Echinococcosis: diagnosis and diagnostic interpretation in population studies

Echinococcus multilocularis Detection in Live Eurasian Beavers (Castor fiber) Using a Combination of Laparoscopy and Abdominal Ultrasound under Field Conditions

Echinococcus multilocularis is an important pathogenic zoonotic parasite of health concern, though absent in the United Kingdom. Eurasian beavers (Castor fiber) may act as a rare intermediate host, and so unscreened wild caught individuals may pose a potential risk of introducing this parasite to disease-free countries through translocation programs. There is currently no single definitive ante-mortem diagnostic test in intermediate hosts. An effective non-lethal diagnostic, feasible under field condition would be helpful to minimise parasite establishment risk, where indiscriminate culling is to be avoided. This study screened live beavers (captive, n = 18 or wild-trapped in Scotland, n = 12) and beaver cadavers (wild Scotland, n = 4 or Bavaria, n = 11), for the presence of E. multilocularis. Ultrasonography in combination with minimally invasive surgical examination of the abdomen by laparoscopy was viable under field conditions for real-time evaluation in beavers. Laparoscopy alone does not allow the operator to visualize the parenchyma of organs such as the liver, or inside the lumen of the gastrointestinal tract, hence the advantage of its combination with abdominal ultrasonography. All live beavers and Scottish cadavers were largely unremarkable in their haematology and serum biochemistry with no values suspicious for liver pathology or potentially indicative of E. multilocularis infection. This correlated well with ultrasound, laparoscopy, and immunoblotting, which were unremarkable in these individuals. Two wild Bavarian individuals were suspected E. multilocularis positive at post-mortem, through the presence of hepatic cysts. Sensitivity and specificity of a combination of laparoscopy and abdominal ultrasonography in the detection of parasitic liver cyst lesions was 100% in the subset of cadavers (95%Confidence Intervals 34.24–100%, and 86.7–100% respectively). For abdominal ultrasonography alone sensitivity was only 50% (95%CI 9.5–90.6%), with specificity being 100% (95%CI 79.2–100%). For laparoscopy alone sensitivity was 100% (95% CI 34.2–100%), with specificity also being 100% (95% CI 77.2–100%). Further immunoblotting, PCR and histopathological examination revealed one individual positive for E. multilocularis, whilst the other individual was positive for Taenia martis.

Predictors of Echinococcus multilocularis Prevalence in Definitive and Intermediate Hosts: A Meta-Analysis Approach

Echinococcus multilocularis (EM) is a pathogenic and potentially fatal cestode causing human alveolar echinococcosis (AE). A meta-analysis was conducted using a generalized estimation equation approach (GEE) to assess the effect of taxonomic, environmental, and diagnostic variables on EM prevalence in different hosts. Red foxes ( Vulpes vulpes ) had significantly higher prevalence of EM than domestic dogs ( Canis lupus familiaris), with the diagnostic method playing an important factor in assessing prevalence. For intermediate hosts genera was significantly associated with EM prevalence, although there was some indication of publication bias in this dataset. This study also highlights the possible importance of temperature and precipitation to EM transmission. This implies the possibility of a changing climate affecting the future distribution of the parasite.

A semi-automated magnetic capture probe based DNA extraction and real-time PCR method applied in the Swedish surveillance of Echinococcus multilocularis in red fox (Vulpes vulpes) faecal samples

Background

Following the first finding of Echinococcus multilocularis in Sweden in 2011, 2985 red foxes (Vulpes vulpes) were analysed by the segmental sedimentation and counting technique. This is a labour intensive method and requires handling of the whole carcass of the fox, resulting in a costly analysis. In an effort to reduce the cost of labour and sample handling, an alternative method has been developed. The method is sensitive and partially automated for detection of E. multilocularis in faecal samples. The method has been used in the Swedish E. multilocularis monitoring program for 2012–2013 on more than 2000 faecal samples.

Methods

We describe a new semi-automated magnetic capture probe DNA extraction method and real time hydrolysis probe polymerase chain reaction assay (MC-PCR) for the detection of E. multilocularis DNA in faecal samples from red fox. The diagnostic sensitivity was determined by validating the new method against the sedimentation and counting technique in fox samples collected in Switzerland where E. multilocularis is highly endemic.

