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Strongyloides

Strongyloides is a genus of parasitic nematodes belonging to the family Strongyloididae within the order Rhabditida, comprising approximately 50 species that primarily infect the small intestines of vertebrates, including mammals, birds, reptiles, and amphibians.^[1] These thread-like worms are notable for their unique biphasic life cycle, which alternates between free-living adults in the soil and parasitic females in the host's gastrointestinal tract, with the parasitic generation reproducing parthenogenetically to produce eggs that develop into either infectious filariform larvae or free-living adults.^[1] The most significant species for human health is Strongyloides stercoralis, a soil-transmitted helminth that causes strongyloidiasis, an infection affecting an estimated 300–600 million people worldwide (as of 2024), particularly in tropical and subtropical regions with poor sanitation.^[2] Transmission occurs when filariform larvae in contaminated soil penetrate the skin, typically of the feet, migrate through the bloodstream to the lungs, and are swallowed to reach the small intestine, where they mature; autoinfection—where larvae reinfect the host internally—allows chronic infections to persist for decades, often asymptomatically, but can lead to hyperinfection syndrome in immunocompromised individuals, with mortality rates up to 90% if untreated.^[3] Another zoonotic species, S. fuelleborni, primarily affects primates but can cause infections in humans in parts of Africa and Papua New Guinea.^[3] Recognized as a neglected tropical disease by the World Health Organization, strongyloidiasis is diagnosed through stool examination for larvae or serological tests, and treated with antiparasitic drugs like ivermectin.^[4] The genus's biology, including its compact genome and high host specificity, makes it a valuable model for studying nematode parasitism and evolution.^[1]

Taxonomy and etymology

Classification

The genus Strongyloides is classified within the kingdom Animalia, phylum Nematoda, class Chromadorea, order Rhabditida, family Strongyloididae.^[1] This placement reflects its position among the chromadorean nematodes, which are characterized by their diverse parasitic and free-living lifestyles.^[1] Phylogenetically, Strongyloides resides in the Rhabditina clade (clade IVa) of the Rhabditida, showing close relationships to other rhabditid nematodes such as genera Rhabditis, Rhabdias, and its sister genus Parastrongyloides.^[1] Molecular analyses, particularly of the small subunit ribosomal RNA (18S rRNA) gene, support this positioning, revealing two distinct clades within Strongyloides that do not align perfectly with traditional morphological species boundaries.^[5] These genetic studies highlight its evolutionary ties to soil-dwelling microbivores while underscoring adaptations for parasitism.^[5] Historically, the genus was formalized by Giovanni Battista Grassi in 1879, who unified several nematode species previously described under the genus Anguillula based on shared morphological and biological traits; Strongyloides stercoralis was designated as the type species.^[1] This establishment distinguished Strongyloides from superficially similar strongylid nematodes, emphasizing its unique facultative free-living phase in the life cycle.^[1] The family Strongyloididae was subsequently recognized to accommodate these distinguishing features.^[1] Currently, approximately 50 species are recognized in the genus Strongyloides, primarily obligate gastrointestinal parasites of vertebrates, though molecular phylogenetic revisions continue to refine species delineations and uncover cryptic diversity.^[1]

Etymology

The genus name Strongyloides derives from the Greek words strongylos (round) and eidos (form or resemblance), alluding to the nematodes' slender yet rounded, thread-like body morphology. This nomenclature was established by Italian parasitologist Giovanni Battista Grassi in 1879, who recognized the parasitic and free-living stages as belonging to a single species rather than distinct entities.^[1] Prior to this, French physician Arthur Bavay had described the free-living adult and parasitic generations separately as species within the genus Anguillula in 1876 and 1877, based on specimens from human hosts in Cochinchina (modern-day Vietnam).^[1] Common names for Strongyloides species include "threadworm," emphasizing their thin, elongated appearance, and "anguillula," a diminutive form of the Latin anguilla (eel), which highlights their serpentine, eel-like shape in early observations. These terms reflect the 19th-century focus on the parasite's distinctive morphology during its initial discovery and classification in tropical regions.^[1]

