Hydatid disease: research and control in Turkana. II. The role of immunological techniques for the diagnosis of hydatid disease

Serological Assays for Alveolar and Cystic Echinococcosis—A Comparative Multi-Test Study in Switzerland and Kyrgyzstan

Both alveolar (AE) and cystic echinococcosis (CE) are lacking pathognomonic clinical signs; consequently imaging technologies and serology remain the main pillars for diagnosis. The present study included 100 confirmed treatment-naïve AE and 64 CE patients that were diagnosed in Switzerland or Kyrgyzstan. Overall, 10 native Echinococcus spp. antigens, 3 recombinant antigens, and 4 commercial assays were comparatively evaluated. All native E. multilocularis antigens were produced in duplicates with a European and a Kyrgyz isolate and showed identical test values for the diagnosis of AE and CE. Native antigens and three commercial tests showed high diagnostic sensitivities (Se: 86–96%) and specificities (Sp: 96–99%) for the diagnosis of AE and CE in Swiss patients. In Kyrgyz patients, values of sensitivities and specificities were 10–20% lower as compared to the Swiss patients’ findings. For the sero-diagnosis of AE in Kyrgyzstan, a test-combination of an E. multilocularis protoscolex antigen and the recombinant antigen Em95 appears to be the most suitable test strategy (Se: 98%, Sp: 87%). For the diagnosis of CE in both countries, test performances were hampered by major cross-reactions with AE patients and other parasitic diseases as well as by limited diagnostic sensitivities (93% in Switzerland and 76% in Kyrgyzstan, respectively).

Using specific synthetic peptide (p176) derived AgB 8/1-kDa accompanied by modified patient's sera: a novel hypothesis to follow-up of Cystic echinococcosis after surgery

Cystic echinococcosis (CE) is caused by the larval stage of the tapeworm Echinococcus granulosus. Until now, CE does not have an effective follow-up after surgery. To date, CE follow-up is conducted based on either antibody or antigen detection assays by double antibody sandwich ELISA. Unlike antigen detection, antibodies to imply exposure to an Echinococcus infection while their titration could remain for a longer period (1-10years) after surgery. Likewise, antibody respond may be related to the location of a mature hydatid cyst. Antigen detection shows presence of CE infection, it is extremely important and necessary in follow-up of CE after surgery. The circulating antigen (CAg) titration decrease faster than circulating antibody (during 1-3weeks) after operation. Location of hydatid cyst in detecting antigen is affected less than antibody also. Regarding this subject, antigen detection has several limitations that lead to be used less in CE follow-up. Although, AgB 8/1-kDa subunit is considered as a principle and immunogenic CAg but sensitivity of CAg detection compared to with antibody has variable range, between 33% and 85% which owing to formation of circulating immune complexes (CICs) in result of antigen - antibody complex. The another problem is non using specific CAg (AgB 8/1-kDa subunit) for production of specific paratopes (rabbit hyper immune antiserum) against AgB 8/1-kDa which is used as capture (primary) antibody in double antibody sandwich ELISA assay. The designation of synthetic peptides from conserved regions of AgB 8/1-kDa can help to this problem. These regions (motifs) should be selected for allelic, dominant, immunogenic and conserved without any genetic variation. The first part of this hypothesis suggests which patient's sera should be treated with acidic buffers such as boric acid, acetic acid, glycine/HCl, polyethylene glycol (PEG) or combination of each of them accompanied by boiling patient's sera which causes breaking Ag-Ab complexes and in result of releasing AgB 8/1. These modifications are effective to releasing CAg from CIC. To date, the synthetic peptides have been widely used in CE serodiagnosis based on circulating antibody detection only. In second part of this hypothesis suggests the using synthetic peptide of p176 derived AgB 8/1-kDa subunit containing conserved specific epitopes for preparation of specific paratopes (rabbit hyper immune antiserum) based on CAg detection. So, there is no need any native antigens for preparation of non-specific rabbit hyper immune antiserum. These novel improvements can help to decrease the cross-reactivity with other parasitic diseases (specificity). Increasing antigen detection could make a chance in sensitivity of patient's sera and in result of the best and suitable tool for CE follow-up.

Evaluation of Dot-ELISA and enzyme-linked immuno-electrotransfer blot assays for detection of a urinary hydatid antigen in the diagnosis of cystic echinococcosis

Background:

Several serological assays are used for detection of a hydatid antigen in serum for diagnosis of cystic echinococcosis (CE). However, it requires technical expertise and is associated with the risk of acquiring blood-borne infections. Of late, interests have been shifted to other body fluids like urine, saliva, tear drops as alternate specimens in the diagnosis of CE.

Aim:

The aim of the study was to evaluate the dot enzyme-linked immunosorbent assay (Dot-ELISA) and electro-immunotransfer blot (EITB) for detection of a hydatid antigen in the urine for diagnosis of CE.

Materials and Methods:

100 ml of urine samples were collected from the patients with confirmed CE (n=30), patients with suspected CE (n=30), patients with other diseases (n=30) and healthy controls (n=30). A hydatid antigen in urine was detected by Dot-ELISA and EITB using only polyclonal antibodies raised against a complete homogenate hydatid (CHH) antigen in rabbits.

Results and Conclusions:

The Dot-ELISA using polyclonal antibodies showed a sensitivity of 53.33% and specificity of 96.66%, whereas EITB showed a sensitivity of 46.66%. The Dot-ELISA and EITB employing polyclonal antibodies showed no significant difference in sensitivity (P=0.426). Hence, the Dot-ELISA being a simple procedure can be used for detection of a hydatid antigen in urine for diagnosis of CE.