Results

Of 177 foxes analysed by the sedimentation and counting technique, E. multilocularis was detected in 93 animals. Eighty-two (88%, 95% C.I 79.8-93.9) of these were positive in the MC-PCR. In foxes with more than 100 worms, the MC-PCR was positive in 44 out of 46 (95.7%) cases. The two MC-PCR negative samples originated from foxes with only immature E. multilocularis worms. In foxes with 100 worms or less, (n = 47), 38 (80.9%) were positive in the MC-PCR.

The diagnostic specificity of the MC-PCR was evaluated using fox scats collected within the Swedish screening. Of 2158 samples analysed, two were positive. This implies that the specificity is at least 99.9% (C.I. = 99.7 -100).

Conclusions

The MC-PCR proved to have a high sensitivity and a very high specificity. The test is partially automated but also possible to perform manually if desired. The test is well suited for nationwide E. multilocularis surveillance programs where sampling of fox scats is done to reduce the costs for sampling and where a test with a high sensitivity and a very high specificity is needed.

Cystic echinococcosis is an occupational disease?

Cystic echinococcosis (CE) is considered as an occupational infection and among different careers greengroceries have a close contact with raw vegetables which can transmit eggs of Echinococcus granulosus. Therefore, the objective of this survey was to determine the seroprevalence of CE among greengroceries using ELISA test in Mazandaran and Gilan Provinces, northern Iran. Overall, 160 serum samples (60 male and 100 female) were collected from greengroceries in Mazandaran and Gilan Provinces, 2012. Sera were surveyed employing ELISA assay for diagnosis of CE. In addition, before sampling, a questionnaire was filled out for each subject. Seropositivity was 2.4 % (four cases) and females 1.8 % (three cases) were more positive compared to males 0.8 % (one case). Age group of 40-60 years encompassed the highest rate of positivity (1.8 %) and the least rate was in 20-40 years old age group (0 %). Besides, 1.8 % of seropositive subjects were dog owner, unaware of the disease and lives in rural areas. In conclusion, seroprevalence of cystic hydatid disease among greengroceries is relatively high in Mazandaran and Gilan Provinces. More continuous serological researches and preventive measures should be taken into consideration owing to the significance of the disease.

Evaluation of purified 27.5 kDa protoscolex antigen-based ELISA for the detection of circulating antigens and antibodies in sheep and human hydatidosis

Hydatidosis is a zoonotic disease caused by the larval stage of Echinococcus granulosus, and the diagnosis of hydatidosis to date remains unresolved despite the development of many serological techniques. The present study aimed to develop an antigen-based enzyme-linked immunosorbent assay (ELISA) using IgG anti-27.5 kDa protoscolex antigen (27.5 PA) for measuring circulating protoscolex antigen (CPA), for comparison with an antibody detection assay, in sera of naturally infected sheep and humans in highly endemic areas in Egypt. In sheep, the sensitivity of ELISA in detecting anti-27.5 PA IgG and CPA was 75.0 and 60.0%, respectively, and the recorded specificity was 80.0 and 88.0%, respectively. In humans, the sensitivity of ELISA in detecting anti-27.5 PA IgG and CPA was 62.5 and 52.5%, respectively, while the specificity of the assay was 66.7 and 75.0%, respectively. In conclusion, an antibody detection assay is still superior and is more sensitive than an antigen detection assay, especially in diagnosing an active infection in which hydatid cysts are predominant. An antigen detection assay may be a useful approach to assessment of the efficacy of treatment, especially after removal of the cyst. Further studies are recommended to improve the diagnostic efficacy of an antigen-based ELISA method by using a highly purified recombinant antigen.

A comparison of loop-mediated isothermal amplification (LAMP) with other surveillance tools for Echinococcus granulosus diagnosis in canine definitive hosts

BACKGROUND

Cystic echinococcosis is highly prevalent in northwest China. A cost-effective, easy to operate diagnostic tool with high sensitivity and specificity would greatly facilitate the monitoring of Echinococcus infections in canine definitive hosts.

METHODS

The primers used in the LAMP assay were based on the mitochondrial nad5 gene of E. granulosus sensu stricto (E. granulosus s.s., or E.g.s.s.) and were designed using Primer Explorer V4 software. The developed LAMP assay was compared with a conventional PCR method, copro-ELISA and microscopy, using the faeces of dogs experimentally infected with E.g.s.s., and field-collected faeces of domestic dogs including 190 from Qinghai province highly endemic for E.g.s.s. and 30 controls from an area in Gansu, where a domestic dog de-worming program was in operation.

