Nematocidal effect of Piper retrofractum Vahl on morphology and ultrastructure of Strongyloides stercoralis third-stage infective larvae.

In a previous research work aimed at discovering natural helminthicides as alternatives to conventional synthetic drugs, Piper retrofractum fruit hexane extract (PHE) has been shown to possess promising nematocidal activity against the third-stage infective larvae of Strongyloides stercoralis. Thus, this study was designed to evaluate the chemical composition and the impact of PHE on symptom and structural alterations of S. stercoralis. Chemical analysis of PHE by gas chromatography-mass spectrometry demonstrated 26 different compounds, constituting 100% of the total composition. The main components were 4-acetylphenyl (4-benzoylphenoxy) acetate (14.86%) and octyl methoxycinnamate (12.72%). Nematocidal bioassays revealed promising potential of PHE against S. stercoralis larvae, with an LC50 value of 0.059 mg/ml, while the reference drug ivermectin exerted higher efficacy, with an LC50 value of 0.020 µg/ml. Behavioural observations under light microscopy revealed that PHE-treated S. stercoralis larvae moved slowly, became paralysed and eventually died during 24 h of incubation. The dead larvae appeared under light microscope as straight worms with unknown vacuoles of different sizes inside their internal bodies. Morphological alterations of the PHE-treated S. stercoralis larvae, such as straight bodies with swollen cuticle, faded transverse annulations and faded longitudinal striations, as well as shallow and smooth lateral longitudinal grooves, were seen clearly under scanning electron microscopy. Ultrastructural changes in the treated larvae, such as protruded lateral longitudinal grooves, loose muscle with vacuolation, dissociation between the hypodermis and cuticle and marked intracellular disorganization with vacuolation, were detected under transmission electron microscopy. The results of this study provide evidence that PHE is toxic against S. stercoralis and also a potential new alternative for anti-Strongyloides chemotherapy.

Transrenal DNA-based diagnosis of Strongyloides stercoralis (Grassi, 1879) infection: Bayesian latent class modeling of test accuracy.

For epidemiological work with soil transmitted helminths the recommended diagnostic approaches are to examine fecal samples for microscopic evidence of the parasite. In addition to several logistical and processing issues, traditional diagnostic approaches have been shown to lack the sensitivity required to reliably identify patients harboring low-level infections such as those associated with effective mass drug intervention programs. In this context, there is a need to rethink the approaches used for helminth diagnostics. Serological methods are now in use, however these tests are indirect and depend on individual immune responses, exposure patterns and the nature of the antigen. However, it has been demonstrated that cell-free DNA from pathogens and cancers can be readily detected in patient's urine which can be collected in the field, filtered in situ and processed later for analysis. In the work presented here, we employ three diagnostic procedures-stool examination, serology (NIE-ELISA) and PCR-based amplification of parasite transrenal DNA from urine-to determine their relative utility in the diagnosis of S. stercoralis infections from 359 field samples from an endemic area of Argentina. Bayesian Latent Class analysis was used to assess the relative performance of the three diagnostic procedures. The results underscore the low sensitivity of stool examination and support the idea that the use of serology combined with parasite transrenal DNA detection may be a useful strategy for sensitive and specific detection of low-level strongyloidiasis.

Acute strongyloidiasis in a traveller returning from South East Asia.

We report a case of acute strongyloidiasis, presenting with fever, pronounced eosinophilia and a disseminated skin rash, in a traveller returning from South East Asia.

Immunization with the recombinant antigen Ss-IR induces protective immunity to infection with Strongyloides stercoralis in mice.

Human intestinal infections with the nematode Strongyloides stercoralis remain a significant problem worldwide and a vaccine would be a useful addition to the tools available to prevent and control this infection. The goal of this study was to test single antigens for their efficacy in a vaccine against S. stercoralis larvae in mice. Alum was used as the adjuvant in these studies and antigens selected for analysis were either recognized by protective human IgG (Ss-TMY-1, Ss-EAT-6, and Ss-LEC-5) or were known to be highly immunogenic in humans (Ss-NIE-1 and Ss-IR). Only mice immunized with the Ss-IR antigen demonstrated a significant decrease of approximately 80% in the survival of larval parasites in the challenge infection. Antibodies, recovered from mice with protective immunity to S. stercoralis after immunization with Ss-IR, were used to locate the antigen in the larvae. Confocal microscopy revealed that IgG from mice immunized with Ss-IR bound to the surface of the parasites and observations by electron microscopy indicated that IgG bound to granules in the glandular esophagus. Serum collected from mice immunized with Ss-IR passively transferred immunity to naïve mice. These studies demonstrate that Ss-IR, in combination with alum, induces high levels of protective immunity through an antibody dependent mechanism and may therefore be suitable for further development as a vaccine against human strongyloidiasis.