Morphology and biology

Physical characteristics

Strongyloides nematodes are slender, thread-like worms characterized by their cylindrical bodies and smooth cuticles. Adult females, which are the primary reproductive form in the parasitic stage, measure approximately 2 to 3 mm in length and are about 50 to 70 µm in diameter, with a pointed tail and a filariform esophagus occupying roughly one-third of the body length.^[3]^[1]^[6] The parasitic females embed in the submucosa of the host's small intestine and produce eggs parthenogenetically, as males are absent in this stage.^[3] Free-living adult females are smaller, reaching up to 1.0 mm in length, with a rhabditiform esophagus and a vulva positioned near the midpoint of the body.^[1]^[6] Males are rare and occur only in the free-living stage, measuring up to 0.75 mm long, with a ventrally curved tail and spicules for mating.^[3]^[1] This sexual dimorphism underscores the predominance of parthenogenetic reproduction in females across Strongyloides species.^[1] Larval stages exhibit distinct morphologies adapted to their roles. Rhabditiform larvae (L1 and L2), which are 180 to 380 µm long, feature a short buccal canal, a rhabditoid esophagus comprising about one-third of the body length, and a prominent genital primordium.^[3]^[6] In contrast, infective third-stage filariform larvae (L3) are longer, up to 600 µm, with a filariform esophagus about half the body length, a notched or forked tail, and no surrounding sheath.^[3]^[1]^[6] Diagnostic features include a thin anterior end, smooth cuticle without striations prominent enough for easy visualization, and posterior phasmidial pores.^[1] Unlike hookworms, Strongyloides lacks an oral capsule, and its filariform larvae have a characteristic forked tail.^[1]

Life cycle

The life cycle of Strongyloides species is heterogonic, featuring both free-living and parasitic generations that alternate depending on environmental and host conditions. In the free-living phase, eggs deposited in the environment hatch into rhabditiform first-stage larvae (L1), which develop into free-living adults (males and females) in moist soil. These adults mate, and the females produce eggs that hatch into rhabditiform first-stage larvae (L1). The L1 larvae undergo further development: some molt through four stages to become free-living adults, perpetuating the cycle for a single generation, while others molt into infective third-stage filariform larvae (L3), which are capable of penetrating host tissues.^[1]^[7] Upon host contact, the infective filariform larvae (L3) initiate the parasitic phase by penetrating the skin or mucosal surfaces. These larvae migrate through the bloodstream to the lungs, where they ascend the trachea, are swallowed, and reach the small intestine. There, they mature into parthenogenetic females that embed in the intestinal mucosa and produce eggs asexually. The eggs hatch directly into rhabditiform larvae (L1) within the host's gut, which are then excreted in the feces to continue the free-living cycle or, in some cases, undergo further development internally.^[1]^[7] A distinctive feature enabling chronic infections is autoinfection, where rhabditiform larvae in the intestine molt into filariform larvae (L3) without exiting the host. These internal L3 larvae can reinvade the intestinal wall or migrate through tissues back to the duodenum, perpetuating the parasitic cycle indefinitely and allowing infections to persist for decades in immunocompetent hosts.^[1]^[7] In certain conditions or species, a homogonic variant occurs, bypassing the free-living adult stage. Here, rhabditiform L1 larvae from eggs develop directly through molts into infective filariform L3 larvae, facilitating rapid parasitic transmission without an environmental phase. Free-living adults live 2–4 days, with the external cycle completing in up to 3 weeks under optimal conditions (e.g., 20–28°C and high moisture), while the parasitic phase can last from weeks to over 60 years via autoinfection mechanisms.^[1]^[7]

Species diversity

Species infecting humans

The primary species of Strongyloides infecting humans is S. stercoralis, the type species of the genus, which has a cosmopolitan distribution in tropical and subtropical regions and is the causative agent of strongyloidiasis. This soil-transmitted helminth is estimated to infect around 600 million people globally, with prevalence rates varying from 1.4% in Bangladesh to 7.8% in Cambodia based on recent surveys.^[8] Although primarily anthropophilic, S. stercoralis exhibits zoonotic potential, with transmission occurring between humans, dogs, and non-human primates, and it can lead to rare but severe hyperinfection syndromes in immunocompromised individuals.^[9] Genetic analyses of S. stercoralis reveal significant diversity, including distinct multilocus genotypes such as A (associated with human and dog infections) and B (more dog-specific), alongside novel haplotypes that highlight geographic variation and historical introgression events. This diversity, evidenced by over 15,000 single nucleotide polymorphisms across sampled populations, has implications for transmission dynamics.^[9]^[8] A second species infecting humans is S. fuelleborni, which encompasses subspecies such as S. f. fuelleborni (found in Africa and Asia) and S. f. kellyi (endemic to Papua New Guinea), both of which are neglected causes of human helminthiasis. Unlike S. stercoralis, S. fuelleborni is predominantly zoonotic, spilling over from Old World non-human primates to humans via skin penetration by filariform larvae, though evidence of limited interhuman transmission exists. Parasitic females reproduce parthenogenetically in the human small intestine, shedding larvated eggs in feces rather than rhabditiform larvae.^[10] In Papua New Guinea, infections with Strongyloides fuelleborni (including those historically attributed to S. f. kellyi) are particularly significant among infants. Historical reports indicate prevalence reaching up to 60% in the first year of life, with detections as early as 18 days of age, and suggest potential transmammary transmission, though recent studies have not detected larvae in breast milk and transmission remains unconfirmed. Recent phylogenetic analyses using markers like cox1 and 18S rRNA indicate that many such infections are due to S. f. fuelleborni rather than S. f. kellyi, which appears rare, confirming S. f. kellyi as part of the Asia-Pacific clade of S. f. fuelleborni, genetically distinct from S. stercoralis. Overall human prevalence remains underreported but is increasing in recognition across Africa, Asia, and Oceania.^[11]^[10]