RESULTS

The positivity rates obtained for the field-collected faecal samples were 12.6%, 1.6% and 2.1% by the LAMP, PCR and copro-ELISA assays, respectively. All samples obtained from the control dogs were negative. Compared with the conventional PCR, the LAMP assay provided 88.8% specificity and 100% sensitivity. The higher sensitivity of the LAMP method was also shown by the fact that it could detect the presence of laboratory challenge dog infections of E. granulsous s.s. four days earlier than the PCR method. Three copro-samples shown positive by the commercial copro-ELISA were all negative by LAMP, PCR and microscopy, which suggests these samples may have originated from another infection rather than E. granulsous s.s., possibly E. shiquicus or E. Canadensis, which is also present in China.

CONCLUSIONS

We have developed a potentially useful surveillance tool for determining the prevalence of canine E. granulosus s.s. infections in the field. The LAMP assay may lead to a more cost-effective and practicable way of tracking Echinococcus infections in canids, especially when combined with the copro-ELISA.

Humoural immune response and pathological analysis in patients with false immune diagnosis of cystic echinococcosis

The patients with false immune diagnosis of hydatid disease were investigated for the humoural immune response to analyse the possible reasons and mechanism leading to false immune diagnosis. Two hundred and thirty-nine patients with nature-unknown cysts and 30 healthy controls were detected by immunological assays (four hydatid antigen-based immunogold filtration assay and enzyme-linked immune absorbent assay) and ultrasound. Sensitivity of and specificity of immunological assay and ultrasound were calculated, respectively. The serological diagnosis was compared with surgical pathology to screen the patients with false immune diagnosis for the immunoglobulin measurement and pathological analysis. The history and cyst characteristics were also reviewed. The results indicate the immunoglobulin has little influence on false immunodiagnosis. The false-negative immunodiagnosis was caused by the cysts' inactive status while the false positive caused by previous rupture, antigen cross-reaction. The clinical diagnosis of cystic echinococcosis requires a combination of immunodiagnosis and ultrasonography, which is the necessary complementary confirmation.

Morphological and molecular analyses of larval taeniid species in small mammals from contrasting habitats in Denmark

Taeniid infections in intermediate hosts manifest themselves as extraintestinal larval stages which, in early development, lack species-specific characteristics. The inability to distinguish infections of zoonotic importance such as Echinococcus multilocularis from other taeniid infections that have mainly veterinary significance stimulated the development of species-specific molecular diagnostics. In this study, the prevalence of taeniid infections in potential intermediate hosts was evaluated using both morphological diagnosis and a newly described multiplex polymerase chain reaction (PCR) for species determination. Small mammals (N= 719) were trapped in three different types of habitats in north-east Zealand, Denmark. The sensitivity of the multiplex PCR (90.5%) exceeded that of morphological examination (57.9%) for identifying 95 taeniid infections. The use of the multiplex PCR resulted in higher prevalence rates due to improved detection of immature liver infections with Hydatigera taeniaeformis and Versteria mustelae, but did not affect the observed prevalence rates of peritoneal metacestodes of Taenia polyacantha. The prevalence of taeniid infections showed a significant difference according to habitat type, potentially identifying a 'sylvatic' transmission and an 'urban' transmission, with marked variation among different taeniid species. Versteria mustelae and T. polyacantha were more prevalent in rural forests, while infections with H. taeniaeformis were dominant in urban parks/forests and in residential and farm gardens. The multiplex PCR facilitated a better utilization of wildlife samples by yielding a higher number of definitive diagnoses of ambiguous taeniid infections in liver lesions, allowing for more accurate epidemiological data and, hence, a more accurate risk assessment.

Molecular identification of Echinococcus multilocularis infection in small mammals from Northeast, Iran

BACKGROUND

Alveolar echinococcosis is a zoonotic disease caused by the metacestode of Echinococcus multilocularis. Many species of small mammals, including arvicolid rodents or Ochotona spp., are natural intermediate hosts of the cestode. The main aim of this study was to identify natural intermediate hosts of E. multilocularis in Chenaran County, Razavi Khorasan Province, northeastern Iran, where the prevalence of infected wild and domestic carnivores is high.