Immunology and immunodiagnosis of cystic echinococcosis: an update

Cystic echinococcosis (CE) is a cosmopolitan zoonosis caused by the larval cystic stage of the dog tapeworm Echinococcus granulosus. This complex multicellular pathogen produces various antigens which modulate the host immune response and promote parasite survival and development. The recent application of modern molecular and immunological approaches has revealed novel insights on the nature of the immune responses generated during the course of a hydatid infection, although many aspects of the Echinococcus-host interplay remain unexplored. This paper summarizes recent developments in our understanding of the immunology and diagnosis of echinococcosis, indicates areas where information is lacking, and suggests possible new strategies to improve serodiagnosis for practical application.

Differential expressions of MHC-DQB1 mRNA in Chinese merino sheep infected with Echinococosus granuclosus

The purpose of the present study was to investigate the dynamic changes of MHC-DQB1 mRNA expression in sheep infected with Echinococosus granuclosus. A total of 14 healthy Chinese merino sheep were experimentally infected with E. granuclosus. The blood samples were collected on days 0 (initiation of the infection), 7, 21, 30, and 60 post-infection, respectively. On day 60 post-infection, when the experiment was terminated, all sheep were euthanized to make a diagnosis of cystic echinococcosis (CE) using routine meat inspection and microscopical examination, respectively. The sheep were then divided into two groups according to the diagnostic results: group A (n = 8) consisted of sheep which were diagnosed as CE infection, while group B (n = 6) comprised sheep diagnosed as self-cured or healthy controls. Blood samples obtained during the period of the study were correspondingly divided into groups A and B. The mRNA expression levels of DQB1 revealed significant alterations detected at different stages of E. granuclosus infection in the two groups. Results showed that in group A, DQB1 mRNA expression underwent a progressive increase from day 0 to day 21 post-infection (P = 0.073), and suddenly, suffered from a dramatic drop until day 30 post-infection, and then jumped rapidly and peaked on day 60 post-infection (P = 0.004). Meanwhile, in group B, DQB1 mRNA expression displayed a sharp increase from day 0 to day 7 post-infection (P = 0.000), which thereafter showed a marked decrease until day 30 post-infection, and experienced a plateau from day 30 to day 60 post-infection, remaining at or above that on day 0. It is concluded that DQB1 mRNA expression levels varied in different stages of E. granuclosus infection in sheep. In addition, it appears that the ability to eliminate the parasites possibly depends, at least in part, on the DQB1 expression in the early stage of infection, especially in the first week post-infection.

Isolation and molecular characterization of recombinant Echinococcus granulosus P29 protein (recP29) and its assessment for the post-surgical serological follow-up of human cystic echinococcosis in young patients

We synthesized recombinant Echinococcus granulosus protoscolex recP29 antigen to be preliminarily assessed by ELISA and immunoblotting. RecP29-serology was carried out on 54 young patients with cystic echinococcosis (CE). Patients were classified into either cured (CCE) (n=40) or non-cured (NCCE) (n=14) CE patients. RecP29 ELISA showed a gradual decrease of antibody concentrations in all CCE cases that were initially (before treatment) seropositive to this antigen (25 out of 40) or that seroconverted following treatment. A complete seronegativity was reached within 3 years post-surgery in all of these cases. Conventional HCF ELISA yielded seronegativity in only 10% of initially recP29-seropositive CCE patients (P=0.086). Likewise, recP29 immunoblotting yielded seronegativity in 93% of 29 out of 40 initially recP29-immunoblot-positive CCE patients after 3 years follow-up, compared with 72% in the HCF immunoblotting (P=0.060). Eleven out of 14 NCCE patients were initially positive by recP29 ELISA, and 10 out of these maintained a marked anti-recP29 antibody reactivity until the endpoint of the follow-up period. All 14 NCCE cases were initially seropositive by recP29 immunoblotting, and 13 cases remained seropositive until the end of the study. Thus, recombinant P29 protein appears prognostically useful for monitoring those post-surgical CE cases with an initial seropositivity to this marker.

Assessment of Echinococcus granulosus somatic protoscolex antigens for serological follow-up of young patients surgically treated for cystic echinococcosis

Echinococcus granulosus protoscolex soluble somatic antigens (PSSAs) were assessed for their prognostic value in the serological follow-up of young patients treated for cystic echinococcosis (CE), compared to conventional hydatid fluid (HF) antigen. Based on different clinical courses and outcome of infection, as well as imaging findings, patients were retrospectively classified into two different groups including either cured CE (CCE; i.e., absence of active cysts or presence of inactive cysts, respectively) and noncured CE (NCCE) patients still presenting active cysts at the end of an up to 5-year follow-up period. An immunoglobulin G (IgG)-PSSA enzyme-linked immunosorbent assay (ELISA) showed a gradual decrease in antibody levels in CCE cases, reaching seronegativity in 20% of the cases at least within 5 years postsurgery. In comparison, the conventional IgG-HF ELISA showed a significantly lower progressive decrease in antibody levels, serology becoming negative in only 15% of CCE patients at the endpoint of the follow-up period. Serological analysis of PSSA by immunoblotting yielded an interesting immunoreactive double band of 27 and 28 kDa that, in 15 (75%) of 20 CCE cases, exhibited a rapid decrease and subsequent disappearance of respective antibody reactivities within 3 years postsurgery. Conversely, anti-27- and -28-kDa antibody reactivity strongly persisted until the endpoint of the follow-up period in all of the five NCCE patients. Further analysis of the 27- and 28-kDa doublet by using affinity-purified antibodies showed that the double band was not detectable in HF. Furthermore, a predominantly IgG4 subclass-restricted humoral immune response against the 27- and 28-kDa antigens was demonstrated in seroreactive CE patients. Overall, an anti-27- and -28-kDa response appeared to correlate with cyst activity. In conclusion, PSSA represents a useful candidate to carry out a serologic follow-up of CE subsequent to treatment and deserves further respective evaluation for other age groups of CE patients.

