• 1

    Williams JA, Lopez Adaros H, Trejos A, 1971. Prevalence and distribution of hydatidosis with special reference to the Americas. Am J Trop Med Hyg 20 :222–236.

    • Search Google Scholar
    • Export Citation
  • 2

    Parija SC, Rao RS, 1987. Evaluation of combined use of indirect haemagglutination and Casoni’s skin test in the diagnosis of hydatid disease. Indian J Pathol Microbiol. 30 :117–127.

    • Search Google Scholar
    • Export Citation
  • 3

    Gottstein B, 1984. An immunoassay for the detection of circulating antigens in human echinococcosis. Am J Trop Med Hyg 33 :1185–1190.

  • 4

    Parija SC, 1991. Recent trends in the serodiagnosis of hydatid disease. Southeast Asian J Trop Med Public Health 22 (Suppl):371–376.

  • 5

    Craig PS, Nelson GS, 1984. The detection of circulating antigen in human hydatid disease. Ann. Trop Med Parasitol 78 :219–227.

  • 6

    Parija SC, 1993. Simple immunoassay in the serodiagnosis of hydatid disease in the field or poorly equipped laboratories. Indian J Med Microbiol 11 :1–4.

    • Search Google Scholar
    • Export Citation
  • 7

    Parija SC, 1994. New approaches in the serodiagnosis of hydatid disease (editorial). J Indian Med Assoc. 92 :281–284.

  • 8

    Shariff GM, Parija SC, 1991. Countercurrent immunoelectrophoresis for the serodiagnosis of hydatid disease by detection of circulating hydatid antigen. J Microbiol Methods. 14 :71–76.

    • Search Google Scholar
    • Export Citation
  • 9

    Shariff GM, Parija SC, 1993. Co-agglutination (Co-A) test for circulating antigen in hydatid disease. J Med Microbiol 38 :231–234.

  • 10

    Parija SC, Rao RS, 1986. Enhancement of sensitivity of the haemagglutination test for echinococcosis by use of Staphylococcus aureus protein A. J Med Microbiol 22 :241–244.

    • Search Google Scholar
    • Export Citation
  • 11

    Parija SC, Mishra SR, Rao RS, 1986. Sensitized chick cells in the indirect haemagglutination test for echinococcosis. J Med Microbiol 22 :237–239.

    • Search Google Scholar
    • Export Citation
  • 12

    Forbes BA, Sahm DF, Weissfeld AS, eds, 1998. Bailey and Scott’s Diagnostic Microbiology. 10th edition. St. Louis, MO: Mosby Publishers, 60–65.

  • 13

    Vamsy AS, Parija SC, Sibal RN, 1991. Abdominal hydatidosis in Pondicherry, India. Southeast Asian J Trop Med Public Health 22 (Suppl):365–370.

    • Search Google Scholar
    • Export Citation
  • 14

    Harris KM, Morris D, Tudor R, Toghill P, Hardcastle JD, 1986. Clinical and radiographic features of simple hydatid cysts of the liver. Br J Surg 73 :835–838.

    • Search Google Scholar
    • Export Citation
  • 15

    Babba H, Messdi A, Masmoudi S, Zribi M, Grillot R, Ambriose-Thomas P, Beyroati I, Sahnoun Y, 1994. Diagnosis of human hydatidosis: comparison between imaging and six serologic techniques. Am J Trop Med Hyg 50 :64–68.

    • Search Google Scholar
    • Export Citation
  • 16

    Gray LD, Fedorko DP, 1992. Laboratory diagnosis of bacterial meningitis. Clin Microbiol Rev 5 :130–145.

  • 17

    Bagchi AK, Tiwari S, Gupta S, Katiya JC, 1998. The latex agglutination test. Standardization and comparison with direct agglutination and dot ELISA in the diagnosis of visceral leishmaniasis in India. Ann Trop Med Parasitol 92 :159–163.

    • Search Google Scholar
    • Export Citation
  • 18

    Arya SC, 1997. Latex agglutination test for the visceral leishmaniasis (letter). Trans R Soc Trop Med Hyg. 91 :366.

