Dynamics of egg counts and circulating antigen levels in a recent Schistosoma mansoni focus in northern Senegal

Katja Polman*, F. Stelma, Sake J. de Vlas, S. Sow, L.M. Fathers, S. Le Cessie, I. Talla, A.M. Deelder, B. Gryseels

*Corresponding author for this work

Research output: Contribution to JournalArticleAcademicpeer-review

Abstract

Serum circulating anodic antigen (CAA) levels were compared with faecal egg counts in four subsequent population samples, randomly selected at 8-month intervals, in a recent Schistosoma mansoni focus in northern Senegal. In all four samples, antigen levels showed the same age-intensity profiles as egg counts, with a strong decline in adults. Also across population samples, a consistent relationship was found between egg counts and antigen levels. Assuming the level of CAA to be a direct reflection of worm burden, these findings support the idea that the observed egg count patterns and levels indeed reflect dynamics of worm burdens, and not of egg excretion or worm fecundity. Remarkably similar levels of both egg counts and CAA were observed in the first and last sample, collected in the same season (August-September), but 2 years apart. This suggests that a steady state of S. mansoni infection had already been reached shortly after the onset of the epidemic in this focus (3 years). Significantly lower infection levels were found in the intermediate population samples collected in January and April. The differences in infection levels across the four population samples may be because of seasonal transmission patterns. They would indicate a substantial turnover of worm populations, with an estimated average life span of only 7 months, probably less, in this recently emerged, intense S. mansoni focus.

Original languageEnglish
Pages (from-to)538-544
Number of pages7
JournalTropical Medicine and International Health
Volume6
Issue number7
DOIs
Publication statusPublished - 2001
Externally publishedYes

Keywords

  • Circulating anodic antigen (CAA)
  • Faecal egg counts
  • Schistosoma mansoni
  • Seasonality
  • Senegal
  • Worm longevity

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