Post-surgical follow-up (by ELISA and immunoblotting) of cured versus non-cured cystic echinococcosis in young patients

The study was designed to determine comparatively the prognostic value of immunoblotting and ELISA in the serological follow-up of young cystic echinococcosis (CE) patients exhibiting either a cured or a progredient (non-cured) course of disease after treatment. A total of 54 patients (mean age 9 years, range from 3 to 15 years) with surgically, radiologically and/or histologically proven CE were studied for a period up to 60 months after surgery. Additionally, some of the patients underwent chemotherapy. Based on the clinical course and outcome, as well as on imaging findings, patients were clustered into 2 groups of either cured (CCE), or non-cured (NCCE) CE patients. ELISA showed a high rate of seropositivity 4 to 5 years post-surgery for both CCE (57.1%) and NCCE (100%) patients, the difference found between the two groups was statistically not significant. Immunoblotting based upon recognition of AgB subcomponents (8 and 16 kDa bands) showed a decrease of respective antibody reactivities after 4 years post-surgery. Only sera from 14.3% of CCE patients recognized the subcomponents of AgB after 4 years, while none (0%) of these sera was still reactive at 5 years post-surgery. At variance, immunoblotting remained positive for AgB subcomponents in 100% of the NCCE cases as tested between 4 and 5 years after surgical treatment. Immunoblotting therefore proved to be a useful approach for monitoring post-surgical follow-ups of human CCE and NCCE in young patients when based upon the recognition of AgB subcomponents.

Prevention and control of cystic echinococcosis

Human cystic echinococcosis (hydatid disease) continues to be a substantial cause of morbidity and mortality in many parts of the world. Elimination is difficult to obtain and it is estimated that, using current control options, achieving such a goal will take around 20 years of sustained efforts. Since the introduction of current (and past) hydatid control campaigns, there have been clear technological improvements made in the diagnosis and treatment of human and animal cystic echinococcosis, the diagnosis of canine echinococcosis, and the genetic characterisation of strains and vaccination against Echinococcus granulosus in animals. Incorporation of these new measures could increase the efficiency of hydatid control programmes, potentially reducing the time required to achieve effective prevention of disease transmission to as little as 5-10 years.

Molecular study of Echinococcus in west-central China

West-central China is an important endemic focus of both alveolar and cystic echinococcosis where several species of intermediate host are commonly infected with Echinococcus granulosus and E. multilocularis . Isolates of E. granulosus were collected from humans and other animals from different geographical areas of Qinghai, Ningxia, Gansu and Sichuan, and genotyped using the mitochondrial DNA marker ATP synthase subunit 6 gene (atp6). The sheep strain (G1 genotype) of E. granulosus was shown to be the only genotype present in sheep, cattle, goats, yaks and humans in the study areas. However, some heterogeneity in the atp6 sequence was evident in a number of the isolates with the most frequent change being a silent substitution (G/A) at position 360 compared with the G1 reference sequence representing isolates collected from the majority of hosts except humans. Two E. multilocularis isolates examined also had sequences that varied from each other and from the reference E. multilocularis atp6 sequence. The genotypic variation we report may reflect phenotypic differences with important consequences in terms of increased host infectivity for hosts by local Echinococcus strains, possibly impacting on the epidemiology and control of echinococcosis. Such adaptations may also result in different sensitivity to drugs or increased virulence for hosts that will impede control efforts and even affect vaccination strategies against Echinococcus.

Echinococcus granulosus in Jordan: assessment of various antigenic preparations for use in the serodiagnosis of surgically confirmed cases using enzyme immuno assays and the indirect haemagglutination test

The Enzyme linked immunosorbent Assay (ELISA), indirect haemagglutination (IHA), and immunoblot techniques (IB) were used for the serodiagnosis of surgically confirmed cystic echinococcosis (CE) caused by the tapeworm Echinococcus granulosus. Antigens used for the detection of IgG or total antibodies included crude sheep hydatid fluid (CSHF), autoclaved antigen B (AAB), boiled antigen B (BAB), and homogenate protoscoleces antigen (HPA). The overall sensitivity of the ELISA and IHA tests used for the serodiagnosis of 57 surgically confirmed human cases was 91.2% and 68.4%, respectively. The sensitivity of both tests was comparable in groups whose sera were collected one week before surgery and up to one year after surgery at 95.8% and 87.5%, respectively. In contrast, the sensitivity of the ELISA was significantly higher than that of IHA for sera of patients collected after one year of surgery. There was a positive correlation (r = 0.61) between the titers of antibodies detected by the ELISA and IHA. Using the IB technique, antigen B fractions (8/12, 16, and 24 KDa) were detectable by sera of 68.4% using either CSHF or AAB, 49.1% using BAB and 22.8% using HPA as detecting antigens. The overall sensitivity of the three AgB fractions was identical or similar to that of the 8/12 KDa fraction alone, indicating that the detection of the latter fraction is sufficient for the serodiagnosis of CE infection in humans. In conclusion, the ELISA is the test of choice for the serodiagnosis of CE and the follow up of cases following surgery using CSHF as an antigen. The IB test is a confirmatory test when antigen B fractions of CSHF or AAB are detected.

