A statistical approach to schistosome population dynamics and estimation of the life-span of <i>Schistosoma mansoni</i> in man

Fulford, Anthony J. C.; Butterworth, Anthony E.; Ouma, John H.; Sturrock, R. F.

doi:10.1017/s0031182000080896

Cited by 108 publications

(90 citation statements)

References 17 publications

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“…55,56 The mean life span of S. mansoni worms is estimated to be 6-10 years. 57 Thus, exposure to antigens from naturally dying worms in untreated populations could explain the age-dependent resistance to reinfection. Age was unlikely to be a confounder in this study because the age of the resistant persons ranged from 10 to 60 years, and infected persons were matched by age.…”

Section: Discussionmentioning

confidence: 99%

Factors Associated with Resistance to Schistosoma mansoni Infection in an Endemic Area of Bahia, Brazil

Oliveira¹,

Figueiredo²,

Cardoso³

et al. 2012

The American Society of Tropical Medicine and Hygiene

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Abstract. Detailed knowledge of factors associated with resistance to Schistosoma mansoni infection in endemic areas might facilitate more effective schistosomiasis control. We conducted a cross-sectional study of persons resistant to schistosomiasis and found no association between socioeconomic status and resistance to infection. Mononuclear cells of resistant subjects produced higher levels of interleukin-5 (IL-5), IL-13 and interferon-g upon stimulation with soluble egg antigen (SEA) compared with infected persons. When stimulated with Sm21.6 or Sm22.6, levels of IL-10 were higher in cell culture of resistant persons. Levels of IgE against soluble adult worm antigen (SWAP) and against interleukin-4-inducing principle from S. mansoni eggs (IPSE) and levels of IgG4 against SWAP, SEA, and Sm22.6 were lower in the resistant group compared with the susceptible group. Our data suggest that socioeconomic status could not fully explain resistance to S. mansoni infection observed in the studied area. However, a mixture of Th1 and Th2 immune responses and low levels of specific IgG4 against parasite antigens could be mediating resistance to infection.

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Section: Discussionmentioning

confidence: 99%

Factors Associated with Resistance to Schistosoma mansoni Infection in an Endemic Area of Bahia, Brazil

Oliveira¹,

Figueiredo²,

Cardoso³

et al. 2012

The American Society of Tropical Medicine and Hygiene

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“…Most experimental murine infections are acute or subacute and are monitored for several months at most, whereas individuals living in areas of endemicity have often been chronically infected for many years. In a typical murine infection, the immune system would not be exposed to dying adult worms, because the average adult S. mansoni worm would outlive a mouse by several years (12). Typically SEA-specific immune responses in experimentally infected mice coincide with the onset of egg laying, when infected animals are exposed to egg-derived antigens (14).…”

Section: Discussionmentioning

confidence: 99%

“…In areas of high transmission, children become infected when they are old enough to come into contact with contaminated water. In these areas, the combination of the longevity of individual worms (12) and susceptibility to reinfection may result in those exposed to the parasite being infected for most of their lives. However, infection intensity in areas of endemicity rises in early childhood, peaking during the early teenage years and then declining, and adults are more resistant to reinfection than young children (18).…”

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confidence: 99%

Cytokine Production in Whole Blood Cultures from a Fishing Community in an Area of High Endemicity forSchistosoma mansoniin Uganda: the Differential Effect of Parasite Worm and Egg Antigens

et al. 2004

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The human host is continuously exposed to the egg and the adult worm developmental stages of Schistosoma mansoni during chronic infections with the parasite. To assess the cytokine responses induced by these different costimulating stages and how they are influenced by host age and infection intensity, whole blood samples from a cross-sectional cohort of 226 members of a Ugandan fishing community who had been resident in an area with high transmission of S. mansoni for the previous 10 years or from birth were stimulated with S. mansoni egg antigen (SEA) or worm antigen (SWA). SWA-specific gamma interferon (IFN-␥) production increased with age, and the levels of SWA-and SEA-specific interleukin 3 (IL-3) were weakly correlated with schistosome infection intensity. The production of most cytokines was little affected by age or infection intensity but was either SEA or SWA specific. One hundred thirty-two members of the cohort coproduced IL-5 and IL-13 specifically in response to SWA, whereas only 15 produced these cytokines, and at much lower levels, in response to SEA. IL-10, IL-4, and IFN-␥ were also produced in response to SWA, whereas the response to SEA consisted almost exclusively of IL-10. Our results suggest that, in contrast to what has been described for the murine model of S. mansoni and during acute human infections, chronic intense exposure to and infection with S. mansoni in this cohort resulted in very low levels of response to SEA in vitro in the presence of a vigorous and mixed Th1-Th2 response to SWA.

