Diagnostic efficacy of a recombinant cysteine protease of Spirometra erinacei larvae for serodiagnosis of sparganosis

Case Report: Moving Tumor-Like Foci Behind Refractory Epilepsy-Cerebral Sparganosis Successfully Treated by Surgery After Failure of Praziquantel Treatment

Cerebral sparganosis is clinically non-specific and easily misdiagnosed, exposing patients to the risk of severe brain damage and neurological dysfunction caused by actively migrating larvae. Diagnostic biomarkers from typical cases can help to establish an early diagnosis and proper treatment. We present a 25-year-old woman who suffered from 9 years of refractory epilepsy and was misdiagnosed with glioma and subjected to surgery. The postoperative pathology confirmed granuloma, and the tumor-like foci reappeared 3 months later. Along with the “tunnel sign” on MRI, cerebral sparganosis was suspected and confirmed by positive serum and cerebrospinal fluid antibodies against Spirometra mansoni. The patient visited us after a failure of four cycles of praziquantel treatment, recurrent seizures and hemiplegia with basal ganglia foci. Craniotomy was not carried out until the larva moved to the superficial lobe on follow-up MRIs, and pathology revealed sparganosis granuloma. The patient became seizure-free and recovered myodynamia but had long-lasting cognitive dysfunction due to severe brain damage. This case indicated the importance of tunnel signs and moving tumor-like foci on MRI as diagnostic clues of cerebral sparganosis. An early diagnosis is vitally important to avoid severe neural dysfunction by the long-living and moving larvae. Surgical removal of the larva is a critical remedy for cases failed by praziquantel treatment.

Standardization of recombinant Ancylostoma caninum cysteine protease 2 (rAcCP2) based indirect ELISA for serodiagnosis of hookworm infection in dogs

Diagnosis of hookworm infection in dogs during pre-patentency or in pregnant bitches harbouring encysted larvae in tissues can be achieved by employing serological tests using proteins derived from somatic or excretorysecretory products of adult or larvae of Ancylostoma caninum. In the present study, cathepsin-B protease (AcCP2) of A. caninum, which helps in development of parasitism and nutrient digestion, was used to develop an indirect ELISA for detection of specific antibodies to A. caninum in dogs. The rAcCP2 (approx. 59.0 kDa) was cloned, expressed and purified under denaturing conditions. Serum samples of 20 known A. caninum positive and 15 known negative dogs were used for the standardization of indirect ELISA. The sensitivity and specificity of the assay was determined by using sera samples from 123 dogs (48 positive for A. caninum eggs in faeces and 75 faecal negative). Out of the 48 A. caninum faecal positive sera, 46 were tested positive (OD > 0.306) by indirect ELISA; whereas, 14 out of 75 faecal negative samples were also tested positive (OD > 0.306) by indirect ELISA. Based on the results, the sensitivity and specificity of rAcCP2 based indirect ELISA was calculated to be 95.8% and 84.3%, respectively. No cross-reactions were observed with serum from dogs naturally infected with B. canis vogeli, B. gibsoni, E. canis, Dirofilaria immitis and Toxocara canis. The results of the present study indicate that indirect ELISA with rAcCP2 protein might be appropriate in large scale epidemiological screening and for serological diagnosis of A. caninum infection in dogs.

Molecular Identification of Spirometra erinaceieuropaei Tapeworm in Cases of Human Sparganosis, Hong Kong

Human sparganosis is a foodborne zoonosis endemic in Asia. We report a series of 9 histologically confirmed human sparganosis cases in Hong Kong, China. All parasites were retrospectively identified as Spirometra erinaceieuropaei. Skin and soft tissue swelling was the most common symptom, followed by central nervous system lesions.

Clinical Features of Pulmonary Sparganosis

BACKGROUND

Sparganosis is an infectious disease caused by the sparganum of Spirometra species, which seldom invades the respiratory system. The aim was to describe the clinical features and outcomes of pulmonary sparganosis.

METHODS

A total of 40 patients with pulmonary sparganosis were reviewed, including 12 cases known from this experience and 28 cases reported in the literature.

RESULTS

Among these 40 patients at an average age of 45.4 ± 11.1 years (men 29), 34 (85%) had a history of ingesting raw or undercooked meat (mainly frogs or snakes). The top 3 symptoms were coughing (60.0%), fever (57.5%) and chest pain (42.5%). Peripheral blood eosinophilia was found in 30 cases (75%). Lesions were located in lung parenchyma, airway, pleura and pulmonary vessels of the patients. Thirty-one patients (77.5%) had pleural effusion. The diagnosis was established by antisparganum antibody test in 30 cases (75%) and by pathology in 9 cases (22.5%); 1 case was not mentioned. Among the 35 cases with follow-up information, 2 treated with complete surgical removal and 31 with oral administration of praziquantel had no recurrence; the remaining 2 died without effective treatments.