Concepts in immunology and diagnosis of hydatid disease

Echinococcosis is a cosmopolitan zoonosis caused by adult or larval stages of cestodes belonging to the genus Echinococcus (family Taeniidae). The two major species of medical and public health importance are Echinococcus granulosus and E. multilocularis, which cause cystic echinococcosis (CE) and alveolar echinococcosis (AE), respectively. Both CE and AE are both serious diseases, the latter especially so, with a high fatality rate and poor prognosis if managed inappropriately. This review discusses new concepts and approaches in the immunology and diagnosis of CE, but comparative reference has also been made to AE infection and to earlier pivotal studies of both diseases. The review considers immunity to infection in the intermediate and definitive hosts, innate resistance, evasion of the immune system, and vaccination of intermediate and definitive hosts, and it particularly emphasizes procedures for diagnosis of CE and AE, including the value of immunodiagnostic approaches. There is also discussion of the new advances in recombinant and related DNA technologies, especially application of PCR, that are providing powerful tools in the fields of vaccinology and molecular diagnosis of echinococcosis.

The immunodiagnostic potential of protoscolex antigens in human cystic echinococcosis and the possible influence of parasite strain

The results of ELISA, SDS-PAGE and western blotting indicated that the protoscolex antigens of Echinococcus granulosus (of 10-125 kDa) included antigens recognized by sera from human cases of cystic echinococcosis (CE). Some of the latter antigens (of approximately 79, 59, 45, 38, 31 and 29 kDa) exhibited cross-reactivity with sera from humans with other parasitic infections, including alveolar echinococcosis, cysticercosis and African trypanosomiasis. The 31-kDa antigen recognized by IgG antibodies in human CE sera only appeared to be present in the extracts of protoscoleces from sheep, and not in the corresponding extracts from horse or camel cysts. In contrast, the human CE sera recognized a 45-kDa protoscolex antigen only present in the horse cysts and a 125-kDa antigen present in the camel and horse (but not sheep) cysts. Extracts of protoscoleces from different species of hosts might therefore provide a source of strain-specific diagnostic antigens for human CE.

Molecular tools for the diagnosis of cystic and alveolar echinococcosis

In the past years, the diagnostic tools applied to identify alveolar (AE) and cystic echinococcosis (CE) in human patients have not only increased in number but also substantially improved in quality. The identification and characterization of species-specific parasite proteins/antigens allowed to generate subsequently recombinant or synthetic polypeptide antigens, as well as corresponding monoclonal antibodies. Some of these new tools have already demonstrated operating characteristics superior to conventional tests used for the immunodiagnosis of CE and AE, and thus may be suggested for routine laboratory application. Powerful molecular techniques, such as the polymerase chain reaction (PCR), have been developed and adapted to advance laboratory diagnosis of AE and CE. Detecting minute amounts of parasite DNA and mRNA, not only to identify but also to characterize the biological status of parasite material, thus becomes a complementary method to synergize immunodiagnostic techniques. This review focuses on recent developments of molecular tools, discussing their potential use as a primary or a supporting diagnostic element. We also outline some future developments to be undertaken in the field of molecular diagnosis, linked to clinical and laboratory problems.

Hydatid cyst in the soft tissue of the face without any primary

Hydatid cyst of the subcutaneous tissue is rare, and often presents as a simple soft-tissue mass. A case of primary subcutaneous hydatid disease arising in the malar region is reported. Histopathological examination revealed the characteristic findings, which are consistent with soft-tissue hydatid disease. There was no sign of echinococcal involvement of organs other than the soft tissue of the face. To the authors' knowledge, this is the first reported case of a primary subcutaneous hydatid cyst arising in the skin in the absence of internal involvement. The patient remains disease free 14 months after surgery. The authors present their clinical findings, diagnostic techniques, and treatment of the patient, and review the literature.

Antibody responses of patients with cystic hydatid disease to recombinant myophilin of Echinococcus granulosus

Hydatid patients were investigated for the presence of specific serum antibodies against a recombinant Echinococcus granulosus antigen, designated myophilin. The clinical history of each patient was examined to determine any correlation between factors such as cyst location and medical treatment on the presence or absence of antibodies to myophilin. Specific antibodies against recombinant myophilin were detected by Western blot analysis in 38.8% (7 of 18) of the hydatid patients examined. These patients also had the highest titres in ELISA against sheep hydatid cyst fluid antigen. There was an association between the presence of antibodies to myophilin and the patients having undergone recent treatment by chemotherapy and/or surgery, suggesting that the destruction of hydatid cysts may lead to an immune response against myophilin.

Dot immunobinding assay as a new diagnostic test for human hydatid disease

Bovine and human hydatid antigens collected from hepatic cysts and characterized by SDS-PAGE immunoblotting show similar patterns. The bovine hydatid antigen has been used to develop a simple and fast in vitro diagnostic assay for human hydatidosis. This method, named HA-DIA (hydatid antigen dot immunobinding assay), consists of incubation of a serum sample with a textile colloidal dye (pink) and a nitrocellulose stick to which the hydatid antigen has been bound. The presence of parasite-specific antibodies leads to dyeing of the stick reactive area, and a coloured spot appears. HA-DIA sensitivity and specificity have been studied in comparison with RAST-IgE and ELISA-IgG by testing 17 sera of patients with hydatid disease and 36 control sera from patients affected with other parasitic and non-parasitic diseases. HA-DIA showed positive results in all the patients' sera and in none of the control sera. Correlation with ELISA--IgG and RAST-IgE was significant. HA-DIA has been demonstrated to be of good predictive value, allowing a speedy diagnosis of hydatid disease. In view of its simplicity, not requiring any laboratory instruments, it is particularly suitable for large-scale field screening.

