Adaptation of Ritchie Method for diagnosing Helminthes and Protozoa in samples of sewage silt with chemical substances minimization

DOI: 10.15343/0104-7809.20094427431

Abstract

Ritchie Method (1948) is an efficient methodology for diagnosing parasitic organisms in environmental matrixes, but the use
of ethylic ether and formaldehyde is an disadvantage, for these are toxic reagents that damages the environment and affects occupational
health. The objective of this study was to standardize a suitable technique of Ritchie Method for the identification of parasites in sewage
silt, which avoids the use of toxic substances and can be used in parasitological laboratories. Samples of silt were submitted to Ritchie
Method (RM) and Method of Modified Ritchie by Régis Anécimo (MMRRA), in which water at 45°C and neutral detergent substitute for
chemical substances. Results show that in RM the percentage of Ancylostoma sp was 19%, Hymenolepis sp 79%, Ascaris sp 2% and Trichuris
trichiura 0% from a total of 1970 visualized helminthes, whereas in MRMRA the percentage of Ancylostoma sp was 56%, Hymenolepis sp
40%, Ascaris sp 4% and Tricuris trichiura 0% in a total of 398 helminthes. Evaluated quantitatively MRMRA was less efficient, for these
results show a significant difference in the number of helminthes identified by the methods. However, a qualitative analysis shows the
technique to be valid, since the quality of parasites identification is the same in both methods. We may conclude that MRMRA is a simple
and easy method to be used in the routine of laboratories and sewage treatment stations.