  • 19

    Mazumder P, Chuang HY, Wentz MW, Wiedbrauk DL, 1988. Latex agglutination test for the detection of antibodies to Toxoplasma gondii.J Clin Microbiol 26 :2444–2446.

    • Search Google Scholar
    • Export Citation
  • 20

    Barbieri M, Sterla S, Battisoni J, Nieto A, 1993. High performance latex reagent for hydatid serology using an Echinococcus granulosus lipoprotein antigen fraction purified from cyst fluid in one step. Int J Parasitol 23 :565–572.

    • Search Google Scholar
    • Export Citation
  • 21

    D’Amelio R, Pontesilli O, Palmisano L, Pezzella M, Vullo V, Delia S, de Rose F, Sorice F, Aiuti F, 1983. Detection and partial characterization of circulating immune complexes in hydatid disease. J Clin Microbiol 18 :1021–1026.

    • Search Google Scholar
    • Export Citation
  • 22

    Collori EA, Varela-Dias VM, 1975. Penetration of host IgG molecules into hydatid cysts. J Parasitenkd 48 :47–51.

  • 23

    Ravinder PT, Parija SC, Subba Rao KSVK, 1997. Evaluation of human hydatid disease before and after surgery and chemotherapy by demonstration of hydatid antigen and antibodies in serum. J Med Microbiol 47 :859–864.

    • Search Google Scholar
    • Export Citation
  • 24

    Kanwar R, Vinayak VK, 1984. The significance of free and immunocomplexed hydatid specific antigen(s) as an immunodiagnostic tool for human hydatidosis. J Med Microbiol 37 :396–403.

    • Search Google Scholar
    • Export Citation

 

 

 

 

A NEW SERUM HYDATID ANTIGEN DETECTION TEST FOR DIAGNOSIS OF CYSTIC ECHINOCOCCOSIS

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  • 1 Department of Microbiology, Jawaharlal Institute of Postgraduate Medical Education and Research, Pondicherry, India

Cystic echinococcosis (CE) is a major public health problem with a worldwide distribution in both humans and animals. Diagnosis of this disease by simple and rapid immunoassays is a priority. The objective of the present study was to standardize and evaluate the latex agglutination test (LAT) as a simple test for the detection of circulating hydatid antigen in serum. The subjects in this study included 141 patients in the following groups: surgically confirmed CE cases (18), ultrasound-proven cases (26), presumptive CE cases (47), controls with other parasitic disease (25), and healthy controls (25). A polystyrene latex (0.81 μm) suspension was used as a carrier particle for hydatid antibodies in the test. The latex particles were sensitized with hyperimmune hydatid antiserum raised in rabbits. The hydatid antibody-sensitized latex particles were used for the detection of hydatid antigens in serum. The results of the study showed that the LAT could detect the circulating hydatid antigen in 13 (72%) of 18 patients with surgically confirmed CE, 17 (65%) of 26 patients with ultrasound-proven CE, and 19 (40%) of 47 presumptive cases of CE. The test detected antigen in 1 (4%) of 25 controls with other parasitic disease, and no antigen was detected in the serum of 25 healthy controls. The LAT showed a sensitivity of 72%, a specificity of 98%, a positive predictive value of 93%, and a negative predictive value of 91%. The present study is the first report of the LAT for the detection of hydatid antigen in serum in the diagnosis of CE.

INTRODUCTION

Cystic echinococcosis (CE) is a silent cyclozoonotic infection of humans and domestic animals caused by larvae of the cestode Echinococcus granulosus. It has a worldwide distribution and variable geographic incidence.1 Different assays have been developed and used for the detection of specific antibodies in serum with variable results.2 However, detection of serum antibody has a major drawback in that demonstration of specific antibodies against hydatid antigen cannot differentiate between recent and past infections.3,4 This is because circulating antibodies against hydatid antigen persist even after clinical or parasitologic cure.5,6

Circulating antigen in serum and other body fluids has been described in a variety of parasitic infections, including CE. Circulating hydatid antigen is present in the serum only during active infection, and the levels of this antigen continue to decrease after surgical removal of the hydatid cyst or successful chemotherapy. Therefore, the detection of circulating hydatid antigen in serum may be more useful than the detection of circulating serum antibodies in the diagnosis of the active or recent CE.7 There are a few immunoassays available for the detection of circulating hydatid antigen in serum for the diagnosis of CE. These include enzyme-linked immunosorbent assays,5,6 countercurrent immunoelectrophoresis,8 and a co-agglutination (Co-A) test.9

In the present study, we report the standardization and evaluation of the latex agglutination test (LAT), a simple and rapid slide agglutination test for the detection of circulating hydatid antigen in the serum for the diagnosis of CE. In this test, latex particles were sensitized with polyclonal hydatid antisera and used to detect hydatid antigen in the serum.

