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

• Published in: Revista do Instituto de Medicina Tropical de São Paulo 1998-07, Vol.40 (4), p.225-231
• Main Authors: Kanamura, H Y, Dias, L C, Glasser, C M, da Silva, R M, Patucci, R M, Chiodelli, S G, Addiss, D G
• Format: Article
• Language: English
• Subjects: Adolescent; Animals; Antibodies, Helminth - blood; Brazil; Child; Child, Preschool; Epidemiology; Feces - parasitology; Follow-Up Studies; Humans; Immunodiagnosis; Immunoglobulin M - blood; Incidence; Parasite Egg Count; Prevalence; Prospective Studies; Rural Population; Schistosoma mansoni; Schistosoma mansoni - immunology; Schistosomiasis mansoni - diagnosis; Schistosomiasis mansoni - epidemiology; Schistosomiasis mansoni - immunology; Schistosomiasis mansoni - transmission; Seasons; Sensitivity and Specificity; Seroconversion; TROPICAL MEDICINE
• ISSN: 0036-4665; 1678-9946; 0036-4665; 1678-9946
• DOI: 10.1590/S0036-46651998000400004

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.