Abstract
Strongyloidiasis is a neglected tropical disease caused mainly by Strongyloides stercoralis, a nematode that can persist for decades in the human host with a very low parasitic burden and without specific symptoms. Hence, it is difficult to diagnose and control. Larval concentration and culture methods with fecal samples show higher sensitivity for the diagnosis of Strongyloides-infected individuals; however, these techniques are not routinely used, primarily due to the challenges associated with processing a substantial volume of fecal samples. In the current study, we comparatively evaluated the sensitivity and applicability of modifications made to the Rugai parasitological method for the diagnosis of strongyloidiasis in fecal samples of experimentally infected rats and in 68 individuals from an urban community close to Maceió, Brazil. The presence and quantity of parasite larvae in the feces were comparatively evaluated using different parasitological techniques. In the experimental model, we demonstrated that the modified Rugai technique (RMOD) allowed for significantly higher recovery of larvae than the original Rugai technique (RO). Moreover, the sediment was cleaner and easier to evaluate using optical microscopy. Compared to other parasitological techniques, such as agar-plate culture (A-PC) and spontaneous sedimentation (SS), the RMOD technique showed higher sensitivity in the detection of larvae in all infected groups and presented comparatively better performance, especially in rats with a low parasite burden. In the human population, among the 68 stool samples evaluated, Strongyloides larvae were detected in the feces of six individuals with an estimated prevalence of 8.82%. However, the performance of each parasitological method was remarkably different. SS identified Strongyloides larvae in only two individuals and A-PC in three, whereas RMOD was able to identify six infected individuals, resulting in sensitivities of 33.3%, 50%, and 100%, respectively. In conclusion, the modifications introduced to the Rugai technique resulted in improved sensitivity for the detection of Strongyloides spp. infections, especially in stool samples with a low parasite burden, in comparison with other routinely used parasitological techniques.
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Acknowledgements
We are grateful for the assistance of José Carlos and Elizabeth De Lacorte for the technical support provided.
Funding
The experimental work received financial support from the “Fundação de Amparo à Pesquisa do Estado de Alagoas, PPSUS”: Edital Saúde/Decit-SCTIE-MS/CNPq/FAPEAL/SESAU-AL process # EFP_00023144, and “Conselho Nacional de Desenvolvimeto Científico e Tecnológico—CNPq” for research in neglected tropical diseases, Edital CNPq/MS-SCTIE-DECIT process CNPq #442994/2019–2. DN-C is recipient of CNPq-Research Fellowship.
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JGMR and DAN-C: conceptualization. JGMR, GSM, GMAC, VFR, JKAOS, CBGG, and DAN-C: performed experiments. JGMR, WJNP, and FSW: field collection. JGMR, GSM, GMAC, VRF, JKAOS, CBGG, WJNP, FSW, SMG, and DAN-C: data analysis. JGMR and DAN-C: supervision and project administration. JGMR, GSM, GMAC, WJNP, FSW, SMG, and DAN-C: writing and editing the original draft. All the authors reviewed and approved the final version of this manuscript.
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All experimental procedures performed in rats were approved by the Ethics Committee for Animal Use (CEUA/UFMG), under protocol number 129/2020. The human study protocol was approved by the local Ethics Committee for Human Research (COEP) and registered on the Brazilian Platform for Research with Human Subjects (Plataforma Brasil) under the number CAAE#55239522.3.0000.5149.
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Rodrigues, J.G.M., Miranda, G.S., Camelo, G.M.A. et al. Modifications to the parasitological technique of Rugai increase the diagnostic sensitivity for strongyloidiasis. Parasitol Res 123, 101 (2024). https://doi.org/10.1007/s00436-023-08111-y
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DOI: https://doi.org/10.1007/s00436-023-08111-y