MATERIALS AND METHODS

Sera.

Test sera were collected from patients with CE and control sera from patients with other diseases and healthy students and blood donors at the Jawaharlal Institute of Postgraduate Medical Education and Research (JIPMER) Hospital in Pondicherry, India. Sera were stored at −20°C until used. Five groups were included in the study.

Group 1 was 18 individuals with surgically confirmed CE. Cysts removed during surgery were confirmed to be of hydatid cyst etiology by histopathologic evidence of germinal layer in the wall of the cyst and demonstration of scolices and hooklets in the aspirated cyst fluid. The sera from these patients were collected before surgery on admission to surgical ward.

Group 2 was 26 individuals with ultrasound-proven CE who did not undergo surgery. Cysts that showed daughter cysts or prominent septation and pathognomonic hydatid sands in cysts were detected by ultrasonography.

Group 3 was 47 clinically diagnosed presumptive cases of CE. These patients presented with the clinical signs and symptoms of CE but did not undergo surgery; thus, they were not surgically proven cases.

Group 4 was 25 cases (controls) with other parasitic diseases. This group included patients with other parasitic diseases such as filariasis, amoebic liver abscess, and intestinal worm infestations.

Group 5 was 25 healthy controls. This group included healthy adults (blood donors and students) who had not had CE or any other disease in the recent past.

Informed consent was obtained from all adult participants and from parents or legal guardians of minors .The project was reviewed and approved by the JIPMER Research Council.

Hydatid antigen.

Human hydatid cyst fluid (HHCF) was obtained during surgery from cases of CE of the liver caused by E. granulosus and was processed according to the method described by Parija and Rao.10 Briefly, the hydatid fluid was aspirated aseptically and checked for the presence of scolices and hooklets. The fluid was filtered using a Seitz filter (Carlson Ford Sales, Ltd., Ashton-under-Lyne, United Kingdom) and checked for the sterility aerobically. The antigen was aliquoted and stored at −20°C until used.

Hyperimmune hydatid antiserum.

Hyperimmune hydatid antiserum was raised in rabbits as per the procedure described by Shariff and Parija.9 Briefly; HHCF was emulsified with an equal volume of Freund’s complete adjuvant. Adult rabbit (3–4 kg) were injected with 0.5 mL of this emulsion in all four limbs intramuscularly. After six weeks, they were reinjected intramuscularly with 0.5 mL of the same antigen in Freund’s incomplete adjuvant in each limb. After 10 days, blood samples were taken by ear vein bleeding and monitored for the antibodies to HHCF antigen by an indirect hemagglutination assay (IHA).11 The serum was collected when the titer of the antibodies was ≥ 1:1,024.

Antiserum was purified as per the method described by Gottstein.3 Briefly, 1 mL of cold serum was mixed with 1 mL of cold saline, pH 7. The serum-saline mixture (2 mL) was added dropwise to 2 mL of cold saturated ammonium sulfate, pH 7, with stirring for 30 minutes on ice and then centrifuged at 3,000 × g for 15 minutes at 0°C. The supernatant was then discarded and the precipitate was suspended in 2 mL of saline and the procedure was repeated until the supernatant was colorless. The final precipitate was suspended in 1 mL of saline and dialyzed against phosphate-buffered saline (PBS), pH 7.2, to remove all the residual ammonium sulfate. The titer of the purified antiserum was 1:2,048 by the IHA.

Detection of hydatid antigen in serum.

Latex agglutination test.

A polystyrene latex suspension (0.81 μm; Sigma, St. Louis, MO) was used in this test. A 1% standardized polysterene latex suspension was prepared by mixing 0.1 mL of latex suspension with 9.9 mL of glycine-buffered saline (GBS), pH 8.4. This was stored at 4°C until used.

