Schistosoma mansoni: reinfections and concomitant immunity in mice. Importance of perfusion time after challenge infection for evaluation of immunoprotection

The concomitant immunity in the presence of repeated infections (with 15 cercariae) was studied in mice sacrificed on the 20th day after each infection. The comparison of the averages of immature worms, recovered from mice submitted to reinfection, with those of their respective controls (previously uninfected) showed a significantly lower worm recovery rate in the animals with previous infections (concomitant immunity). However, statiscally significant differences could not be detected among the various groups of animals, when the mice that accumulated worms in this mature stage were perfused. The theoretical projection based on the accumulation of young worms which developed to adult ones indicates a lower recovery rate of adult worms in the animals with concomitant immunity, but this projection was not corroborated by the experimental data. The visceral hemodynamic alterations that occurred in reinfections due to the pathogeny, favouring recirculation of the recent arriving worms to the other organs on the occasion of perfusion of the portal system. These results suggest that special care should be taken when one wants to investigate concomitant immunity in mice based on the distinction of the immature worms from challenge infection and the mature ones from primary infection.

Aspects of the granulomatous reaction in the liver of mice infected and reinfected with two different geographical strains of schistosoma mansoni

In this study, which was undertaken in relation to the histopathologic behavior of two different strains (LE - Belo Horizonte, MG and SJ - Sao José dos Campos, SP) in infections and reinfections (homologous or heterologous) with Schistosoma mansoni, the authors confirmed a more accentuated pathogenicity of the SJ strain. All the reinfections showed the presence of typical granulomas of the acute phase, when performed either with the same strain (homologous) or with a different strain (heterologous) of the parasite of the primo infection. The possible mechanisms responsible for reactivation of the immunopathologic response in reinfections are discussed.

Estudo comparativo da prevalência de parasitoses intestinais em escolares de Belo Horizonte, MG / Intestinal parasites in children from Belo Horizonte schools - a comparative study

Säo apresentados os resultados de 1.352 exames parasitológicos de fezes, realizados pelo método de MIFC, em escolares de Belo Horizonte, MG. O estudo foi desenvolvido durante os anos de 1985 a 1991 em 1352 crianças com idade variando de 7 a 15 anos, provenientes de três escolas públicas. As prevalências, global e específica, de helmintos e protozoários foram estatisticamente analisadas, revelando uma elevada percentagem de exames positivos nas três escolas, sendo a média de 78,3 porcento. Foram detectados todos os parasitos intestinais comumente encontrados no exame parasitológico de fezes, exceto Taenia sp. Em duas escolas, o Trichocephalus trichiurus foi o parasito mais prevalente (60,9 porcento e 44,3 porcento), enquanto na terceira o Ascaris lumbricoides apresentou a maior prevalência (34,0 porcento). Os altos índices de parasitoses intestinais observados, säo analisados e discutidos em relaçäo ao nível sócio-econômico da populaçäo e a falta de saneamento básico nas regiöes atendidas pelas escolas