Use of specific antibody and circulating antigen serum levels in the hydatid immunodiagnosis of asymptomatic population

Levels of specific antibodies (Ab) and circulating antigens (CAg) were tested by ELISA in sera from 115 surgically confirmed hydatid patients, 41 individuals exhibiting other parasitic and unrelated diseases and 69 healthy subjects. Addition of CAg data to Ab detection in this sera collection increased sensitivity from 85% (only Ab) to 89% (Ab + CAg). Combination of ultrasonography with Ab and CAg serology for diagnosis of asymptomatic population in endemic areas was analyzed. One field survey (163 persons) involved both blood extraction and ultrasonography to all the population. Three people exhibited cyst images and all of them were Ab positive, while 6 Ab and 1 CAg positive individuals exhibited no cyst image. Another survey (1620 persons) involved a selection of 85 subjects for serology according to ultrasound data and record of family hydatid history. Twelve per cent exhibited no hydatid image being serologically positive and 14% were serologically negative but exhibited cyst image. Ultrasonography and serology (Ab and CAg) should be used in combination to maximize the diagnostic yield in asymptomatic population.

Serodiagnosis and seroepidemiology of human unilocular hydatidosis in Jordan

A total of 2182 serum samples from 38 patients with surgically confirmed unilocular hydatidosis, 19 clinically assessed patients, 15 patients with parasitic infections other than hydatidosis, 104 hospital outpatients, and 2006 normal Jordanians were serodiagnosed for the presence of IgG antibodies against hydatid fluid, circulating immune complexes (CIC), and/or hydatid circulating antigen (CA). Anti-hydatid IgG antibodies were detected in the sera of 77.4% of patients with hydatid disease and persist for very long periods postsurgery. As many as 54.1% of patients with hydatidosis had positive levels of CIC, and 16.1% had circulating antigen in their sera. The search for circulating antigen and CIC decreased the number of false-negative hydatid cases from seven to three, and the combined sensitivity of the assays thus increased from 77.4% to 90.3%. Using the immunoblot technique, 16- and < 14.4-kDa Echinococcus granulosus-specific bands were detected in sera from 54.1% and 61.5% of patients with hydatid disease who were tested before and after surgery, respectively. The seropositivity rate for anti-hydatid IgG antibodies was 2.4% for the general Jordanian population and 5.8% for hospital outpatients.

Sero-epidemiology of hydatid disease in the non-intervention area of north-east Turkana

In 1983 an intensive programme for the eradication of human cystic hydatid disease was established in north-west Turkana by the African Medical and Research Foundation. The north-east region of the district, approximately 200 km away, was not part of the programme and was effectively left untouched. This presented an opportunity to compare the current seroprevalence of hydatid disease in the north-eastern, non-intervention area with that in the north-west, where the eradication programme has been underway for a decade. Finger-prick blood samples, taken from 538 Turkana volunteers from 10 study sites in north-eastern Turkana in March and April 1991, were dried on filter paper before being tested for anti-Echinococcus antibodies by ELISA. Eighty-eight (16.4%) of the volunteers were found to be seropositive and 22 of these (4.1%) were classified as strongly positive. The level of seroprevalence and the social/cultural framework in the non-intervention area studied appear to be similar to those in the eradication programme area. Transmission of Echinococcus therefore seems to be continuing throughout northern Turkana.

The potential of vervet monkeys (Cercopithecus aethiops) and baboons (Papio anubis) as models for the study of the immunology of Echinococcus granulosus infections

Nine vervet monkeys and nine baboons were infected with eggs of Echinococcus granulosus per os. Six of the vervets and one of the baboons possessed hydatid cysts at autopsy, 15-28 months post-infection. The sequential IgG response to hydatid fluid and protoscolex antigens showed considerable inter-animal variation. Infected vervets and baboons became seropositive after an average of 8 months post-infection. Considerable fluctuation in the IgG response was observed, particularly to the hydatid fluid antigen which, in humans, may contribute to the existence of a significant proportion of seronegative individuals. Vervets, in particular, may be useful to study immunological events associated with exposure, development and resolution of hydatid disease in outbred human populations.

Hydatid disease in the Hamar of Ethiopia: a public health problem for women

A population-based study of hydatid disease was conducted among the Hamar of Ethiopia. Seven of 990 patients examined with a portable ultrasound scanner proved to have cysts (0.7% prevalence). Cysts were most common (4.7%) among women > or = 40 years of age. Only one male presented with a cyst. These results indicate a sex-specific hydatid public health problem in this tribe.

Partial characterization of antigens in circulating immune complexes in cystic hydatid patients treated with albendazole

Immune complexes were precipitated by 3% polyethylene glycol (PEG) from 4 sera from albendazole-treated hydatid patients from Uruguay, and together with sheep hydatid cyst fluid were analysed by ion-exchange fast protein liquid chromatography (FPLC). FPLC-eluted fractions of serum preparations and cyst fluid were tested in an enzyme-linked immunosorbent assay for the detection of specific Echinococcus granulosus antigens and also for presence of specific immunoglobulin (Ig) M and IgG in the serum samples. Two peaks (nos 13 and 25) were found to have antigenic activity. Antigens were identified in both serum and cyst fluid preparation (fraction 25) after sodium dodecyl sulphate-polyacrylamide gel electrophoresis immunoblotting analysis, with approximate molecular masses 50 kDa and 62 kDa. Specific IgM antibody was also detected in the same FPLC fraction (no. 25) of PEG-precipitated serum complexes.

