Clinical laboratory diagnostic techniques used in the identification of the helminth Ascaris lumbricoides, a review of the literature

Abstract

Ascariasis is a disease caused by the helminth Ascaris lumbricoides (intestinal worm), which infects an average of 819 million individuals. Approximately more than 60 000 people die worldwide each year from this parasite. It is classified as a neglected subtropical endemic disease and is frequently found in Africa, Latin America, and East Asia. Ascariasis is detected by conventional tests, which are based on the direct identification of A. lumbricoides by direct macroscopic examination, traditional microscopy, formaldehyde concentration method, Kato-Katz, McMaster, flotation techniques (such as FLOTAC and Mini-FLOTAC), with the aim of observing helminth eggs; all these are cost-effective tests, but of low or moderate sensitivity. Therefore, molecular biology methods such as conventional PCR and multiplex PCR are an option for the detection of this parasite due to their high sensitivity and specificity, but their low accessibility in endemic countries due to the high prices of reagents and equipment should be considered. Indirect methods based on serology have been used for the identification of A. lumbricoides, but they have generated cross reactions with infections by other helminths so there is no specific serological test for this parasite at present. Nowadays, new techniques have been designed with high sensitivity and specificity that allow the diagnosis of ascariasis, among which we can mention detection and identification of A. lumbricoides eggs through optical imaging and loop-mediated isothermal amplification