Susceptibility of a Brazilian wild rodent isolate of Schistosoma mansoni to praziquantel in mice.

The therapeutic effects of praziquantel (PZQ) against a Schistosoma mansoni isolate derived from Nectomys squamipes (isolate R) and a susceptible isolate (BH) were analyzed in Swiss mice by fecal egg counting, adult worm reduction and oogram pattern. Infected mice were orally administrated with 62.5mg/kg (group 1), 125mg/kg (group 2), 250mg/kg (group 3) and 500mg/kg (group 4), each dose divided over 3 days (49, 50 and 51 days after infection). The data were analyzed using one-way analysis of variance (ANOVA). In regard to isolate R, no fecal eggs were observed with 250 mg/Kg and 500 mg/kg (p<0.05), whereas BH excretion reached zero with all doses. Mean worm burden reduction was significantly (p<0.05) higher at the two highest concentrations, regardless of isolate. At 62.5mg/kg, the percentage of immature eggs varied from 17% (isolate R) to 38% (isolate BH). At 125 mg/kg, the percentage of immature eggs varied from 20% (isolate R) to 16% (isolate BH). At 250 mg/kg, immature eggs dropped significantly to 1% (isolate R) and 4% (isolate BH). At 500 mg/kg, no immature eggs were found in isolate R, whereas in BH was 8%. No dosage significantly (p>0.05) affected the percentage of mature eggs, regardless of isolate. There was a large increase (p<0.001) in the percentages of dead eggs in all treated groups of 62% and 64% in groups 3 and 4, respectively (isolate R). The percentage of dead eggs rose from 34% (group 1) to 58% (group 3) in isolate BH. Although group 4 showed lowest increase in the percentage of dead eggs (46%), it was higher (p<0.001) compared to the 8% in the control. Our findings indicate that the wild isolate from N. squamipes is susceptible to PZQ.

Parasitological and morphological study of Schistosoma mansoni and diabetes mellitus in mice.

Schistosomes are blood-dwelling flukes which are highly dependent on the host metabolism. The aim of this study was to investigate possible relationship between streptozotocin-induced diabetes and the outcome of acute murine schistosomiasis mansoni. Male and female SW mice were treated by a single intraperitoneally injected dose of streptozotocin (180 mg/kg). Seven days after induction, both control and diabetic animals were infected with 70 Schistosoma mansoni cercariae (BH strain). Diabetics and their controls were weighed 45 days after birth and for the last time prior to killing. Susceptibility to infection was evaluated twice a week by quantifying fecal egg excretion 7-9 weeks post-infection by the Kato-Katz' thick smear method. Mice were euthanized the day after the last fecal examination was performed. Adult worms were recovered from the portal system and mesenteric veins, whereas liver and intestine were removed for enumeration of egg load. No differences in worm length or in measurements of the reproductive organs, tegument, and suckers were detected. Also oviposition was unaffected as the total number of eggs per female worm from the liver, the small and the large intestine was the same in both groups. An oogram evaluation revealed a lower percentage of mature (23.0% vs. 40.7%) and a higher percentage of immature (69.1% vs. 51.7%) eggs in the small intestine of the diabetic mice. We suggest that principally a hampered egg passage through the intestine tissue caused this reduction and that probably both the eggs and the impaired host response play a role.

Parasitological characteristics of Schistosoma mansoni infection in swiss mice with underlying malnutrition.

The effects of a protein-restricted diet (8% protein, 81% carbohydrate and 11% lipids) on Schistosoma mansoni infectivity, fecal egg excretion and intestinal egg distribution in Swiss (SW) mice were studied. Pregnant mice received a deficient diet from the middle of gestation until delivery. Seven-days-old mice were exposed to 50 cercariae (BH strain, Brazil). Offspring mice had a free access to the deficient diet since lactation until adulthood. The controls were fed with a commercial mice diet. A parasitological examination was performed between six and eight weeks post-infection while both groups were necropsied one week later. Mice on the experimental diet showed a significant loss in body weight. There was no significant difference (p > 0.05) in pre-patent period, kinetics of egg excretion and worm recovery from mice on either diet. Significant differences (p < 0.05) were found concerning to the percentage of deposited eggs in the distal segment of the small intestine from hosts on the experimental diet. Our data suggest that experimental malnutrition induced for a long term has no detrimental effect on the acute schistosomiais infection in SW mice.

Parasitological characteristics of Schistosoma mansoni infection in swiss mice with underlying malnutrition

The effects of a protein-restricted diet (8 percent protein, 81 percent carbohydrate and 11 percent lipids) on Schistosoma mansoni infectivity, fecal egg excretion and intestinal egg distribution in Swiss (SW) mice were studied. Pregnant mice received a deficient diet from the middle of gestation until delivery. Seven-days-old mice were exposed to 50 cercariae (BH strain, Brazil). Offspring mice had a free access to the deficient diet since lactation until adulthood. The controls were fed with a commercial mice diet. A parasitological examination was performed between six and eight weeks post-infection while both groups were necropsied one week later. Mice on the experimental diet showed a significant loss in body weight. There was no significant difference (p > 0.05) in pre-patent period, kinetics of egg excretion and worm recovery from mice on either diet. Significant differences (p < 0.05) were found concerning to the percentage of deposited eggs in the distal segment of the small intestine from hosts on the experimental diet.Our data suggest that experimental malnutrition induced for a long term has no detrimental effect on the acute schistosomiais infection in SW mice