Improvements in the serodiagnosis of helminthic zoonoses

Development of a Luminex Bead Based Assay for Diagnosis of Toxocariasis Using Recombinant Antigens Tc-CTL-1 and Tc-TES-26

The clinical spectrum of human disease caused by the roundworms Toxocara canis and Toxocara cati ranges from visceral and ocular larva migrans to covert toxocariasis. The parasite is not typically recovered in affected tissues, so detection of parasite-specific antibodies is usually necessary for establishing a diagnosis. The most reliable immunodiagnostic methods use the Toxocara excretory-secretory antigens (TES-Ag) in ELISA formats to detect Toxocara-specific antibodies. To eliminate the need for native parasite materials, we identified and purified immunodiagnostic antigens using 2D gel electrophoresis followed by electrospray ionization mass spectrometry. Three predominant immunoreactive proteins were found in the TES; all three had been previously described in the literature: Tc-CTL-1, Tc-TES-26, and Tc-MUC-3. We generated Escherichia coli expressed recombinant proteins for evaluation in Luminex based immunoassays. We were unable to produce a functional assay with the Tc-MUC-3 recombinant protein. Tc-CTL-1 and Tc-TES-26 were successfully coupled and tested using defined serum batteries. The use of both proteins together generated better results than if the proteins were used individually. The sensitivity and specificity of the assay for detecting visceral larval migrans using Tc-CTL-1 plus Tc-TES-26 was 99% and 94%, respectively; the sensitivity for detecting ocular larval migrans was 64%. The combined performance of the new assay was superior to the currently available EIA and could potentially be employed to replace current assays that rely on native TES-Ag.

Unusual presentations of neurocysticercosis

INTRODUCTION

Neurocysticercosis (NCC) is the most common helminthic infection of the central nervous system. It is a major public health problem in developing countries, however, rarely reported in Saudi Arabia. As far as our knowledge, this is the first case report of NCC in Saudi Arabia. An increasing number of immigrants from endemic areas is the cause.

CASE REPORTS

Here, we report three interesting cases of NCC in three adult females with very unusual clinical presentation. These include: (case 1) progressive spasticity of the four limbs with severe pseudobulbar manifestations, precipitancy of micturition, cognitive impairment and no eye involvement; (case 2) dystonic movement of right upper and lower limbs together with weight gain, lethargy, mental dullness and goitre; and (case 3) depressive manifestations together with disturbance of writing, mild deep sensory loss, limb-kinetic apraxia, lack of coordination and dystonia of the right upper limb. The clinical details and possible mechanisms for the uncommon presentations are discussed.

CONCLUSION

NCC should be kept in mind and raise a high level of suspicion for unusual neurological manifestations in Saudian patients particularly as there has been increasing percentage of immigration from endemic areas during the last few years.

Visceral larva migrans associated with earthworm ingestion: clinical evolution in an adolescent patient

A 16-year-old girl developed a cough, hypereosinophilia (absolute eosinophil count: 32000/mm3), hypergammaglobulinemia, and multiple noncavitary pulmonary nodules 1 month after having ingested an earthworm on a dare. Spirometry revealed moderate restriction and reduced gas diffusion. Parabronchial biopsy demonstrated eosinophilic organizing pneumonitis with multiple eosinophilic microabscesses, and Toxocara titers were elevated (>1:4096). Ophthalmologic examination ruled out ocular larva migrans. The patient received a 10-day course of albendazole (400 mg orally twice daily) and demonstrated significant clinical improvement with resolution of cough and pulmonary function abnormalities. Her white blood cell count and hypergammaglobulinemia normalized within 20 days, yet eosinophils (absolute eosinophil count: 1780/mm3) and Toxocara serologies (>1:4096) remained elevated 3 months after completing antihelminthic therapy. In this instance, the ingested earthworm served as the paratenic carrier of Toxocara larvae from the soil to the patient. This case highlights the clinical evolution of pulmonary visceral larva migrans infection caused by Toxocara spp. associated with a discrete ingestion in an adolescent patient. In addition, it provides a rare opportunity to define the incubation period of visceral larva migrans and emphasizes the importance of education regarding sources of Toxocara infection.

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.

Serological assays for the identification of Oesophagostomum dentatum infections in pigs

Oesophagostomum dentatum antigen preparations of third (L3) or fourth (L4) stage larvae were characterised by Western blotting. Panels of sera obtained from pigs infected with O dentatum and Ascaris suum, respectively, reacted with the same bands of L3 antigen. In contrast high specificity against a characteristic band, was observed when L4 extract was employed as antigen. To establish an enzyme-linked immunosorbent assay (ELISA), a panel of homologous and heterologous sera was tested against O dentatum L4 extract. The best combined specificity and sensitivity was obtained when horseradish peroxidase (HRP) goat anti swine IgG conjugate was used rather than HRP rabbit anti swine Ig conjugate. Testing series of sera from pigs infected with single doses of either 2000, 20,000 or 200,000 infective larvae by the ELISA, a significant dose dependency in the antibody response was observed between the low and high dosage groups. This assay may be useful in future studies of the immune-mechanisms against nodular worm infections in pigs.

