title: Natural History of Cryptosporidiosis in a Birth Cohort in Southern India.
abstract: BACKGROUND
  Cryptosporidium is a leading cause of moderate to severe childhood diarrhea in resource-poor settings. Understanding the natural history of cryptosporidiosis and the correlates of protection are essential to develop effective and sustainable approaches to disease control and prevention.
  
  
  METHODS
  Children (N = 497) were recruited at birth in semiurban slums in Vellore, India, and followed for 3 years with twice-weekly home visits. Stool samples were collected every 2 weeks and during diarrheal episodes were tested for Cryptosporidium species by polymerase chain reaction (PCR). Serum samples obtained every 6 months were evaluated for seroconversion, defined as a 4-fold increase in immunoglobulin G directed against Cryptosporidium gp15 and/or Cp23 antigens between consecutive sera.
  
  
  RESULTS
  Of 410 children completing follow-up, 397 (97%) acquired cryptosporidiosis by 3 years of age. PCR identified 1053 episodes of cryptosporidiosis, with an overall incidence of 0.86 infections per child-year by stool and serology. The median age for the first infection was 9 (interquartile range, 4-17) months, indicating early exposure. Although infections were mainly asymptomatic (693 [66%]), Cryptosporidium was identified in 9.4% of diarrheal episodes. The proportion of reinfected children was high (81%) and there was clustering of asymptomatic and symptomatic infections (P < .0001 for both). Protection against infection increased with the order of infection but was only 69% after 4 infections. Cryptosporidium hominis (73.3%) was the predominant Cryptosporidium species, and there was no species-specific protection.
  
  
  CONCLUSIONS
  There is a high burden of endemic cryptosporidiosis in southern India. Clustering of infection is suggestive of host susceptibility. Multiple reinfections conferred some protection against subsequent infection.
authors.affiliation: Departments of Gastrointestinal Sciences and.
authors.forename: Deepthi
authors.initials: D
authors.lastname: Kattula
authors.affiliation: Departments of Gastrointestinal Sciences and.
authors.forename: Nithya
authors.initials: N
authors.lastname: Jeyavelu
authors.affiliation: Departments of Gastrointestinal Sciences and.
authors.forename: Ashok D
authors.initials: AD
authors.lastname: Prabhakaran
authors.affiliation: Biostatistics, Christian Medical College, Vellore, Tamil Nadu, India; and.
authors.forename: Prasanna S
authors.initials: PS
authors.lastname: Premkumar
authors.affiliation: Departments of Gastrointestinal Sciences and.
authors.forename: Vasanthakumar
authors.initials: V
authors.lastname: Velusamy
authors.affiliation: Departments of Gastrointestinal Sciences and.
authors.forename: Srinivasan
authors.initials: S
authors.lastname: Venugopal
authors.affiliation: Departments of Gastrointestinal Sciences and.
authors.forename: Jayanthi C
authors.initials: JC
authors.lastname: Geetha
authors.affiliation: Departments of Gastrointestinal Sciences and.
authors.forename: Robin P
authors.initials: RP
authors.lastname: Lazarus
authors.affiliation: Departments of Gastrointestinal Sciences and.
authors.forename: Princey
authors.initials: P
authors.lastname: Das
authors.affiliation: Departments of Gastrointestinal Sciences and.
authors.forename: Karthick
authors.initials: K
authors.lastname: Nithyanandhan
authors.affiliation: Departments of Gastrointestinal Sciences and.
authors.forename: Chandrabose
authors.initials: C
authors.lastname: Gunasekaran
authors.affiliation: Departments of Gastrointestinal Sciences and.
authors.forename: Jayaprakash
authors.initials: J
authors.lastname: Muliyil
authors.affiliation: Departments of Gastrointestinal Sciences and.
authors.forename: Rajiv
authors.initials: R
authors.lastname: Sarkar
authors.affiliation: Division of Geographic Medicine and Infectious Diseases, Tufts Medical Center.|Department of Public Health and Community Medicine, Tufts University School of Medicine, and.
authors.forename: Christine
authors.initials: C
authors.lastname: Wanke
authors.affiliation: Departments of Gastrointestinal Sciences and.
authors.forename: Sitara Swarna Rao
authors.initials: SS
authors.lastname: Ajjampur
authors.affiliation: Departments of Gastrointestinal Sciences and.
authors.forename: Sudhir
authors.initials: S
authors.lastname: Babji
authors.affiliation: Department of Public Health and Community Medicine, Tufts University School of Medicine, and.|Friedman School of Nutrition Science and Policy, Tufts University, Boston, Massachusetts.
authors.forename: Elena N
authors.initials: EN
authors.lastname: Naumova
authors.affiliation: Division of Geographic Medicine and Infectious Diseases, Tufts Medical Center.|Department of Public Health and Community Medicine, Tufts University School of Medicine, and.
authors.forename: Honorine D
authors.initials: HD
authors.lastname: Ward
authors.affiliation: Departments of Gastrointestinal Sciences and.
authors.forename: Gagandeep
authors.initials: G
authors.lastname: Kang
mesh_terms: D015331:Cohort Studies; D003457:Cryptosporidiosis / Q000453:epidemiology* / Q000276:immunology / Q000469:parasitology / Q000517:prevention & control; D003458:Cryptosporidium / Q000145:classification / Q000235:genetics / Q000302:isolation & purification*; D003968:Diarrhea, Infantile / Q000453:epidemiology* / Q000276:immunology / Q000469:parasitology / Q000517:prevention & control; D019353:Endemic Diseases; D005243:Feces / Q000469:parasitology; D005260:Female; D006801:Humans; D007074:Immunoglobulin G / Q000097:blood; D015994:Incidence; D007194:India / Q000453:epidemiology; D007223:Infant; D007231:Infant, Newborn; D008137:Longitudinal Studies; D008297:Male; D036801:Parturition; D011204:Poverty Areas; D011446:Prospective Studies
chemical_list: D007074:Immunoglobulin G
keywords: India.; birth cohort; children; cryptosporidiosis; diarrhea; natural history