of echinococcosis in northern Israel: prevalence in domestic animals.

In a survey carried out in 1991-1992 in the town of Yirka in Northern Israel, 49 dogs were examined for Echinococcus granulosus infection and abattoir data, based on organs condemned for the presence of parasites, was collected. The presence of E. granulosus by arecoline test was demonstrated in 7 (14.2%) of the dogs examined, but not parasites were found in the intestines of five stray dogs shot in the area. A survey of sheep slaughtered in the local abattoir during a one-month period revealed Echinococcus cysts in 10% of the 255 animals examined. No Echinococcus parasites were detected in 21 dogs examined 3 months after the initiation of praziquantel treatment. Echinococcosis seems to be a very serious public health problem in Israel and a control programme needs to be given a high priority.

Serum antibodies in canine echinococcosis

Gasser R. B., Jenkins D. J., Paolillo E., Parada L., Cabrera P. and Craig P. S. 1993. Serum antibodies in canine echinococcosis. International Journal for Parasitology 23: 579–586. Specific IgG, IgA and IgE antibodies against E. granulosus protoscolex antigen were detected by enzyme-linked immunosorbent assay (ELISA) in sera from dogs experimentally or naturally infected with E. granulosus. The specificities of the IgG, IgA and IgE ELISAs were 100,100 and 97.3%, respectively. Sera from 626 dogs of different categories and geographic regions in Australia, Uruguay and Kenya were tested. There were distinct differences in antibody responses in experimentally infected canids and in the number of naturally infected dogs found seropositive, depending on geographic region. The overall sensitivities of the ELISA (IgG, IgA and IgE) ranged between 73 and 84%, except for one geographic region where it was 54%. Genetic differences of the dogs and/or antigenic variations of the parasite appear to be responsible for the variations in specific antibody levels in infected dogs. In average, approximately one third of dogs from hyperendemic hydatid regions, without E. granulosus worms at autopsy or negative for E. granulosus infection by arecoline testing, were seropositive for anti- E. granulosus antibodies, suggesting previous infection with or exposure to the parasite. The results of this study demonstrate that, although the diagnosis of current intestinal E. granulosus infection on an individual dog basis is not always reliable by serology, serum antibody ELISA is useful as an epidemiological/educational tool for seroprevalence studies on canine echinococcosis.

Intracranial Hydatid Cysts in Children

Brain involvement in hydatid disease occurs in 1 to 2% of all Echinococcus granulosus infections. Fifty to 75% of intracranial hydatid cysts are seen in children. This study included 19 children who underwent surgery for intracranial hydatid cysts between January 1979 and September 1992. There were 12 boys and 7 girls, ages 3 to 16 years (mean, 8.1 yr). Headache and vomiting were the predominant symptoms. Papilledema was present in 16 patients, and 2 patients had secondary optic atrophy. A round, cystic lesion without perifocal edema and rim enhancement was detected on the computed tomographic scans of 13 patients. The cystic lesions with rim enhancement and perifocal edema were noted on the computed tomographic scans of 3 patients. Of these three patients, two subsequently had a recurrence. Total removal of the cyst without rupture was achieved in 12 patients. Only a 3-year-old boy in whom the cyst ruptured at surgery died. Seven patients in whom either the hydatid cyst ruptured at surgery or there was systemic hydatid disease received mebendazole therapy. Mebendazole seems to be effective in hydatid disease. Cerebral hydatid cysts should be removed in toto without rupture. The preoperative diagnosis is very important in planning surgery. When a cystic lesion is detected on computed tomographic scan, hydatid disease should be taken into consideration in countries where hydatid disease is endemic.

Intracranial Hydatid Cysts in Children

Brain involvement in hydatid disease occurs in 1 to 2% of all Echinococcus granulosus infections. Fifty to 75% of intracranial hydatid cysts are seen in children. This study included 19 children who underwent surgery for intracranial hydatid cysts between January 1979 and September 1992. There were 12 boys and 7 girls, ages 3 to 16 years (mean, 8.1 yr). Headache and vomiting were the predominant symptoms. Papilledema was present in 16 patients, and 2 patients had secondary optic atrophy. A round, cystic lesion without perifocal edema and rim enhancement was detected on the computed tomographic scans of 13 patients. The cystic lesions with rim enhancement and perifocal edema were noted on the computed tomographic scans of 3 patients. Of these three patients, two subsequently had a recurrence. Total removal of the cyst without rupture was achieved in 12 patients. Only a 3-year-old boy in whom the cyst ruptured at surgery died. Seven patients in whom either the hydatid cyst ruptured at surgery or there was systemic hydatid disease received mebendazole therapy. Mebendazole seems to be effective in hydatid disease. Cerebral hydatid cysts should be removed in toto without rupture. The preoperative diagnosis is very important in planning surgery. When a cystic lesion is detected on computed tomographic scan, hydatid disease should be taken into consideration in countries where hydatid disease is endemic.

Assessment of monoclonal antibodies to Echinococcus granulosus antigen 5 and antigen B for detection of human hydatid circulating antigens.

Four monoclonal antibodies (MAb) to Echinococcus granulosus Antigen 5 (Ag5) and Antigen B (AgB) were assessed in an enzyme-linked immunosorbent assay (ELISA) for detection of circulating antigens (CAg) in sera of human patients with E. granulosus infection. Around 5.5-8% of 200 sera from 42 surgically proven hydatid patients contained detectable CAg by individual MAb. The combined detection rate for CAg, using four MAb, was 19% (38/200). Although hydatid CAg was detected by MAb in at least one serum sample from 21 of 42 patients, some patients remained negative in the assay regardless of the time when serum samples were taken (pre- or post-operatively), or of the continuing presence of hydatid cysts, their location or fertility. In addition, it was observed that the binding capacity of MAb for sheep hydatid cyst fluid antigen (SHCF) was somewhat reduced in the presence of normal human serum. The CAg detection assay would only be useful for assessment of hydatid infection status in patients with detectable CAg in serum samples.

IgG Subclasses in Human Hydatid Disease: Prominence of the lgG4 Response

To assess the participation of the four subclasses of IgG in the humoral response to Echinococcus granulosus infection, we determined total and parasite-specific IgG1, IgG2, IgG3 and IgG4 in sera from 46 patients with hydatid disease using an enzyme-linked immunosorbent assay (ELISA). Parasite-specific IgG subclass antibodies were quantitatively measured by means of standard curves obtained by affinity chromatography. Sera from 35 healthy individuals served as controls. The total component of IgG1, IgG2, and IgG3 showed a slight increase in patients with hydatidosis in comparison to normal control subjects with no significant differences. For the IgG4 subclass, however, a marked elevation was found in the patients group (p = 0.001 by analysis of variance). IgG1 and IgG4 subclasses showed a high anti-echinococcus antibody response, whereas there was a low parasite-specific IgG2 and IgG3 response. Indeed IgG-specific antibodies were found to belong mainly to IgG1 (63%) and to IgG4 (30%) and to a lesser extent to IgG2 (5%) and IgG3 (2%). The percentage of the total serum IgG4 antibodies that were specific for hydatid antigen reached a mean level of 18%, significantly higher than that of any of the other three IgG subclasses (p < 0.001 by Student's t test). Thus, the continuous antigenic stimulation of hydatidosis may result in an enhanced IgG4 subclass response.