Projects arrow Diagnostics and Prophylaxis of Amebiasis

G-617

Prevention of Amebiasis and Creation of Diagnostic Test-Systems for E. histolytica Strains Isolated in Georgia

Project Status: 8 Project completed
Commencement Date: 01.10.2001
Duration in months: 54 months

Objective

Entamoeba histolytica infects about 500 million people annually, but only about 10% experience symptomatic disease. People infected without clinical manifestation of the disease spontaneously spread the infection. The most common way of transmission is through contaminated water and food. The epidemiology, management and laboratory diagnosis of amebiasis must be paid great attention to in Georgia. There was a significant number of cases of intestinal amebiasis (1334 in 1998 and 660 in 1999) registered in Tbilisi, with 404 cases of amebic liver abscess. Serological testing carried out by CDC, Atlanta and the University of Virginia, in Tbilisi during the 1998 outbreak of amebiasis showed a high (9–14%) level of seropositive cases in control groups, and documented that 71% (37/52) of patients examined with amebic liver abscess had antibodies against E. histolytica. Filtration and disinfection of the city’s surface water supply were not adequate to remove or kill E. histolytica cysts and water and sewage pipe breaks are common (more than 200 per month). Self reported interruptions in the home water supply (OR=4.52, CI=1.03, 10.94), decreases in water pressure (OR=1.49, CI=1.05, 2.08), and increased water consumption during June (OR=4.63, CI=1.79, 12.02) and July (OR=5.96, CI=2.14, 16.59) were significantly associated with developing disease (Barwick et al., Program and Abstracts of the American Society of Tropical Medicine and Hygiene Annual Meeting, Washington, D.C., November 29-December 2, 1999).

The real range of amebiasis in Georgia is still unknown; the number of registered patients does not show the complete picture, and additional clinical and laboratory testing is urgently required. Methodological and material resources for detection and isolation of E. histolytica in drinking water, feces, biopsy material and other substrates and their further cultivation is inadequate. Therefore, the improvement of monitoring and surveillance systems of E. histolytica and other pathogenic protozoan infections in Georgia is of high priority.

New approaches to the detection of E. histolytica and E. dispar are based on antigen detection in stool. Antigenic differences in the lectin of E. histolytica and E. dispar amebae enable specific identification of the disease-causing amebae E. histolytica in feces. The mAb-based antigen detection tests have proven to be more sensitive, specific, rapid and technically simple than microscopy. However these tests have not been applied successfully to the screening of water supplies. Thus, rivers, lakes, reservoirs and treated drinking water in two largest regions of Georgia (Tbilisi and Kutaisi) must be tested for the presence of E. histolytica, and it is likely that this will require the development of new approaches to detection.

In addition, studies of the amebiasis outbreak in Georgia have indicated that the strain(s) of E. histolytica responsible for the Georgia is characterised by certain unique characteristics, most notably an unusual propensity to cause liver abscess. Hence, it is of great importance to isolate the Georgian strain of E histolytica and elucidate the biochemical differences between this and other known strains of this pathogen.

The data obtained from the proposed project will allow the development of test-systems specific for the detection of the E. histolytica strain isolated in Georgia, enable the screening of water supplies for the parasite, and provide deeper insights into the biochemical differences contributing to pathogenic peculiarities of E. histolytica.

Participating Institutions

LEADING

National Center for Disease Control and Public Health (NCDC)