Analysis of the in vitro lymphoproliferative responses and antibody levels to the arc-5 antigen in patients with cystic hydatid disease

Using a commercially-available, purified, arc-5 antigen, we examined the in vitro proliferative responses of peripheral blood mononuclear cells from hydatid patients and from healthy controls. Antibody levels of different immunoglobulin classes were also measured against the same antigen, in sera of both groups. Our findings indicate that lymphocytes from healthy controls do not proliferate to the arc-5 antigen, whereas lymphocytes from the majority of patients do. The negative or weak responses observed among a few patients were not due either to increased release of prostaglandins in culture or to a lack of responsiveness to Interleukin-2. Antibodies of all three classes, G, M and A, measured by an ELISA, were elevated in sera of patients when compared with controls. However, only levels of specific IgG antibodies gave an excellent discrimination of the disease state and these were of diagnostic value. No direct or inverse correlations between lymphoproliferative responses and antibody levels were observed in either group, although a few patients with relatively low antibody titres demonstrated very high proliferative responses. The possible use of the proliferative assay as an adjunct to serology in the diagnosis of hydatid disease is indicated.

Molecular and immunological diagnosis of echinococcosis

Echinococcosis is an infectious disease of humans caused by the larval (metacestode) stage of the cestode species Echinococcus granulosus (cystic echinococcosis or hydatid disease) or Echinococcus multilocularis (alveolar echinococcosis or alveolar hydatid disease). Clinical manifestations depend primarily on localization and size of hepatic lesions and may include hepatomegaly, obstructive jaundice, or cholangitis. Prognostically, alveolar echinococcosis is considered similar to liver malignancies, including a lethality rate of 90% for untreated cases. Diagnosis is based on imaging techniques coupled with immunodiagnostic procedures. Antibody detection tests for E. multilocularis have markedly improved with the use of affinity-purified Em2 antigen and recombinant antigen II/3-10 in enzyme immunoassays. Antigens of corresponding quality for E. granulosus are still unavailable. The detection of circulating antigens and immune complexes in the sera of patients with cystic echinococcosis, the demonstration of in vitro lymphocyte proliferation in response to stimulation with Echinococcus antigens, and the discrimination of serum immunoglobulin isotype activity to various Echinococcus antigens in both cystic and alveolar echinococcosis have been suggested for diagnostic purposes as well as for monitoring patients after treatment. New diagnostic molecular tools include DNA probes for Southern hybridization tests and polymerase chain reaction for the amplification of E. multilocularis and E. granulosus species-specific DNA fragments.

Enzyme-linked immunoelectrotransfer blot test for diagnosis of human hydatid disease

Sera from 71 patients with surgically confirmed hydatid disease (which is caused by Echinococcus granulosus) were studied by an enzyme-linked immunoelectrotransfer blot (EITB) assay. Sera from patients either with other cestode infections or with another illness were used as controls. Results of the EITB test for hydatidosis were compared with those of the double-diffusion (DD5) test and an enzyme-linked immunosorbent assay (ELISA). In the EITB assay with bovine lyophilized hydatid fluid, three antigen bands of 8, 16, and 21 kDa were diagnostically important. The sensitivity of the assay by using these antigen bands was 80% for hepatic cysts, 56% for pulmonary cysts, and 56% for cysts located in multiple organs. In sera from controls, the specificity of the EITB assay was 100%. Cross-reactions to the 8-, 16-, and 21-kDa bands occurred, respectively, in 12, 4, and 4% of sera from patients with cysticercosis. No cross-reactions were noted in patients infected with Hymenolepis nana. The ELISA in which swine hydatid fluid was used as the antigen was as sensitive as the EITB test but was less specific (80%) and frequently cross-reacted with sera from patients with other cestode infections. The sensitivity of the DD5 test, which uses sheep hydatid fluid, was low (47%) , but its specificity was as high as that of the EITB assay. However, in patients with cysticercosis, cross-reactions were observed in 23% of sera tested. Despite the higher sensitivity found with the EITB assay, 23% (n = 5) of the serum samples that were positive by the DD5 test were not detected by the EITB assay. The EITB assay offers greater sensitivity and specificity than do the ELISA and the DD5 test. The highest proportion of hydatid cases is detected when the EITB and DD5 tests are run simultaneously.

Hydatid disease of the urinary tract: evaluation of diagnostic methods

Eight patients with histologically proven hydatid disease of the urinary tract underwent eosinophil count, ultrasonography (US) and computed tomography (CT). The findings were compared with those in 8 age-matched controls with simple renal cysts. Eosinophilia was not significantly different in the 2 groups. Mixed echogenicity on US and multivesicular cyst with mixed density on CT were the diagnostic features of hydatid cysts. Using these factors, both US and CT could diagnose or exclude hydatid disease in a significant number of patients with renal cysts. However, CT was more sensitive (88 vs 50%) and accurate (94 vs 75%) than US in the diagnosis of urinary tract hydatid disease. Retrograde pyelography confirmed communicating renal hydatid cysts in 2 patients. A practical algorithm for the investigation of urinary tract hydatid disease is suggested.

Evaluation of a rapid dot-ELISA as a field test for the diagnosis of cystic hydatid disease

A rapid dot enzyme-linked immunosorbent assay (dot-ELISA) was developed as a field test for the diagnosis of cystic hydatid disease caused by Echinococcus granulosus. The 30 min test was based on the detection of antibodies to antigen B of hydatid fluid and was carried out using 50 microliters of whole blood in a field assessment in the Turkana region of north-west Kenya. Initial laboratory studies showed antigen B to be preferable to crude cyst fluid, with 94% sensitivity and 90.3% specificity for Echinococcus infections. The field test was rapid, inexpensive and simple to perform and is considered to be a useful back-up to ultrasound scanning.