Species infecting animals

The genus Strongyloides encompasses approximately 50 species of parasitic nematodes that primarily infect vertebrates, with the majority exhibiting strict host specificity, though some demonstrate broader compatibility across related hosts.^[1] These animal-infecting species play significant roles in veterinary parasitology, often targeting specific taxa and contributing to health challenges in livestock and wildlife populations.^[12] Among ruminants, Strongyloides papillosus is a prominent species infecting cattle, sheep, and goats worldwide, residing in the small intestine and known to induce diarrhea particularly in young animals.^[13]^[14] This parasite has a global distribution in domesticated and wild ruminants, with prevalence varying by region and host age.^[15] In equines, Strongyloides westeri serves as the primary intestinal threadworm, mainly affecting horses and donkeys, with infections concentrated in foals up to several months of age.^[16] It inhabits the proximal small intestine and is prevalent in warm, humid environments conducive to larval development.^[17] Other mammalian hosts harbor distinct species, such as Strongyloides procyonis in raccoons (Procyon lotor), where it is a common intestinal parasite with notable prevalence in wild populations.^[18]^[19] Strongyloides dasypodis specifically infects armadillos (Dasypus novemcinctus), targeting the large intestine in these xenarthrans. In pigs, Strongyloides ransomi is the key species, primarily affecting piglets through transmammary or environmental transmission.^[20] Non-mammalian vertebrates also host Strongyloides species, including Strongyloides ardeae in birds such as herons (Ardea herodias), where it occupies the gastrointestinal tract.^[21] In reptiles, Strongyloides serpentis and Strongyloides gulae infect snakes, with S. serpentis found in the intestine of various colubrids and S. gulae in the esophagus of multiple snake species.^[22] Among primates, Strongyloides cebus parasitizes New World monkeys, such as capuchins (Cebus spp.) and woolly monkeys (Lagothrix cana), often leading to intestinal infections in captive and wild settings.^[23]^[24]

Pathogenicity

Disease in humans

Strongyloidiasis, the disease caused by infection with Strongyloides stercoralis in humans, typically begins with acute symptoms following larval penetration of the skin, leading to a pruritic rash known as ground itch at the site of entry. As larvae migrate through the bloodstream to the lungs, they induce a cough, wheezing, and shortness of breath resembling Loeffler's syndrome, often accompanied by transient pulmonary infiltrates and eosinophilia. Upon reaching the gastrointestinal tract, larvae cause abdominal pain, nausea, and diarrhea, with rhabditiform larvae detectable in stool samples.^[25]^[26] In the chronic phase, infections often persist asymptomatically for years due to the parasite's unique autoinfection cycle, where rhabditiform larvae in the intestines develop into infective filariform larvae that reinvade the host mucosa or perianal skin. Symptomatic cases may present with mild, intermittent gastrointestinal issues such as epigastric pain, bloating, diarrhea alternating with constipation, and weight loss, alongside dermatological manifestations like urticaria or the fast-moving larva currens rash. Eosinophilia is common but variable in this stage.^[25]^[26] Hyperinfection syndrome arises in immunocompromised individuals, such as those receiving corticosteroids, with HIV/AIDS, or undergoing organ transplantation, where suppressed cell-mediated immunity allows massive larval proliferation and dissemination beyond the gut and lungs. This leads to severe complications including sepsis from gram-negative bacteremia (e.g., Escherichia coli), acute respiratory distress syndrome (ARDS), gastrointestinal bleeding, and multi-organ failure, with larvae invading distant sites like the brain or meninges. Mortality rates in hyperinfection cases exceed 80%, often approaching 100% in disseminated forms without prompt intervention.^[25]^[26] Infections with Strongyloides fuelleborni, particularly subspecies kellyi, cause similar symptoms to S. stercoralis but are more frequently associated with pulmonary involvement in human infants, especially in Papua New Guinea. Heavy infections manifest as swollen belly syndrome, characterized by abdominal distension, diarrhea, respiratory distress, and protein-losing enteropathy due to intestinal villus atrophy and malabsorption, leading to high infant mortality rates of up to 8% in affected villages prior to treatment.^[27]^[1] Pathophysiologically, Strongyloides larvae invade the intestinal mucosa, causing ulcerations, inflammation, and crypt hyperplasia in the duodenum and jejunum, which disrupts nutrient absorption and elicits a Th2 immune response. This response features peripheral eosinophilia and elevated serum IgE levels in 38-59% of cases, promoting larval expulsion but also contributing to allergic symptoms like pruritus and wheezing during migration. In hyperinfection, mucosal barrier breakdown facilitates bacterial translocation, exacerbating systemic inflammation and sepsis.^[26]^[25]

