Detection of IgM antibodies to Schistosoma mansoni gut-associated antigens for the study of the dynamics of schistosomiasis transmission in an endemic area with low worm burden.
For a period of 2 years, five follow-up measures of prevalence and incidence rates were estimated in a prospective study of S. mansoni infection in a group of schoolchildren who were living in a rural area of the Municipality of Itariri (São Paulo, Brazil), where schistosomiasis is transmitted by Biomphalaria tenagophila. Infection was determined by the examination of three Kato-Katz stool slides, and the parasitological findings were analyzed in comparison to serological data. In the five surveys, carried out at 6-month intervals (March-April and September-October), the prevalences were, respectively, 8.6, 6.8, 9.9, 5.8 and 17.2% by the Kato-Katz, and 56.5, 52.6, 60.8, 53.5 and 70.1% by the immunofluorescence test (IFT). Geometric mean egg counts were low: 57.8, 33.0, 35.6, 47.3 and 40.9 eggs per gram of feces, respectively. Of the total of 299 schoolchildren, who submitted five blood samples at 6-month intervals, one for each survey, 40% were IFT-positive throughout the study, and 22% were IFT-negative in all five surveys. Seroconversion from IFT negative to positive, indicating newly acquired S. mansoni infection, was observed more frequently in surveys carried out during March-April (after Summer holidays), than during September-October. Seasonal trends were not statistically significant for detection of S. mansoni eggs in stool. The results indicate that the use of IgM-IFT is superior to parasitological methods for detection of incidence of S. mansoni infection in areas with low worm burden.
Kanamura
H Y
HY
Faculdade de Ciências Farmacêuticas, Universidade de São Paulo, Brazil. kanamura@usp.br
Dias
L C
LC
Glasser
C M
CM
da Silva
R M
RM
Patucci
R M
RM
Chiodelli
S G
SG
Addiss
D G
DG
D000293:Adolescent; D000818:Animals; D000909:Antibodies, Helminth / Q000097:blood*; D001938:Brazil; D002648:Child; D002675:Child, Preschool; D005243:Feces / Q000469:parasitology; D005500:Follow-Up Studies; D006801:Humans; D007075:Immunoglobulin M / Q000097:blood*; D015994:Incidence; D010270:Parasite Egg Count; D015995:Prevalence; D011446:Prospective Studies; D012424:Rural Population; D012550:Schistosoma mansoni / Q000276:immunology*; D012555:Schistosomiasis mansoni / Q000175:diagnosis* / Q000453:epidemiology / Q000276:immunology* / Q000635:transmission; D012621:Seasons; D012680:Sensitivity and Specificity
D000909:Antibodies, Helminth; D007075:Immunoglobulin M