Practical experience in using the mini parasep solvent- free faecal parasite concentrator for the Cryptosporidium spp. oocysts detection in stool

Abstract

Introduction. Cryptosporidiosis is a protozoan illness caused by the protozoans of genus Cryptosporidium (type Apicomplexa), that are able to parasitize in the enterocytes of the intestinal mucosa villi, causing a specific infectious process with such manifestations as “watery diarrhea“. The efficacy of prophylaxis and treatment of this parasitosis is based on the timely and quality laboratory diagnostics that is most often carried out with the help of microscopic methods. In order to increase the productivity of oocysts determination in the fecal samples different methods of enrichment in the latter are being used. The aim of the study – evaluation of the efficacy of application of Mini Parasep® Solvent Free Faecal Parasite Concentrator compared to the traditional method of concentration (centrifugation in the formalin ethyl - acetate mix) in course of focused study of the fecal samples for Cryptosporidium spp. oocysts presence. Materials and methods. The object of the study were 102 fecal samples (with 10,0 % aqueous formalin at the ratio 1:1) from children with diarrhea aged from one month to 17 years that were provided with regular medical aid. Purification and concentration of cryptosporidia oocysts was carried out with the help of centrifugation in formalin ethyl-acetate mix was carried out according to the widely accepted method. During the application of Mini Parasep® Solvent Free Faecal Parasite Concentrator (“Apacor Ltd.”, England) the method recommended by the provider was adhered to, except the sedimentation by centrifugation stage that was carried out at 1100g for 3 minutes instead of 1 minute. Smears were prepared from the supernatant that were stained with the modified (cold) Ziehl-Neelsen staining method. The oocyst purification and concentration procedure was carried out by different specialists with taking into account of each stage chronometry. During microscopy of the stained smears of enriched fecal sediment the following parameters were evaluated: cryptosporidia oocysts presence, size, shape, typical inner structure, as well as the probability of concealment of the oocysts that was calculated by the number of big conglomerates (³ 1/5 field of vision of the microscope).  Results and discussion. In the studies 102 fecal samples from children during parallel application of both methods complete coincidence of parameters of quality oocysts determination/non-determination (rф=1) was established. Oocysts were found in 4 (3,9 %) studied samples that was in the range of this parameter values in similar groups of increased risk in developed world countries. Despite such drawbacks of Mini Parasep® Solvent Free Faecal Parasite Concentrator application as the almost two-fold increase in overall study cost and the 3,8 increase in quantity of the big sized conglomerates that could potentially conceal the parasitic types being sought, this method had a number of significant rating advantages compared to the traditional method of centrifugation in formalin ethyl acetate mix: the low material cost and significantly lesser (2,2-2,6 times) labor cost, the moderate validity level, high biosafety and higher (1,5 times) productivity of the microscopic determination of the general quantity of cryptosporidia oocysts.  Conclusions. The advantages and disadvantages of cryptosporidia oocysts purification and concentration procedures in application of traditional variant of centrifugation in formalin ethyl acette mix and in application of Mini Parasep® Solvent Free Faecal Parasite Concentrator determined in course of the study do not contradict the topic data from foreign scientists. It is expedient to optimize the cryptosporidia oocysts purification and concentration procedures for determination of the latter in the fecal samples with the help of microscopy with the help of parasitological concentrator of the Parasep® type.