Formol-petrol stool concentration method (Wirkom-Tata's stool concentration method): A Cheap Novel Technique For Detecting Intestinal Parasites In Resource-Limited Countries

摘要

In search of a new method for stool concentration and to establish the incidence of intestinal parasites infection amongst primary school pupils in Djottin, Cameroon, 477 stool samples were examined in the Medical Laboratory of ST. Elizabeth's Catholic Mission Shisong. Formol-ether concentration technique detected 35.76% of the total number of parasites seen. Formol- petrol concentration method was 34.50% effective, direct smear method was 27.20% effective while the saturated sodium chloride (flotation) method detected only 2.27% of the parasites. The high incidence of intestinal parasite infection in these children was found to be linked to poor hygiene and low level of education of the pupils. The Formol- petrol stool concentration technique which gave a parasite recovery rate of 34.50% which indicates that, it is a new and cheap and very effective method for examination of human stool samples. Introduction Intestinal parasitic infections remain a health problem especially in the developing countries of the world [6]. It should be noted that most of these infections are as a result of low standard of living, poverty, poor sanitation and lack efficient diagnostic facilities.According to World Health Organisation [11] human intestinal parasites cause significant morbidity and mortality through out the world, particularly in under developed countries and especially in children. Infection by soil- transmitted helminths (intestinal worms) has been increasingly unrecognized as an important public health problem. In the 1993 World Development Report, intestinal parasite ranked first as the main cause of disease burden in children aged 5-14 years and also ranked highly as the disease that can be efficiently controlled by cost- effective intervention.In order to diagnose intestinal parasites, many methods can be considered. The choice of a particular technique will depend on its affordability, ease to carry out, its effectiveness and level of professionalism involved. Examples of these methods are DNA probes, PCR and direct fluorescent antibody methods [8], which are highly sensitive but are too costly to be used in the developing countries. It has been proved that direct stool smear, formol-ether and salt flotation techniques in stool microscopy offers many advantages over other diagnostic methods of detecting intestinal parasites. If performed correctly, these methods are sensitive, simple and economical [8].Direct stool smear [4], formol-ether concentration [1] and flotation methods are used in diagnosing intestinal parasites by hospital and researchers in developing countries because of their affordability, simplicity and sensitivity.For the fact that the density of the parasite in the faeces is low, direct smear method is useful for the observation of motile protozoan trophozites and examination of exudates, but is not recommended solely for the routine examination of suspected parasitic infections [2]. Therefore there is need for increase probability of finding the parasite in the faecal samples to allow for accurate diagnosis, hence there is need to concentrate. Though direct stool smear technique is quick to prepare and inexpensive when compared with modified formol-ether concentration methods, it can miss parasites (ova, cysts and larvae) if concentration is too low or if too much debris or fat is present. Sand, seeds or other faecal debris can make fixing cover slips onto slide difficulty. Most diagnostic centers show high performance to this method, owing to the fact that it is inexpensive and non-time –consuming thereby disregarding the consequences of misdiagnosis, which has led to prevalence of parasitic diseases and morbid conditions. Such complications resulting from misdiagnosis have been described [3].Formol-ether concerntration techniques described by Allen and Ridley employs the use of ether or ethyl acetate as a lipid solvent and 10% formol saline as a fixative.This method recovers must ova,cysts and larvae and m