SYMPOSIUM

Year : 2020  |  Volume : 10  |  Issue : 2  |  Page : 71-73

Pondicherry declaration on the identification and detection of Entamoeba histolytica

Subhash Chandra Parija¹, Rakesh Sehgal², Ujjala Ghoshal³, Sumeeta Khurana¹, Vinay Khanna⁴, Debadatta Dhar Chanda⁵, Tapashi Ghoshal⁶, Namrata K Bhosale^7
1 Vice-Chancellor, Sri Balaji Vidyapeeth, Puducherry, India
² Department of Medical Parasitology, Post Graduate Institute of Medical Education and Research, Chandigarh, India
³ Department of Microbiology, Sanjay Gandhi Postgraduate Institute of Medical Sciences, Lucknow, Uttar Pradesh, India
⁴ Department of Microbiology, Kasturba Medical College, Manipal, Karnataka, India
⁵ Department of Microbiology, Silchar Medical College, Silchar, Assam, India
⁶ Department of Microbiology, Bankura Sammilani Medical College, Bankura, West Bengal, India
⁷ Department of Microbiology, Mahatma Gandhi Medical College and Research Institute, Puducherry, India

Correspondence Address:
Namrata K Bhosale
Department of Microbiology, Mahatma Gandhi Medical College and Research Institute, Pillaiyarkuppam, Pondy-Cuddalore Main Road, Puducherry - 607 402
India

Source of Support: None, Conflict of Interest: None

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DOI: 10.4103/tp.TP_111_20

Abstract

Stake holders meet on “Identification and Detection of Entamoeba histolytica” was conducted on July 21, 2019 at Sri Balaji Vidyapeeth Deemed-to-be-University, Pondicherry. This programme was of national importance, since the amoebiasis is being increasingly reported from different parts of India because of poor socioeconomic conditions and sanitation levels. Experts in amoebiasis research across India attended this meeting. This meeting was conducted with an objective to frame the guidelines on the identification and detection of E. histolytica with reference to conventional diagnostic methods and molecular diagnosis targeting appropriate genes of E. histolytica. The recommendations of the panel were released as declaration on the diagnosis of amoebiasis and were circulated to various administrative and scientific bodies in India as reference policy document on the diagnosis of amoebiasis.

Keywords: Amoebiasis, Entamoeba, immunodiagnosis, microscopy, molecular

Introduction

Diagnosis Of Intestinal Amoebiasis

• Microscopic examination of stool samples is not very useful in the specific identification and diagnosis of E. histolytica infection but can be used for screening of E. histolytica-look-alike nonpathogenic species (e.g., Entamoeba dispar, Entamoeba moshkovskii) which cannot be differentiated from E. histolytica on microscopy.^[1],[2]

• Antibody-based serological tests may be useful in the diagnosis of amoebiasis in developed countries since E. histolytica infection is uncommon. Whereas in developing countries, infection due to E. histolytica remains endemic. This makes a definite diagnosis of amoebiasis by antibody detection difficult because of the difficulty to differentiate between the present from past infection. However, a negative test may rule out the possibility of invasive amoebiasis
• Fecal-antigen detection: Specific-antigen detection tests are available like enzyme-linked immunosorbent assay (ELISA) and immunochromatographic rapid kits, using Lectin antigen for E. histolytica in faecal samples. These may be used for specific diagnosis of E. histolytica infections.[2]

• Conventional, Nested, or Real-Time polymerase chain reaction (PCR) should be used for the confirmation of E. histolytica infection as these can differentiate it from E. dispar and E. moshkovskii. PCR has very high sensitivity and specificity. PCR assay targeting 18SrDNA with species-specific probes are the most common and recommended test. However, it has some limitations in terms of cost, the expertise required and a good infrastructural setup to prevent cross and carry-over contamination.^[3],[4]

Diagnosis of Extra-Intestinal Amoebiasis

• This has a very limited role in the diagnosis of extra-intestinal amoebiasis such as amoebic liver abscess, as parasites would not be visible in the majority of aspirated liver pus samples.

• Antibody detection in serum: This is not very useful for diagnosis in areas where amoebiasis is endemic. Positive test cannot differentiate between current and past infection. However, negative test may rule out the possibility of invasive amoebiasis
• Antigen detection in serum and amoebic liver abscess pus: Among the antigen detection assays, ELISA has been widely used to study amoebiasis. ELISA remains an important diagnostic tool in patients with invasive amoebiasis. Commercial antigen detection tests are available, but they do not have good sensitivity for detection of E. histolytica in liver abscess and are not recommended.

• Conventional, Nested or Real-Time PCR should be used for the confirmation of the diagnosis of E. histolytica infection. PCR has a very high sensitivity and specificity. PCR assay targeting 18SrDNA with species-specific probes are the most common and recommended test
• Accurate identification of pathogenic E. histolytica from nonpathogenic Entamoeba species is crucial in the management of patients and epidemiological study of amoebiasis outbreaks. Molecular-based techniques have been proven to be adequate to satisfy these needs and hence has emerged as the gold standard diagnostic tests in the current era.^{[1],[2],[3],[4]}

• E. histolytica may be infecting only a fraction of the population based on the data available from various studies which were mainly based on microscopy and/or serology and detect Entamoeba species. As these could not differentiate between the pathogenic and nonpathogenic species, there is an urgent need to initiate accurate prevalence based study in different parts of the country for estimating the true prevalence of E. histolytica. There is also an urgent need to introduce specific tests for accurate diagnosis of E. histolytica infections at the field level.^[5],[6],[7]

References

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2.	Parija SC, Khairnar K. Entamoeba moshkovskii and Entamoeba dispar-associated infections in Pondicherry, India. J Health Popul Nutr 2005;23:292-5.
3.	Philips SA, Manochitra K, Padukone S, Parija SC. Detection of Entamoeba Species: A Comparative analysis of nested-multiplex PCR and recombinase polymerase amplification. Int J Curr Microbiol App Sci 2018;7:1803-8.
4.	Parija SC, Mandal J, Ponnambath DK. Laboratory methods of identification of Entamoeba histolytica and its differentiation from look-alike Entamoeba spp. Trop Parasitol 2014;4:90-5.   [PUBMED]  [Full text]
5.	WHO | Amoebiasis. WHO. Available from: https://www.who.int/ith/diseases/amoebiasis/en/. [Last accessed on 2018 Dec 19].
6.	Garcia LS. Diagnostic Medical Parasitology. Washington, DC, USA: ASM Press; 2016. p. 552-82. Available from: http://doi.wiley.com/10.1128/9781555819002. [Last accessed on 2020 Jul 26].
7.	WHO/PAHO/UNESCO report. A consultation with experts on amoebiasis. Mexico City, Mexico 28-29 January, 1997. Epidemiol Bull 1997;18:13-4.