Disease in animals

In ruminants, Strongyloides papillosus primarily affects young calves and lambs, causing hemorrhagic diarrhea, weight loss, and malnutrition due to intestinal damage from larval migration and adult worms.^[28] Heavy infections can lead to hyperinfection syndromes, including sudden cardiac death from larval invasion of the heart and lungs, as observed in outbreaks affecting over 150 weaned dairy calves in Japan, over 50 in New York, USA, and 150 lambs in Uruguay, where affected animals exhibited weakness, enophthalmos, and dehydration.^[14]^[29]^[30] These cases are exacerbated by high stocking densities and poor management, though the parasite is often considered of minor concern at low infection levels.^[31] In equines, Strongyloides westeri infects foals up to about four months of age, typically via transmammary transmission from mares, resulting in colic, anemia, acute diarrhea, and weakness from small intestinal inflammation and villous atrophy.^[32]^[33] High egg counts exceeding 2000 eggs per gram of feces correlate with clinical signs, but infections are generally self-limiting and sporadic, with prevalence below 10% in young horses.^[12] In pigs, Strongyloides ransomi causes nodular enteritis in piglets through prenatal and transmammary transmission, leading to anorexia, anemia, diarrhea, growth retardation, and intestinal nodules from chronic inflammation.^[20]^[34] Severe experimental infections can result in up to 30% mortality, though subclinical infections predominate under modern husbandry practices with low prevalence rates of 2-3.3%.^[12] Among wildlife, Strongyloides procyonis infections in raccoons are typically asymptomatic, though heavy larval burdens may cause mild gastroenteritis without significant clinical impact.^[3] Similarly, S. dasypodis in armadillos is often incidental and detected postmortem without associated disease syndromes.^[35] Zoonotic risks arise from potential spillover of Strongyloides fuelleborni from nonhuman primates, such as macaques and vervet monkeys, where human infections have been documented in Africa and Asia, occasionally causing mild intestinal symptoms.^[23] Rare reports suggest S. stercoralis transmission from dogs or cats to humans, though molecular evidence indicates host-specific strains with limited cross-infection potential.^[36] In birds and snakes, Strongyloides spp. can induce respiratory issues through larval migration to the lungs, manifesting as distress, anorexia, and pneumonia in colubrid snakes, while intestinal involvement leads to diarrhea and weight loss in both groups.^[37]^[38]

Epidemiology and transmission

Global distribution

Strongyloides stercoralis, the primary species infecting humans, is endemic in tropical and subtropical regions worldwide, including parts of Asia, sub-Saharan Africa, Latin America, the Caribbean, and Oceania, but is notably absent in colder climates such as northern Europe and high-altitude areas.^[3] The parasite's global burden is estimated at 300–600 million infections, with the highest prevalence in Southeast Asia, Africa, and the Western Pacific regions, which account for over 75% of cases.^[39]^[2] Additionally, approximately 2.6 billion people are at risk of infection due to suitable environmental conditions in these areas.^[40] The 2024 WHO guideline on strongyloidiasis recommends mass drug administration with ivermectin in endemic areas with prevalence ≥5%.^[2] Strongyloides fuelleborni, another human-infecting species, has a more restricted distribution, primarily in Central and West Africa and Papua New Guinea, often linked to primate reservoirs in forested regions.^[41] Among animal species, S. papillosus is globally distributed in livestock, particularly ruminants like cattle, sheep, and goats, with widespread occurrence in both tropical and temperate farming areas.^[42] In contrast, S. westeri predominantly affects young horses in temperate regions, such as parts of North America and Australia, where breeding farms are common.^[43] Wildlife infections, exemplified by S. procyonis in raccoons, are localized mainly to North America.^[18] The distribution of Strongyloides species is heavily influenced by environmental factors, with warm, moist soils favoring the survival and development of free-living larval stages, thereby promoting transmission in humid tropical and subtropical zones.^[44] Human prevalence is further exacerbated by socioeconomic conditions, including poverty and inadequate sanitation, which facilitate soil contamination in endemic areas.^[45] Recent trends show increasing cases in non-endemic regions among migrants and refugees from high-prevalence countries, highlighting the role of human mobility in expanding the parasite's footprint.^[46]