One milliliter of 1% latex suspension was mixed with 1 mL of purified hyperimmune antisera raised against HHCF in rabbits. The mixture was incubated at 37°C for two hours in a water bath. After incubation, antibody-sensitized latex particles were washed two times with GBS, pH 8.4, and centrifuged at 3,000 × g for five minutes. The pellet of antibody-sensitized latex particles was emulsified with GBS, pH 8.4, and 1% bovine serum albumin to make a suspension of 2%. The particles were stored at 4°C until used. Latex particles coated with normal rabbit serum were used as control.

The test was performed on a clean slide divided with a glass marking pen into two halves. A drop of test serum was placed on each half of the slide. An equal volume of sensitized latex reagent was added to the serum on one half. The same volume of a control latex suspension was added to the serum on the other half as a control. The slide was then manually rotated for two minutes and inspected. Agglutination with sensitized latex reagent and not with the control latex reagent was considered a positive result. Appropriate controls were examined in parallel in each test.

The circulating antigen titer in the serum was estimated by performing a quantitative test. It was performed by testing serum at several dilutions. The highest dilution of the serum showing agglutination was the LAT titer.

Co-agglutination test.

All serum samples were also tested in parallel for hydatid antigen by a Co-A test as per the method described by Shariff and Parija.9 Briefly, Staphylococcus aureus (Cowan’s strain 1) protein A-containing (SAPA) cells were grown on Muller Hinton agar at 37°C for 18 hours, harvested, centrifuged at 3,000 × g for 10 minutes, and washed three times in PBS, pH 7.2, containing 0.05% sodium azide. The pellet was fixed in 10 volumes of 1.5% formaldehyde in PBS, pH 7.2, at room temperature for 90 minutes, washed in PBS, and resuspended in 10 volumes of PBS containing 0.05% sodium azide, and heated for five minutes at 80°C. The SAPA cells were sensitized with purified hyperimmune hydatid antiserum immediately after their preparation. The hydatid antibody-sensitized SAPA cells were stored at 4°C in small aliquots for use in the test.

The test was performed on glass slide divided with a glass marking pencil into two halves. A drop of serum to be tested was placed on each half of a glass slide. An equal volume of 2% sensitized SAPA cell suspension was added to the serum on one half. The same volume of 2% unsensitized SAPA cell suspension was added to the serum on the other half as a cell control. The slide was rotated manually for two minutes and inspected. Agglutination with the sensitized SAPA cells suspension and not with the unsensitized SAPA cell suspension was considered a positive result. Appropriate controls were examined in parallel in each test.

Detection of antibodies to hydatid antigen in serum.

Circulating antibodies to hydatid antigen were detected in serum by an IHA, as per the procedure described by Parija and others.11 Briefly, double aldehyde–stabilized chick cells (DAS) were prepared by treating the chick cells with pyruvic aldehyde. A reaction mixture of 12 mL of 1.7% NaCl, 4 mL of 40% pyruvic aldehyde, 35 mL of 1.0% NaHCO3, and 7 mL of Sorensen’s phosphate buffer, pH 7.2, was prepared and refrigerated. To this, 10 mL of a 50% suspension of chick cells was added. The mixture was stirred for 30 minutes and stored for 24 hours at 4°C. The cells were then washed three times in PBS and a 2.5% suspension was made. An equal volume of cold tannic acid (diluted 1:25,000 in PBS) was added and the mixture was kept at 4°C for 30 minutes. The cells were then washed three times in PBS and a 4% suspension was made using the same diluent. An equal volume of 2% [v/v] glutaraldehyde in PBS was added and the suspension was mixed with a magnetic stirrer for two hours. The cells were then washed three times with PBS and stored as a 50% [v/v] suspension in this diluent. This DAS cells were sensitized with the optimum sensitizing dose of hydatid antigen. A 1% suspension of sensitized cells was made in PBS, 7.2, with bovine serum albumin, and the IHA was performed in microtiter plates. The results were read by observing the settling pattern of the cells in the microtiter plates after incubation for 45 minutes at room temperature. The cut-off titer above which a test result was considered positive was 1:128.

Statistical analysis.

