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The Parasite's Way of Life
Published in Eric S. Loker, Bruce V. Hofkin, Parasitology, 2023
Eric S. Loker, Bruce V. Hofkin
Another question relates to the evolution of the complex migration observed in some parasites. The tissue migration of many intestinal nematodes with direct life cycles, for example, appears to defy logic. Ascaris suum is illustrative (Figure 3.21). This species is a common intestinal roundworm of swine and is similar to (and arguably even the same species as) the human parasite A. lumbricoides. As in all nematodes, there are characteristic life cycle stages. Fertile eggs are produced by the adult female. A first stage larva, called an L1 larva, develops within the egg. The larva undergoes four molts that are followed by periods of growth giving rise to L2, L3 and L4 larvae and ultimately to an adult. The larval stage that emerges from the egg may be the L1, L2 or L3 larva, depending on the species. In the genus Ascaris, following ingestion by the host, an L3 larva, still covered by the L2 cuticle, emerges from the egg in the small intestine. Note that some researchers prefer to call immature nematodes juveniles instead of larvae and thus refer to the L1 to L4 stages as J1 to J4.
Effect of Neutrophils on Airway Smooth Muscle Responsiveness
Published in Devendra K. Agrawal, Robert G. Townley, Inflammatory Cells and Mediators in Bronchial Asthma, 2020
Hutson and collaborators59 utilized aerosolized albumin challenge to sensitize guinea pigs and have shown that subsequent aerosol albumin challenge provokes an early fall in specific lung conductance followed by later falls (measured at 17 and 72 h). Allergen challenge is associated with an increase in BAL neutrophils and eosinophils at 17 h. The neutrophil influx could be inhibited by pretreatment with the (β-adrenergic agonist albuterol without affecting the LR. They suggest, therefore, that the neutrophil is not necessary for the LR. Using guinea pigs systemically sensitized to Ascaris suum antigen, Iijima et al.60 found that subsequent aerosol challenge of the animals resulted in an LR in 40%, but there was no difference in the neutrophils in BAL or airway walls between those animals with an ER and those with both an ER and LR. Thus, there is a dissociation in these two studies between the presence of neutrophils and the presence of the LR. These results suggest that, in the immunized guinea pig, neutrophil influx is not necessary for the development of the LR. Whether or not the neutrophil may play a role in any increased nonspecific airway reactivity remains to be investigated.
Ascaris
Published in Dongyou Liu, Handbook of Foodborne Diseases, 2018
Stefano D'Amelio, Viliam Snabel, Serena Cavallero
At present the genus Ascaris includes several valid species, with a large number of former species now placed in synonymy,6 but only Ascaris lumbricoides Linnaeus 1758, a parasite of humans, and Ascaris suum Goeze 1782, mainly affecting pigs, have been extensively investigated. Despite their presence in different hosts, these two species are morphologically conservative, with little or no variation in morphological traits. A. suum is prevalent worldwide in both intensive and extensive pig production systems, having negative impact on weight gain and marketability7; A. lumbricoides infects 1.2 billion people globally, and even if disability-adjusted life years is around 10.5 million, ascariasis is still considered a neglected tropical disease.8 Around 1.3 billion infections were estimated globally, with 59 million at risk of some morbidity.9 The estimate for acute illness was 12 million cases per year with around 10,000 deaths. The infection is widespread in warm and humid climates, including temperate zones during warmer months, and is found in association with poor personal hygiene, poor sanitation, and/or in areas where human feces are used as fertilizer.
Exploration of extracellular vesicles from Ascaris suum provides evidence of parasite–host cross talk
Published in Journal of Extracellular Vesicles, 2019
Eline P. Hansen, Bastian Fromm, Sidsel D. Andersen, Antonio Marcilla, Kasper L. Andersen, Anne Borup, Andrew R. Williams, Aaron R. Jex, Robin B. Gasser, Neil D. Young, Ross S. Hall, Allan Stensballe, Vladimir Ovchinnikov, Yan Yan, Merete Fredholm, Stig M. Thamsborg, Peter Nejsum
The large roundworm, Ascaris suum, is one of the most important and prevalent parasitic nematodes of pigs. Although mostly subclinical, infections are associated with production losses due to impaired nutrient utilisation and reduced weight gain, but pigs may also be affected by a high worm burden [1]. In addition, A. suum infection may increase the pathogenicity of bacterial co-infections and compromise vaccine efficacy [2]. A. lumbricoides is highly prevalent in humans and 819 million people are estimated to be infected [3]. Due to the high genetic relatedness between A. suum and A. lumbricoides and the pronounced similarities in host physiology, A. suum infections in pigs can be used as model system for studying A. lumbricoides infections in humans [4].
Bifidobacterium animalis subspecies lactis modulates the local immune response and glucose uptake in the small intestine of juvenile pigs infected with the parasitic nematode Ascaris suum
Published in Gut Microbes, 2018
Gloria Solano-Aguilar, Terez Shea-Donohue, Kathleen B. Madden, Alejandro Quinoñes, Ethiopia Beshah, Sukla Lakshman, Yue Xie, Harry Dawson, Joseph F. Urban
Clinical studies suggest that some probiotic bacteria can promote health and prevent disease;1,8,21,22 however the mechanisms underlying these beneficial effects are not well understood. In this study, the in vivo effect of Bifidobacterium animalis subspecies lactis (Bb12) on intestinal function and immunity against a parasitic nematode was evaluated. Ascaris suum is a persistent and common problem in swine raised worldwide, and the related species in humans, A. lumbricoides (large roundworm) infects an estimated 804 million people.23 Although infections are common in countries with poor sanitation, ascariasis exhibit a cosmopolitan distribution with sporadic cases also described in developed countries24 where pigs can be a source of infection.25 Examination of the immunological and physiological responses to intestinal helminths also has been used to study local and systemic allergic disease.26,27