METHODOLOGY/PRINCIPAL FINDINGS

A program of trapping was carried out in five villages in which this cestode was reported in carnivores. The livers of 85 small mammals were investigated for the presence of E. multilocularis infection using multiplex PCR of mitochondrial genes. Infections were identified in 30 specimens: 23 Microtus transcaspicus, three Ochotona rufescens, two Mus musculus, one Crocidura gmelini, and one Apodemus witherbyi.

CONCLUSIONS/SIGNIFICANCE

A range of small mammals therefore act as natural intermediate hosts for the transmission of E. multilocularis in Chenaran County, and the prevalence suggested that E. multilocularis infection is endemic in this region. The existence of the life cycle of this potentially lethal cestode in the vicinity of human habitats provides a significant risk of human infection.

Towards risk-based test protocols: estimating the contribution of intensive testing to the UK bovine tuberculosis problem

Eradicating disease from livestock populations involves the balancing act of removing sufficient numbers of diseased animals without removing too many healthy individuals in the process. As ever more tests for bovine tuberculosis (BTB) are carried out on the UK cattle herd, and each positive herd test triggers more testing, the question arises whether ‘false positive’ results contribute significantly to the measured BTB prevalence. Here, this question is explored using simple probabilistic models of test behaviour. When the screening test is applied to the average UK herd, the estimated proportion of test-associated false positive new outbreaks is highly sensitive to small fluctuations in screening test specificity. Estimations of this parameter should be updated as a priority. Once outbreaks have been confirmed in screening-test positive herds, the following rounds of intensive testing with more sensitive, albeit less specific, tests are highly likely to remove large numbers of false positive animals from herds. Despite this, it is unlikely that significantly more truly infected animals are removed. BTB test protocols should become based on quantified risk in order to prevent the needless slaughter of large numbers of healthy animals.

Latent-class methods to evaluate diagnostics tests for Echinococcus infections in dogs

Background

The diagnosis of canine echinococcosis can be a challenge in surveillance studies because there is no perfect gold standard that can be used routinely. However, unknown test specificities and sensitivities can be overcome using latent-class analysis with appropriate data.

Methodology

We utilised a set of faecal and purge samples used previously to explore the epidemiology of canine echinococcosis on the Tibetan plateau. Previously only the purge results were reported and analysed in a largely deterministic way. In the present study, additional diagnostic tests of copro-PCR and copro-antigen ELISA were undertaken on the faecal samples. This enabled a Bayesian analysis in a latent-class model to examine the diagnostic performance of a genus specific copro-antigen ELISA, species-specific copro-PCR and arecoline purgation. Potential covariates including co-infection with Taenia, age and sex of the dog were also explored. The dependence structure of these diagnostic tests could also be analysed.

Principle findings

The most parsimonious result, indicated by deviance-information criteria, suggested that co-infection with Taenia spp. was a significant covariate with the Echinococcus infection. The copro-PCRs had estimated sensitivities of 89% and 84% respectively for the diagnoses of Echinococcus multilocularis and E. granulosus. The specificities for the copro-PCR were estimated at 93 and 83% respectively. Copro-antigen ELISA had sensitivities of 55 and 57% for the diagnosis of E. multilocularis and E. granulosus and specificities of 71 and 69% respectively. Arecoline purgation with an assumed specificity of 100% had estimated sensitivities of 76% and 85% respectively.

Significance

This study also shows that incorporating diagnostic uncertainty, in other words assuming no perfect gold standard, and including potential covariates like sex or Taenia co-infection into the epidemiological analysis may give different results than if the diagnosis of infection status is assumed to be deterministic and this approach should therefore be used whenever possible.

