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PubMed2003

Immunological studies on mice vaccinated with irradiated cercaria and IL-12 against Schistosoma mansoni infection.

Protective immunity against Schistosoma mansoni infection correlates with increased levels of IgE and blood eosinophilia which are considered as markers of anti-parasitic cell-mediated immunity. IL-5 participates as well in the induction and regulation of IgE and eosinophilia, consequently in the development of acquired immunity. Swiss Webster female mice were subcutaneously injected with either 50 microg of gamma-irradiated cercarial homogenate (400 Gy) twice weekly for three weeks alone or plus a single dose of IL-12 (0.8 ng/Kg). The efficiency of immunization regimens were assessed 45 days post infection with 100 live cercariae/mouse by the number of worm burden, ova count, production of IL-5, eosinophils, and IgE levels in the vaccinated groups compared with the non-immunized group. The results demonstrated a significant reduction of ova count in the livers of vaccinated groups (57.19 and 40.13%) and worm couples compared with the non -immunized group. Furthermore, a decrease of IL-5 level as well as eosinopenia was recorded in both vaccinated groups. Scanning electron microscope (SEM) of adult worms recovered from the immunized groups revealed marked damage on the tegumental surface in males rather than females as well as constrictions and intensive corrugation of intertubercles.

Animals↗
PubMed1991

Comparison of Th1- and Th2-associated immune reactivities stimulated by single versus multiple vaccination of mice with irradiated Schistosoma mansoni cercariae.

Mice immunized against Schistosoma mansoni by a single percutaneous exposure to radiation-attenuated parasite larvae demonstrate partial resistance to challenge infection that has been shown to correlate with development of cell-mediated immunity, whereas mice hyperimmunized by multiple exposure to attenuated larvae produce antibodies capable of transferring partial protection to naive recipients. Measurement of Ag-specific lymphokine responses in these animals suggested that the difference in resistance mechanisms may be due to the differential induction of Th subset response by the two immunization protocols. Thus, upon Ag stimulation, singly immunized mice predominantly demonstrated responses associated with Th1 reactivity, including IL-2 and IFN-gamma production, whereas multiply immunized animals showed increased IL-5, IL-4, and IgG1 antibody production associated with enhanced Th2 response. These responses demonstrated some degree of organ compartmentalization, with splenocytes demonstrating higher Th1-related lymphokine production and cells from draining lymph nodes showing stronger proliferation and Th2 type reactivity. However, hyperimmunized mice also continued to demonstrate substantial Th1-associated immune reactivity. Moreover, in vivo Ag challenge elicited activated larvacidal macrophages in hyperimmunized animals. These observations indicate that protective cell-mediated mechanisms associated with induction of CD4+ Th1 cell reactivity predominate in singly vaccinated mice. Further vaccination stimulates Th2 responses, such as enhanced IgG1 production, that may also contribute to protective immunity.

Animals↗
PubMed1990

Schistosoma haematobium cercariae transmission patterns in freshwater systems of Anambra State, Nigeria.

The seasonality of infection of Bulinus (Ph.) globosus, the snail host of Schistosoma haematobium is reported. The pattern of snail infection was shown to vary with the type of habitats. The cercarial "transmission potential" was calculated based on the number of infected snails and the level of cercarial production. It is consequently assumed that the transmission pattern varies with season and habitat type. Dry season transmission potential was found to be high in running water habitats while low in stagnant water habitats. In the wet season, the reverse seems to be the case. The implication of these observations in the epidemiology of urinary schistosomiasis and in planning its control in the area is discussed.

Animals↗
PubMed1990

The effects of single exposures of Aedes aegypti larvae and pupae to Plagiorchis noblei cercariae in the laboratory.

The mortality of Aedes aegypti pre-imagos harboring metacercariae of Plagiorchis noblei Park, 1936, is governed by the stage of development of the host at the time of infection and the location of the parasite in the insect body. First and second instar larvae generally succumbed to infection, regardless of site. Infections of the head and thorax of third and fourth instar larvae were generally lethal or gave rise to imparied adults. However, older instars frequently survived abdominal infections. Pupae showed greater tolerance to cephalic, thoracic and abdominal infections and generally emerged as adults. Again, many such infected adults were impaired.

Aedes↗
PubMedDate not supplied

[Ultrastructure of the tail appendage in microphallid cercariae (Trematoda, Microphallidae)].

The tail structure of larvae of Maritrema subdolum and Microphallus claviformes is similar in essence. Its wall is made by the tegument and underlying layers of muscles. The syncytial anucleated tegumental lamina with the only type of secretory inclusions forms regular circular folds along the tail. The outer muscle layer is formed by the smooth muscular cells. It is underlaid by the longitudinal cross-striated muscles with the strongly pronounced sarcomere organization. The nucleus-containing bodies of the muscle cells occupy the axial part of the tail excepting the central cavity. The functional joining of tail and body musculatures is provided by thick muscle bundles in the caudal department of the larval body.

Animals↗
PubMed1985

[Chetotaxic polymorphism and development of sensillary associations in the cercaria of Schistosoma mansoni from Cameroon].

A survey of the variation of the cercarial papillae patterns, in wild cameroonese samples of S. mansoni, shows ranges of values quite different from those already recorded in Africa. African chaetotype frequency is very low and American-Caribbean one relatively highest. Ecological isolation and possible interbreeding between strains of S. mansoni, transmitted by the 2 sympatric species of snail vector, would have occurred to select the third chaetotype.

Animals↗