Ascaris (parasite)

Résumé

L’ascaris lombricoïde (Ascaris lumbricoides) est un ver nématode (genre des ascarides) parasite intestinal qui provoque l’ascaridiose, maladie strictement humaine. C’est le plus grand des nématodes, et la plus fréquente des helminthiases, qui concernent l'homme. L’ascaris lombricoïde est cosmopolite mais est plus fréquent dans les zones tropicales et subtropicales ainsi que celles avec une hygiène inadéquate. « L'ascaris des chiens et des chats » appartient à d'autres ascarides (Toxocara canis chez le chien, Toxocara cati chez le chat), provoquant la toxocarose, qui peut aussi toucher l'homme. Histoire Fréquents et de grande dimension, les ascaris lombricoïdes ne pouvaient pas passer inaperçus. Aussi des médecins historiens de la fin du ont identifié comme ascaris le ver Hefat mentionné dans le papyrus Ebers, mais cela n'est pas confirmé un siècle plus tard. En Chine, l'ascaris serait mentionné dans le Nei Jing. Les anciens grecs ont pensé que ce ver était engendré

Source officielle

https://fr.wikipedia.org/wiki/Ascaris_(parasite)

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Les nématodes (Nematoda), ou vers ronds et effilés, constituent un embranchement de vers non segmentés. Classés parmi les ecdysozoaires, ils sont recouverts d'une épaisse cuticule. Ils représ

vignette|Femelle de , une des très nombreuses espèces de petites guêpes (parasitoïdes de la famille des Pteromalidae, souvent spécialisées dans le parasitage d'une seule autre espèce d'insectes). vign

Une helminthiase est un terme désignant les maladies parasitaires, causées par des vers parasites intestinaux, les helminthes. Ces vers constituent un important problème de santé publique dans les pa

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There is an urgent need to develop comprehensive and sustainable sanitation systems in developing countries, including faecal sludge (FS) treatment technologies that help reduce environmental and human health risks. Anaerobic digestion (AD) is widely used for the treatment of biowastes but its potential for FS sanitization still needs to be assessed. The goal of this work was to evaluate pathogens inactivation during thermophilic AD of a synthetic surrogate for FS through biomethane potential (BMP) tests. Salmonella, Ascaris suum eggs and phages T4 and MS2 were selected as models for bacterial, parasitic and viral pathogens, respectively. Salmonella were not detected anymore after 110 minutes of thermophilic AD. In anaerobic conditions at 55°C, concentrations of phages T4 and MS2 were below detection levels after 3 and 4 days, and no potentially viable Ascaris eggs were found after 15 days. Methods need to be optimized in order to improve the reliability of viability checks on Ascaris eggs. Future experiments could focus on this model, which will a priori be the limiting factor for the dimensioning of anaerobic digesters that yield safe-to-use end products.

2014

Chargement

Faecal sludge treatment: Optimization of Ascaris eggs enumeration and inactivation, and start-up of an anaerobic thermophilic acid-phase digester

Léa Cécile Randin

Faecal sludge (FS) accumulates in onsite sanitation technologies, which play a prevailing role in low- and middle-income countries. However, FS management is generally lacking. FS is usually directly discharged in the environment despite its high organic load and concentration in pathogens, including parasites such as Ascaris sp.. It is therefore urgent to find an adequate treatment to stabilise and sanitize FS. One possibility, which still needs to be assessed, is the so called temperature-phased anaerobic digestion (TPAD). The main objective of this study was to evaluate the potential of inactivation of Ascaris eggs in the first phase of TPAD, the acid-phase. However, standard methods to enumerate Ascaris eggs – which are microscopic methods involving an incubation - are lacking. The first part of this study focused on the improvement of existing methods to reliably evaluate the treatment performances. Then, inactivation efficiency of Ascaris eggs at 55°C in pure solution and sludge was evaluated. Inactivation efficiency was finally tested after injection of Ascaris eggs in a 1L anaerobic reactor operated at 55°C, which had been started-up to favour the acid-phase. By following the development of the eggs during the incubation time, it was observed that a period of incubation of 14 days is appropriate. Indeed, 14 days allow all eggs to develop to the larval stage while reducing the loss of eggs due to hatching or lysis. It was also found that the presence of FS does not influence the time of incubation. The inactivation experiments have shown that the temperature as a clear impact on the eggs, and that inactivation was accelerated in the presence of substrate and by anaerobic conditions. Indeed, eggs were inactivated within 3 hours when they were heated at 55°C, in 1h30 when they were introduced in digested sludge at 55°C and in less than 45 minutes when they were injected in the acid phase reactor at 55°C. The exploitation of the acid-phase reactor, with synthetic FS imitating the characteristics of FS as a substrate, allows recommending a hydraulic retention time of four days. This enables to run a stable acid-phase process. Standard methods for the enumeration of Ascaris eggs propose an incubation time of three to four weeks. Its reduction to two weeks is a clear advantage as it decreases the time before obtaining the results. Moreover, this study has shown that TPAD is a possible technology to inactivate Ascaris eggs. If the second phase of TPAD permits to stabilise FS, then this technology would be an adequate treatment for FS in low- and middle-income countries.

2015

Chargement

Immune serum-activated human macrophages coordinate with eosinophils to immobilize Ascaris suum larvae

Tiffany Babette Angélique Bouchery, Julia Esser-von Bieren, Kathleen Shah, Beatrice Volpe

Helminth infection represents a major health problem causing approximately 5 million disability-adjusted life years worldwide. Concerns that repeated anti-helminthic treatment may lead to drug resistance render it important that vaccines are developed but will require increased understanding of the immune-mediated cellular and antibody responses to helminth infection. IL-4 or antibody-activated murine macrophages are known to immobilize parasitic nematode larvae, but few studies have addressed whether this is translatable to human macrophages. In the current study, we investigated the capacity of human macrophages to recognize and attack larval stages of Ascaris suum, a natural porcine parasite that is genetically similar to the human helminth Ascaris lumbricoides. Human macrophages were able to adhere to and trap A suum larvae in the presence of either human or pig serum containing Ascaris-specific antibodies and other factors. Gene expression analysis of serum-activated macrophages revealed that CCL24, a potent eosinophil attractant, was the most upregulated gene following culture with A suum larvae in vitro, and human eosinophils displayed even greater ability to adhere to, and trap, A suum larvae. These data suggest that immune serum-activated macrophages can recruit eosinophils to the site of infection, where they act in concert to immobilize tissue-migrating Ascaris larvae.

WILEY2020

Chargement

Faecal sludge treatment: Optimization of Ascaris eggs enumeration and inactivation, and start-up of an anaerobic thermophilic acid-phase digester

Léa Cécile Randin

2015