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Abstract
BackgroundIn resource-limited countries, stool microscopy is the diagnostic test of choice for intestinal parasites (soil-transmitted helminths and/or intestinal protozoa). However, sensitivity and specificity is low. Improved diagnosis of intestinal parasites is especially important for accurate measurements of prevalence and intensity of infections in endemic areas.MethodsThe study was carried out in Orán, Argentina. A total of 99 stool samples from a local surveillance campaign were analyzed by concentration microscopy and McMaster egg counting technique compared to the analysis by multi-parallel quantitative real-time polymerase chain reaction (qPCR). This study compared the performance of qPCR assay and stool microscopy for 8 common intestinal parasites that infect humans including the helminths Ascaris lumbricoides, Ancylostoma duodenale, Necator americanus, Strongyloides stercoralis, Trichuris trichiura, and the protozoa Giardia lamblia, Cryptosporidium parvum/hominis, and Entamoeba histolytica, and investigated the prevalence of polyparasitism in an endemic area.ResultsqPCR showed higher detection rates for all parasites as compared to stool microscopy except T. trichiura. Species-specific primers and probes were able to distinguish between A. duodenale (19.1 %) and N. americanus (36.4 %) infections. There were 48.6 % of subjects co-infected with both hookworms, and a significant increase in hookworm DNA for A. duodenale versus N. americanus (119.6 fg/μL: 0.63 fg/μL, P < 0.001) respectively. qPCR outperformed microscopy by the largest margin in G. lamblia infections (63.6 % versus 8.1 %, P < 0.05). Polyparasitism was detected more often by qPCR compared to microscopy (64.7 % versus 24.2 %, P < 0.05).ConclusionsMulti-parallel qPCR is a quantitative molecular diagnostic method for common intestinal parasites in an endemic area that has improved diagnostic accuracy compared to stool microscopy. This first time use of multi-parallel qPCR in Argentina has demonstrated the high prevalence of intestinal parasites in a peri-urban area. These results will contribute to more accurate epidemiological survey, refined treatment strategies on a public scale, and better health outcomes in endemic settings.
Highlights
In resource-limited countries, stool microscopy is the diagnostic test of choice for intestinal parasites
This study investigated the prevalence of polyparasitism and the differences in the epidemiology of hookworm infection
Comparison of quantitative real-time polymerase chain reaction (qPCR) with microcopy The results of qPCR and microscopy for all studied intestinal parasites are summarized in Table 1. qPCR was significantly more sensitive than stool microscopy in identifying S. stercoralis (21.2 % versus 3.0 %, P < 0.05), G. lamblia (63.6 % versus 8.1 %, P < 0.05), and total hookworm infections (37.4 % versus 21.2 %, P < 0.05)
Summary
In resource-limited countries, stool microscopy is the diagnostic test of choice for intestinal parasites (soil-transmitted helminths and/or intestinal protozoa). Soil-transmitted helminths (STH) and intestinal protozoa are distributed widely throughout the world and are more prevalent in tropical and sub-tropical regions. STH (Ascaris lumbricoides, Ancylostoma duodenale, Necator americanus, Strongyloides stercoralis, and Trichuris trichiura) affect more than 2 billion people worldwide [2]. These species produce a wide array of symptoms, from asymptomatic (not reporting intestinal complaints) to including diarrhea, abdominal pain, general malaise, and weakness that may impact learning capacities and impaired physical growth [3,4,5]. In northern Argentina, mainly in the Yungas rainforest and Chaco regions, recent reports indicate prevalence rates of over 20 %, with some areas approaching 50 % [7, 8]
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