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Updated: Jun 15, 2026
Experimental Infection of Mice with the Parasitic Nematode Strongyloides ratti
Published on: January 17, 2025
Faecal examination and PCR to detect Strongyloides venezuelensis in experimentally infected Lewis rats
Nelson Mendes Marra1, Fernanda Chiuso-Minicucci, Gabriel Capella Machado
1Departamento de Microbiologia e Imunologia, Instituto de Biociências, Universidade Estadual Paulista, Botucatu, SP, Brasil, 18618-000.
Abstract:
More sensitive methodologies are necessary to improve strongyloidiasis diagnosis. This study compared the sensitivities of the McMaster modified technique and polymerase chain reaction (PCR) assays, both performed in faecal samples. Lewis rats were subcutaneously infected with 4,000, 400 or 40 infective third-stage larvae, considered as high, moderate or low infection, respectively. Seven days later, they were euthanized to count adult nematodes recovered from the small intestine. Stool samples were used to count the number of eggs per gram (EPG) of faeces and to detect parasite DNA by PCR performed with a species and a genus primer pair. The sensitivity of these assays depended upon parasite burden and the primer specificity. All assays presented 100% sensitivity at the highest parasite load. In the moderate infection, EPG and PCR with the genus primer maintained 100% specificity, whereas PCR sensitivity with the species primer decreased to 77.7%. In low infection, the sensitivity was 60% for EPG, 0% for PCR with the species primer and 90% for PCR done with the genus primer. Together, these results suggest that PCR with a genus primer can be a very sensitive methodology to detect Strongyloides venezuelensisin faeces of Lewis rats infected with very low parasite burden.
Insights
Sensitive molecular diagnostic methods are crucial for diagnosing strongyloidiasis. Polymerase chain reaction (PCR) using a genus primer demonstrated high sensitivity for detecting Strongyloides venezuelensis in low-burden infections in rats.
Area of Science:
- Veterinary Parasitology
- Molecular Diagnostics
- Infectious Disease Research
Background:
- Accurate diagnosis of strongyloidiasis is essential for effective treatment and control.
- Current diagnostic methods may lack sensitivity, particularly in low-parasite-burden cases.
- Novel molecular techniques are being explored to improve diagnostic accuracy.
Purpose of the Study:
- To compare the diagnostic sensitivity of the McMaster modified technique and polymerase chain reaction (PCR) assays for detecting Strongyloides venezuelensis.
- To evaluate the impact of parasite burden and primer specificity on assay performance.
- To identify the most sensitive method for diagnosing low-level infections.
Main Methods:
- Lewis rats were infected with varying doses of Strongyloides venezuelensis larvae (high, moderate, low).
- Fecal samples were analyzed using the McMaster modified technique (eggs per gram - EPG) and PCR with species- and genus-specific primers.
- Parasite burden was assessed by counting adult nematodes in the small intestine.
Main Results:
- All methods achieved 100% sensitivity at the highest parasite load.
- In moderate infections, EPG and genus-specific PCR maintained 100% sensitivity, while species-specific PCR sensitivity dropped to 77.7%.
- In low infections, sensitivity was 60% for EPG, 0% for species-specific PCR, and 90% for genus-specific PCR.
Conclusions:
- Polymerase chain reaction (PCR) with a genus primer exhibits high sensitivity for detecting Strongyloides venezuelensis.
- This genus-specific PCR assay is a promising tool for diagnosing strongyloidiasis, especially in cases with very low parasite burdens.
- The findings highlight the importance of primer selection in PCR-based diagnostics for parasitic infections.