The serum samples were tested in a single blind manner. The sources of the specimen (whether they were from the patients or from control subjects) were not known to those performing the different tests with these specimens. The sensitivity, specificity, positive predictive value, negative predictive value, and efficiency of the tests were calculated according to the method described by Forbes and others.12

RESULTS

The results of the LAT with serum from CE patients and control subjects are summarized in Table 1. The LAT detected circulating hydatid antigen in 13 (72%) of 18 patients with surgically confirmed CE, 17 (65%) of 26 patients with ultrasound-proven CE, and 19 (40%) of 47 patients with presumptive CE. This test also detected 1 (4%) of 25 controls with other parasitic diseases. Antigen was not detected in the serum of healthy controls. The LAT titer in serum was estimated by a performing quantitative test.

The Co-A test detected hydatid antigen in 15 (83%) of 18 patients with surgically confirmed CE, 19 (73%) of 26 patients with ultrasound-proven CE, and 22 (47%) of 47 patients with presumptive CE. This test also detected 1 (4%) of 25 controls with other parasitic diseases. Antigen was not detected in the serum of healthy controls.

Hemagglutinating antibodies could be demonstrated by the IHA in all groups of CE patients and controls. The IHA detected these antibodies in 77% of the surgically confirmed cases of CE, in 77% of the ultrasound-proven cases of CE, in 64% of the presumptive cases of CE, and 16% of the controls with other parasitic diseases. The IHA did not detect any positive titers in the healthy controls.

A comparative evaluation of the LAT, Co-A test, and IHA in the diagnosis of CE is shown in Table 2. A comparison of the sensitivity, specificity, positive predictive value, negative predictive value, and efficiency of the LAT, Co-A test, and IHA for the diagnosis of CE is shown in Table 3.

DISCUSSION

Cystic echinococcosis is a major health problem worldwide, particularly in sheep-rearing regions of Australia, South America, northern Africa, Russia, and China.1 This disease is also an emerging disease in India, with CE being reported throughout the country.4,13 The clinical manifestations of CE in humans are variable and non-specific. Thus, it is difficult to diagnose this disease. Imaging methods (ultrasound, computed tomography scan, and magnetic resonance imaging) in combination with immunologic tests are now extensively used to supplement the clinical diagnosis of this disease.14,15 However, imaging methods are costly and are not widely available in most of the hospitals in developing countries. Therefore, development of a simple and rapid serologic test for the diagnosis of CE that can be used under field conditions is a priority.

The LAT is one of the simplest slide agglutination serologic tests available in a diagnostic parasitology laboratory. The test, first described by Severin, has been used in the diagnosis of meningococcal meningitis.16 Since then, latex agglutination has been used to detect antibodies in a variety of parasitic diseases such as visceral leishmaniasis,17,18 toxoplasmosis,19 and CE.20 Although the LAT has been used to detect antibodies to hydatid antigens in serum, the test has yet to be evaluated for the detection of hydatid antigen in serum.

The present study shows for the first time the successful application of an LAT as a simple and specific laboratory test for the detection of circulating antigens in the diagnosis of CE. The data presented in this study show that the LAT using polystyrene latex particles (0.81 μm) coated with polyclonal hydatid antisera is able to detect the circulating hydatid antigen in both undiluted sera and in sera diluted to 1:32 in patients with CE (Table 1). The LAT showed a sensitivity of 72% and a specificity of 98% in the diagnosis of CE compared with a sensitivity of 83% and a specificity of 98% for the Co-A test in the detection of circulating hydatid antigen in serum (Table 3).

The negative results observed in the LAT in five surgically confirmed cases of CE could be due to various reasons. One possibility is that the intact cysts of E. granulosus may release only small amounts of antigens or no antigen into the circulation. This view is supported by the fact that macromolecules such as host albumin and immunoglobulin penetrate only 20% of the cysts under in vitro conditions. These macromolecules may pass into the parasite only after fissuring of the cyst wall.21 The other possibility is that the antigen released from the parasite form immune complexes with the antibodies. These immune complexes have been detected in serum in related studies.22 Finally, the strain type, anatomic location of the cyst, cyst wall structure, and the speed and type of growth are other factors that may influence the level of circulating antigen.8

