Uso de imunocromatografia rápida e outras técnicas parasitológicas para o diagnóstico laboratorial da Wuchereria bancrofti (Cobbold, 1877) em área endêmica de filariose linfática em Maceió, Alagoas

Abstract

Lymphatic filariasis is a highly impact disease because it can impair workers and make difficult their social life. Early diagnosis is very important for efficacy of the treatment. The aim of this study was to establish, in a defined population, the prevalence of Wuchereria bancrofti, the causative agent of lymphatic filariasis, using rapid immunochromatographic card test and thick blood smears; compare the immunochromatographic test with the thick blood smear parasitological method, and evaluate different parasitological techniques. Inhabitants of lymphatic filariasis endemic area were examined in Maceió, Alagoas State, Northeasth Brazil (at the edge of a channel - Reginaldo Canal - that crosses the city sectors Feitosa, Jacintinho and Pitanguinha). The examination of 3,000 children between 5 and 10 years old by immunochromatographic test revealed 10 (0,33%) antigen-positive, and of 411 individuals older than 10 years of age only one (0,24%) was antigen-positive. By thick blood smear method, in the same endemic area, among 5,261 children examined between 5 and 10 years old 4 (0,076%) microfilaremic were detected, and 25 (0.13%) from 19,875 individuals older than 10 years of age were found to be microfilaraemic. The parasite antigen assay using rapid immunochromatographic for diagnosis made possible to carry out tests during daytime, in opposition of the traditional thick blood smears method. Comparing the results from immunochromatographic test and thick smears, a increased ability for parasite detection by the immunological method was observed when children between 5-10 years old were examined, being odds relative 4.4 (I.C. 95% = 1.3 - 16.6). However, with individuals older than 10 years of age, no significant difference on parasites detection ability between these techniques was observed. All antigen-positive individuals by immunochromatographic test were examined by membrane blood filtration and none of them were microfilaraemic. Positive individuals by immunochromatographic test and thick blood smears were also positive when submitted to the enzyme-linked immunosorbent assay. The enzyme-linked immunosorbent assay was better than immunochromatographic test in detected W. bancrofti antigen. From the results of immunochromatographic test with children between 5 and 10 years old (age group preconized by WHO to verify active transmission of lymphatic filariasis) it was possible to show a very low prevalence of parasitism in the delimited area, meaning that in a short time Maceió can be free from lymphatic filariasis transmission