Parasite enzymes and the control of roundworm and fluke infestation in domestic animals

The potential application of parasite enzymes to the serodiagnosis and control of veterinary helminthiases is reviewed. Consideration is given to the use of secreted enzymes as potential antihelminth vaccine components, in the search for novel anthelmintic agents and as serodiagnostic targets. The discussion focuses on recent advances in the definition of the molecular and functional properties of helminth enzymes and the application of this information to the development of novel anthelmintics as well as vaccines. Enzymes included are acetylcholinesterases, enzymes of polyamine and carbohydrate metabolism, proteases and detoxifying activities such as superoxide dismutases and glutathione S-transferases.

Dynamics of porcine humoral responses to experimental infections by Spanish Trichinella isolates: comparison of three larval antigens in ELISA

Five groups of six helminth-free pigs of the Iberian and Landrace x White breeds were each experimentally-infected randomly at a dose of 150 larvae per kg, body weight with one of the five Trichinella isolates, coded as Gm-1, Co-77, Laso, C-76 and Mad-83. These isolates were selected from the two Trichinella species (T. spiralis and T. britovi) so far identified in the Iberian Peninsula. Specific antibodies against the infections were measured on days -14, 0, 6, 16, 20, 27, 34, 49, 63 and 82 post-infection (p.i.), in a comparative indirect ELISA assay using three different antigens prepared from the muscle stage of the parasite. The antigens were a crude saline larval extract (CSLE), excretory-secretory (ES) and surface stripped cetyl-trimethyl ammonium bromide detergent (CTAB) products. Over all, the dynamics of antibody responses were very similar for infections with the five different isolates, although a significant delay in positive and maximum antibody titres was seen in the group infected with C-76, the isolate exhibiting a marked low infectivity to domestic mammals. ELISA with the crude antigen was more sensitive (positive antibody titres appeared between days 6 and 16 p.i.) than with the ES and CTAB preparations (positive titres appeared between days 16 and 20 p.i.). For infections with the C-76 isolate, positive titres appeared between days 16 and 20 p.i. with the CSLE antigen and, on day 27 p.i. with the ES and CTAB antigens. Little cross-reactivity with other common porcine helminth infections appeared only when ELISA was carried out with CSLE and CTAB antigens.

Taenia crassiceps metacestode vesicular fluid antigens shared with the Taenia solium larval stage and reactive with serum antibodies from patients with neurocysticercosis

After removal of host (mouse) serum proteins (albumin, transferrin, IgG and another five unidentified proteins) by immunoaffinity chromatography, the vesicular fluid of T. crassiceps metacestodes (TcVF) was immunoelectrophoretically examined for antigens recognized by rabbit antiserum to aqueous crude extract of T. solium cysticerci. Based on a precipitate pattern developed in electroimmunodiffusion, nine cross-reactive antigens could be demonstrated. In the ELISA, TcVF was shown to be a potent antigen for the demonstration of IgG antibodies in the sera of Mexican patients (n = 14) with confirmed neurocysticercosis (mean E490 values +/- SD: 0.39 +/- 0.38) although it was less sensitive when compared to T. solium VF (0.95 +/- 0.54). Sensitivity was much higher using cross-reactive TcVF antigens selected by immunoaffinity chromatography with rabbit IgG antibodies to larval T. solium crude extract (0.87 +/- 0.57). SDS-PAGE fluorograph of cross-reactive, radioiodinated TcVF protein antigens and selected by antibodies of individual neurocysticercosis sera (n = 13), exhibited six to nine bands depending on the serum tested. Altogether ten 125I-labelled proteins (Mr range from about 20,000 to 200,000) were recognized by neurocysticerosis antibodies. Four proteins (Mr about 22,000, 25,000, 32,000 and 45,000) were detected by all sera.

New aspects of parasitic zoonoses

Selected parasitic zoonoses are discussed with emphasis on epidemiological, diagnostic and some chemotherapeutic aspects. Pneumocystosis, toxoplasmosis, cryptosporidiosis and microsporidiosis are briefly reviewed as "AIDS-related zoonoses". Up to now 5 genera of Microsporidia have been identified as causative agents of human infections, including Encephalitozoon cuniculi, Enterocytozoon bieneusi and Pleistophora sp. which were found in AIDS patients. From the many "other parasitic zoonoses", giardiasis, echinococcosis and taeniosis/cysticercosis are discussed as examples. Significant advances in the understanding of transmission dynamics, in strain characterisation and diagnosis of the diseases have been achieved.