Modes of transmission

The primary mode of transmission for Strongyloides species, particularly S. stercoralis in humans, occurs through percutaneous penetration of the skin by infective third-stage filariform (L3) larvae present in soil contaminated with feces containing rhabditiform larvae.^[3] These larvae actively seek out and invade exposed skin, such as bare feet or hands, facilitating entry into the host's bloodstream and initiating migration to the lungs and intestines.^[25] Oral ingestion represents a rarer transmission route, potentially occurring through consumption of contaminated water, food, or soil via geophagia (soil-eating behavior), which can introduce larvae directly into the gastrointestinal tract.^[47] This pathway is less efficient than skin penetration and is more commonly associated with poor sanitation or cultural practices involving soil contact.^[25] Zoonotic transmission from animal reservoirs to humans has been documented, primarily involving S. stercoralis from dogs and nonhuman primates, where shared environments enable larval exposure.^[48] Evidence supports bidirectional transmission between humans and dogs in endemic areas, though vertical transmission (e.g., transplacental or transmammary) remains unconfirmed in humans despite observations in canine models.^[49]^[50] A unique feature of Strongyloides infection is autoinfection, where rhabditiform larvae in the host's intestines develop into filariform larvae that penetrate the intestinal mucosa or perianal skin, re-entering the circulation and perpetuating the infection without external environmental exposure.^[3] This internal recycling mechanism allows chronic, asymptomatic infections lasting decades and prevents natural clearance by the host immune system.^[25] Filariform larvae exhibit limited environmental survival, remaining viable for up to three weeks in moist soil under optimal conditions of 20–30°C and high humidity, during which they can develop from free-living stages.^[7] Survival is significantly reduced by dryness, extreme temperatures, or ultraviolet (UV) exposure, which disrupt larval motility and development, thereby limiting transmission potential in arid or sanitized environments.^[51]^[52]

Diagnosis, treatment, and prevention

Diagnostic approaches

Diagnosis of Strongyloides stercoralis infection primarily relies on laboratory methods to detect larvae, antibodies, or parasite DNA, as clinical symptoms alone are nonspecific.^[53] The gold standard remains parasitological examination of stool samples, which identifies rhabditiform larvae, though intermittent shedding necessitates multiple specimens—often up to seven—for adequate sensitivity.^[53] Specialized techniques enhance detection, including the Baermann concentration method, agar plate culture, and nutrient agar plate cultures, which can increase yield fourfold compared to direct smears or formal-ether concentration techniques.^[53]^[54] Duodenal aspirates or biopsies may also reveal larvae in gastric crypts or eosinophilic infiltration, offering higher sensitivity than stool in some cases, particularly for immunocompromised patients.^[53] Serological tests, such as enzyme-linked immunosorbent assay (ELISA) detecting anti-Strongyloides IgG, provide high sensitivity (70–95%) for chronic infections and are useful when parasitological methods fail, but they exhibit cross-reactivity with other helminths like filariae, schistosomes, and Ascaris lumbricoides.^[53]^[55] More specific assays, including those using recombinant antigens like NIE in luciferase immunoprecipitation system (LIPS) or ELISA, achieve specificities up to 100% with minimal cross-reactivity (0–11.3%), though persistent antibodies post-treatment can indicate historical rather than active infection.^[55] The Centers for Disease Control and Prevention (CDC) offers reference serologic testing to confirm equivocal results.^[53] Molecular methods, particularly polymerase chain reaction (PCR) targeting genes such as 18S rRNA or cox1 on stool or duodenal aspirates, offer high specificity (93–95%) and are especially valuable for detecting low-burden or hyperinfection cases, with real-time PCR sensitivities ranging from 64–72% against composite references as of 2024.^[54]^[56] These assays address limitations of microscopy but face challenges from PCR inhibitors in stool and irregular larval output, requiring optimization for routine use.^[54] Emerging molecular tools, such as species-specific PCR assays developed in 2025, enable differentiation between S. stercoralis and S. fuelleborni, enhancing surveillance in zoonotic contexts.^[57] The World Health Organization (WHO) notes PCR as more efficient than traditional stool culture, though no standardized diagnostic protocol exists.^[58] In cases of complications like hyperinfection syndrome, imaging such as endoscopy or bronchoalveolar lavage can visualize worms or larvae, while peripheral eosinophilia supports suspicion but is not diagnostic.^[53] Key challenges include low sensitivity of parasitological tests (often <50% in light infections), serologic cross-reactivity, and the need to distinguish Strongyloides larvae from those of hookworms based on morphology, such as the prominent genital primordium in rhabditiform stages.^[53]^[54] Overall, combining methods—e.g., serology with parasitology—improves accuracy in endemic or high-risk settings.^[58]