Dogs are a key definitive host of Echinococcus spp; hence, accurate diagnosis in dogs is important for the surveillance and control of echinococcosis. A perfect diagnostic test would detect every infected dog (100% sensitivity) whilst never giving a false positive reaction in non-infected dogs (100% specificity). Since no such test exists, it is important to understand the performance of available diagnostic techniques. We used the results of a study that used three diagnostic tests on dogs from the Tibetan plateau, where there is co-endemicity of E. granulosus and E. multilocularis. In this study opro-antigen ELISA and copro-PCR diagnostic tests were undertaken on faecal samples from all animals. The dogs were also purged with arecoline hydrobromide to recover adult parasites as a highly specific but relatively insensitive third diagnostic test. We used a statistical approach (Bayesian latent-class models) to estimate simultaneously the sensitivities of all three tests and the specificities of the copro-antigen and copro-PCR tests. We also analysed how some determinants of infection can affect parasite prevalence. This approach provides a robust framework to increase the accuracy of surveillance and epidemiological studies of echinococcosis by overcoming the problems of poor diagnostic test performance.

Echinococcusinfections in Chinese dogs: a comparison of coproantigen kits

Coproantigen test kits forEchinococcusspp. worms in dogs, designed for commercial use, were obtained from three different Chinese producers, and were compared with a laboratory kit using reagents from New Zealand. None of the three producers would provide details of their test validation. From a known set of dog faeces obtained at necropsy from infected and uninfected dogs, and from faeces collected from dogs necropsied in the field, results differed between the kits. For field material, the Tiankang kit showed the best specificity but lacked sensitivity. The Combined kit showed best sensitivity but lacked specificity. Results for the Haitai kit were intermediate. With samples from experimentally infected dogs, both the Haitai and Combined kits lacked sensitivity. Kits will need to be validated by the user before they can be relied on to predict progress inEchinococcusspp. control in China or in other countries.

A monoclonal antibody-based copro-ELISA kit for canine echinococcosis to support the PAHO effort for hydatid disease control in South America

Cystic echinococcosis is still a major concern in South America. While some regions show advances in the control of the disease, others have among the highest incidence in the world. To reverse this situation the Pan American Health Organization (PAHO) has launched a regional project on cystic echinococcosis control and surveillance. An early concern of the program was the lack of a standardized diagnostic tool to monitor infection in dogs, a key target of control programs. Under this premise, we have developed a new copro-ELISA test after extensive screening of a large panel of monoclonal antibodies (MAbs) and polyclonal sera, which performs with high standards of sensitivity (92.6%) and specificity (86.4%) as established by necropsy diagnosis of dogs. The key component of the test, MAbEg9 has a convenient IgG isotype and reacts with a periodate-resistant epitope found in high molecular weight components of the worm. Time-course analysis of experimentally infected dogs showed that even animals with a very low number of parasites could be detected as early as day 20 post infection. The test was formulated in a ready-to-use kit format with proven stability of each component for a minimum of 3 months at room temperature. This characteristic facilitates its standardized use and shipping to other laboratories, which was demonstrated by the identical results obtained by two different laboratories in Peru and our own laboratory when a large number of field samples were analyzed independently in a blind fashion.

Cystic echinococcosis, caused by infection with the larval stage of the Echinococcus granulosus tapeworm, is a life-threatening zoonosis of worldwide distribution. The adult worm parasitizes the small intestine of dogs, which become infected after eating offal of an animal contaminated with the parasite, and releases eggs into the environment that can be accidentally ingested by domestic animals or humans, maintaining the life cycle of the parasite. Deworming of dogs is a major component of control programs, and simple and reliable methods are needed to monitor the base-line infection in the canine population. The lack of these tests was recognized as a major obstacle to the PAHO effort to control the disease in South America. This paper describes the development of a diagnostic assay that detects parasite antigens in dog feces. The key component is a monoclonal antibody carefully selected to attain high levels of sensitivity and specificity, which were established with a large panel of field fecal samples obtained from animals diagnosed by necropsy. Several aspects of the long-term stability of the test were optimized to facilitate its shelf-life and transference to other laboratories.

Challenges for diagnosis and control of cystic hydatid disease

This paper is based on the experience of the authors, with the aim to define the challenges for Echinococcus granulosus (E.g./CE) diagnosis and control for those countries that may now or in the future be contemplating control of hydatid disease. A variety of methods are available for diagnosis in humans but a universal gold standard is lacking. Diagnosis in definitive hosts can avoid necropsy by the use of methods such as coproantigen detection but test performance is variable between populations. A sylvatic cycle adds challenges in some countries and the epidemiology of the parasite in these hosts is poorly understood. Control by solely administering praziquantel to dogs is not effective in developing countries where the disease is endemic. Additional avenues to pursue include the instigation of participatory planning, use of an existing vaccination for intermediate hosts and development of a vaccine and long-acting anthelmitic implants for definitive hosts. Promoting public acceptance of control of the dog population by humane euthanasia and reduced reproduction is also essential.

