Rate of Destruction of Schistosoma mansoni Eggs and Adult Worms in the Tissues of Rhesus Monkeys

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  • U. S. Department of Health, Education, and Welfare, National Institutes of Health, National Institute of Allergy and Infectious Diseases, Laboratory of Parasitic Diseases, Bethesda, Maryland 20014

Since destruction influences the number of Schistosoma mansoni eggs in the tissues, relative rates of egg destruction were studied in mice and rhesus monkeys after treatment of experimental infections and intravenous injection of eggs. After treatment in the 7th week of infection, eggs in tissues had a half-life of 8 days in rhesus monkeys, compared with about 4 weeks in mice. Eggs injected intravenously were rapidly destroyed by infected monkeys; uninfected monkeys destroyed injected eggs more slowly. In untreated mice, dead eggs accumulated steadily in the tissues, and the proportion of live eggs decreased with the duration of infection. In untreated rhesus monkeys, the proportion of living and dead eggs remained nearly constant. The extremely rapid rate of egg destruction in monkeys is the most important determinant of lesser accumulation in tissues of this species. Worms killed by treatment with antimonials were more rapidly destroyed in rhesus monkeys than in mice, and fibrosis about dead worms or in regressing circumoval granulomas was rare in monkeys but common in mice.

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