Therapeutic options

The primary treatment for chronic strongyloidiasis in humans is ivermectin, administered orally at a dose of 200 μg/kg as a single dose or repeated for 1–2 days, achieving cure rates exceeding 90% in most cases.^[59]^[60] Alternative options include albendazole at 400 mg twice daily for 3–7 days, though it demonstrates lower efficacy, with cure rates around 45–86% depending on the regimen and population.^[59]^[61] Thiabendazole, historically used at 25 mg/kg twice daily for 2–3 days, has comparable efficacy to albendazole but is associated with more frequent side effects such as gastrointestinal upset and vertigo, and it has been largely discontinued in favor of ivermectin.^[62]^[63] Emerging treatments include emodepside, an investigational anthelmintic that showed high efficacy in a 2025 phase 2 trial, with cure rates up to 96% at doses of 15–30 mg, positioning it as a promising alternative to ivermectin due to its broad-spectrum activity and safety profile.^[64] In cases of hyperinfection or disseminated strongyloidiasis, particularly in immunocompromised patients, treatment involves higher-dose oral ivermectin (200 μg/kg daily) continued until stool or sputum examinations are negative for larvae for at least two weeks; rectal or subcutaneous administration may be used if oral intake is not possible, and broad-spectrum antibiotics are added to address secondary bacterial infections due to larval migration through the intestinal wall.^[59]^[65] Reducing or discontinuing immunosuppressive therapy is also critical to improve outcomes.^[59] For animal infections, similar anthelmintics are employed, with ivermectin at 200 μg/kg administered every four days for three to four doses or fenbendazole at 50 mg/kg daily for 7–14 days showing high efficacy against Strongyloides species in dogs and other hosts.^[36]^[66] Ivermectin resistance in Strongyloides is rare, with isolated reports of treatment failures attributed to high parasite burdens or reinfection rather than true resistance, necessitating post-treatment monitoring via serial stool examinations 2–4 weeks after therapy to confirm parasitological cure.^[59]^[67]

Preventive measures

Preventing Strongyloides transmission requires multifaceted strategies at individual, community, and global levels, focusing on interrupting the parasite's fecal-oral cycle through soil contamination. At the individual level, basic sanitation practices are essential, including the use of proper footwear to avoid direct skin contact with contaminated soil in endemic regions and improved fecal disposal to reduce environmental contamination. ^[68] ^[69] Avoiding barefoot walking in areas with poor sanitation, such as tropical and subtropical zones where the parasite thrives, significantly lowers infection risk, as larvae penetrate the skin primarily through the feet. ^[70] ^[65] Community-level interventions emphasize mass drug administration (MDA) programs, particularly in high-risk populations. The World Health Organization recommends annual MDA with a single dose of ivermectin (200 μg/kg) for individuals aged 5 years and older in endemic areas where prevalence among school-aged children is ≥5% as part of neglected tropical disease control efforts, which has demonstrated substantial reductions in Strongyloides prevalence. ^[2] ^[71] Studies in regions like Papua New Guinea and Australia have shown that ivermectin-based MDA, often combined with other anthelmintics, effectively targets Strongyloides alongside soil-transmitted helminths, achieving long-term prevalence decreases of up to 50% in treated communities. ^[72] ^[73] Education campaigns promoting hygiene, such as handwashing and safe water use in tropical settings, further support these efforts, while routine screening for immigrants and refugees from endemic zones helps prevent importation and hyperinfection in vulnerable hosts. ^[74] ^[75] Veterinary measures are crucial to curb zoonotic potential, as Strongyloides species can infect animals like dogs, horses, and livestock, potentially serving as reservoirs. Regular deworming of companion animals and livestock using ivermectin or fenbendazole, combined with quarantine protocols for wildlife trade, reduces animal-to-human transmission risks. ^[36] ^[76] Environmental management in veterinary settings, including prompt feces removal and disinfection of kennels or stables, prevents larval persistence in soil. ^[77] ^[78] Despite these approaches, challenges persist in fully controlling Strongyloides spread. Climate change is expanding suitable habitats for the parasite by warming temperatures and altering precipitation patterns, potentially increasing distribution into previously non-endemic temperate areas. ^[79] ^[80] Incomplete MDA coverage in remote or underserved communities further hinders progress, underscoring the need for integrated surveillance and resource allocation. ^[81] ^[82]