Seroprevalence of Echinococcus granulosus infection in a Uruguayan rural human population

Serological tests using hydatid cyst fluid (HCF) are useful as a primary screen for detecting asymptomatic infections due to Echinococcus granulosus in human populations. An enzyme-linked immunosorbent assay (ELISA) performed with whole sheep HCF was used to determine the prevalence of hydatid antibodies in a rural human population in Uruguay. In order to eliminate cross-reactions with sheep proteins in HCF, 1% normal sheep serum was added to each human serum before testing. ELISA seropositives were further tested using the double diffusion test (DD5) and confirmed where possible by ultrasound and X-ray examination. Serum samples were obtained from 420 individuals inhabiting rural areas in the Department of Paysandu (160), Rivera (21) and San José (239). An overall seroprevalence of 1.24% was obtained. Two of 17 seroreactors were subsequently proven to have hydatidosis. These results confirm and extend previous studies indicating an unusually high prevalence of E. granulosus infection in the Uruguayan population.

High prevalence of human hydatid disease (echinococcosis) in communities in northern Israel: epidemiologic studies in the town of Yirka

The resurgence of hydatid disease in communities in northern Israel led to epidemiologic studies in 1988 in the town of Yirka, a semirural Druze community of 8200 persons. In domestic animal surveys, 8% of 63 dogs tested after an arecoline purge and 10% of 255 sheep at the abattoir were found to be infected. In a randomized serosurvey of 758 persons using the indirect hemagglutination test (positive titer greater than or equal to 1:512), 9% (68) had a titer greater than or equal to 1:64, 2.2% had a titer greater than or equal to 1:256 and 0.9% had a titer greater than or equal to 1:512. Of those with titers greater than or equal to 1:64, 59 were evaluated by abdominal sonography and chest x-ray: 6 of the 59 were found to be persons who previously had had a liver or a lung hydatid cyst surgically removed; 6 other persons (5 with negative indirect hemagglutination titers) were found to have a newly detected asymptomatic cyst. Of the latter group, hydatid confirmation was subsequently obtained by surgery for 2 persons and by arc 5 and/or immunoblot assay for 4 persons. Thus, the cumulative percentage of confirmed present or recent past hydatid infections was 12/758 (1.6%) leading to an extrapolated rate of 1583/100,000 persons. This ranks Yirka among the highly endemic areas for hydatidosis worldwide. The study also showed that imaging methods were more sensitive than the indirect hemagglutination serologic test for conducting a prevalence survey.

Echinococcus granulosus: the potential use of specific radiolabelled antibodies in diagnosis by immunoscintigraphy

Diagnosis of hydatid disease in man is frequently dependent on the imaging of cysts in situ by techniques such as ultrasonography and CAT scans. Such methods are useful but are not specific and can lead to errors in diagnosis. The present work reports preliminary experiments on the development of a specific imaging technique for hydatid cysts using radiolabelled antibodies. A purified preparation of antigen B of hydatid fluid was used to raise polyclonal antisera in rabbits and the resulting affinity-purified IgG labelled with 131I. Gerbils with an established Echinococcus granulosus infection were injected intraperitoneally with the labelled antibody and imaged 48 h later with a gamma camera. Hydatid cysts could be identified within the peritoneal cavity and post-mortem assessment of activity showed the cysts to contain approximately four times as much activity as the surrounding organs thereby indicating successful targeting of the antibody to the cysts.

Observations on human echinococcosis (hydatidosis) and evaluation of transmission factors in the Maasai of northern Tanzania

An attempt was made to estimate the prevalence of hydatid disease amongst the Maasai people of northern Tanzania and to examine the factors which would contribute to the transmission of the disease in this region. Retrospective review of hospital records revealed an annual surgical rate of hydatid disease for 1977 through 1986 of 11 per 100,000 people. Ten (1%) of 959 people screened by ultrasound scanning had hydatid cyst-like echoes, giving a prevalence estimation of 1.4%. Thirty per cent of positive ultrasound cases were also positive in an ELISA antibody test. Three of four dogs necropsied and two of six dogs purged were found to harbour patent Echinococcus infections. Quantitative man:dog contact studies, examination of soil and water samples for Echinococcus eggs and comparison of the anti-Echinococcus antibody responders revealed that there are few marked differences in exposure to infection between the Maasai and the Turkana, who have a much higher prevalence of hydatidosis and perhaps the highest prevalence in the world. Hypotheses to explain the differences in the infection rate between these two groups of pastoralists who share a similar traditional lifestyle are presented. The Maasai, like the Turkana, had no knowledge of hydatid disease, and it is suggested that the best way to control the disease in Maasailand would be by proven dog control measures, supported by a suitable, more durable, educational programme.

ELISA IgG as screening test for the research of true prevalence of human hydatidosis in Badajoz, Spain

IgG antibodies against E. granulosus were investigated in order to determine the true prevalence of human echinococcosis in Badajoz, Spain. The seroepidemiological survey was carried out on 1540 subjects not suspected of suffering from hydatidosis, in order to add this morbidity rate to that already declared. Because of its high sensitivity and specificity, a standardized immunoenzymatic technique, ELISA was used, and the results subsequently compared using a classical technique for seroepidemiological surveys, namely indirect hemagglutination test (IHA). According to ELISA, 2.2% of the tested subjects were positive. This indicates a higher morbidity in our province than that declared. This test was found to be ideal for seroepidemiological surveys since it is reproducible, easily and rapidly conducted and safe. It requires economical reagents, a large number of samples can be processed simultaneously and it offers a totally objective reading.