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“…Adult S. mansoni worms can live in the human bloodstream for many years (15), and many antigens will be released only when the worm dies. Schistosome eggs, however, are repeatedly deposited in the host's tissues, where, although short-lived, they secrete soluble antigens.…”

Section: Vol 72 2004 Schistosomiasis Cure In Ugandan Men: Immune Rementioning

confidence: 99%

Chemotherapy for Schistosomiasis in Ugandan Fishermen: Treatment Can Cause a Rapid Increase in Interleukin-5 Levels in Plasma but Decreased Levels of Eosinophilia and Worm-Specific Immunoglobulin E

et al. 2004

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Chemotherapy for blood-dwelling schistosomes kills the worms and exposes parasite antigen to the circulation. In many people from areas of endemicity, this treatment increases parasite-specific immunoglobulin E (IgE) and other Th2 responses in the months following therapy, responses that have been associated with subsequent resistance to reinfection. Here we investigate much earlier changes in immune reactions after praziquantel therapy in Schistosoma mansoni-infected fishermen working in an area of high transmission in Uganda. The subjects gave blood before treatment and at 1 and 21 days posttreatment. Blood cultures were incubated with schistosome soluble worm antigen (SWA) or soluble egg antigen (SEA). Interleukin-4 (IL-4), IL-5, IL-10, IL-13, gamma interferon, and transforming growth factor ␤ levels were measured in the cultures and in plasma. A marked transient increase in plasma IL-5 levels was observed in 75% of the subjects (n ‫؍‬ 48) by 1 day posttreatment. This response was dependent on pretreatment intensity of infection and was accompanied by a transient decrease in eosinophil numbers. One day posttreatment, blood cultures from the 16 subjects with the greatest increase in plasma IL-5 level (>100 pg/ml) displayed reduced IL-5, IL-13, and IL-10 responses to SWA, and in contrast to the rest of the cohort, these high-IL-5 subjects displayed reduced levels of SWA-specific IgE in plasma 21 days posttreatment. Twenty months after treatment, the intensity of reinfection was positively correlated with the increase in plasma IL-5 level seen 1 day posttreatment. These studies describe the heterogeneity in early immune reactions to treatment, identifying subgroups who have different patterns of reaction and who may have different capacities to mount the responses that have been associated with resistance to reinfection.Schistosomiasis is a condition caused by parasitic helminths of the genus Schistosoma, with S. mansoni, S. haematobium, and S. japonicum accounting for most of the world's estimated 200 million cases of human schistosomiasis. The disease is contracted from waterborne larvae that penetrate the skin and enter the bloodstream, where they develop, pair, and reach sexual maturity. Adult pairs of S. mansoni reside in the mesenteric veins of the intestine, where each female lays up to 300 eggs per day.In numerous treatment studies carried out in areas of endemicity (4,6,7,11,12,16,23,45,46), the intensity of reinfection after chemotherapy has been shown to be highest in children and adolescents and then to decrease during adult life. This suggests that acquired resistance to infection may develop gradually with age. It has, however, been difficult to draw firm conclusions from these age profiles, as in most communities of endemicity adults have less contact with infected water than do children. For this reason, Kabatereine et al. (28) examined the intensity of S. mansoni reinfection in a Ugandan fishing community following treatment with praziquantel (PZQ). Due to occupational contact with water in the...

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A statistical approach to schistosome population dynamics and estimation of the life-span of Schistosoma mansoni in man

Cited by 108 publications

References 17 publications

Factors Associated with Resistance to Schistosoma mansoni Infection in an Endemic Area of Bahia, Brazil

Factors Associated with Resistance to Schistosoma mansoni Infection in an Endemic Area of Bahia, Brazil

Cytokine Production in Whole Blood Cultures from a Fishing Community in an Area of High Endemicity forSchistosoma mansoniin Uganda: the Differential Effect of Parasite Worm and Egg Antigens

Chemotherapy for Schistosomiasis in Ugandan Fishermen: Treatment Can Cause a Rapid Increase in Interleukin-5 Levels in Plasma but Decreased Levels of Eosinophilia and Worm-Specific Immunoglobulin E

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