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Nov 27, 2023 · Strongyloides cebus was listed in several species of New World primates in America based on morphology of adults [40], although most studies ...Abstract · Introduction · Strongyloides in non-human... · Strongyloides distribution...
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Strongyloides Cebus (Nematoda: Strongyloididae) in Lagothrix ...
Seven cases of Strongyloides cebus were found in Lagothrix cana, causing moderate to severe disease, diarrhea, and one death. Ivermectin was effective. ...
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Sep 4, 2023 · Review the life cycle and mechanism of infection of Strongyloides stercoralis. Describe the clinical presentation of a patient infected with ...
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Strongyloides stercoralis Infection in Humans: A Narrative Review of ...
Oct 12, 2023 · Strongyloidiasis hyperinfection syndrome includes the symptoms of common S. stercoralis infection along with more severe symptoms such as ...
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Heavy S. fuelleborni subsp. kellyi infection has been implicated as the cause of swollen belly syndrome (SBS), a rapidly fatal disease in infants around 2 ...
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Strongyloides papillosus | CABI Compendium
This nematode infection is widely distributed in young hosts. It may cause severe disease in 1-3 month old calves and 2-6 week old lambs or kids. It rarely ...
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Strongyloidiasis (Strongyloides papillosus) in lambs in Uruguay
Affected animals showed weakness, weight loss, enophthalmos and, in some cases, sudden death. Postmortem examination revealed muscle atrophy, dehydration, and ...
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Strongyloides papillosus
Strongyloides papillosus is sometimes considered a minor pathogen of little concern to domestic ruminants, especially when fecal testing detects low counts of ...
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Gastrointestinal Parasites of Minor Clinical Importance in Horses
Strongyloides westeri is an intestinal threadworm (see S westeri adult image) that commonly infects young foals. It has been associated with small intestinal ...
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Dec 15, 2017 · Strongyloides westeri is a threadworm parasite found in the small intestine mainly in foals at up to about 4 months of age.
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Infection with S. ransomi occurs only in swine. The parasite has a cosmopolitan distribution and is of importance in warmer countries or areas.
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Intestinal parasites of Tolypeutes matacus, the most frequently ...
This armadillo is one of the most frequently consumed species by people in this area. The objective of this work was test for zoonotic species among helminths ...Missing: raccoons | Show results with:raccoons
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Jul 2, 2025 · Strongyloides stercoralis is found infecting dogs and humans worldwide. · The estimated global prevalence of canine strongyloidiasis is 6%. · The ...
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Parasitic Diseases of Reptiles - Exotic and Laboratory Animals
Strongyloides spp frequently inhabit the intestinal tract of reptiles; larvae are present in the respiratory tract and respiratory exudate. In snakes, the ...
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Jul 17, 2023 · This report documents morbidity, mortality, and non-enteric disease manifestations due to Strongyloides hyperinfections in a captive colubrid snake colony.Missing: serpentis | Show results with:serpentis
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Sep 29, 2025 · Strongyloidiasis is a chronic parasitic infection caused by Strongyloides stercoralis, transmitted through skin contact with contaminated soil. ...Key Facts · Diagnosis And Therapy · Prevention And Control
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Mapping the global distribution of Strongyloides stercoralis and ...
Jun 8, 2022 · We used the ecological niche models MaxEnt and Kuenm R library to estimate the global distribution of S. stercoralis and hookworms.
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Strongyloidiasis—An Insight into Its Global Prevalence and ... - PMC
Strongyloides stercoralis, one of the most common and globally distributed human pathogens of clinical importance, infects 30–100 million people worldwide [1].
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Strongyloides spp in Cows (Bovis) - Vetlexicon
Genus: Strongyloides. Species: S. papillosus. Distribution. Worldwide. Significance. Usually of little clinical significance. However, under ...
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Molecular detection of Strongyloides sp. in Australian Thoroughbred ...
Sep 3, 2021 · Strongyloides westeri is found in the small intestine of young horses, mainly in foals up to about 16 weeks of age.
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Strongyloides stercoralis - Learn About Parasites
Taxonomy. Phylum: Nematoda Class: Secernentea Order: Rhabditida Family: Strongyloididae. As well as S. stercoralis, the genus includes several other species of ...
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Strongyloides stercoralis: Global Distribution and Risk Factors
It is endemic world-wide, yet more prevalent in hot and humid climates as well as resource poor countries with inadequate sanitary conditions. The difficult ...
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Human strongyloidiasis: identifying knowledge gaps, with emphasis ...
Aug 20, 2014 · We do not know what environmental factors might control Strongyloides distribution (such as moisture and nutrients), and we do not know of any ...
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Strongyloidiasis: a neglected Neglected Tropical Disease (NTD)
Strongyloidiasis, the human disease caused by infection with Strongyloides stercoralis, and in rare instances in restricted geographic locations.Missing: swollen belly
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Autochthonous Human and Canine Strongyloides stercoralis ...
Jun 3, 2020 · Thus, this study is the first to provide convincing evidence of natural zoonotic transmission of S. stercoralis between dogs and humans.
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Transmammary transmission of Strongyloides stercoralis in dogs
Vertical transmission of larvae is a major pathway in the life cycle of several species of Strongyloides, but evidence for it occurring in humans or dogs ...
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Strongyloidiasis: Background, Pathophysiology, Etiology
Feb 18, 2022 · The genus Strongyloides is classified in the order Rhabditida, and most members are soil-dwelling microbiverous nematodes. Most of the 52 ...
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A Review of Strongyloides spp. Environmental Sources Worldwide