Human immunoglobulin G mediates protective immunity and identifies protective antigens against larval Strongyloides stercoralis in mice.

Protective immunity to larval Strongyloides stercoralis in mice has been shown to be dependent on antibody, complement, and granulocytes. The goals of the present study was to determine the following: (1) whether human serum could passively transfer immunity to mice, (2) the mechanism by which the serum mediated killing, and (3) whether the antigens (Ags) recognized by the protective human antibody could induce protective immunity in mice. Immunoglobulin G (IgG) from a S. stercoralis-seropositive individual passively transferred immunity to mice. The antibody required granulocytes, but not eosinophils, and complement activation to kill the larvae. Antibody-dependent cellular cytotoxicity was not required for larval killing. Immunization of mice with soluble larval Ags isolated by use of the protective immune IgG resulted in protective immunity. In conclusion, immunity could be transferred to mice by IgG from immune humans, and Ags identified by the immune human IgG induced protective immunity in mice, which thereby suggests their possible use in a vaccine against this infection.

[Autochthonous strongyloidosis in an 81-year-old woman]. / Autochthone Strongyloidose bei einer 81-jährigen Frau.

Strongyloidosis is an parasitic disease, caused by an intestinal nematode endemic in tropic and subtropic regions. In Central Europe it occurs only sporadically. The infective larvae in the soil penetrate the human skin. Following circulation through the lungs the larvae settle in the small intestine and mature into adult worms. Chronic strongyloidosis recurring up to 15 years is possible through endogenous autoinfection. Clinical feature of the disease are gastrointestinal symptoms, hypereosinophilia and skin rashes. We describe the case of an 81-year-old woman who presented with scaly exanthema, fever and perianal fistulation. A microscopic examination of a stool sample demonstrated filariform larvae of Strongyloides stercoralis. An autochthonous mode of infection was assumed. After starting treatment with mebendazole eosinophilia and rash gradually disappeared. The laboratory finding of eosinophilia in patients with gastrointestinal symptoms or exanthema should prompt the differential diagnosis of a parasitosis. Stool examination is necessary to find rare autochthonous infections by intestinal nematodes. Pathogenesis, clinical manifestation and treatment of strongyloidosis are discussed along with the clinical picture.

Strongyloides stercoralis: ultrastructural study of newly hatched larvae within human duodenal mucosa.

AIM: To investigate the ultrastructural features of the newly hatched larvae of Strongyloides stercoralis in human duodenal mucosa. METHODS: Duodenal biopsies from an AIDS patient were studied by transmission electron microscopy to investigate morphology, location, and host-worm relations of newly hatched larvae. RESULTS: Newly hatched larvae were found in the Lieberkuhn crypts within the tunnels formed by migration of parthenogenic females. Delimiting enterocytes were compressed. Release of larvae into the gut lumen was also documented. It was shown that both a thin and a thick membrane surrounded the eggs and larvae, as a tegument derived respectively from parasite and host. Segmentary spike-like waves, caused by contractures of worm body musculature, were observed on the surface of newly hatched larvae, and their intestinal lumen was closed and empty, with no budding microvilli. Immaturity of the cuticle and some degree immaturity of amphidial neurones were found, but there was no evidence of either immaturity or signs of damage to other structures. CONCLUSIONS: Newly hatched larvae of S stercoralis appear to be a non-feeding immature stage capable of active movement through the epithelium, causing mechanical damage. The tegument resulting from the thin and the thick membrane may protect the parasite and reduce any disadvantage caused by immaturity.

Cryo-microtome sections of coproculture larvae of Strongyloides stercoralis and Strongyloides ratti as antigen sources for the immunodiagnosis of human strongyloidiasis

Comparou-se o emprego de cortes em congelacao de larvas de S. stercoralis e de S. ratti como fonte de antigenos na reacao de imunofluorescencia indireta (RIF) para o diagnostico da estrongiloidiase humana. Os antigenos foram obtidos de coproculturas de fezes humanas e de ratos, respectivamente. Soros de 123 individuos foram analisados sendo 54 de pacientes com estrongiloidiase e 69 controles. Empregou-se conjugado anti IgG humano marcado com fluorescencia nos titulos ideais de 10 para S. stercoralise 100 para S. ratti. A sensibilidade da RIF foi de 94,4 por cento e 92,5 por cento e a especificidade de 94,2 por cento e 97,1 por cento respectivamente para os antigenos de S. stercoralis e S. ratti...