Evaluation of rabbit antibody response against 8 and 16 kDa recombinant subunits of antigen B from Echinococcus granulosus

OBJECTIVE

To immunize rabbits with 12 and 16 kDa recombinant subunits of antigen B from Echinococcus granulosus (E. granulosus) and measuring polyclonal antibody and humoral immune response using ELISA and gel diffusion.

METHODS

Two mentioned antigens were cloned and expressed in expression vector and purified by affinity chromatography. Four young rabbits were selected and challenged intradermally with yielded recombinant antigens. Rabbits' sera were collected post infection and were tested using ELISA and gel diffusion for polyclonal antibody detection 10 days after last injection.

RESULTS

The specific antibody against the recombinant peptides was efficiently produced within 4 weeks post infection.

CONCLUSIONS

Produced recombinants proteins could induce the immune response of the rabbits successfully. This process might improve the clarification of diagnosis and vaccination as regards hydatidosis.

Annotation of the transcriptome from Taenia pisiformis and its comparative analysis with three Taeniidae species

Background

Taenia pisiformis is one of the most common intestinal tapeworms and can cause infections in canines. Adult T. pisiformis (canines as definitive hosts) and Cysticercus pisiformis (rabbits as intermediate hosts) cause significant health problems to the host and considerable socio-economic losses as a consequence. No complete genomic data regarding T. pisiformis are currently available in public databases. RNA-seq provides an effective approach to analyze the eukaryotic transcriptome to generate large functional gene datasets that can be used for further studies.

Methodology/Principal Findings

In this study, 2.67 million sequencing clean reads and 72,957 unigenes were generated using the RNA-seq technique. Based on a sequence similarity search with known proteins, a total of 26,012 unigenes (no redundancy) were identified after quality control procedures via the alignment of four databases. Overall, 15,920 unigenes were mapped to 203 Kyoto Encyclopedia of Genes and Genomes (KEGG) pathways. Through analyzing the glycolysis/gluconeogenesis and axonal guidance pathways, we achieved an in-depth understanding of the biochemistry of T. pisiformis. Here, we selected four unigenes at random and obtained their full-length cDNA clones using RACE PCR. Functional distribution characteristics were gained through comparing four cestode species (72,957 unigenes of T. pisiformis, 30,700 ESTs of T. solium, 1,058 ESTs of Eg+Em [conserved ESTs between Echinococcus granulosus and Echinococcus multilocularis]), with the cluster of orthologous groups (COG) and gene ontology (GO) functional classification systems. Furthermore, the conserved common genes in these four cestode species were obtained and aligned by the KEGG database.

Conclusion

This study provides an extensive transcriptome dataset obtained from the deep sequencing of T. pisiformis in a non-model whole genome. The identification of conserved genes may provide novel approaches for potential drug targets and vaccinations against cestode infections. Research can now accelerate into the functional genomics, immunity and gene expression profiles of cestode species.

A retrospective survey of human hydatidosis based on hospital records during the period of 10 years

Hydatid cyst is a parasitic infection that is widely seen endemically in the Middle East countries. We studied hydatid cyst pattern in hospitalized adult patients in our hospital from 2000 to 2010. In this study 89 patients, 50 females and 39 males who were diagnosed to have hydatid cyst were evaluated. The mean age of the patients was 37.3 and the mean hospital stay was 10.1 days. The main complaint was abdominal pain (66.2%). The most common localization of cysts was the liver and the most radiological method to diagnose the disease was ultrasonography followed by CT scan. Our recurrence rate was more than average. We had no mortality and did not find any serious postoperative complication. Safe surgery is a role for hydatid cysts.