CONCLUSIONS

As an extremely rare and life-threatening parasitic zoonosis, pulmonary sparganosis should be diagnosed by combining the epidemiology, patient history, eosinophilia and the positive antisparganum antibody test result together if no worm was detected. Oral praziquantel is considered to be an effective treatment.

Human sparganosis, a neglected food borne zoonosis

Human sparganosis is a food borne zoonosis caused by the plerocercoid larvae (spargana) of various diphyllobothroid tapeworms of the genus Spirometra. Human infections are acquired by ingesting the raw or undercooked meat of snakes or frogs, drinking untreated water, or using raw flesh in traditional poultices. More than 1600 cases of sparganosis have been documented worldwide, mostly in east and southeast Asia. Sporadic cases have been reported in South America, Europe, and Africa, and several cases have been described in travellers returning from endemic regions. Epidemiological data suggest that the increased effect of sparganosis on human health is because of greater consumption of raw meat of freshwater frogs and snakes. This Review provides information about the Spirometra parasites and their lifecycles, summarises clinical features, diagnosis, and treatment of human sparganosis, and describes geographical distribution and infection characteristics of Spirometra parasites in host animals.

Characterization of Spirometra erinaceieuropaei Plerocercoid Cysteine Protease and Potential Application for Serodiagnosis of Sparganosis

Background

Sparganosis is a neglected but important food-borne parasitic zoonosis. Clinical diagnosis of sparganosis is difficult because there are no specific manifestations. ELISA using plerocercoid crude or excretory–secretory (ES) antigens has high sensitivity but has cross-reactions with other helminthiases. The aim of this study was to characterize Spirometra erinaceieuropaei cysteine protease (SeCP) and to evaluate its potential application for serodiagnosis of sparganosis.

Methodology/Principal Findings

The full length SeCP gene was cloned, and recombinant SeCP (rSeCP) was expressed and purified. Western blotting showed that rSeCP was recognized by the serum of sparganum-infected mice, and anti-rSeCP serum recognized the native SeCP protein of plerocercoid crude or ES antigens. Expression of SeCP was observed at plerocercoid stages but not at the adult and egg stages. Immunolocalization identified SeCP in plerocercoid tegument and parenchymal tissue. The rSeCP had CP activity, and the optimum pH and temperature were 5.5 and 37°C, respectively. Enzymatic activity was significantly inhibited by E-64. rSeCP functions to degrade different proteins and the function was inhibited by anti-rSeCP serum and E-64. Immunization of mice with rSeCP induced Th2-predominant immune responses and anti-rSeCP antibodies had the potential capabilities to kill plerocercoids in an ADCC assay. The sensitivity of rSeCP-ELISA and ES antigen ELISA was 100% when performed on sera of patients with sparganosis. The specificity of rSeCP-ELISA and ES antigen ELISA was 98.22% (166/169) and 87.57% (148/169), respectively (P<0.05).

Conclusions

The rSeCP had the CP enzymatic activity and SeCP seems to be important for the survival of plerocercoids in host. The rSeCP is a potential diagnostic antigen for sparganosis.

Sparganosis is a neglected tropical disease; its diagnosis is difficult and it is often misdiagnosed. ELISA using the crude or ES antigens of plerocercoids cross reacts with other helminthiases. Cysteine protease is a type of hydrolase and plays important roles in the development and survival of parasites; it has been used for diagnostic markers and vaccine targets for some parasitic diseases. In this study, a 36 kDa Spirometra erinaceieuropaei cysteine protease (SeCP) was expressed and purified. The results showed that SeCP was a plerocercoid stage-specific protein located in the teguments and parenchymal tissue. The rSeCP had cysteine protease activity and functioned to degrade host proteins. Vaccination of mice with rSeCP induced high levels of IgG1 and anti-rSeCP antibodies with the ability to kill plerocercoids in an ADCC assay. The rSeCP had a high sensitivity and specificity for detecting anti-plerocercoid antibodies, and could be used as a potential antigen for serodiagnosis of sparganosis.

Development of a rapid diagnostic kit that uses an immunochromatographic device to detect antibodies in human sparganosis

A diagnostic kit using an immunochromatographic device was developed to replace the time-consuming immunodiagnostic methods for human sparganosis. The kit was found to be faster and easier to use than an enzyme-linked immunosorbent assay (ELISA) and showed higher sensitivity and specificity. It will be useful for the laboratory diagnosis of hospitalized cases of sparganosis.