The LAT is a very simple and easy to perform slide agglutination test. The test offers many advantages for its use in the diagnosis of CE in poorly equipped laboratories and under field conditions. First and foremost is that paramedical health personnel in a rural health center can perform this test on a microscopic glass slide. The test does not require any training or specific skills. Second, this test is cost-effective and does not require any special equipment or reagents. Third, the LAT is a rapid test, in which results can be obtained within minutes of performing the test. Finally, the detection of hydatid antigen in serum by the LAT can be used as a prognostic test in the presurgical and post-surgical/chemotherapeutic evaluation of cases, as shown in our earlier studies using the Co-A test23 and in other studies.5,24

Table 1

Distribution of hydatid antigen titers in serum of CE cases and controls by the LAT*

No. of sera positive for hydatid antigen dilution
Subject groupsNo. of subjectsNone248163264No. negativeNo. positive
* CE = cystic echinococcosis; LAT = latex agglutination test.
Surgically confirmed CE180252310513
Ultrasound-proven CE260822320917
Presumptive CE4755602102819
Controls with other parasitic diseases251000000241
Healthy controls250000000250
Table 2

Evaluation of LAT, Co-A, and IHA in the diagnosis of CE*

No. (%) of sample positive for
Subject groupsNo. of subjectsSerum antigen by LATSerum antigen by CO-ASerum antibody by IHA
* LAT = latex agglutination test; Co-A = co-agglutination; IHA = indirect hemagglutination assay; CE = cystic echinococcosis.
Surgically confirmed CE1813 (72)15 (83)14 (77)
Ultrasound-proven CE2617 (65)19 (73)20 (77)
Presumptive CE4719 (40)22 (47)30 (64)
Controls with other parasitic diseases2501 (4)01 (4)04 (16)
Health controls250 (0)0 (0)0 (0)
Table 3

Statistical analysis of LAT, Co-A, and IHA in the diagnosis of CE*

Statistical ParameterSerum antigen by LATSerum antigen by Co-ASerum antibody by IHA
* For definitions of abbreviations, see Table 2.
Sensitivity (%)728378
Specificity (%)989893
Positive predictive value (%)939478
Negative predictive value (%)919493
Efficiency (%)919493

Authors’ address: C. Sheela Devi and Subhash C. Parija, Department of Microbiology, Jawaharlal Institute of Postgraduate Medical Education and Research, Pondicherry 605 006 India.

REFERENCES

  • 1

    Williams JA, Lopez Adaros H, Trejos A, 1971. Prevalence and distribution of hydatidosis with special reference to the Americas. Am J Trop Med Hyg 20 :222–236.

    • Search Google Scholar
    • Export Citation
  • 2

    Parija SC, Rao RS, 1987. Evaluation of combined use of indirect haemagglutination and Casoni’s skin test in the diagnosis of hydatid disease. Indian J Pathol Microbiol. 30 :117–127.

    • Search Google Scholar
    • Export Citation
  • 3

    Gottstein B, 1984. An immunoassay for the detection of circulating antigens in human echinococcosis. Am J Trop Med Hyg 33 :1185–1190.

  • 4

    Parija SC, 1991. Recent trends in the serodiagnosis of hydatid disease. Southeast Asian J Trop Med Public Health 22 (Suppl):371–376.

  • 5

    Craig PS, Nelson GS, 1984. The detection of circulating antigen in human hydatid disease. Ann. Trop Med Parasitol 78 :219–227.

  • 6

    Parija SC, 1993. Simple immunoassay in the serodiagnosis of hydatid disease in the field or poorly equipped laboratories. Indian J Med Microbiol 11 :1–4.

    • Search Google Scholar
    • Export Citation
  • 7

    Parija SC, 1994. New approaches in the serodiagnosis of hydatid disease (editorial). J Indian Med Assoc. 92 :281–284.

  • 8

    Shariff GM, Parija SC, 1991. Countercurrent immunoelectrophoresis for the serodiagnosis of hydatid disease by detection of circulating hydatid antigen. J Microbiol Methods. 14 :71–76.

    • Search Google Scholar
    • Export Citation
  • 9

    Shariff GM, Parija SC, 1993. Co-agglutination (Co-A) test for circulating antigen in hydatid disease. J Med Microbiol 38 :231–234.

