Estimating occurrence of Strongyloides stercoralis in the Caribbean island countries: Implications for monitoring and control

Genetic characterization of Strongyloides fuelleborni infecting free-roaming African vervets (Chlorocebus aethiops sabaeus) on the Caribbean island of St. Kitts

Human strongyloidiasis is an important neglected tropical disease primarily caused by the nematode Strongyloides stercoralis, and to a lesser extent Strongyloides fuelleborni which mainly infects non-human primates. Zoonotic sources of infection have important implications for control and prevention of morbidity and mortality caused by strongyloidiasis. Recent molecular evidence suggests that for S. fuelleborni, primate host specificity is variable among genotypes across the Old World, and consequently that these types likely vary in their capacity for human spillover infections. Populations of free-roaming vervet monkeys (Chlorocebus aethiops sabaeus), introduced to the Caribbean Island of Staint Kitts from Africa, live in close contact with humans, and concern has arisen regarding their potential to serve as reservoirs of zoonotic infections. In this study, we sought to determine the genotypes of S. fuelleborni infecting St. Kitts vervets to explore whether they are potential reservoirs for human-infecting S. fuelleborni types. Fecal specimens were collected from St. Kitts vervets and S. fuelleborni infections were confirmed microscopically and by PCR. Strongyloides fuelleborni genotypes were determined from positive fecal specimens using an Illumina amplicon sequencing-based genotyping approach targeting the mitochondrial cox1 locus and 18S rDNA hypervariable regions I and IV of Strongyloides species. Phylogenetic analysis of resultant genotypes supported that S. fuelleborni from St. Kitts vervets is of an exclusively African variety, falling within the same monophyletic group as an isolate which has been detected previously in a naturally infected human from Guinea-Bissau. This observation highlights that St. Kitts vervets may serve as potential reservoirs for zoonotic S. fuelleborni infection, which warrants further exploration.

Strongyloides spp. in cats: a review of the literature and the first report of zoonotic Strongyloides stercoralis in colonic epithelial nodular hyperplasia in cats

BACKGROUND

Four species of Strongyloides, Strongyloides felis, Strongyloides planiceps, Strongyloides stercoralis and Strongyloides tumefaciens, have been identified in cats based on morphology and location in the host with limited data on the prevalence and disease potential of these different species. Strongyloides tumefaciens adults are located in colonic nodules while the other three species are in the small intestine. The literature on Strongyloides in cats is scattered and has never been compiled. The aim of this article is to provide a short review of the existing literature on Strongyloides spp. in cats, to describe the pathology of colonic nodules containing Strongyloides sp. seen at necropsies of cats in St. Kitts, West Indies, and to provide the first unequivocal report of zoonotic S. stercoralis in cats based on sequencing analysis of a portion of the cytochrome c oxidase subunit 1 (cox1) gene, and supported by phylogenetic analysis.

RESULTS

Colonic nodules containing sections of nematodes, histologically compatible with Strongyloides sp. were seen during necropsy in six cats in St. Kitts, West Indies. Sequencing of the cox1 gene of the mitochondrial DNA extracted from colonic nodules from two of these cats matched sequences of the zoonotic strain of S. stercoralis.

CONCLUSIONS

The morphological similarities between S. stercoralis-associated colonic nodules and previous reports of S. tumefaciens, together with the insufficient defining criteria for S. tumefaciens raises questions about the validity of the species. Further sampling and genetic characterization of isolates is needed to understand the species in cats and their zoonotic potential.

Strongyloides stercoralis hyperinfection syndrome: a deeper understanding of a neglected disease

Strongyloides stercoralis hyperinfection syndrome (SHS) is a life-threatening condition that warrants early detection and management. We describe the pathogenesis, organ-specific clinical manifestations, and risk factors associated to this condition. A comprehensive review of the literature was conducted in PubMed, LILACS, EBSCO and SciELO by using the keywords: "hyperinfection syndrome"; "Strongyloides stercoralis"; "disseminated strongyloidiasis"; "systemic strongyloidiasis", "pathogenesis" and "pathophysiology". Relevant articles on this topic were evaluated and included by consensus. Also, a secondary search of the literature was performed. Articles in English and Spanish language were included. SHS has been described in tropical and sub-tropical regions. However, there is growing evidence of cases detected in developed countries favored by increasing migration and the advance in immunosuppressive therapies for oncologic and inflammatory diseases. SHS is characterized by massive multiplication of larvae, typically in immunocompromised hosts. Clinical manifestations vary according to the organ involved and include diarrhea, intestinal bleeding, alveolar hemorrhages, heart failure, jaundice, bacteremia among others. Despite advances in the understanding of this condition, fatality rates are near 90%. Clinicians should consider SHS in the differential diagnosis of acutely ill patients with multiple organ damage and epidemiological risk factors. Adverse outcomes are common, especially with delayed anti-parasitic treatment.