Cross-Reaction between the Crude Hydatid Cyst Fluid Antigens of Human and Animals Origin in Response to Human IgG Class and Subclasses

The current work aimed to evaluate the cross-reactivity of human immune sera against crude hydatid fluid antigens of sheep, human, mouse, cattle, as well as B fraction of cystic fluid antigen. 30 balb/c mice were infected with sheep hydatid cyct fluid antigen containing protoscolex after the viability of these protoscolices was assessed. ANOVA was used to test the difference of themean of optical density (OD) values among case and control groups. The highest human IgG class antibody was against antigen B (0.93) and the lowest against cattle HCF antigen (0.32). The differences between responses to these antigens were statistically significant (P < 0.001). The sensitivity and specificity of ELISA test used for evaluating the responses of human total IgG to different hydatid cyst fluid (HCF) antigens among the case and control groups were 100 and 95.8%, respectively. Cross-reaction of human IgG class and subclasses responses was found almost for all the antigens with the best reaction against human and cattle (HCF) antigens and antigen B using a ratio of mean OD value to each antigen divided by the cut-off point value for the same antigen. Human sera showed a considerable cross-reactivity against all antigens by using ELISA.

Serological diagnosis of echinococcosis: the diagnostic potential of native antigens

PURPOSE

Human alveolar (AE) and cystic echinococcosis (CE) caused by the metacestode stages of Echinococcus multilocularis and E. granulosus, respectively, lack pathognomonic clinical signs. Diagnosis therefore relies on the results of imaging and serological studies. The primary goal of this study was to evaluate the efficacy of several easy-to-produce crude or partially purified E. granulosus and E. multilocularis metacestode-derived antigens as tools for the serological diagnosis and differential diagnosis of patients suspicious for AE or CE.

METHODS

The sera of 51 treatment-naïve AE and 32 CE patients, 98 Swiss blood donors and 38 patients who were initially suspicious for echinococcosis but suffering from various other liver diseases (e.g., liver neoplasia, etc.) were analysed.

RESULTS

According to the results of enzyme-linked immunosorbent assays (ELISA), metacestode-derived antigens of E. granulosus had sensitivities varying from 81 to 97% and >99.9% for the diagnosis of CE and AE, respectively. Antigens derived from E. multilocularis metacestodes had sensitivities ranging from 84 to 91% and >99.9% for the diagnosis of CE and AE, respectively. Specificities ranged from 92 to >99.9%. Post-test probabilities for the differential diagnosis of AE from liver neoplasias, CE from cystic liver lesions, and screening for AE in Switzerland were around 95, 86 and 2.2%, respectively. Cross-reactions with antibodies in sera of patients with other parasitic affections (fasciolosis, schistosomosis, amebosis, cysticercosis, and filarioses) did occur at variable frequencies, but could be eliminated through the use of confirmatory testing.

CONCLUSIONS

Different metacestode-derived antigens of E. granulosus and E. multilocularis are valuable, widely accessible, and cost-efficient tools for the serological diagnosis of echinococcosis. However, confirmatory testing is necessary, due to the lack of species specificity and the occurrence of cross-reactions to other helminthic diseases.

Multiplex PCR identification of Taenia spp. in rodents and carnivores

The genus Taenia includes several species of veterinary and public health importance, but diagnosis of the etiological agent in definitive and intermediate hosts often relies on labor intensive and few specific morphometric criteria, especially in immature worms and underdeveloped metacestodes. In the present study, a multiplex PCR, based on five primers targeting the 18S rDNA and ITS2 sequences, produced a species-specific banding patterns for a range of Taenia spp. Species typing by the multiplex PCR was compared to morphological identification and sequencing of cox1 and/or 12S rDNA genes. As compared to sequencing, the multiplex PCR identified 31 of 32 Taenia metacestodes from rodents, whereas only 14 cysts were specifically identified by morphology. Likewise, the multiplex PCR identified 108 of 130 adult worms, while only 57 were identified to species by morphology. The tested multiplex PCR system may potentially be used for studies of Taenia spp. transmitted between rodents and carnivores.

Gene cloning, expression and serological evaluation of the 12-kDa antigen-B subunit from Echinococcus granulosus