Strongyloides spp. are parasitic nematodes that are transmitted through the environment and are capable of causing disease. These nematodes affect an ...
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Tricky with Heat and Salt: Soil Factors, Thermotaxis, and Potential ...
May 16, 2025 · Heat treatment for human fecal pit soil required 60 °C and 60 min of exposure to inactivate Strongyloides larvae [32]. Only strong acid (pH 1.2) ...
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Clinical Overview of Strongyloides - CDC
Feb 14, 2024 · Key points · Strongyloides infection can range from subclinical to fatal. · Patients using high-dose corticosteroids may have severe illness.
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Accuracy of molecular biology techniques for the diagnosis of ...
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Diagnostic Accuracy of Five Serologic Tests for Strongyloides ...
NIE-LIPS is the most accurate serologic test for the diagnosis of S. stercoralis infection. IFAT and each of the ELISA tests are sufficiently accurate, above a ...
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Clinical Care of Strongyloides - CDC
Feb 16, 2024 · Ivermectin and albendazole can treat Strongyloides infections. In severe cases, immunosuppressive therapy should be reduced or stopped if ...
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Effectiveness of Ivermectin treatment among adult patients infected ...
May 12, 2025 · The study found a 90% cure rate for the current 2-day Ivermectin treatment regimen (200 μg/kg) against Strongyloides stercoralis in Ethiopia.
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A comparative trial of a single-dose ivermectin versus ... - PubMed
In 301 children with Strongyloides stercoralis infection, treatment with ivermectin or albendazole resulted in cure rates of 83% and 45%, respectively. While ...Missing: efficacy | Show results with:efficacy
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Ivermectin has been shown to be more effective for treating chronic uncomplicated strongyloidiasis. The efficacy and tolerability of these drugs in a series of ...
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Strongyloidiasis Medication: Anthelmintics - Medscape Reference
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Strongyloidiasis - Infectious Diseases - Merck Manuals
Like hookworms, Strongyloides larvae penetrate human skin, migrate via the bloodstream to the lungs, break through pulmonary capillaries, ascend the respiratory ...
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Identification and treatment of Strongyloides stercoralis infection in a ...
Dec 6, 2023 · Off-label ivermectin may be an alternative to fenbendazole for the treatment of Strongyloides spp. infection in dogs. Keywords ...
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The efficacy of IVM has been reported to have lessened over time in some regions as a consequence of prolonged use and mass treatment campaigns.
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About Strongyloides - CDC
Sep 10, 2024 · Strongyloides is a parasitic roundworm that infects people. · It can cause stomachaches, diarrhea, and rashes. · Most people have no symptoms, but ...
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Strongyloidiasis: Causes, Symptoms, Prevention & Treatment
Strongyloidiasis is an infection with the parasitic worm Strongyloides. It lives in contaminated soil and infects you through your skin.Missing: armadillos | Show results with:armadillos
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Strongyloidiasis: Symptoms, Causes, Treatment, and More - Healthline
Strongyloidiasis can't always be prevented. However, exercising good personal hygiene, using sanitary facilities, and not walking barefoot when traveling to ...
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WHO releases guideline on public health control of human ...
Aug 2, 2024 · The GDG formulated a key recommendation supporting annual mass drug administration with single-dose ivermectin 200 μg/kg in all age groups from 5 years and ...
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Impact of mass drug administration with ivermectin ...
This study highlights the added benefit of MDA with IDA that now includes ivermectin that treats non-target parasites like Strongyloides, and other STHs that ...
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Effectiveness of one and two doses of ivermectin mass drug ...
Our study highlights the long-term benefits of ivermectin MDA in reducing the burden of Strongyloides spp. and T. trichiura.
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Impact of the health education and preventive equipment package ...
Oct 19, 2018 · Strongyloidiasis is prevalent in northeast Thailand. This study aimed to evaluate the impact of the Health Education and Preventive ...
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Intestinal Parasites | Immigrant and Refugee Health - CDC
Ivermectin is the drug of choice for strongyloidiasis. CDC presumptive overseas ivermectin treatment was initiated in 2005. Epidemiology. Prevalence in ...
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Strongyloides sp in Small Animals - Digestive System
Strongyloides is a zoonotic parasite in dogs and cats, acquired via ingestion or skin penetration, causing diarrhea and malabsorption, especially in young ...
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Efficacy of ivermectin to control Strongyloides stercoralis infection in ...
Results of the study confirm that ivermectin was an effective treatment option to control S. stercoralis infection in dogs.
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First identification of Strongyloides stercoralis infection in a pet dog ...
Oct 27, 2023 · Strongyloides stercoralis is a soil-transmitted intestinal nematode that affects humans, non-human primates, dogs, and occasionally cats [1,2,3] ...
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Thermosensory behaviors of the free-living life stages of ... - NIH
We find that Strongyloides free-living adults are exclusively attracted to near-tropical temperatures, despite their inability to infect mammalian hosts.
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The impact of global climate change on the spread of parasitic ...
Climate changes may influence the frequency, intensity and geographical distribution of parasites, directly affecting their dispersive stages in the ...<|separator|>
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Mapping the global distribution of Strongyloides stercoralis and ...
Jun 8, 2022 · Annual precipitation, annual temperature, soil carbon content and land cover were the main associated environmental variables. The ecological ...
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[PDF] Thermosensory behaviors of the free-living life stages of ... - bioRxiv
Sep 15, 2024 · Strongyloides free-living adults, we tested the impact of ... The impact of global climate change on the spread of parasitic nematodes.