  • 10

    Parija SC, Rao RS, 1986. Enhancement of sensitivity of the haemagglutination test for echinococcosis by use of Staphylococcus aureus protein A. J Med Microbiol 22 :241–244.

    • Search Google Scholar
    • Export Citation
  • 11

    Parija SC, Mishra SR, Rao RS, 1986. Sensitized chick cells in the indirect haemagglutination test for echinococcosis. J Med Microbiol 22 :237–239.

    • Search Google Scholar
    • Export Citation
  • 12

    Forbes BA, Sahm DF, Weissfeld AS, eds, 1998. Bailey and Scott’s Diagnostic Microbiology. 10th edition. St. Louis, MO: Mosby Publishers, 60–65.

  • 13

    Vamsy AS, Parija SC, Sibal RN, 1991. Abdominal hydatidosis in Pondicherry, India. Southeast Asian J Trop Med Public Health 22 (Suppl):365–370.

    • Search Google Scholar
    • Export Citation
  • 14

    Harris KM, Morris D, Tudor R, Toghill P, Hardcastle JD, 1986. Clinical and radiographic features of simple hydatid cysts of the liver. Br J Surg 73 :835–838.

    • Search Google Scholar
    • Export Citation
  • 15

    Babba H, Messdi A, Masmoudi S, Zribi M, Grillot R, Ambriose-Thomas P, Beyroati I, Sahnoun Y, 1994. Diagnosis of human hydatidosis: comparison between imaging and six serologic techniques. Am J Trop Med Hyg 50 :64–68.

    • Search Google Scholar
    • Export Citation
  • 16

    Gray LD, Fedorko DP, 1992. Laboratory diagnosis of bacterial meningitis. Clin Microbiol Rev 5 :130–145.

  • 17

    Bagchi AK, Tiwari S, Gupta S, Katiya JC, 1998. The latex agglutination test. Standardization and comparison with direct agglutination and dot ELISA in the diagnosis of visceral leishmaniasis in India. Ann Trop Med Parasitol 92 :159–163.

    • Search Google Scholar
    • Export Citation
  • 18

    Arya SC, 1997. Latex agglutination test for the visceral leishmaniasis (letter). Trans R Soc Trop Med Hyg. 91 :366.

  • 19

    Mazumder P, Chuang HY, Wentz MW, Wiedbrauk DL, 1988. Latex agglutination test for the detection of antibodies to Toxoplasma gondii.J Clin Microbiol 26 :2444–2446.

    • Search Google Scholar
    • Export Citation
  • 20

    Barbieri M, Sterla S, Battisoni J, Nieto A, 1993. High performance latex reagent for hydatid serology using an Echinococcus granulosus lipoprotein antigen fraction purified from cyst fluid in one step. Int J Parasitol 23 :565–572.

    • Search Google Scholar
    • Export Citation
  • 21

    D’Amelio R, Pontesilli O, Palmisano L, Pezzella M, Vullo V, Delia S, de Rose F, Sorice F, Aiuti F, 1983. Detection and partial characterization of circulating immune complexes in hydatid disease. J Clin Microbiol 18 :1021–1026.

    • Search Google Scholar
    • Export Citation
  • 22

    Collori EA, Varela-Dias VM, 1975. Penetration of host IgG molecules into hydatid cysts. J Parasitenkd 48 :47–51.

  • 23

    Ravinder PT, Parija SC, Subba Rao KSVK, 1997. Evaluation of human hydatid disease before and after surgery and chemotherapy by demonstration of hydatid antigen and antibodies in serum. J Med Microbiol 47 :859–864.

    • Search Google Scholar
    • Export Citation
  • 24

    Kanwar R, Vinayak VK, 1984. The significance of free and immunocomplexed hydatid specific antigen(s) as an immunodiagnostic tool for human hydatidosis. J Med Microbiol 37 :396–403.

    • Search Google Scholar
    • Export Citation

Author Notes

Reprint requests: Subhash C. Parija, Department of Microbiology, Jawaharlal Institute of Postgraduate Medical Education and Research, Pondicherry 605 006 India, Telephone: 91-413-225-3016, E-mail: parijasc@vsnl.com.
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