Barren female Strongyloides stercoralis from occult chronic infections are rejuvenated by transfer to parasite-naive recipient hosts and give rise to an autoinfective burst.

It is widely assumed that barren Strongyloides stercoralis occurring in chronically infected carriers can become fecund when immunity wanes. Evidence for this involves corticosteroid treatment of hosts harboring occult infections that subsequently return to patency. However, nematodes have ecdysteroid receptors, and it has been suggested that corticosteroids act directly on the parasite, inducing autoinfective development, rather than indirectly by suppressing host immunity. To test these competing concepts, barren females were recovered from donor dogs when the dogs' fecal examinations turned negative. Groups of 100 active barren worms were surgically transplanted into the small intestines of each of 6 naive canine recipients. Three were examined at necropsy at 4-5 days postinfection (PI), before autoinfection could amplify the number of successfully transferred parasites. The remaining recipients were examined 21-22 days PI when, if autoinfection had occurred, the worm populations should have increased. At 4-5 days, gravid worms occurred in each of the recipients (19 +/- 6 worms/dog). By 21-22 days, a remarkable population increase had occurred (522.6 +/- 296 worms/dog). Worms from chronically infected donors were stunted, and electron microscopy revealed damage to the intestine and ovaries. Successfully transplanted worms recovered at days 4-5 PI were ovigerous and less stunted and showed repair of intestinal and ovarian tissues.

Sensory neuroanatomy of a skin-penetrating nematode parasite Strongyloides stercoralis. II. Labial and cephalic neurons.

Host recognition, contact, and skin-penetration by Strongyloides stercoralis infective larvae are crucially important behavioral functions mediating transition from free-living to parasitic life. The sensilla of the worm's anterior tip presumably play an important role in these processes. Besides the main chemosensilla, the amphids, which are of central importance, the larva has 16 putative mechanosensilla. There are six inner labial sensilla: two dorsal, two ventral, and two lateral. The two dorsal and ventral pairs are each innervated by two neurons, whereas each lateral sensillum is singly innervated. The six outer labial and four cephalic sensilla are all singly innervated. All of these have the characteristics of mechanoreceptors: they are closed to the external environment, and closely associated with the overlying cuticle. Distally, their dendritic processes contain granular material and associated microtubules. With two exceptions, the relevant neuronal cell bodies lie in lateral ganglia adjacent to the nerve ring, their positions remarkably similar to those of their homologues in the free-living nematode, Caenorhabditis elegans. Cell bodies of two neuronal pairs, one of two dorsal inner labial neurons and one of two ventral inner labial neurons per side, are however, found far anterior to the remaining cell bodies. All labial and cephalic sensilla are apparently mechanoreceptors, complementing the well-developed chemosensilla. Presumably infective larvae require touch and stretch receptors, not only to initiate skin penetration by finding irregularities as points of access, but also to bore through tissue to reach their ultimate enteral destination.

Strongyloides stercoralis: histopathology of uncomplicated and hyperinfective strongyloidiasis in the Mongolian gerbil, a rodent model for human strongyloidiasis [corrected].

Tissues from corticosteroid-treated gerbils hyperinfected with Strongyloides stercoralis were compared grossly and microscopically to similar tissues from animals with uncomplicated strongyloidiasis. Gerbils with hyperinfection developed severe pulmonary alveolar haemorrhage with a variable degree of subacute eosinophilic interstitial pneumonia associated with numerous alveolar, vascular and interstitial larvae. Hyperinfection induced by corticosteroids, given either before inoculation of S. stercoralis larvae or after a chronic Strongyloides infection was established, produced similar lesions. In contrast, lungs from gerbils with uncomplicated Strongyloides infection had severe eosinophilic perivasculitis and vasculitis with very little haemorrhage, no pneumonia and no larvae. Sections of adult worms were present in the proximal part of the intestinal tract, lodged in spaces between mucosal epithelial cells. Adult worms were not associated with inflammation and were more common in the corticosteroid-treated gerbils. In corticosteroid-treated gerbils only, there were numerous larvae in the distal intestinal tract, throughout the intestinal wall and adjacent mesentery, within interstitial tissues and in lymphatic vessels. Significant inflammation with associated larvae was only present in the caecum and mesenteric lymph nodes, suggesting that the caecum was the main site for initiation of parenteral migration with subsequent invasion of the lymphatic system and lungs. The lesions in these gerbils were similar to those found in humans. Infection of gerbils with S. stercoralis is the best rodent model of human strongyloidiasis.