Evaluation of the patterns of Schistosoma mansoni infection and re-infection in Senegal, from faecal egg counts and serum concentrations of circulating anodic antigen.
Infection and re-infection patterns were evaluated in a recent Schistosoma mansoni focus in northern Senegal, by determining concentrations of serum circulating anodic antigen (CAA), as a measure of worm burden, and counting eggs in faeces before, 6 or 12 weeks and 1 year after praziquantel treatment in two subsequent cohorts (cohort A and B). No differences in egg counts and CAA concentrations or their relationship were found between the cohorts, which were examined 2 years apart. Within both cohorts, CAA concentrations showed the same, typical, age-related patterns as egg counts, with a peak in children and a strong decline in adults. These trends were apparent both before and 1 year after treatment. The results indicate that an age-related resistance to infection and to re-infection has been firmly established, at a steady level, in the recent S. mansoni focus investigated, with no indication of a gradual development of immunity or anti-fecundity immunity over a period of 2 years. Both shortly and 1 year after treatment, the decrease in egg counts was stronger than that in CAA concentrations, indicating that that there had been a reduction in worm fecundity after treatment. The possibility that praziquantel may induce anti-fecundity immunity has important implications for the use and interpretation of the results of (egg-count-based) re-infection studies designed to follow the development of naturally acquired immunity.
Polman
K
K
Department of Parasitology, Leiden University Medical Centre, P.O. Box 9600, 2300 RC Leiden, The Netherlands. kpolman@itg.be
Stelma
F F
FF
Le Cessie
S
S
De Vlas
S J
SJ
Falcão Ferreira
S T M
ST
Talla
I
I
Deelder
A M
AM
Gryseels
B
B
D000293:Adolescent; D000328:Adult; D000367:Age Factors; D000818:Animals; D000871:Anthelmintics / Q000627:therapeutic use; D000947:Antigens, Helminth; D002648:Child; D002675:Child, Preschool; D015331:Cohort Studies; D003627:Data Interpretation, Statistical; D005243:Feces / Q000469:parasitology; D005298:Fertility / Q000187:drug effects; D006023:Glycoproteins / Q000097:blood*; D015801:Helminth Proteins / Q000097:blood*; D006801:Humans; D007223:Infant; D007231:Infant, Newborn; D016014:Linear Models; D008875:Middle Aged; D010270:Parasite Egg Count / Q000379:methods; D011223:Praziquantel / Q000627:therapeutic use; D012008:Recurrence; D012550:Schistosoma mansoni / Q000276:immunology*; D012552:Schistosomiasis / Q000188:drug therapy / Q000276:immunology*; D012675:Senegal
D000871:Anthelmintics; D000947:Antigens, Helminth; D006023:Glycoproteins; D015801:Helminth Proteins; C090907:circulating anodic antigen, Schistosoma mansoni; D011223:Praziquantel