A 12-kDa subunit of antigen B from Echinococcus granulosus has recently been cloned, expressed and used in diagnostic ELISA to test human sera for evidence of cystic echinococcosis. The performance of the ELISA based on the recombinant antigen (rAgB) was compared with that of similar assays based on native antigen B (nAgB) or hydatid-cyst fluid. For the preparation of the rAgB, total RNA was extracted from Ec. granulosus protoscoleces so that antigen-B complementary DNA could be synthesised, amplified by PCR, and then cloned into the pQE30 expression vector. The recombinant plasmid was transformed in Escherichia coli and induced using isopropyl-beta-D-thiogalactopyrano-side. Bacterial samples were collected, lysed and then analysed by SDS-PAGE and western blotting. The recombinant protein was purified by affinity chromatography. Although the performance of the ELISA based on cyst fluid appeared identical to that of the assay based on the recombinant antigen (with a sensitivity, specificity, positive predictive value and negative predictive value of 96.0%, 97.0%, 97.2% and 95.5%, respectively), the corresponding results for the ELISA based on nAgB (98.6%, 100%, 100% and 98.5%) were slightly better. Despite this difference (which was not statistically significant), the comparative ease with which large quantities of the recombinant antigen could be produced make the antigen a potentially useful tool in the diagnosis of cystic echinococcosis.

Pulmonary cystic echinococcosis

PURPOSE OF REVIEW

Pulmonary cystic echinococcosis, a zoonosis caused by the larvae of the dog tapeworm Echinococcus granulosus, is considered as a major public health problem in countries where dogs are used to care for large herds. Despite its frequency and widespread endemicity, the literature on pulmonary cystic echinococcosis is scarce and not systematic. We aimed to summarize currently available information to provide a comprehensive overview for clinicians facing cases of pulmonary cystic echinococcosis.

RECENT FINDINGS

Despite discrepancies in the literature, some patterns can be discerned. The ratio of lung:liver involvement is higher in children than in adults. Most pulmonary cases are discovered incidentally on routine radiograph evaluation; also most infected individuals remain asymptomatic until the cyst enlarges sufficiently to cause symptoms. Symptoms are usually caused by mass effect from the cyst. Complications (cyst rupture, aggregated infection) change the clinical presentation, producing cough, chest pain, hemoptysis, or vomica. Diagnosis is obtained by chest radiographs or computed tomography, and supported by serology. Presurgical chemotherapy reduces the chances of seeding and recurrence. Treatment with benzimidazoles is an option when surgery is unavailable or complete removal is unfeasible.

SUMMARY

Diagnosis of pulmonary cystic echinococcosis is primarily made by imaging, and surgery remains the main therapeutic approach.

Study on the prevalence of cystic hydatidosis and its economic significance in cattle slaughtered at Hawassa Municipal abattoir, Ethiopia

A cross-sectional study was conducted from December 2008 to March 2009 to assess the status of cystic hydatidosis in cattle slaughtered at Hawassa Municipal abattoir. Out of the total 632 cattle examined visually and manually (palpation and incision), 333 (52.69%) were found harboring hydatid cysts. A significantly higher infection was detected in older cattle (P < 0.05, chi(2) = 4.36) than young. Regarding body condition score, no significant variation (P > 0.05, chi(2) = 2.148) was observed as the prevalence was 54.55% for lean cattle followed by medium (53.83%) and fat (46.88%). Of the total 333 infected, 123 (36.9%) had hydatid cysts only in the lung, 23 (6.9%) in the liver, 12 (3.6%) in the spleen, five (1.5%) in the heart, and three (0.9%) in the kidney while the rest 167 (50.2%) had multiple organ infections. Of the 530 viscera harboring hydatid cysts, the highest (52.83%) was lung followed by liver (34.15%), spleen (9.06%), heart (3.39%), and kidney (0.56%). Size assessment made on 874 cysts indicated that 308 (35.3%) were small, 251 (28.7%) medium, 89 (10.2%) large, and 226 (25.9%) were calcified. The distribution of characterized cysts in different organs based on their size was found to be statistically significant (P < 0.05). In addition, out of the total 874 cysts collected, 26.9% were fertile, 47.3% sterile, and 25.9% calcified or purulent cysts. There was a significant difference in fertility of cyst from different organs (P < 0.05, chi(2) = 27.96), those of lung origin being highly fertile. Likewise, out of the 121 fertile cysts subjected for viability test, 68 (56.2%) were viable. Considering the current result, the total annual economic loss from organ condemnation and carcass weight loss due to bovine hydatidosis at Hawassa Municipal abattoir was estimated at 1,791,625.89 Ethiopian Birr (ETB; 1USD = 12.93ETB). Results in the study were discussed in light of the situation in different parts of Ethiopia and abroad, and finally, relevant recommendations were forwarded.