Molecular typing of Strongyloides stercoralis in Latin America, the clinical connection

Abstract

This study analysed Strongyloides stercoralis genetic variability based on a 404 bp region of the cox1 gene from Latin-American samples in a clinical context including epidemiological, diagnosis and follow-up variables. A prospective, descriptive, observational study was conducted to evaluate clinical and parasitological evolution after ivermectin treatment of 41 patients infected with S. stercoralis. Reactivation of the disease was defined both by clinical symptoms appearance and/or direct larvae detection 30 days after treatment or later. We described 10 haplotypes organized in two clusters. Most frequent variants were also described in the Asian continent in human (HP24 and HP93) and canine (HP24) samples. Clinical presentation (intestinal, severe, cutaneous and asymptomatic), immunological status and eosinophil count were not associated with specific haplotypes or clusters. Nevertheless, presence of cluster 1 haplotypes during diagnosis increased the risk of reactivation with an odds ratio (OR) of 7.51 [confidence interval (CI) 95% 1.38–44.29, P = 0.026]. In contrast, reactivation probability was 83 times lower if cluster 2 (I152V mutation) was detected (OR = 0.17, CI 95% 0.02–0.80, P = 0.02). This is the first analysis of S. stercoralis cox1 diversity in the clinical context. Determination of clusters during the diagnosis could facilitate and improve the design of follow-up strategies to prevent severe reactivations of this chronic disease.

Strongyloides genotyping: a review of methods and application in public health and population genetics

“…The second cluster contained 11 isolates, nine of which belonged to a single haplotype. This work found that those patients infected with haplotypes belonging to the first cox1cluster had higher odds of reactivation after ivermectin treatment (odds ratio7.51; P=0.026) compared with those infected with haplotypes from the second cox1 cluster (Repetto et al, 2021). This work suggests that genotype may be associated with lower efficacy of ivermectin for infection clearance.…”

“…from a Philippine slow loris (Nycticebus menagensis) sampled in Borneo and applied phylogenetic analysis based on cox1 sequences. It was demonstrated to be belonged to S. stercoralis group rather than S. f. fuelleborni group (Frias et al, 2018;Repetto et al, 2021) (Fig. 1).…”

“…A recent study found an association of the genotype of a 404 bp sequence cox1 in 29 human S. stercoralis isolates (28 from South America and one from the Caribbean) with clinical outcomes in those patients (Repetto et al, 2021). Although 41 patients were initially tested, 12 were lost to follow up.…”

From past to present: opportunities and trends in the molecular detection and diagnosis of Strongyloides stercoralis

“…For the 18S rRNA gene, Hasegawa et al (2009) [ 40 ] suggested the use of the hypervariable regions (named HVR-I, II, III, IV) to explore genetic differences between S. stercoralis populations [ 40 ]. With its high sequence variation, the mitochondrial COI gene is another genetic marker used to study the population genetics and diversity of S. stercoralis in different hosts and localities [ 41 – 43 ]. These genetic markers have proven helpful for the molecular identification of cryptic species and in aiding to shed light on the zoonotic potential of S. stercoralis through comparative molecular studies on dog and human isolates [ 42 ].…”

Comparison of different PCR amplification targets for molecular diagnosis of Strongyloides stercoralis

“…The most frequent variants have also been described on the Asian continent in humans and canine samples. Regarding symptoms, the presence of group 1 haplotypes increased the risk of reactivation of the infection (Repetto et al 2022).…”