Hydatid liver disease: problems in diagnosis in the Middle East endemic area

Imaging techniques such as ultrasound (US), liver scan and computerized tomography (CT) localize mass lesions in the liver and abdomen, and are valuable tools in the differential diagnosis of hydatid disease. However, we present two cases from Kuwait in the Middle East which demonstrate that these techniques alone are not as accurate as claimed in this geographical area. A sensitive and specific serological test is essential for a pre-operative diagnosis of hydatid disease. Discrepancies between radiological imaging and serological diagnosis are best resolved by cytology of the drained fluid and/or histopathological examination of the excised cyst. Negative serology would indicate ultrasound-guided aspiration of cyst fluid for cytological verification or enzyme immunoassay.

Seroepidemiology of human hydatidosis: use of dried blood samples on filter paper

Programmes for the control of hydatidosis caused by Echinococcus granulosus in Argentina use an enzyme immunoassay (EIA) as a screening test for population surveys aimed at detecting asymptomatic patients. Persons thus selected are referred to health centres for the arc 5 double diffusion test and imaging techniques. One of the most costly procedures of these surveys is the collection of blood samples under field conditions; the possibility of collecting dry blood samples on filter paper was therefore investigated. In a survey of 497 rural inhabitants of an endemic area, the same number of hydatidosis cases (22) were identified by EIA using (i) serum samples and (ii) capillary blood samples obtained by finger prick and collected on filter paper. The latter system was both simpler and cheaper.

Immunodetection of Echinococcus eggs from naturally infected dogs and from environmental contamination sites in settlements in Turkana, Kenya

A species-specific indirect immunofluorescence test using an anti-Echinococcus oncosphere monoclonal antibody (EgOH6-4E5) was applied to identify Echinococcus oncospheres released from taeniid eggs collected in environmental soil and water samples, and from perianal or faecal samples of naturally infected dogs, in northern Turkana, Kenya. The specificity of immunodetection of Echinococcus eggs by specific fluorescence of Echinococcus oncospheres from naturally infected dogs was 100% when compared to Taenia hydatigena infections, and a sensitivity of 73% was obtained in the detection of dogs infected with Echinococcus using perianal Scotch tape swabs. Taeniid eggs were recovered from various soil samples inside Turkana manyattas (settlements) and from waterhole samples. Some oncospheres obtained from taeniid eggs recovered from all sampled areas, but particularly from inside Turkana huts (akai) and from water samples from open waterholes used by the people and their livestock, reacted positively with the Echinococcus 4E5 monoclonal antibody. The potential importance of contamination of such sites with Echinococcus eggs is discussed in relation to the transmission of echinococcosis in this hyperendemic region of northern Kenya.

Cystic hydatid disease in Auckland, New Zealand, 1967-1982

The development of anthelmintic chemotherapy has provoked re-evaluation of the management of hydatid disease. We reviewed the case records of 74 patients with 93 episodes admitted to hospitals in Auckland, New Zealand, between 1967 and 1982. Median stay was 29 d (range 1-172). 46 (62%) of the patients were male: 34 (45%) were European and 38 (51%) Maori. The median age was 39 years (range 14-85). The majority of patients presented with symptoms and signs related to local effects of the cyst. 57 (77%) patients had at least one operation and while 34 (60%) had a major surgical complication, only 3 died. At follow-up in 1984, 38 (67%) of the surgical patients and 10 of the 17 (65%) who were not operated on were alive. 9 mebendazole recipients were evaluated: 5 (55%) responded symptomatically, but only one was cured by mebendazole alone. One stopped mebendazole because of side-effects. 2 patients took albendazole: one was cured and one had a symptomatic response. Thus surgery is not always needed. The role of chemotherapy requires further evaluation.

Portable ultrasound scanner versus serology in screening for hydatid cysts in a nomadic population

3553 nomads in Turkana, a remote area of north-west Kenya, were screened for hydatid cysts by a portable ultrasound scanner and by serology. 198 (5.6%) proved to have liver or upper abdominal cysts. In the group screened by both techniques (2644) 174 (6.6%) cases of hydatidosis were detected by ultrasonography and 76 (2.9%) by serology. Ultrasonography gave immediate results and was less expensive and more acceptable and educationally valuable to the people. This non-invasive rapid technique also provided important clinical information about the cysts. The prevalence data thus obtained will contribute to the surveillance of a hydatid control programme.

Improvements in the serodiagnosis of helminthic zoonoses

Remarkable progress has been achieved in developing improved serodiagnostic assays for a group of diseases for which other diagnostic methods are often lacking. Toxocariasis, trichinellosis, dirofilariasis, Taenia solium cysticercosis and the cystic and alveolar forms of hydatid disease are occult infections in humans and sometimes in lower animal hosts. Although Strongyloides stercoralis achieves patency in humans, parasitologic diagnosis is often very difficult. Efforts to develop reliable immunodiagnostic methods have spanned several decades but progress had been slow until recently. The complexity and nonspecificity of helminth antigens were major problems which prevented the full realization of the benefits of the highly sensitive assay systems now available. Modern immunologic methods including hybridoma technology, immunoaffinity chromatography and immunoblotting, however, have yielded improved reagents and the means to characterize their nature and function. The outcome of this research has been more sensitive and specific serologic tests based on measurement of both circulating antigens and antibodies as well as improved understanding of the nature of host-parasite interactions. Although much remains to be done, many improved immunodiagnostic procedures are already being applied in clinical diagnosis, epidemiologic studies and control programs directed against the helminthic zoonoses.